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Mangshan section is a scarce and valuable high-sedimentation deposit at the southeastern margin of the Chinese Loess Plateau for high-resolution paleoclimate reconstructions. Although the chronology of the deposit above the paleosol layer S2 has been pinned down on the glacial-interglacial timescale, it still needs to be refined at orbital timescale, especially at the boundary from loess layer L2 to paleosol layer S1. In the age model by correlation of loess grain size with the benthic oxygen isotope (δ18O) records, the lack of paleosol and low magnetic susceptibility during the marine isotope stage 5e are substantially different from the observations in other loess-paleosol sequences on the Chinese Loess Plateau. Here, we analyzed the oxygen isotope composition of microcodium from the upper loess layer L2 and paleosol layer S1 of the Mangshan section to reconstruct the oxygen isotopic stratigraphy. Comparing it with the absolute-dating speleothem δ18O record, we suggest corresponding the paleosol layer S1 to the last interglacial, which is consistent with other loess-paleosol sequences on the Chinese Loess Plateau. Our study provides a new method for the loess chronology by tuning the microcodium δ18O record to the absolute-dating speleothem δ18O record. [ABSTRACT FROM AUTHOR]

To investigate the risk levels of collapse associated with different Low-Impact Development (LID) measures employed in constructing stormwater systems within collapsible loess areas, the study utilized the High-Efficiency and High-Precision Urban Stormwater Model (GAST) to analyze the risk of waterlogging. The aim was to propose a method that integrates the analysis of waterlogging accumulation time with considerations of the correlation between the collapsibility coefficient and soil parameters, thereby assessing the collapse risk level of various LID measures. This method was applied to examine the changing patterns of settlement risk levels in grassed swales and rain gardens under different rainfall return periods (P1 = 20 years, P2 = 50 years, P3 = 100 years) and water accumulation durations (T1 = 0.5 days, T2 = 5 days). Findings reveal a direct correlation between rainfall return periods and collapse risk levels. Specifically, at P3 = 100 years, 50% of the collapse risk level in the study region reaches level III. However, when the water accumulation duration is extended to 5 days, the percentage of locations classified as category III increases to 75%. Despite rain gardens' superior water storage capacity compared to grass swales, they also elevate the risk of collapse. Therefore, diligent monitoring of rain garden durability during prolonged periods of frequent rainfall is essential. The evaluation approach proposed in this research demonstrates a 75% accuracy rate, affirming its initial reliability for evaluating the risk associated with constructing LID stormwater systems in collapsible loess areas. Furthermore, it can be utilized for further investigations into the collapsibility impacts of LID measures in regions characterized by collapsible loess. [ABSTRACT FROM AUTHOR]

Flow-like events usually occur during heavy rainfall and pose significant threats to ecosystems and human life and property because of their suddenness, high speed, and long distances. To study the solid–fluid transition and subsequent high fluidity and hypermobility mechanism of redeposited loess, we conducted a series of flume tests and rheological tests, and the results showed that loess exhibits different degrees of fluidized movement characteristics under different rainfall intensities, and a rainfall intensity of 90 mm/h was the most likely to trigger loess flowslides. Additional rheological analyses indicated that viscosity (shear rate) bifurcation characterizes the rheological response of loess solid–fluid transition, and the decrease in viscosity caused by shear thinning can explain the drag reduction effect and its high fluidity in the process of solid–fluid transition, which corresponds well with the results of flume tests. We proposed a two-step yielding characteristic and introduced structural dynamics to establish a unified solid–fluid transition model incorporating a hydro-mechanical coupling and rheological property. The model can be used to describe both the solid-like behavior of soil before phase transition using an elastoplastic model and fluid-like behavior after phase transition using a viscoplastic model. The research results provide a new understanding of solid–fluid phase transition characteristics of loess from the perspective of rheology, which can also provide a new idea for studying the fluidization movement of rock avalanches and pyroclastic flows and their geomorphic evolution. [ABSTRACT FROM AUTHOR]

In order to explore the influence of water glass on the strength and microscopic mechanism of loess, water glass with different content and Baume degree was used to solidify loess. Unconfined compressive strenght test, particle analysis tests, mercury intrusion tests and SEM tests were carried out to qualitatively and quantitatively analyze the strength characteristics and microstructure changes of loess and water glass solidified loess under different conditions. The results showed that the unconfined compressive strength of water glass solidified loess increased with the increase of the water glass content, the Baume degree and the curing period. After 28 days of curing, the unconfined compressive strength reached the maximum value when the Baume degree of water glass was 52 Be’ and the content was about 20%. The incorporation of water glass gradually increased the cements attached to the loess skeleton particles and their surfaces. The particle diameter increased and the macropores were filled with cements. The macropores in the soil gradually decreased and the integrity was enhanced. The reason for the increase in the strength of water glass solidified loess was that the cementing material generated by the hydration reaction of water glass enhanced the degree of cementation between soil particles and increased the mutual friction between particles, which made the soil structure more stable and improved the soil strength. The research results provide a reference for the selection of relevant parameters in the design of improved loess engineering. [ABSTRACT FROM AUTHOR]

In this work, the effect of gas jets used in the deep vertical vibratory compaction technique are studied. Gas jets play a vital role in treating structured loess foundations by the pneumatic-vibratory probe compaction method. Utilizing the geotechnical particle finite-element method numerically, we estimate the limit gas injection pressure and delineate the injection-induced damage and plastic zones. The behavior of structured soil is described using an elastoplastic constitutive model considering its structure evolution. The analysis of structured loess under gas injection is based on the cavity expansion approach. Experimentally, we performed a scale model test of gas injection to investigate the mechanism of the gas jets on the surrounding soil and compared relevant results with numerical results. Numerical results show that the limit gas injection pressure for structured loess beyond a depth of 8.0 m ranges from 1,409.7 to 1,467.2 kPa, increasing with the increase of overburden depth while the current cavity expansion radius decreases. The radius of the plastic zone induced by cavity expansion is 2.0 to 3.0 times the current cavity radius within this depth range; for the damage zone, however, it ranges from 0.1 to 0.4 times. The horizontal pressure recorded during the model test is observed to be lower compared with the numerical simulation results. This discrepancy can be attributed to factors such as the neglect of gas leakage within the soil and the utilization of a uniform parameter. The gas jets expand soil in cyclic shear form. It goes through a process from destruction of soil structure to compression in the horizontal direction; then, its pressure gradually drops to zero in the expansion direction of the dominant channel in soil. [ABSTRACT FROM AUTHOR]

In order to reveal the destructive mechanism of loess landslide induced by stagnant water on the combined surface, and to clarify the influence of the main control factors, this paper takes a typical loess landslide in northern Shaanxi as the research object, analyzes the structure of the rock and soil body, and the excavation and filling construction through the geohazard survey, and analyzes the process of traction sliding caused by the stagnant water on the combined surface at the different stages of the project by combining with the calculation of the stability of the slope body. Further the article analyses the process of traction sliding caused by water on the combined area due to construction by means of a discrete element model, and delves into the mechanism of strength reduction of saturated loess. The results show that: 1) the combined surface stagnant water type loess landslide has the characteristics of sudden sliding and rapid evolution, which is highly hazardous and difficult to prevent and control; 2) the slope destabilization is controlled by the engineering geological conditions, and the slope excavation changes the original mechanical equilibrium conditions of the slope, which provides the dynamic conditions for the traction sliding of the slope; 3) the change of the hydrogeological environment results in the obstruction of the natural drainage channel, which leads to the formation of continuous sliding surface due to stagnant water on the combined surface, and the formation of a continuous sliding surface due to stagnant water on the combined surface. Surface stagnant water to form a continuous slippery surface, inducing the overall destabilization of the slope damage; 4) loess strength index with the increase of saturation and the exponential function form of reduction, and when the saturation degree reaches more than 80%, the strength index of the soil body to reach the basic stability. The article expanding the ideas of landslide control and analysis, and the research results will provide a theoretical basis for the design of junction landslide management in the loess areas of northern Shaanxi. [ABSTRACT FROM AUTHOR]

Loess has high water sensitivity and exhibits poor characteristics such as weak cementation and high porosity. Under heavy rainfall, loess fill slopes are prone to erosion and landslides, posing serious threats to public safety and property. In light of these serious threats, this study employed the method of spraying polyvinyl alcohol (PVA) solution to improve loess fill slopes and systematically examine its protective effects. Through field investigations and combined laboratory and outdoor tests, this study comprehensively evaluated the mechanical properties, anti-aging and anti-erosion performance of loess after PVA solution spraying. Scanning electron microscopy was used to reveal the mechanism of PVA action at the microscopic level. The results showed that after treatment with PVA solutions of varying concentrations, the mechanical properties of loess samples were significantly enhanced, while also exhibiting excellent anti-aging and water resistance performance. Additionally, PVA-treated loess fill slopes exhibited excellent rain erosion resistance. A microscopic structural analysis showed that PVA fills the internal pores of loess, strengthens inter-particle bonding, and uses its hydrophobic groups' water-repellent action to effectively enhance slope stability and erosion resistance. In conclusion, PVA treatment not only significantly enhances the protective effects of loess fill slopes but also holds important value in improving soil sustainability and environmental protection. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive palaeoenvironmental reconstruction of the southern part of the Danube–Tisza interfluve in the Carpathian Basin from the Late Pleistocene to Early Holocene, addressing the region's response to global climate forcings and local environmental factors based on multi-proxy analyses of two key protected areas: the Katymár brickyard and the hay meadows and loess banks of Hajós. By integrating radiocarbon-dated malacological, macrobotanical, pollen, phytolith, geochemical, and sedimentological analyses, it was possible to provide a picture of past climate–ecosystem interactions. The Katymár North sequence provides an extended chronology from Marine Isotope Stage 3 (MIS3, ca. 36,000 cal BP) through the Last Glacial Maximum (LGM) and into the Early Holocene, while the Hajós sequence offers high-resolution data for the LGM–Holocene transition. By the late Ice Age, humidity and surface moisture superseded temperature as primary palaeoecological limiting factors, promoting ecotone-like forest–steppe environments during cooling periods. [ABSTRACT FROM AUTHOR]

The regional loess stratigraphy in the Vojvodina region, in the southeastern Carpathian Basin, has often been successfully correlated to the global palaeoclimate. This is a quasi‐continuous sedimentary record that provides detailed environmental reconstruction during the last four glacial/interglacial cycles. In this study, we present a standardized loess stratigraphy and illustrate how it correlates with the marine oxygen isotope and Chinese loess stratigraphical records. We argue that the loess stratigraphy in Vojvodina region is an important link in the integration of European terrestrial stratigraphical schemes and the deep‐sea stratigraphical model. We highlight how the loess record can better illustrate terrestrial environmental change through multiple glacial cycles than other records, such as glacial records. The investigated loess record enables direct links to be made between the loess sediments and their glacial sources. This reveals evidence of glaciations during every glacial cycle of the Saalian Stage complex, equivalent to Marine Isotope Stage (MIS) 10, 8 and 6. Therefore, Serbian loess has the potential to provide a direct link between terrestrial glaciations and wider records of global climate change, which is an enigma for many other continental records. These loess records display a strong relationship with the intensity of European glaciations during different glacial cycles. Loess sedimentation rates are highest in the most intensive European glaciation of the Saalian complex (MIS 6) and much lower during the weaker 'missing' glaciations equivalent to MIS 8 and 10. A key observation from the Vojvodina loess is the gradual increase in interglacial aridity through the late Middle Pleistocene. The explanation for the progressively increasing aridity in the investigated region at this time is still unclear. However, this trend is consistent with the idea of the Saalian complex as representing a 400 ka mega glacial cycle modulated by shorter classic 100 ka glacial cycles. [ABSTRACT FROM AUTHOR]

The enrichment and migration patterns of different chemical elements record paleoclimatic information in loess formations. The chemical elemental measurements of 245 samples from the Shiyang profile in the Weinan Region were compared with the geochemical characteristics of typical wind-formed profiles, and the paleoclimatic evolution was discussed. The results showed the following: (1) the standardized curves of the cumulative concentrations of SiO2, Al2O3, and CaO along with the Upper Continental Crust (UCC) in the Shiyang profile exhibited significant similarities with typical wind-formed profiles. This strongly suggests that the Shiyang profile has a wind-formed origin. (2) The mean value of the chemical index of alteration (CIA) of the Shiyang profile is 62.06, indicating that the Shiyang profile has been in the stage of primary chemical weathering. (3) The ratios of K2O/Al2O3, TiO2/Al2O3, and Fe2O3/Al2O3 in the Shiyang profile are comparable to those found in typical wind-formed profiles, suggesting a common source area and supporting the premise that the Shiyang profile is of wind-induced origin.(4) The regional climate has undergone a series of transitions: from a dry and cool phase in the early Holocene to warm and humid yet unstable conditions in the middle Holocene, and returning to dry and cool during the late Holocene. [ABSTRACT FROM AUTHOR]

[Objective] This study aims to comprehend the spatial distribution patterns of arable soil nutrients in various geomorphic conditions of the Loess Plateau, to unveil the driving factors behind these changes, and to provide the critical insights for precision management in the regional agriculture and the construction of agricultural projects. [Methods] Based on the 2020 soil nutrient data from the Loess Plateau in Shaanxi, the Kriging interpolation method was employed to analyze the spatial patterns of soil nutrients across four different geomorphic types. The driving factors behind these nutrient spatial variations was explored by using the geodetector model. [Results] (1) In the Loess Plateau, spanning from the Great Wall's sandy lands, through the hilly and gully regions of northern Shaanxi, the loess table lands in northern of Weihe River, to the Guanzhong Plain, the average contents of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK) exhibited a gradual increasing trend. Specifically, the SOM content averaged 10.20, 10.08, 15.28, and 18.78 g/kg, respectively, across these regions. TN averaged 0.63, 0.66, 0.98, and 1.19 g/kg. AP level averaged 12.99, 13.10, 16.97, and 27.24 mg/kg, and AK averaged 117.72, 149.94, 217.27, and 252.83 mg/kg, respectively. This trend indicated a consistent increase from the sandy lands to the plains. (2) In the loess area of Shaanxi, the duration of sunshine had most significant factor influencing overall nutrient contents, followed by annual temperature and fertilizer use. The distribution of nutrients in the windy area was predominantly affected by soil bulk density, whereas in the hilly and gully areas, plateau areas, and plains, fertilizer use was the primary influencing factor. The interaction of various factors provided a more comprehensive explanatory of nutrient dynamics than individual factor alone. [Conclusion] To optimize soil health, it is advisable to increase nutrient input and enhance soil fertility retention in sandy areas and hilly and gully areas. In contrast, the focus should be on improving nutrient utilization efficiency for plateau and plain areas. Additionally, in the process of farmland, it is crucial to tailor human activities to suit the environmental characteristics and specific conditions of different geomorphic regions. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to investigate the historical and future trends of drought, precipitation, and the water requirement of major crops, to gain insights into the evolving characteristics of meteorological drought and the water balance for key crops in the loess hilly region of northern Shaanxi, and to provide the reference for implementing effective irrigation practices and optimizing crop cultivation in this region. [Method] The daily-scale basic meteorological data from the loess hilly region of northern Shaanxi for the period 1980 to 2017 were utilized. The Mann-Kendall method with pre-whitening and the R/S method were employed to analyze the trend changes in drought, precipitation and crop water requirement during the crop growing season (April to October) in past and future. [Results (1) Drought showed a decreasing trend from April to June and an increasing trend from July to October. The variation in effective precipitation exhibited different patterns across the months and regions, Crop water requirement showed an increasing trend from April to August. (2) In the future, the effective precipitation in May, July, and October is projected to decrease, while the effective precipitation in August and September will experience an increasing trend. Drought and crop water requirement in Yan' an will exhibit opposite trends from April to June compared to that in Yulin. [Conclusion] The frequent droughts occur, and the available precipitation is insufficient to meet crop water requirements in the Loess Plateau of northern Shaanxi. The measures to control the cultivation area of jujube and apples, to increase investment in millet cultivation, and to implement a combination of rainwater harvesting and mulching are suggested in order to meet crop water requirements, achieve higher yields and increase income. [ABSTRACT FROM AUTHOR]

Lignin, an abundant biopolymer derived from plants, is a green binder for stabilizing soil. This study investigates the thermal conductivity of lignin [e.g., sodium ignosulfonate (SL), calcium lignosulfonate (CL), and lignin fiber (LF)] and lignin-stabilized loess. The effects of the source of loess samples, lignin content, curing time, water content, and dry density on the thermal conductivity of the stabilized soils were experimentally evaluated. Furthermore, mineralogy and microstructure of the stabilized loess were investigated using X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry tests to provide insights into the mechanisms of lignin-based soil stabilization. The test results showed that lignin had a lower thermal conductivity than water and soil minerals. The addition of lignin reduced the thermal conductivity of loess, with CL and SL causing a slightly greater reduction than LF. Mixing lignin with loess did not generate new crystalline material. The incorporation of CL and SL altered the microstructure of loess, resulting in a densely packed structure with distinct particle bonds and intra-aggregate pores. In contrast, LF provide microscale reinforcement for the soil particles, presenting a loose structure with dominant interaggregate pores. [ABSTRACT FROM AUTHOR]

Loess is the most well-known collapsible soil. The field immersion test is one of the effective means to assess the in situ self-weight collapsibility of soil. However, the reason why huge differences appeared in collapse settlements in different regions remains unclear, and which factors largely determine the amount of collapse deformation of loess during field immersion tests are worthy of being discussed. In this study, a numerical model for hydromechanical (HM) behaviors of loess was developed, in which the effects of the porosity on the water retention behavior and intrinsic permeability were incorporated. A field immersion test associated with the monitored collapse settlement, water retention curve measurements, and the variation of self-weight collapsibility with depth were used to testify to the effectiveness of the numerical model. The model was then adopted to clarify the effects of compression index, initial suction, and yield stress on the coupled HM or collapse settlement behavior of loess in field immersion tests. The aforementioned three parameters are relatively easy to be determined from various sites and have obvious differences. Then, a total of 126 numerical cases were conducted by the HM model, with the range of the collapse settlement from 0.334 m to 1.136, which covers the most range of the collapse settlement of the field immersion test systematically summarized by previous researchers. The result shows that yield stress and compression index have a significant influence on collapse settlement. The initial suction has a slight influence on collapse settlement, which mainly affects the velocity of water transport. The model herein can be used in the assessment of the in situ collapsibility of loess, and when the basic physical properties of a site are determined, the numerical simulation database of this study can preliminarily determine the site's collapsibility grade and amount of the collapsibility. [ABSTRACT FROM AUTHOR]

The tensile strength is an important parameter in engineering. Many engineering-related problems in buildings as well as the damage caused to them during natural disasters occur owing to a lack of tensile strength. The unconfined penetration (UP) test is an indirect method to measure the tensile strength of soil. Analyses of the mechanism of the UP test and simulations based on the discrete-element method have shown that the UP test is a complex process involving tensile and shear strengths. In this study, the authors use the modified Mohr–Coulomb model to establish a joint criterion for the failure of the tensile strength and the shear strength of loess, and derive expressions for the correlations between the relevant mechanical parameters. A combination of the results of the aforementioned model and laboratory tests showed the following: (1) the process of failure of loess samples during the UP test consisted of four stages: (I) the shaping of the wedge-shaped split body, (II) tension-induced fracture, (III) the yield stage, and (IV) damage to the sample; (2) the tensile strength of the loess decreased exponentially with its saturation; (3) the ratio of the unconfined compressive and cohesive strengths to the tensile strength of the remolded loess was 1.37 times that of the undisturbed loess, while the ratio of the unconfined compressive strength of remolded loess to its cohesion was similar to that of undisturbed loess; (4) the wedge-splitting angle ranged from 13° to 23°, and had a negative correlation with the internal angle of friction, a positive correlation with the water content, and decreased exponentially with the tensile strength. [ABSTRACT FROM AUTHOR]

The loess region is characterized by complex geomorphological patterns. This region is prone to frequent earthquakes with serious seismic landslide disasters. Loess seismic landslides are affected by a variety of factors, including the topography and geomorphology of loess slopes, stratigraphic lithology, dynamic responses, strength and dynamic characteristics of loess, and hydrogeological conditions. Current research on loess seismic landslides primarily involves laboratory experiments, physical and numerical simulations, field investigations, and remote sensing and monitoring techniques. The research focuses on the mechanisms, development characteristics, distribution, dynamic responses, and stability of loess seismic landslides. This paper reviews the current state of both domestic and international research on loess seismic landslides, introduces the pseudodynamic method that considers seismic wave propagation characteristics, and outlines future research prospects based on this method. By analyzing the mechanics mechanisms of loess seismic landslide, investigating the seismic liquefaction phenomena of loess landslides, and discussing the instability characteristics of these landslides, this study proposes a calculation method to accurately evaluate the stability of loess seismic landslides. This research can provide a theoretical basis for earthquake disaster prevention and mitigation in loess areas, and it represents a key focus for future studies. [ABSTRACT FROM AUTHOR]

Displacement prediction models based on measured data have been widely applied in structural health monitoring. However, most models neglect the particularity of displacement monitoring for arch dams with cracks, nor do they thoroughly analyze the non-stationarity and uncertainty of displacement. To address this issue, the influencing factors of displacement were first considered, with crack opening displacement being incorporated into them, leading to the construction of the HSCT model that accounts for the effects of cracks. Feature selection was performed on the factors of the HSCT model utilizing the max-relevance and min-redundancy (mRMR) algorithm, resulting in the screened subset of displacement influence factors. Next, displacement was decomposed into trend, seasonal, and remainder components applying the seasonal-trend decomposition using loess (STL) algorithm. The multifractal characteristics of these displacement components were then analyzed by multifractal detrended fluctuation analysis (MF-DFA). Subsequently, displacement components were predicted employing the convolutional neural network-long short-term memory (CNN-LSTM) model. Finally, the impact of uncertainty factors was quantified using prediction intervals based on the bootstrap method. The results indicate that the proposed methods and models are effective, yielding satisfactory prediction accuracy and providing scientific basis and technical support for the health diagnosis of hydraulic structures. [ABSTRACT FROM AUTHOR]

To ascertain the effects of conventional hydrochemical components on the presence of endogenous fine loess particles (EFLPs) in groundwater over loess regions, Na+, NO3− and Cu2+, as conventional hydrochemical components, were employed in batch tests with EFLPs from a typical loess as aquifer media in Guanzhong Plain, China. The results showed that EFLPs had high zeta potential (ζ) and remained suspended over 40 h, indicating their good dispersity and potential to be suspended in groundwater. ζ was employed to replace electrostatic repulsion in the DLVO equation to determine the critical coagulation concentrations for Cu(NO3)2 and NaF as 0.1 mmol/L and 50 mmol/L for 1.1 µm D50 EFLPs, which were almost consistent with the batch test results and greater than those in the groundwater, respectively, further implying that EFLPs are likely to be suspended in groundwater. The multi-factor tests showed that the key factors including particle size, hydro-chemical component and concentration interacted with each other and their relative magnitudes varied in the test processes, where the effects of concentration strengthened while those of the component weakened. So, hydrogeochemical conditions were beneficial to the suspension of EFLPs and the benefit got strong along the groundwater flow path, which is conducive to the cotransport of EFLPs with pollutants in groundwater over loess regions. [ABSTRACT FROM AUTHOR]

Background: FIR therapy is used in various medical settings to treat diseases associated with inflammation and edema. Unlike conventional FIR lamp therapy, this study investigated how body fluids change depending on the intensity and duration of FIR irradiation to the whole body. Method: Subjects in group A (n = 27) were exposed to FIR emitted from a loess bio-ball mat set at 40 °C for 30 min, and subjects in group B (n = 27) were exposed to FIR emitted from a loess bio-ball mat set at 30 °C for 7 h during sleep. Changes in bioimpedance parameters and fluid-related values were measured using a body fluid analyzer before and after exposure to FIR. Results: Changes in bioimpedance parameters associated with inflammatory fluids were quantitatively confirmed. In group A, there was a minimal change in fluid-related measurements. However, significant changes in bioimpedance parameters associated with inflammatory fluids were observed in group B exposure to FIR for 7 h during sleep. Conclusions: FIR emitted from loess bio-balls activates biological tissues and lymphatic circulation, gradually reducing the levels of inflammatory fluids over time. [ABSTRACT FROM AUTHOR]

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Seasonal frozen soil has significant impacts on changes in soil mechanical properties, settlement, and damage to foundations. In order to study variations in the temperature and horizontal freezing force of loess during three-dimensional freezing, a three-dimensional freezing model test of loess was carried out. This experiment analyzed and studied the soil temperature change distribution characteristics, horizontal freezing force distribution rules, and water migration phenomena caused by temperature. The research results show that the temperature change in soil samples exhibits a "ring-like" decrease from the outside to the inside. When the soil temperature reaches the supercooling point, the cooling curve jumps and rises, and this is accompanied by a stable section with constant temperature. In the late freezing period, the temperature rate drops slowly. Under the action of freezing, the horizontal freezing forces at different positions have similar change characteristics and can be divided into four change stages: stable stage, rapid freezing stage, "secondary" freezing stage, and freezing–shrinkage–rebound stable stage. At lower moisture contents, loess samples undergo freeze–thaw shrinkage during the freezing process. During the rapid freezing stage of soil samples, the water in the soil sample migrates and causes secondary freezing. After the rapid freezing stage, the soil temperature continues to decrease, and the horizontal freezing force no longer decreases. [ABSTRACT FROM AUTHOR]

Stable Sn isotope ratios are emerging as a novel tracer for a wide range of geological processes; however, the Sn isotopic baseline of the upper continental crust (UCC) is not yet well-constrained. Here, we report high-precision Sn isotope data of a wide range of UCC samples, including granites, pegmatites, and sediments, to document the Sn isotopic composition of UCC. Significant variations in δ122/118Sn 3161a (per mil deviation in 122Sn/118Sn relative to NIST 3161a) values are revealed for I-type (δ122/118Sn 3161a = 0.025 ± 0.026‰ to 0.495 ± 0.046‰, n = 20) and S-type (δ122/118Sn 3161a = 0.156 ± 0.018‰ to 0.501 ± 0.075‰, n = 22) granites. More extreme Sn isotope variability is observed for pegmatites, which have δ122/118Sn 3161a from 0.256 ± 0.047‰ to 0.930 ± 0.049‰ (n = 13). The δ122/118Sn 3161a of I-type granites decrease with decreasing TFe 2 O 3 (total Fe as Fe 2 O 3) and MgO contents and are attributed to the segregation of Fe-bearing minerals. Conversely, the Sn isotope variation of S-type granites appears to reflect source heterogeneity, whereas the Sn isotope variability of pegmatites may reflect fluid activity. In contrast, the loess samples display homogeneous δ122/118Sn 3161a values (0.132 ± 0.034‰ to 0.239 ± 0.020‰, n = 20) that show no correlation with the degree of chemical weathering, suggesting that loess is representative of the average Sn isotope composition of UCC. The δ122/118Sn 3161a values of modern sediments and sedimentary rocks range from 0.080‰ to 0.490‰ (n = 25) and the Sn isotope variations may be related to chemical weathering or sediment provenance. Based on the lithology-weighted average δ122/118Sn 3161a of UCC samples (41 granites and 45 sediments) in this study, the δ122/118Sn 3161a value of UCC is estimated to be 0.233 ± 0.099‰, providing a reference point for further investigations. Tin is isotopically lighter in UCC compared to the mantle, owing to magmatic differentiation and crustal evolution processes. [ABSTRACT FROM AUTHOR]

The diverse and complex morphology of loess particles creates various contact patterns, impacting the mechanical properties of loess, and directly influencing the stability and safety of engineering structures in loess regions. In order to explore the effects of realistic loess particle morphology on mechanical behaviors, the discrete element method (DEM) and image processing techniques were employed to investigate both macro and micro mechanical properties, such as cohesion, internal friction angle, mechanical coordination number, and distribution of contact force. The results demonstrate that particle morphology greatly impacts the mechanical properties of loess samples. Samples with realistic particles exhibit higher peak stress, shear modulus, cohesion, internal friction angle and mechanical coordination number compared to those with spherical particles. Particle morphology has a significant effect on particle rotations and fabric anisotropy, while exerting only a minor influence on particle displacement. A comprehensive understanding of the relationship between the particle morphology and mechanical properties of loess samples contributes to enhancing the stability of engineering structures in loess areas. [ABSTRACT FROM AUTHOR]

The intense changes in glaciers in the southeastern Tibetan Plateau (SETP) have essential impacts on regional water resource management. In order to study the seasonal fluctuations of glaciers in this region and their relationship with climate change, we focus on the Yigong Zangbo River Basin in the SETP, extract the annual and seasonal variations of glaciers in the basin during 2018–2023, and analyze their spatio-temporal characteristics through the seasonal-trend decomposition using the LOESS (STL) method. Finally, combining the Extreme Gradient Boosting (XGBoost) model and the Shapley additive explanations (SHAP) model, we assess the comprehensive impact of meteorological factors such as temperature and snowfall on glacier changes. The results indicate that glaciers in the Yigong Zangbo River Basin experienced remarkable mass loss during 2018–2023, with an average annual melting rate of −0.83 ± 0.12 m w.e.∙yr−1. The glacier mass exhibits marked seasonal fluctuations, with increases in January–March (JFM) and April–June (AMJ) and noticeable melting in July–September (JAS) and October–December (OND). The changes over these four periods are 2.12 ± 0.04 m w.e., 0.93 ± 0.15 m w.e., −1.58 ± 0.19 m w.e., and −1.32 ± 0.17 m w.e., respectively. Temperature has been identified as the primary meteorological driver of glacier changes in the study area, surpassing the impact of snowfall. This study uses advanced altimetry data and meteorological data to monitor and analyze glacier changes, which provides valuable data for cryosphere research and also validates a set of replicable research methods, which provides support for future research in related fields. [ABSTRACT FROM AUTHOR]

The sandy loess deposits in the lowlands of northern Germany present a valuable sedimentary archive for late Weichselian periglacial geomorphodynamics. While other aeolian sediments from the Late Quaternary, especially loess deposits and sand dunes, have been studied and dated in some detail in the last decades, sandy loess has received less scientific attention with respect to its genesis, composition, age and provenance as well as distribution patterns. In this study, we present detailed results for three sediment sections located on the Fläming ridge in the south of the state of Brandenburg. According to our results from luminescence dating, the sandy loess deposits of this area were deposited during the late MIS 2 (19–14 ka) with a highly variable thickness of at least up to 4 m, followed by a deposition of periglacial coversands shortly thereafter. The sandy loess deposits display a homogeneous geochemical composition and grain size characteristics similar to loess sections in the main loess areas to the west and south. Furthermore, we analysed a large dataset of geological drill data and performed a spatial interpolation of sandy loess distribution in the Western Fläming. Despite the strongly dissected modern landscape of the Fläming ridge which is partly the result of intense Holocene soil erosion processes, general patterns of the original loess distribution could be deduced. Based on these findings, we were able to identify the low‐lying areas to the north and north‐east of the study area to be the most likely source areas for the sandy loess as a result of katabatic winds originating from the Fennoscandian Ice Shield. Thereby, this study yields important insights regarding aeolian transport and deposition patterns under periglacial conditions in the Central European Lowlands. [ABSTRACT FROM AUTHOR]

Due to the acceleration of construction of civil, industrial and infrastructure facilities in our republic and the expansion of their area, the construction of many facilities is carried out in mountainous, and foothill areas with complex relief and geomorphological conditions, which in most cases are potentially dangerous landslide slopes. To protect these facilities from the negative impact of dangerous geological, naturaltechnogenic, and anthropogenic processes, to assess the risks arising from the impact of these processes on building structures, to promptly prevent negative phenomena and dangerous situations, to assess the engineering and geological conditions of the construction area to determine the stability of the slope, conducting research in these areas is of great practical importance. Mountainous regions are characterized by the complexity and diversity of geological, hydrological, hydrogeological, and tectonic conditions. Landslides are the most common natural and man-made processes that pose a threat to the safe operation of infrastructure facilities, civil and industrial construction in mountainous and foothill areas. In addition to infrastructure facilities, landslides can destroy vegetation, destroy the habitat of fauna, and also destroy fertile soils located in the area of their activity (Nikolic, 2015; Krivoguz & Bespalova, 2020). The main objective of this article is to apply the results of practically implemented and verified studies in other territories of our republic with similar geomorphological structure and engineering-geological conditions, to correctly assess the negative manifestations caused by landslides and other man-made and anthropogenic impacts, as well as to calculate the stability of the slope and scientifically and technically substantiate measures for engineering protection against landslides. [ABSTRACT FROM AUTHOR]

Based on calibrated radiocarbon ages of terrestrial gastropod shells (Succineidae, Discus , Stenotrema , Webbhelix), the chronology of Peoria Silt (loess) deposition in the Central Lowlands is updated. These taxa provide reliable ages (within ~0.2 ka), based on historical shell dating, shell-organic age comparisons, and stratigraphic consistency. A compilation of 53 new and 36 published Peoria Silt shell ages (calibrated), from 12 localities, date from 30.0 to 17.4 ka. Proximal (fossiliferous) loess from 10 sections had mean loess accumulation rates of 0.6–2.2 mm/yr. Study sites along the upper Mississippi, Illinois, to mid-Mississippi, and Ohio-Wabash Valleys suggest Peoria loess accumulated from ~27 to 15 ka, ~29 to 18 ka, and ~30 to 18 ka, respectively. The cessation age for Peoria Silt, based on surface extrapolations, is ~1–6 ka earlier than some prior Illinois estimates, even assuming slower loess accumulation in the modern solum. Younger loess in northwestern Illinois likely reflects, in part, Superior and Des Moines Lobe glacial-meltwater sediment, and Iowan Erosion Surface inputs to the upper Mississippi Valley, after the Lake Michigan Lobe receded. Furthermore, stronger winds, drier conditions, and reduced vegetation cover in valley deflation areas may have favored higher accumulation rates and later loess deposition in northwestern relative to southeastern areas. [ABSTRACT FROM AUTHOR]

Malan loess possesses unfavourable engineering mechanical properties that may vary depending on the geological context in which it exists. In the context of roadbed loading, the structural characteristics of the loess roadbed often result in uneven settlement, which significantly impacts transportation safety. To investigate the dynamic behaviour of loess under the influence of vehicle loading, groups of dynamic rebound modulus tests were conducted using a dynamic triaxial apparatus. Three key aspects are highlighted: compaction degree, moisture content and stress state. The results reveal that the dynamic rebound modulus of loess tends to increase with higher compaction degrees, decrease with increased moisture content and rise under greater confining pressure. For Maran loess, the water content has the greatest influence on its physical and mechanical properties. Under conditions of a confining pressure of 60 kPa and a deviatoric stress of 30 kPa, as the moisture content increased from w = 9% to w = 18%, the minimum dynamic rebound modulus decreased by 63%. [ABSTRACT FROM AUTHOR]

The water sensitivity and structural characteristics of collapsible loess are two typical factors that significantly influence its mechanical behaviors. This paper presents a simple and practical elastic-plastic model based on the modified Cam-Clay model to well capture the essential behavior of unsaturated intact loess. The model employs deviator stress and spheric stress as the stress variables, with the water content serving as the moisture variable. The critical state surface of the model can be determined by utilizing the shear strength parameters of unsaturated soil under axisymmetric stress conditions. An initial yield surface equation is established by incorporating structural strength into the elliptical yield surface equation, which is used to determine the starting point for elastic-plastic deformation calculations under different humidity and stress combinations. The model comprises several parameters, each of which has a clear physical interpretation and can be conveniently obtained through conventional triaxial tests. The validity of the model for unsaturated intact loess is confirmed through a comparison with the stress–strain relationship of unsaturated intact loess in the axisymmetric stress state. This work has the potential to significantly enhance our ability to predict and mitigate potential geotechnical disasters, such as foundation deformation under axisymmetric conditions and slope stability problems under non-axisymmetric conditions. Ultimately, the application of this model could contribute to the safety and stability of infrastructure and construction projects in loess regions. [ABSTRACT FROM AUTHOR]

Silty lacustrine and paludal records spanning from the penultimate deglaciation (late Illinois Episode) to the present are preserved in kettles formed during marine isotope stage (MIS) 6 that lie adjacent to the MIS 2 Manito terrace along the valleys of the Sangamon and Illinois Rivers. Geochemical, mineralogical, particle-size, and chronological records from two basins, Smith Lake and Lake Ben, provide a unique opportunity to assess loess age and provenance of the southcentral Laurentide ice sheet. Here, I focused on deposits of redeposited loess of the last glaciation (Wisconsin Episode). Other than subtle laminations and fossils of emergent and aquatic plants and animals, the silty texture, chemical composition, and mineralogy of the lake sediment closely resemble Peoria Silt (loess). Sediment-core records sampled from Smith Lake and Lake Ben in Mason County, Illinois, confirm rapid deposition of proximal loess derived from the nearby outwash plain of the Illinois River from ca. 30.9–18.0 calibrated (cal) k.y. B.P. From 18.0–14.7 cal k.y. B.P., deposition of proximal loess was gradually replaced by far-traveled (distal) loess chiefly derived from Superior lobe provenance and global dust. The succession is capped by a cumulic gleysol that was truncated by recent plowing. Proximal loess deposits in lakes Smith and Ben are composed primarily of very fine sand, coarse silt, and medium silt (125– 16 µm) compared to the distal facies (fine silt and finer sediment: <16 µm). Proximal loess that originated from outwash of the Lake Michigan lobe contains abundant Ca, Zr, Sr, illite, and magnetic minerals. The distal facies contains relatively abundant Rb, Al, K, Si, Cu, and Pb, and it is enriched in smectite (relative to illite) and depleted in magnetic minerals. Radiocarbon ages on terrestrial gastropod aragonite in loess from the nearby New Cottonwood School and Thomas Quarry sites indicate that Peoria Silt deposition ended between 18 cal k.y. B.P. and 16 cal k.y. B.P. At these localities, the upper part of the record is complicated by the modern soil, which has altered soil organic matter and leached carbonate. At Lake Ben, the radiocarbon record of emergent aquatic vegetation indicates that sediment accumulation rates and the ratio of proximal to distal loess decreased at the correlative interval that yielded the youngest snail shell ages at Cottonwood School. The upward increase in element concentrations such as Al and decrease in coarse/fine silt ratios in the modern soil are prominent features in the Lake Ben record dating from 18–14 cal k.y. B.P. This correlation strongly suggests that many of the features of the modern soil were not developed into uniform parent material but, rather, were inherited from incremental addition of distal loess to proximal loess, collectively identified as Peoria Silt. The paucity of key elements (Cd, Hg, Se, Ag, Au) in this transition zone suggests limited contributions from western lobes (i.e., Des Moines and James lobes), but abundant Ti and Cu suggest a contribution from the Superior lobe. A new wrinkle in this interpretation is that the rise in elements such as Al, Rb, and Si suggests significant additions from generic dust from unknown sources. [ABSTRACT FROM AUTHOR]

In order to further explore the influence of freezing and thawing on the deformation and strength of loess under the actual working conditions, this paper carries out the compression test of loess after experiencing 0,1, and 4 pressurized freeze-thaw cycles, respectively. The results show that： after experiencing pressurized freeze-thaw, the frozen loess mostly shows brittle damage mode, and the stress-strain curve is strain-hardening curve. The strength of loess decreases by about 35% after one pressurized freezethaw cycle, and the strength decreases by 51% after four pressurized freeze-thaw cycles, which is a nonlinear negative correlation. In the case of the same number of freeze-thaw cycles, with the increase of the water content, the peak stress will be reduced gradually and the strength in the range of water content decreases by nearly 77%. The uniaxial compressive strength of frozen loess shows a significant increase with the increase of initial dry density and the decrease of test temperature, when the temperature decreases from -10℃ to -15℃, the strength increases 1. 5 times, and the strength increases 2 times when the temperature decreases from -15℃ to -20℃. Finally, based on the Gaussian function, a strength model of frozen loess is constructed considering the influence of pressurized freeze-thaw cycles, which can better reflect the strain hardening situation of frozen loess. [ABSTRACT FROM AUTHOR]

The stability and performance of loess infrastructure in cold regions are often challenged by seasonal freezing–thawing action. The action of the foundation loess is a complex thermo-hydro-mechanical coupling process, and it is crucial to understand this process for the loess infrastructure in cold regions. A series of controlled tests were conducted to observe the changes in temperature, moisture, and frost heave variations within loess samples under freezing–thawing, and the influences of cycle period, freezing–thawing amplitude, and cycle number on the thermo-hydro-mechanical behavior of loess were investigated. The results reveal that freeze–thaw cycles significantly affect the heat transfer, water migration, and deformation of the loess. The temperatures of sample at different heights periodically vary under freezing–thawing. Water is absorbed to the samples, which undergoes a rapid water intake stage, a water drained stage, and a slow water intake stage under freezing–thawing, resulting in moisture redistribution in loess. Loess undergoes frost heave, thaw settlement, and consolidation processes during freezing–thawing, and a slight wetting collapse may occur after several freezing–thawing cycles. Within the same cycle, frost heave is the largest while consolidation deformation is the smallest. Frost heave and consolidation deformation reach their maximum values at the second cycle, whereas thaw settlement reaches its maximum value during the second or third cycle. Each stage deformation increases with an extended cycle period and almost decreases as the freezing–thawing amplitude increases. Freeze–thaw cycles can induce wetting collapse of loess, resulting in negative residual deformation. Furthermore, the thermo-hydro-mechanical coupling process and the deformation mechanism of loess have been elucidated. These insights contribute to a more comprehensive understanding of the failure mechanisms in loess engineering in cold regions. [ABSTRACT FROM AUTHOR]

Bonding effects among non-contacting particles are key phenomena that drive the mechanical behavior and fracture process of structural loess. The existing discontinuous deformation analysis (DDA) methods are incapable of taking into account these microstructural interactions. This work presents a modified DDA method considering the bonding effect to analyze the role of bonds in structural loess at the microscale. Spring elements are used to calculate the bonding forces acting on the particle surface covered by bond materials. The proposed modified DDA method is validated through three benchmark tests: the bending of a cantilever beam, the Brazilian disc test and the compression of rods bonded by epoxy. The results show that the numerical solution agrees well with analytical and experimental data. Microstructure models of a structural loess sample with different contents of bond material are also studied and compression tests are simulated using these models. The results indicate that the content of bond material significantly influences the evolution pattern of the pore structure, which determines the deformation behavior of loess. In addition, structural yield stress and pore stability of loess increase with increasing bond content. It is also shown that the modified DDA method can capture the main pore deformation behaviors in real loess during compression. Finally, the study reveals that the bonding effect is crucial for maintaining the stability of the microstructure of loess. [ABSTRACT FROM AUTHOR]

Addressing the challenges of wet and soft loess foundations is crucial in geotechnical engineering due to their inherent low strength and high compressibility. High-temperature sintering technology is a leading method for enhancing loess foundations, known for its fast processing and effective reinforcement. This paper focuses on the effects of saturation on the compressibility of sintered loess, using results from saturation and compression tests. It highlights how saturation influences loess differently under various sintering conditions. Particularly, loess sintered at 200°C breaks down after saturation, losing its resistance to deformation. By contrast, loess sintered at other conditions retains some deformative resistance, but its compressibility still increases. The study finds an inverse relation between sintering temperature and the increase in compressibility after saturation. Additionally, it examines changes in compressibility indices, which include the compression coefficient, compression index, and modulus of compressibility. These are analyzed based on different saturation times, establishing a law that links saturation time to the compressibility of sintered loess. [ABSTRACT FROM AUTHOR]

Collapsibility significantly impacts the bearing capacity of pile foundations in loess areas. To improve the load-bearing capacity of piles, the pile-base postgrouting technique is widely used worldwide. However, there are still several related issues to be solved: the impact of loess collapsibility on the bearing capacity; the effectiveness of the pile-base postgrouting technique in enhancing the bearing capacity; and the diffusion pattern of the grout during the grouting process. To investigate these issues, this experiment utilizes a visual static pressure device combined with numerical simulation. According to the experiment, the maximum axial force and neutral point appeared to shift downward after grouting, resulting in a 17.5% increase in the bearing capacity of the pile foundation. Additionally, an increase in grouting pressure leads to a rise in both the number of shear cracks and the diffusion radius. As the permeability of the grout improves, the number of shear cracks and diffusion radii tend to stabilize after an initial increase. These discoveries enable a thorough analysis of the changes in side friction and base resistance of postgrouted piles in collapsible loess. Furthermore, they provide valuable references and guidance for the implementation of the pile-base postgrouting technique in loess areas. [ABSTRACT FROM AUTHOR]

In order to explore the spatial distribution pattern and intra-specific correlation of Platycladus orientalis population in the Loess hilly region of Inner Mongolia, the natural Platycladus orientalis sparse forest in the typical Loess hilly region of Inner Mongolia was taken as the research object, and the spatial pattern of Platycladus orientalis population in different slope directions was analyzed using the point pattern combined with the complete spatial randomness, the heterogeneous Poisson model and the Poisson aggregation model of the single variable function, and the intra-specific grade was determined after the availability of the age class was determined by the fitting curve, a bivariate function was constructed to study the intra-specific correlation of Platycladus orientalis population. The results showed that the resources of regenerated seedlings were abundant, followed by young trees, and the number of mature trees was the least. The proportion of grade I was as high as 27.79%, grade II was 21.84%, and the cumulative proportion of grade III to grade V was 32.85%. The population distribution of each age class was pyramidal, and the population structure was stable, showing a steady growth trend.The quantity distribution of each age of 4~22 m, and the shady slope presents a small scale of 0~1 m aggregation distribution. The heterogeneous Poisson model showed that the slope direction had an impact on the aggregation degree of Platycladus orientalis population, and the Poisson aggregation model had an aggregation distribution within the range of 1~5 m, indicating that there was a certain relationship between species. There were 3 kinds of correlations in Platycladus orientalis species. The relationship between seedlings and adult trees was positive within 0~1 m of the scale of shady slope and semi-shady slope. The relationship between young trees and adult trees was completely in the confidence interval of sunny slope. The relationship between young trees and adult trees was negative at 6~7 and 3~4 m under the conditions of semi-shady slope and semi-sunny slope, respectively. The relationship between young trees and adult trees was negative at shady slope, semi-shady slope and semi-sunny slope, and the sunny slope was not negative relationship . To sum up, in addition to its own biological characteristics, the impact of microenvironment and intra-specific competition on the distribution of Platycladus orientalis population in the loess hilly area was also very important. Above results provided a basis for the planting and management of Platycladus orientalis and its habitat adaptability. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ground Improvement is the property of Journal of Ground Improvement Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Landslide scale measurement and hazard risk assessment are crucial, especially since landslide deposits often have an expansion effect, and can lead to more serious secondary hazard events. In this study, we obtained substantial high-resolution terrain and orthophoto data through multiple UAV photography and field surveys. Based on GIS spatial analysis and landslide geometric models, sliding and deposit data for 42 loess landslides in the Heifangtai tableland were calculated. The results show that sliding volume and sliding area have the highest correlation with the power-law distribution ($V_e = 1.204A^{1.1360}$ V e = 1.204 A 1.1360 ). The ratio of $H_{max}/L_{max}$ H max / L max increases with the increase of sliding volume and deposit volume of the landslides, with an average value of 0.306. The ratio of H/L has a higher correlation with deposit volume, and the fitting expression is $H_{max}/L_{max} = 0.187V_D^{-0.123}$ H max / L max = 0.187 V D − 0.123 . The VEC of 42 loess landslides ranged from 1.05 to 2.53, while the AVEC was about 1.503. The correlation analysis show that the VEC is positively correlated with AEC, Hmov, Hmov/Lmax and Lmov/Lmax but negatively correlated with Dave. The essence of the volume expansion effect is that landslide fluidity increases, resulting in looser deposit distribution, larger pore scale in the deposit and lower overall compaction. Loess collapse in the Heifangtai tableland lack protection from the liquefaction of the sliding mass basement, resulting in large VEC values. The semi-ellipsoid model is a valuable approach for landslide volume assessment in the Chinese Loess Plateau, yielding an average error rate of restoring the sliding volume of landslides of 13.55%. This study provides a useful reference for accurate evaluations at the landslide scale. [ABSTRACT FROM AUTHOR]

Copyright of Water Conservancy Science & Techonlogy & Economy is the property of Water Conservancy Science & Technology & Economy Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hollowing out of rural areas is a phenomenon of large-scale idle and abandoned rural homesteads in the process of rapid industrialization and urbanization, which has been an urgent problem to be solved in the comprehensive implementation of the rural revitalization strategy. Based on the perspective of population migration, this paper constructs a theoretical framework for rural population migration from three dimensions: urban attractiveness, farmers' willingness to migrate, and macro policy environment. The paper analyzes the mechanism of population migration affecting rural hollowing, and quantitatively analyzes the evolution law and driving mechanism of rural hollowing through the construction of the rural hollowing indexes, taking D village located in loess hilly areas as an example. It is found as follows. (1) With the development of macroeconomic and changes in policy environment, the settlement space of D village has gone through stages of internal migration of residential areas, rapid expansion of villages, differentiation of new and old villages, and revitalization of idle residential land. Accompanied by this is the evolution process of the emergence period, development period, prosperous period, and stable period of rural hollowing. (2) The hollowing out of D village is driven by the core factor of population migration, which is the result of the interaction between the internal migration succession of settlements and rural population loss. From a temporal perspective, the initial rural hollowing is mainly influenced by the dominant role of residential renewal, which is manifested as the hollowing out of homesteads. After the demand for housing construction is saturated, the dominant role gradually weakens, and the implicit role caused by continuous population loss becomes the dominant factor of rural hollowing, and the degree of hollowing out gradually intensifies. (3) Affected by the internal and external support conditions of rural development, rural hollowing may exhibit differentiated trends such as re-solidification, steady hollowing out, and developing hollowing out. The process and evolution direction of rural hollowing can be regulated through institutional reform, basic investment, and industrial development. [ABSTRACT FROM AUTHOR]

The accumulation processes of loess in northeastern (NE) China record the varying characteristics of the East Asian Monsoons (EAM) and the evolution of the local environment. In this study, grain size end-member analysis of the Dajiugang (DJG) section deposited since the Last Glacial in Chifeng City, NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China. Results showed that the Chifeng loess comprises three grain size end-members (EM), EM1 (7.38 µm), EM2 (49.4 µm) and EM3 (90.00 µm), indicating the three transport dynamics of dust delivered to the region. The EM1 represents atmospheric dust as the background. The EM2, mainly derived from relatively distant-sources deposition, and EM3, material transported over a short distance, correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon (EAWM), respectively. Results of climate reconstruction, combined with other records, showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon (EASM) during the stadial-period [Marine Isotope Stage (MIS) 4 and MIS 2 stage]. The climate was predominantly warm and humid, with weak EAWM and surface winds and strong EASM in interstadial- period (MIS 3 and MIS 1 stage). Comparisons between indicators, e.g., EM3, the LR04 benthic δ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation. [ABSTRACT FROM AUTHOR]

Climate change, earthquakes, and human activities are accelerating the degradation of permafrost, leading to loess failures and slope instability. Some engineering corridors (ECs)/infrastructures located on the northeastern margin of the Qinghai-Tibet Plateau (NE-QTP) of China are heavily influenced by landslide phenomena due to being built on permafrost, loess, and seasonally frozen ground. However, few systematic investigations have been carried out in this area. To compile a comprehensive landslide inventory, we visually interpreted 11,914 landslides in GaoFen-6 images taken from 2021 to 2022. We observe that approximately 44.85% of the infrastructures are affected by landslides. Then, based on the ground types and triggering factors, landslides are classified into three types: freeze‒thaw landslides (FTLs), loess landslides (LLs), and general landslides (GLs). More specifically, FTLs are mainly distributed in the boundary regions between permafrost and seasonally frozen ground. The LLs exhibit high-density clustered distribution characteristics. GLs have significant transitional characteristics and commonalities between FTLs and LLs. Furthermore, we apply the geographical detector to determine the controlling factors of the landslides that occurred. We find that the temperature change is the primary controller on the FTLs. The water exhibits a certain correlation with LLs. And the earthquake is the most important factor on the GLs. Our study provides a significant dataset for quantifying the analysis of landslides in NE-QTP. [ABSTRACT FROM AUTHOR]

The thick loess sediments produce a lot of noise during seismic acquisition, typically surface wave. Conventional methods are difficult while suppressing 3D surface waves since they are hyperbolic in the far-array. This study proposed a new model-based, data-driven surface wave attenuation method, which uses dispersion curve analysis of surface wave and joint inversion based on genetic algorithm (GA) and conjugate gradient algorithm, to build an accurate surface wave model, and then to subtract the model data from seismic data to improve the signal to noise ratio (S/N ratio). Located in the southern part of the Ordos Basin, the Loess Plateau has the characteristics of large thickness of loess sedimentary layer, diverse geomorphology, complex geological conditions and developed surface waves. After applying the method to the field seismic data, numerical tests show that joint inversion of dispersion waves was stable, accurate, and efficient in multi-type models, including models with a low-velocity layer and with a high-velocity layer. The result showed that the 3D surface wave attenuation method is effective in surface wave suppression. The low-frequency information and the reflected signal are efficiently preserved. Seismic faces are more apparent for reservoir characterization. This method provided credible data for the exploration of the loess tableland area. [ABSTRACT FROM AUTHOR]

To solve the problem of carbon emissions and pollution of traditional cement, composite geopolymer based on alkali-stimulated slag powder and fly ash was used to solidify loess. The effects of the alkali activator content, the ratio of NaOH to alkali activator, and the ratio of slag powder to silicon-aluminum (Si-Al) raw material on the unconfined compressive strength (UCS) of solidified loess were investigated through different tests. Then, the results from microscopic tests such as scanning electron microscopy (SEM), x-ray diffraction (XRD), and mercury intrusion porosimetry (MIP), as well as the variation results of the UCS, were used to analyze the influencing mechanism of the three factors on the solidified loess. The test results showed that the UCS of the slag powder– and fly ash–based composite geopolymer solidified loess first increased and then decreased with the increasing alkali activator content, and the UCS of the solidified loess also first increased and then decreased with the ratio of NaOH to alkali activator. The UCS increased as the ratio of slag powder to Si-Al raw material increased. The reaction of composite geopolymer solidified loess produces amorphous hydrated calcium silicate hydrates (C─ S─ H), calcium aluminum silicate hydrates (C─ A─ S─ H), and sodium-based aluminosilicate (N─ A─ S─ H) gels. These gels effectively bond and fill the soil particles, leading to a decrease in the number of macropores and total pores in the soil. As a result, the soil becomes more compact and increases the UCS of solidified loess. The results of this study provide a certain basis for engineering applications of the composite geopolymer to solidify loess based on slag powder and fly ash. [ABSTRACT FROM AUTHOR]

Abstract The Ili River Valley in Xinjiang, China, is a typical seasonal frozen area where loess landslide disasters have become increasingly common during the freeze–thaw periods in recent years. This study analyzed the macroscopic mechanical strength and microstructure changes of the Ili loess under different freeze–thaw cycles (FTCs) through the post-freeze–thaw triaxial compression test on the unsaturated soil in laboratory. Apart from the scanning electron microscopy (SEM), and the nuclear magnetic resonance (NMR), the macro–micro correlation analysis and the cluster-principal component analysis were applied for the theoretical discussion. The results indicated that the cohesive force of the loess exhibits an initial decreases, followed by the increases, and eventually keep stable after various FTCs, while the internal friction angle showed the opposite developing trend before the final constant. Similar to the strong correlation between the cohesive force and the particle abundance, the internal friction angle is also closely related to the abundance and orientation fractal dimension of the loess particles. However, the principal component analysis results showed that cohesive force strongly correlates with the average maximum pore size and the pore size fractal dimension, for which the internal friction angle most strongly affected by the average maximum particle size. The possible reason is that the extracted principal components represent a class of microscopic parameters with the same or similar change trend, although there may be a certain offset between them. The mechanical deterioration of loess is attributed to the repeated frost heaving force and the migration potential caused by FTCs. The alterations of the microstructure accelerated the deterioration of the macroscopic mechanical properties of the loess, which further widens the understanding of the mechanism behind the deterioration of loess mechanical strength in the Ili River Valley under FTCs, and contributes to the prevention and management of the local landslide disasters.

On December 18, 2023, an Ms 6.2earthquake occurred in Jishishan County, Linxia Prefecture, Gansu Province, causing a large number of geological disasters and threatening people's lives and the safety of infrastructure. After the earthquake, Gansu and Qinghai provincial governments quickly deployed hundreds of geology professionals to carried out the investigation and verification geological disasters in the earthquake area. Based on the results of the earthquake geohazard investigation and verification, this paper analyses the characteristics, control factors and development trend of the earthquake-induced geohazards, and puts forward suggestions on disaster prevention and risk mitigation measures. Till December 23, a total of 2044 geohazards have been checked, including 78 new geohazards, 88 existing geohazards with intensified deformation due to earthquake, and 1 878 existing geohazards without obvious different from before. Most of new and intensified deforming geohazards are collapse, accounting for 67.5%, followed by landslide, accounting for 31.9%. Most of new and intensified deforming geohazards are small in scale, accounting for 84.9%, followed by medium, accounting for 10.8%. Disaster mode of new and intensified deforming geohazards are mostly small collapse threatening houses and roads. The co-seismic geohazards are densely distributed along the seismic fault, and the spatial density increases with the enhancement of earthquake intensity. Data from 206 groups of accelerate-meters within 50 km from the epicenter of the National Geological Safety Monitoring Network showed that the peak acceleration of the earthquake area was 30.4～1969.7 mg. and decayed logarithm with the increase of the distance from the epicenter. In addition, the surface deformation monitoring equipment also recorded the co-seismic displacement curve of a typical landslide. Analysis shows, earthquake put a deteriorate effect to rock and soil, which decreased their integration and strength. There is a magnificent geohazard after-effect of earthquake; collapse, landslide and debris flow will be much often than before. So the authors suggest: (1) update earthquake geohazard database as soon as possible, (2) work out targeted prevention and control measures for the geohazards with large potential danger, (3) conduct comprehensive remote sensing monitoring and research of earthquake-induced geohazard mechanism, (4) improve the meteorological early warning model and threshold. By all this efforts the risk of geohazards after earthquake will be reduced and controlled.

The Yili Valley, located on the border between China and Kazakhstan, serves as the juncture of North and South Xinjiang, and stands as a pivotal outpost on the Silk Road Economic Belt. This area possesses a fragile ecological environment and experiences frequent debris flow disasters. In this study, four machine learning models:Random Forest (RF), Logistic Regression (LR), Support Vector Machine (SVM), and Decision Tree (DT)-- were employed to evaluate the debris flow susceptibility and compute the weights of evaluation factors. The models were fed inputs comprising 398 identified debris flow channels and 14 feature parameters such as fault density, topographic relief, land use, NDVI, multi-year average rainfall, etc obtained through remote sensing and field surveys. Also, the accuracy of the four machine learning models was evaluated by ROC curves and calculating the Area Under the Curve (AUC). The research results show that: (1) High debris flow susceptibility areas are mainly located in the Tianshan Mountains in the deep river valley region and the loess-covered areas in the mountain front slopes; (2) Multi-year average rainfall, drought index, and topographic relief variability are the top three influential factors controlling the spatial development of debris flows; (3) The AUC values for the validation datasets of the four models were 0.938 (RF), 0.932 (SVM), 0.89 (LR), 0.79 (DT), with the Random Forest model exhibiting superior predictive capability in assessing susceptibility in the region; (4) The disruption of ecological vegetation in the loess-covered region of the study area is a significant cause of frequent debris flow occurrences. Ecological governance and protection efforts should be emplasized to reduce soil erosion and effectively mitigate debris flow disasters at their source.

Abstract Loess structure is the physical key factor that determines its stability and consists of macro-pores, loose texture, and water sensitivity. The structural change characteristics and effects of the undisturbed loess before and after water infiltration are studied using mechanical CT and simulation tests in order to study the structural change process within the undisturbed loess caused by water infiltration. The change in particle state is as follows: the peak frequency point of the equivalent diameter of the loess particles after infiltration ranged from 16.75 to 23.76 μm, and the eroded fine particles consisted primarily of fine particles. The smaller loess particles are removed by water infiltration resulting in coarsening of soil particles. The sphericity of the loess particles gradually changes from spherical pores to angular and dendritic pores. The particle inclination angle transitions to a range greater than 70°, and its proportion is approximately 61%. The change in pore structure is as follows: The loess porosity after infiltration increased by approximately 20%, and the increase in the pore area ratio of the mesopores and the macropores was higher than that of the micropores. Additionally, the small pores increased by more than 5 times the original state of the undisturbed loess. The connected pores expanded less than 60% of the initial state to more than 90% after infiltration, thus, increasing the dominant seepage channel of the undisturbed loess. These changes in particle and porosity further increase the water filtration intensity and promote the migration of fine particles (mainly silt particles), linking loess catastrophes and are the leading cause of loess settlement and slope instability. The process of water infiltration into the loess, the mechanism of loess collapsibility, and the influence of salinity on the loess structure and strength are discussed in this study.

Abstract Loess areas, such as the Loess Plateau, are characterized by a fragile ecological environment, high soil erosion, and frequent geological disasters due to the unique hydrological properties of loess (e.g., collapsibility and permeability). Therefore, the loess must be stabilized for use in engineering construction. Traditional stabilizers (lime, cement, and fly ash) cause environmental problems, such as soil salinization and greenhouse gas emissions. Therefore, this study investigated the effect of nanosilica on the hydrological properties of loess and the microscopic mechanism. Different nanosilica contents (0.2%, 0.4%, 0.8%, 1%, and 3%) were added to loess sample, and the particle size distribution, Atterberg limits, collapsibility, and soil water characteristics were analyzed. The results revealed the following. The addition of nanosilica changed the particle size distribution, liquid limit, plastic limit, and plasticity index of loess. After the addition of nanosilica with different contents, the loess collapsibility coefficient curve shifted downward, the soil water retention curve shifted upward, and the unsaturated permeability coefficient curve shifted downward. The pores between particles were filled, and the number of large and medium pores and the pore connectivity were lower after the nanosilica addition. The surface of the coarse particles adsorbed more fine particles, and a large number of micro-aggregates or clay aggregates were present in the pores between particles. In conclusion, the environmentally friendly material nanosilica can be used to improve the hydrological properties of loess, which is applicable to alleviating soil erosion and preventing geological disasters on the Loess Plateau.