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Engineers have limited control over the process of soil formation, which can pose challenges when it comes to constructing structures such as dams, pavements, rail tracks, and foundations. To address this issue, a study was conducted to examine the mechanical properties of Hormoz Carbonate Sand and Firoozkooh Quartz Sand No 161. The goal was to predict the settlement, particle breakage, and shear strength of these sands. Tall oedometer and direct shear tests were conducted in a drained condition and the samples were prepared with the dry pluviation method in two different relative densities (30% as loose and 80% as dense) and consolidated under various confining pressures. The results revealed that in dense specimens, the particle breakage index increased as the porosity decreased. In the tall oedometer tests, it was observed that the vertical applied stress decreased with increasing height of the soil sample. Additionally, particle breakage decreased with depth in the samples, corresponding to the decreasing vertical applied stress. Furthermore, direct shear tests were performed on soil samples of different heights (0.5, 1, 1.5, 2, and 3 cm) using a direct shear apparatus. It was found that in the lower sample heights (0.5, 1, 1.5 cm), a greater amount of breakage occurred due to a higher percentage of soil volume placed in the shear zone. The results also indicated that increasing the shearing rate led to a reduction in the particle breakage index. [ABSTRACT FROM AUTHOR]

Background: Desertification is the most severe environmental problem in arid and semi-arid regions and has caused great economic loss every year. However, artificial sand fixation barriers function on sand fixation for only 10–20 years. Searching for a native species with long-term sand fixation effect and strong environmental adaptive capacity, and low water consumption is needed. In this study, we investigated the environmental adaption and sand fixation effect of a grass from Poaceae family (Psammochloa villosa) that is indigenous to the desert of Northwest China. Results: The results showed that P. villosa has a streamlined leaf form, strong mechanical strength, and flexibility to adapt to wind. Leaf curling of P. villosa under drought decreased water loss rate through decreased evaporation area to adapt to drought. Significant negative relationship between adventitious root length and horizontal root burial depth indicates that adventitious roots help P. villosa absorb water and nutrients from soil under shallow sand burial condition, which enables P. villosa to adapt to different sand burial conditions. P. villosa fixed sand dunes through the distribution of the population at the top of the dune and the vertical relationship between the direction of windblown sand and the direction of growth of P. villosa, which stopped the expansion of the dune. Conclusions: Growth characteristics of wind and drought tolerant leaf traits and adventitious roots under sand burial indicate that P. villosa is well adapted to dry sandy desert conditions and burial by sand. The distribution of the P. villosa population on the sand dune is a "brake" on its expansion. These findings provide new insight for active sand dune fixation and desertification control using native grass in the desertified regions. [ABSTRACT FROM AUTHOR]

Fungal Induced Calcium Carbonate Precipitation (FICP) is a novel method used in geotechnical engineering that enhances the engineering properties of sand by using the potential of fungal activity. This research is the first attempt to monitor the strength of FICP treated sand using embedded Piezoelectric (PZT) patch based Electromechanical Impedance (EMI) spectroscopy. In the past, the strength of such treated sand has been determined through the destructive methods like Unconfined Compressive Strength (UCS) test. In this study, the sand is mixed with the filamentous fungus Aspergillus Niger and the cementation solution (urea and in the ratio of 1:1) is injected after every 24 h. Results recorded from the cost-effective EVAL AD5933 chip indicate that the shifting of frequency impedance signals in each phase is in good alignment with UCS and calcium carbonate content (CCC). Following the 28-day treatment period, the treated sand achieves a maximum UCS of 3.93 MPa, accompanied by a CCC of 15.19%. In order to correlate EMI signals with treatment cycles, UCS, and CCC, various multi linear regression (MLR) equations for statistical metrics like root mean square deviation (RMSD), mean absolute percentage deviation (MAPD), and correlation coefficient deviation (CCD) are developed. Additionally, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses have been conducted to observe the success of the FICP process in the sand. [ABSTRACT FROM AUTHOR]

The purpose of this study is to locate groundwater-saturated aquifers in the Vindhyan fringe belt in the Mirzapur district of Uttar Pradesh, India, and evaluate their protection using geoelectrical indices. The Schlumberger electrode layout, with a maximum half-current distance between electrodes of 300 m, was used to perform three gradient profilings and six geoelectrical soundings. The inversion IPI2win program and the traditional partial curve matching approach were used for geoelectrical sounding data interpretation. Four to five geologic units are identified in the research region based on the interpretation of the geoelectrical sounding data. These are the top-surface soil, clay, kankar/laterite and sand, weathered sandstone, and compact sandstone. The research region is characterized by HA-type sounding curves, and the obtained findings suggest the presence of groundwater-saturated zones and cracks in the area. The weathered sandstone saturated with water shows resistivity ranges between 375.4 and 407.1 Ω-m and depth ranges from 96.8 to 97.6 m. Thematic maps were prepared for total longitudinal conductance, transverse resistance, overburden thickness, and electrical anisotropy. The protective capacity of the aquifer is measured using the transverse resistance (Tr) and longitudinal conductance (Lc) of the Dar Zarrouk parameters. Based on the longitudinal conductance of the aquifers, the results obtained indicate that the research region is dominated by a good aquifer protective capacity rating. [ABSTRACT FROM AUTHOR]

A pile group under lateral loading is a complex pile‒soil-pile interaction problem. In this study, numerical analysis was used to investigate the lateral behavior of pile groups arranged in a 3 × 3 configuration with varying piles spacings. The hypoplastic constitutive model embedded into ABAQUS software through the UMAT subroutine was used to characterize the stress‒strain relationship of Toyoura sand. The effects of the pile spacing on the load‒displacement relationship of the pile group, the bending moment-depth relationship of each pile in the pile group, the deflection-depth relationship, and the soil resistance distribution were investigated. The results indicate that the lateral bearing capacity of the pile group decreases by more than 50% when the pile spacing is reduced from 7D to 3D. When the pile spacing is greater than 5D, the "edge effect" of the laterally loaded pile group gradually decreases, and when the pile spacing is greater than 7D, the "shadowing effect" can be negligible, and the wedge-shaped failure zone of the pile group occurs within a depth of 5D below the mud surface. [ABSTRACT FROM AUTHOR]

A gradation-dependent hypoplastic model is developed to capture the mechanical behaviours of crushable sands. First, a gradation evolution law is proposed to describe the variation of the grain size distribution (GSD) and the development of the extent of crushing during the loading process. Second, the family of CSLs under different gradations is formulated. Combining the developed CSL function and GSD evolution leads to well-modelling the unique critical state features of crushable sands. Subsequently, critical state features are incorporated into a well-established hypoplastic framework, such that the gradation-dependent hypoplastic model for crushable sands is developed. The accuracy and efficiency of the developed hypoplastic model in capturing the mechanical behaviours of crushable sands are validated against experimental counterparts. [ABSTRACT FROM AUTHOR]

Reinforced calcareous sand is increasingly recognized as a promising roadbed filler. This study evaluated the effects of different reinforcement methods, rubber content, dynamic stress amplitude, and loading frequency on calcareous sand through stress controlled undrained triaxial tests, and studied the dynamic characteristics and particle crushing of reinforced calcareous sand. The results showed that geogrid reinforcement increased the occurrence of particle fragmentation in calcareous sand and had the ability to resist deformation of rubber–calcareous sand mixtures, but the addition of rubber retarded particle fragmentation. In the case of geogrid reinforcement, the increase in rubber particle content from 0 to 10% corresponded to a 23.9% decrease in relative particle fragmentation. In the case with rubber particle reinforcement only, after 1000 cumulative loading cycles, the cumulative axial strain of the specimens increased 2.9 times when the rubber content was increased from 10 to 30%; the cumulative axial strain increased 60.7% when the amplitude of the dynamic stress was increased from 40 to 80 kPa; and the cumulative axial strain decreased 1.7% when the loading frequency was increased from 0.5 to 2 Hz, from 2.46 to 1.825%. The results of the study can provide reference and guidance for practical engineering. [ABSTRACT FROM AUTHOR]

Microbially induced calcium carbonate precipitation (MICP) technology is an emerging and environmentally sustainable method for improving the strength and stiffness of soil. Specifically, this innovative approach has gained favor in marine engineering due to the advantaged compatibility between precipitated calcium carbonate induced by MICP and coral sand. Sand containing fines is susceptible to liquefy. Whereas, the impact of fines contents on cyclic behavior of MICP-treated calcareous sand remains uncertain. Consequently, this technical note aims to investigate the liquefaction behavior of biocemented calcareous silty sand by conducting undrained cyclic triaxial shear tests and microscopic analysis. The results revealed the patterns of the excess pore water pressure curves and cyclic deformation characteristics as the fines contents increased. The liquefaction resistance of biocemented sand initially decreases with the addition of fines but subsequently exhibits an increasing trend. Microscopic analysis showed that at the cementation level with the cementation solution concentration of 1 mol/L, the calcium carbonate crystals are mainly attached to the surface of sand grains and this pattern does not directly affect the force chain. [ABSTRACT FROM AUTHOR]

Rail-sanding is employed to improve the train's wheel–rail traction loss in low adhesion conditions. This can significantly impede trains' kinematics, operation, and performance by hindering the train's acceleration and deceleration, resulting in delays and unreliability of transport system as well as causing safety risks and in the worst cases train collisions. Rail-sanding has its own merits in recovering the wheel–rail traction but can result in a sand wastage of more than 80% due to its low sand entrainment efficiency. In this research, computational fluid dynamics is coupled to discrete element modelling to study the behaviour of sand particles during rail-sanding. A parametric study based on the train characteristics, including train velocity, sand flow rate, and the geometry of the sander nozzle, is performed by comparing the entrainment efficiency of the sand particles. It is found that train velocities over 30 m/s result in the entrainment efficiency of almost zero. A moving air layer generated at the wheel–rail interface influences the lower bound of acceptable particle size range. The flow rate and nozzle geometry can be designed to enhance entrainment efficiency. [ABSTRACT FROM AUTHOR]

Fabric anisotropy significantly influences the mechanical behavior of sandy soils, potentially resulting in diverse failure patterns during shield tunneling owing to insufficient support pressure. In this paper, a set of specimens with bedding angles (α ) and an isotropic specimen are well generated to simulate active failure at the tunnel face using DEM. The evolving failure of the soil in distinct α are scrutinized, and ground settlement is further explored. Furthermore, microscopic information is juxtaposed to systematically elucidate the influence of α on failure patterns at a microscopic level. Macroscopic findings reveal that, aside from specimens with α = 0° and 90°, particle displacement experiences deflection as it extends toward the ground surface in other specimens. However, this deflection behavior is only noticeable under conditions of large deformation. Additionally, across all specimens, the maximum displacement of the ground surface is observed in those with α = 90°, while the minimum value is noted in specimens with α = 45°. Notably, considerable particle rotation occurs within the shear face. However, the deflection behavior has not been found in specimens with α = 0° and 90°. Similarly, in specimens with these two specimens, there is no noteworthy deflection observed in the principal direction of contact normal. [ABSTRACT FROM AUTHOR]

Anchors embedded in soil are used to restrain horizontal movement of structures, especially pipelines. Block anchors are not thoroughly studied in the literature as compared to plate anchors. This research paper intended to address this gap and contribute to the field by studying various parameters influencing the behavior of block anchors embedded in sand when subjected to a horizontal load. The behavior focuses on the pullout capacity and displacements/rotation of the block anchor, and the failure mode of the soil. The parameters studied include width, depth, and thickness of the block; depth of embedment below the ground surface; location of the pulling load; and the degree of saturation of the soil. The rigorous research methodology consists of numerical, analytical, and experimental approaches. First, the analytical calculations were based on Rankine, Coulomb, and log spiral theories to obtain values for the pullout capacity, for the 3-D magnification factor, and for the mobilized friction angle. Second, the experimental work included pullout tests, made in the laboratory, on concrete block anchors of various dimensions and on steel plate anchors, embedded in sand at two different depths. The sand was deposited in a box by pluviation to ensure a uniform and reproducible density. Materials properties were determined, and instruments were calibrated. The load and the corresponding horizontal and vertical displacements were recorded, and visual observations of the failed soil surface were captured. Finally, the numerical computations used PLAXIS program for the 2-D cases to obtain the pullout capacity and the deformation for long anchors. The main findings of this study show that the block anchor has a higher pullout capacity than a plate anchor; and the depth of embedment and the moisture condition of the sand significantly affect the pullout capacity, while the thickness of the block and the exact location of the load do not significantly affect the capacity. The capacity of a short block anchor per unit width decreases with increasing width, as the 3-D effect reduces. With reference to dry sand, the capacity of the anchor is doubled if the sand is unsaturated/wet, but it is reduced to only one half if the sand is saturated. The experimental results were compared with the analytical calculations and also with the numerical computations. The analytical results were also utilized for the experimental design. The results of numerical computations were used to validate the experimental design and to explain experimental findings, especially failure mode and deformation. The findings of this research are also compared with other studies reported in the literature. These findings have very significant implications to the analysis and design of the block anchor. They also contribute to the hazard risk assessment of block anchors embedded in sand subjected to variations in the environmental condition of wetting and drying cycles. [ABSTRACT FROM AUTHOR]

Sand production poses a substantial challenge in the oil and gas field, particularly in formations lacking the requisite strength to withstand pressure differentials during extraction. Many wells produce much less than their capacity due to the need to mitigate sand production and prevent well completion and wellhead erosion. The choice of sand control method depends on various factors, such as reservoir conditions, operational methods, and economic considerations, encompassing both mechanical and chemical approaches. In response to this challenge, this study investigates the application of a novel polymer nanofluid for chemical consolidation in clay-rich sandstone reservoirs, an area of exploration yet to be fully tapped. The research aims to assess the potential of polymer nanofluids as a promising solution for sand control in clay-rich reservoirs, with the overarching goal of bolstering well productivity and mitigating the adverse impacts of sand production. Conducted at a laboratory scale, the experiments involved the injection of 1 Pore Volume of consolidation fluid into sandstone cores with 15% and 30% clay content. Subsequently, the cores were subjected to reservoir temperature and pressure conditions for a period of 24 h. The obtained results show a significant enhancement in compressive strength, exceeding 700 psi, facilitated by the polymer nanofluid. Furthermore, permeability restoration reached approximately 89%, a notable improvement compared to preceding studies. Moreover, the introduction of foam injection rendered the core surface water-wet, suggesting potential advantages for reservoir management. These findings illuminate the promise of polymer nanofluids as an effective tool for sand control in clay-rich sandstone reservoirs. [ABSTRACT FROM AUTHOR]

Sand control is an ongoing challenge in numerous hydrocarbon-producing wells in sand-rich reservoirs. Sand production in these wells can cause damage to equipment, reduce production rates, and lead to erosion that can damage subsea equipment, production equipment, well completions, and surface facilities. This problem can compromise the mechanical integrity of the well, resulting in reduced hydrocarbon production and increased operating expenses. This review evaluates various sand production mechanisms, including geological and mechanical production methodologies, and fluid-related aspects, which are thoroughly investigated to offer a thorough understanding of the complexity of the issue and the state of sand prediction approaches. Empirical correlations, numerical simulations, and analytical models are among the sand production prediction techniques critically assessed in this study. The benefits, drawbacks, and suitability of these techniques for various reservoir environments are discussed. Furthermore, the potential benefits of combining Fiber optic (FO) technologies and machine learning (ML) for real-time monitoring and mitigation are highlighted. This integrated strategy has the potential to transform sand control practices of the industry, as demonstrated by case studies and new research that highlights its effectiveness. The future vision outlined in this review includes developments in automation, data processing methods, and sensor technologies, which should improve the precision and dependability of sand production predictions and mitigation. In conclusion, this review paper provides an extensive analysis of the current level of prediction techniques, as well as the mechanisms behind sand production in oil and gas wells. This highlights how real-time, data-driven solutions for monitoring and addressing sand production problems may be provided by FO and ML, which can ultimately lead to safer and more effective hydrocarbon recovery operations. [ABSTRACT FROM AUTHOR]

The soil-water characteristic curve (SWCC) is an important basis for describing hydraulic properties, which is closely related to environmental problems such as the migration of toxic substances from groundwater and soil. The SWCC models vary considerably with respect to the void ratio or bulk density. However, the void ratio and bulk density of the same soil change at different depths or positions within a flat space. Accurate simulation or calculation requires a precise SWCC, but measuring every SWCC under each density or void ratio condition is difficult. In this study, two particle packing models, the Kwan model and the modified linear packing density model (MLPDM), were introduced into the van Genuchten (VG) model to predict the SWCC for soil at the minimum void ratio (the maximum dry density). Then, the prediction method of the SWCCs for the same soil with different densities or void ratios was given. A series of laboratory tests using quartz sand mixtures were conducted to verify the accuracy of two extended models (the K-VG model and the M-VG model). For the K-VG model, the average RMSE was 0.020. For the M-VG model, the average RMSE was 0.017. In general, the SWCCs predicted by the two extended models were consistent with the measured values. [ABSTRACT FROM AUTHOR]

Object tracking is a challenging task which is required for different problems such as surveillance, traffic analysis and human-computer interaction. The problem of tracking an object can be considered in different categories such as single object tracking, multiple object tracking, short-term tracking, long-term tracking, tracking by detection and detection-free tracking. This study focuses on detection-free tracking for ground targets on aerial images. The studies in the literature show that correlation filter and deep learning based object trackers perform well recently. This paper proposes a new correlation filter-based tracker containing a strategy for re-detection issue. We improve the performance of correlation filter-based tracker by adding a lightweight re-detection ability to the correlation filter tracker in case of a long occlusion or complete loss of target. We use deep features to train Discriminative Correlation Filter(DCF) by integrating sub-networks from pre-trained ResNet and SAND models. The experimental results on the popular UAV123L dataset show that the proposed method(MADCF) improves the performance of DCF tracker and have a reasonable performance for long-term tracking problem. Moreover, we prepare a new tracking dataset (PESMOD tracking) consisting of UAV images, and we evaluate the proposed method and state-of-the-art method in this dataset. We observed that the proposed method performs much better in ground target tracking from VIVID and PESMOD aerial datasets. The proposed MADCF tracker performs better for small targets tracked by UAVs compared to the deep learning-based trackers. The source code and prepared dataset are available at http://github.com/mribrahim/MADCF [ABSTRACT FROM AUTHOR]

The determination of geotechnical correlations and coefficients relies on the assumption of error-free training data used for empirical models, but this assumption may not always hold true. Empirical-risk assessments based on noisy data cannot guarantee the accuracy of regression results. The statistical robustness of empirical-design parameters is influenced both by the soil properties and regression models used. This study proposed a non-stochastic regression method for predicting the hydraulic conductivity of sandy soils based on relevant soil parameters. No changes in content have been made. The approach involved the following steps: data preprocessing, regression-algorithm selection, model optimization, uncertainty estimation, and model selection. The study identified trends in hydraulic conductivity and pore-structure characteristics based on specific model parameters that were derived from empirical data. The paper presents a compilation of a regression model and methods for fine-tuning parametric representations. The prediction results highlighted the best-fitting model and parameter combination with the lowest residuals, comparing favorably to empirical regression models. Machine-learning-based regression models suggest an optimal combination of properties while considering model performance and handling missing values for uncovering the relationships between hydraulic conductivity and multiple, influential, soil properties. [ABSTRACT FROM AUTHOR]

This study examined the composition, distribution, and origins of rare, Noble, and fissionable elements for the first time in black sand deposits from the Northern Delta coastal region. The findings showed that among the elements under investigation, Fe, Ti, Mn, and Sn had the greatest mean levels, while Hf, Cd, and As had the lowest mean amounts. According to the study's elemental composition, black sand is thought to have economic worth for Ti, Zr, Hf, Sn, Ag, and W. The Zr, Co, Cd, Cu, Hf, V, W, and Zn correlation points to the same source origin. It is clear that the accessory mineral composition in the sediments under study especially the heavy ones controls the geochemical patterns of trace elements. The trace element concentrations of interest show a pattern of element variability related to the mineralogy of the sands, as indicated by the principal component analysis and cluster analysis. To explore and exploit heavy minerals in the research region, the study's findings are important. [ABSTRACT FROM AUTHOR]

A differential thermal analysis study was carried out on the formation and decomposition of hydrates in systems containing natural gas, sand, and 5 mass % aqueous NaHCO3 as well as natural gas, sand, and 5 mass % aqueous NaCl with initial gas pressures from 3 to 9 MPa. Equilibrium conditions, enthalpy of dissociation, and the kinetic parameters of hydrate formation were determined. Hydrate formation in the system containing aqueous sodium bicarbonate proceeds at higher temperatures and lower pressures and has higher kinetic parameters than in the system with aqueous sodium chloride of the same concentration. Composition of the solutions is one of the factors affecting hydrate formation in the studied systems. The HCO3– ion is found to have a greater structure-making effect than the Cl– ion, which leads to differences in the thermodynamic conditions and kinetic parameters of natural gas hydrate formation in a porous medium. [ABSTRACT FROM AUTHOR]

Inorganic binder used in casting process has the advantages of low odor, labor-friendly conditions, and relatively low cost, which is one of the main development directions for casting molding materials in the future. However, compared to organic binders (such as resin binders), inorganic binders exhibit lower bonding strength and are more sensitive to environmental humidity. This sensitivity poses challenges, particularly in the reclamation of used sand, thus limiting their broader application. In this paper, the research and application status of inorganic binders (mainly silicate inorganic binders) and their curing methods are summarized. In addition, the research and application of phosphate inorganic binders and 3D printing inorganic binders that are being developed are introduced. Meanwhile, a detailed comparative analysis is conducted on the challenging issue of "reclamation for used sand" in the application of inorganic binders. Finally, the development direction of inorganic binders is clarified. [ABSTRACT FROM AUTHOR]

The possibility of isovalent substitution of zinc and cobalt atoms in the structure of willemite Zn2SiO4 was studied. Ceramic pigments with a willemite structure of blue, violet, and light blue colors were synthesized. Samples of blue color were used in the manufacture of glazes. During the synthesis of the pigments, synthetic silicon oxide was replaced by natural quartz sand. The pigments were synthesized by solid-state method at a temperature of 1270°C. The physical and chemical properties of the synthesized blue pigment were determined. In addition, the pigment was tested for use in traditional glazes for the coloring of ceramic products. It was established that the obtained blue pigment provides high aesthetic and decorative characteristics at a relatively low price. [ABSTRACT FROM AUTHOR]

The purpose of the study was to develop compositions of colored glasses based on basalt from the Osmonsay deposit. To synthesize glasses, compositions based on the basalt – quartz – soda lime system were studied. Quartz sand from the Samarkand deposit was used as a source of quartz. Transparent, translucent, and opaque colored glasses were obtained. The research demonstrated that it is possible to obtain glass of a wide range of colors without the use of coloring components. [ABSTRACT FROM AUTHOR]

Hydrophobized soils have functional hydrophobic coatings to delay or restrict water infiltration and thus prevent infrastructure failure and long-term degradation. Over time, hydrophobized soils will be subjected to degradation under the action of external stresses, leading to the loss of its functional properties. Microencapsulation approaches, initially developed for self-healing applications emerge as a potential solution to enhance, switch (from hydrophilic) or prolong the longevity of hydrophobized soils. The aim of this study is to produce and investigate the effectiveness of microencapsulation to impart hydrophobicity in granular materials in response to external stimuli. In this research, polydimethylsiloxane (PDMS), with hydrophobic properties, is encapsulated in calcium alginate microcapsules with the ionic gelation method. The effectiveness of the microcapsules to induce hydrophobicity is investigated by mixing sand with microcapsules and quantifying the change of the contact angle and water drop penetration time (measures of hydrophobicity) under an external trigger, i.e., under drying and consecutive wetting–drying cycles. The results show that microcapsules release the hydrophobic cargo (PDMS) during shrinkage. After drying, the PDMS content in sand increased to 0.1–0.8% by mass of sand. The released hydrophobic cargo (PDMS) induced hydrophobicity in sands, reflected by a contact angle increase from 29.7° to at least 87.7°. The amount of polydimethylsiloxane encapsulated is a key parameter controlling the release of hydrophobic cargo. In addition, 4% capsule content in sands is identified as an effective microcapsule content in inducing hydrophobicity. [ABSTRACT FROM AUTHOR]

In the present study, the undrained cyclic behaviour of biotreated sands using microbial and enzyme-induced carbonate precipitation was investigated for a wide range of initial void ratio after consolidation ( e 0 ), initial effective normal stress ( σ N 0 ′ ) and calcium carbonate content (CC) under direct simple shear (DSS) testing conditions. The critical state soil mechanics framework for untreated sand was first established using a series of drained and undrained (constant volume) tests, which served as a benchmark for evaluating the undrained cyclic liquefaction behaviour of untreated and biotreated sands. The results indicated that the modified initial state parameter ( ψ m 0 ) in DSS condition showed a good correlation with instability states and phase transformation under monotonic shearing. In undrained cyclic DSS loading condition, samples displayed cyclic mobility indicated by an abrupt accumulation of large strain or σ N 0 ′ transiently reaching zero or a sudden build-up of excess pore water pressure. The linkage between static and cyclic liquefaction was established for untreated and biotreated sand specimens based on the equivalence of characteristic soil states. The number of cycles before liquefaction (NL) for the biotreated sand specimens was mainly controlled by the cyclic stress ratio, e 0 , σ N 0 ′ and CC. For a similar initial state prior to undrained cyclic loading, the biotreated specimens required a larger NL compared to the untreated sand. The cyclic resistance ratio at NL = 15 (CRR15) increased with decreasing ψ m 0 for the untreated sand, while the CRR15 for biotreated sand increased with increasing CC and decreasing σ N 0 ′ . [ABSTRACT FROM AUTHOR]

A set of creative formulation is introduced to estimating the small-strain shear modulus (Gmax) of various sandy soils through the measurement of well-controlled laboratory tests combined with the analysis of experimental data published in the literature. The influences of normalized effective confining pressure ( σ c0 ′ /Pa), void ratio (e), and fines contents (FC) on the values of Gmax are revealed through a series of bender element measurements. Through introducing the equivalent skeleton void ratio ( e sk ∗ ) to describe the intergranular contact state of sandy soils with FC less than a threshold value (FCth), a remarkable finding is that the stress exponent n, characterizing the increase rate of Gmax with increasing σ c0 ′ , is a soil-specific constant and a linear function of the synthesizing material parameter ( C u s C u f ) in log-scale. Another remarkable finding is that a virtually unique form of the correlation between Gmax/( σ c0 ′ /Pa)n and e sk ∗ exists. An unified form of the binary packing material-based Gmax prediction formulation for different types of sandy soils is established. The three coefficients of the proposed Gmax expression in form of explicit equations can be simply determined using some basic index properties of clean sand and pure fines. In this regard, the proposed Gmax prediction formulation provides a significant advantage in the determination of Gmax and associated shear wave velocity Vs of sandy soils in practice. [ABSTRACT FROM AUTHOR]

Piles in offshore constructions have often been reinforced with anchored piles, batter piles, and micro piles to strengthen their uplift load. The opening bladed anchor pile is a recent alternative approach that is presented in this study. This modified pile aims to provide a bearing area underneath the soil during uplift. This method is not incompatible with driving or penetrating piles into the ground. The pullout response of the modified anchor was examined in an experimental investigation. The impact of relative density of the sand, the embedment ratio, and the angle of the blade on the uplift capacity of the anchor pile with blades are studied. The ultimate uplift response of the bladed anchor implanted in sand improves with the increase in embedment ratio and blade angle. The percentage of amelioration in the uplift load at embedment ratio of 32 and blade angle of 90° was (231.1%, 208.6%, and 191.4%) at sand relative densities of (30%, 50%, and 80%), respectively, compared to unbladed anchor. The presence of blades produced a perfect anchoring system. For offshore applications, this piling modification is practical, appropriate for marine constructions, and simple to install. [ABSTRACT FROM AUTHOR]

Accurate determination of the friction angle of sand is crucial for foundation design. Existing research lacks a comprehensive method to ascertain the friction angle specifically for Bangkok Sand based on the Standard Penetration Test (SPT). This study introduces an innovative technique leveraging the concept of the state parameter, a dimensionless metric characterizing the sand's state relative to its critical condition. The method establishes a correlation between the friction angle and data obtained from triaxial tests and the SPT. The relationship between the friction angle and state parameters of Bangkok Sand is derived from triaxial testing. Additionally, a calibration chamber study involving 17 tests explores the connection between SPT values and the state parameter. To predict the state parameter, a fully connected neural network was developed, incorporating the SPT-N value and the prevailing confining stresses. This parameter is subsequently used to estimate the friction angle from triaxial test data. The validity of this approach is confirmed by a high coefficient of determination (R2 = 0.98), demonstrating its precision. Furthermore, the friction angle deduced through this novel approach is compared with those obtained using traditional methods. This study contributes to the field by providing an effective and accurate method for determining the friction angle of Bangkok Sand, essential for geotechnical engineering applications. [ABSTRACT FROM AUTHOR]

The geological hazard of water–sand inrush is a matter of concern for infrastructure construction and resource exploration activities in China, due to the complex interplay between groundwater dynamics and the stability properties of sand particles. This phenomenon is characterized by its intensity, hazardous nature, and unpredictable behavior. Following comprehensive analysis, this study identifies the critical factors influencing water–sand inrush processes as fissure width, water stress (waterhead height), in-situ sand ground stress within the sand stratum, and clay content. To investigate these factors experimentally, a custom-designed hydraulically coupled water–sand inrush test apparatus was used. The apparatus was equipped with a cylinder to apply ground stress, a pneumatic diaphragm pump to regulate water stress, and a bottom opening in the sand layer. Tests were conducted to investigate the dynamic response of water–sand inrush events under various combinations of factor levels. The findings revealed that the critical value for inrush is only present in the fissure width, which was observed to be 3 mm for the tested sand material. Unlike fissure width, the other factors do not have definitive critical values but instead modulate the intensity of the inrush process without determining its occurrence. The 'inrush rate' serves as a measure of the severity of water–sand inrush disasters and shows a linear increase with both increasing groundwater stress and fissure width, a negative exponential function relationship between the inrush rate and the clay content. Notably, ground stress does not exert a significant influence on the intensity of the inrush process itself. Under constant conditions, the inrush rate remains relatively constant across different levels of sand ground stress, for instance, in the experiments, the inrush rate was measured at 1.606 kg/s when the water stress was 0.1 MPa and the fissure width was 5 mm. Grey relation analysis was used to examine the sensitivity of each factor's influence on the inrush rate. The results showed that water stress has the greatest impact on the intensity of water–sand inrush, followed by ground or soil stress, clay content, and the width of the fissures in the sand layer. [ABSTRACT FROM AUTHOR]

During the operation of sandy railways, the challenge posed by wind-blown sand is a persistent issue. An in-depth study on the influence of wind-blown sand content on the macroscopic and microscopic mechanical properties of the ballast bed is of great significance for understanding the potential problems of sandy railways and proposing reasonable and adequate maintenance and repair strategies. Building upon existing research, this study proposes a new assessment indicator for sand content. Utilizing the discrete element method (DEM) and fully considering the complex interactions between ballast and sand particles, three-dimensional (3D) multi-scale analysis models of sandy ballast beds with different wind-blown sand contents are established and validated through field experiments. The effects of varying wind-blown sand content on the microscopic contact distribution and macroscopic mechanical behavior (such as resistance and support stiffness) of ballast beds are carefully analyzed. The results show that with the increase in sand content, the average contact force and coordination number between ballast particles gradually decrease, and the disparity in contact forces between different layers of the ballast bed diminishes. The longitudinal and lateral resistance of the ballast bed initially decreases and then increases, with a critical point at 10% sand content. At 15% sand content, the lateral resistance is mainly shared by the ballast shoulder. The longitudinal resistance sharing ratio is always the largest on the sleeper side, followed by that at the sleeper bottom, and the smallest on the ballast shoulder. When the sand content exceeds 10%, the contribution of sand particles to stiffness significantly increases, leading to an accelerated growth rate of the overall support stiffness of the ballast bed, which is highly detrimental to the long-term service performance of the ballast bed. In conclusion, it is recommended that maintenance and repair operations should be promptly conducted when the sand content of the ballast bed reaches or exceeds 10%. [ABSTRACT FROM AUTHOR]

The sex-specific differences in the growth and population characteristics of the high-commercial-value sand crab Ovalipes punctatus were investigated in Korea. The estimated allometric growth between the sexes showed significant differences in all morphometric measurements. In the classification of growth types, carapace width-chela length exhibited positive and negative allometric growth in males and females, respectively. Carapace width-abdominal width showed positive relative growth in both sexes, and orbital spine width exhibited negative relative growth in both sexes. Consequently, sexual dimorphism was evident in all measured traits. Growth parameters estimated using the ELEFAN function of the FiSAT II program indicated higher values in males compared to females. Asymptotic length (CW∞) for males was estimated at 139.2 mm, whereas for females it was 116.6 mm. Additionally, the growth coefficient (K) was higher in males (0.65) than in females (0.54), suggesting faster growth in males. The winter point (WP) was 1 for males and 0.7 for females, indicating slower growth in males during the colder December and slower growth in females during the spawning period in August. The modified von Bertalanffy growth curves indicated asymptotic growth in all sexes, and the growth performance index (φ') showed higher values in males (4.10) compared to females (3.87), reflecting differences in growth curves. The steady increase in recruitment rates from July to September was associated with the appearance of larvae and their subsequent growth into juveniles, leading to their recruitment into the population during this period. Therefore, O. punctatus exhibited sex-specific differences in growth parameters, suggesting distinct growth strategies between the sexes. [ABSTRACT FROM AUTHOR]

In this research paper, we introduce a novel and sustainable approach for forecasting the hydraulic conductivity of sand layers subjected to microbial-induced carbonate precipitation (MICP) to mitigate the diffusion of toxic pollutants. The proposed model uniquely integrates the impact of varying CaCO3 contents on the void ratio and estimates the average particle size of CaCO3 crystals through scanning electron microscopy (SEM) analysis. By incorporating these parameters into the K-C equation, a simplified predictive model is formulated for assessing the hydraulic conductivity of MICP-treated sand layers. The model's effectiveness is validated through comparison with experimental data and alternative models. The outcomes demonstrate a substantial reduction in hydraulic conductivity, with a decrease ranging between 93 and 97% in the initial assessment and a decrease between 67 and 92% in the follow-up assessment, both at 10% CaCO3 content. Notably, the hydraulic conductivity shows an initial sharp decrease followed by stabilization. These findings provide valuable insights into improving the prediction of hydraulic conductivity in MICP-treated sand layers, promoting a sustainable method for preventing pollution dispersion. [ABSTRACT FROM AUTHOR]

A method and results of model studies of the operation of a proposed new system for mechanized feeding of filler sand to the ladle nozzle are presented. The design solutions incorporated into the system and the relationships obtained to justify its energy-force parameters are validated. [ABSTRACT FROM AUTHOR]

The exploration and development of tight sandstone gas reservoirs are controlled by high-quality river channel sand bodies on a large scale in Sichuan Basin. In order to improve the accuracy of sand body prediction and characterization, Multi-component exploration technology research has been carried out in Northwest Sichuan Basin. First, based on the array acoustic logging data, a forward modeling has been established to analyze the seismic response characteristics of the PS-wave data and P-wave data. The result shows that the response characteristics of the P-wave and PS-wave to the sand bodies with different impedance are different. And then through the analysis of logging data, the effectiveness of the forward modeling has been proved. When the sandstone velocity is close to the surrounding rocks, the P-wave performs as a weak reflection, which may lead to reduce the identification range of the sand bodies. However, the PS-wave exhibits strong reflection, which can identify this type of sand bodies. Finally, by comparing and explaining the PS-wave data and P-wave data, and integrating their attributes, the prediction accuracy of sand bodies is improved. Compared with the interpretation of a single P-wave, the results can significantly expand the distribution range of sand bodies, laying a foundation for improving the production capacity of single wells and reserve submission. [ABSTRACT FROM AUTHOR]

Self-healing approaches are increasingly being explored in various fields as a potential method to recover damaged material properties. By self-recovering without external intervention, self-healing techniques emerge as a potential solution to arrest or prevent the development of large strains problems in soils (e.g., landslides) and other ground effects that influence the serviceability of structures (e.g., differential settlement). In this study, a microcapsule-based self-healing sand was developed, and its performance during mixing and compaction, shearing, and recovery of shear strength was demonstrated. The cargo used for sand improvement, a hardening oil, tung oil, was encapsulated in calcium alginate capsules by the ionic gelation method. The surface properties, internal structure, thermal stability and molecular structure of the capsules were evaluated by advanced material characterization techniques. The survivability of capsules during mixing and compaction was assessed by measuring the content of tung oil released into the sand, while their influence on sand shear strength and its recovery was assessed with shear box tests. The results showed that the capsules could rupture due to movement of the sand particles, releasing the tung oil cargo, leading to its hardening and minimizing its strain-softening response and enhancing up to 76% of the sand shear strength (at a normal stress of 10 kPa and capsules content of 4%). This study demonstrates the potential of a capsules-based self-healing system to provide 'smart' autonomous soil strength recovery and thus with potential to actively control the large strain behavior of soils. [ABSTRACT FROM AUTHOR]

The problem considered in this paper is the passive earth pressure determination under various rigid wall geometry with negative wall-soil friction. An exact solution based on statically admissible stress fields is employed to evaluate the impact of negative wall-soil friction and inclined walls on the design of retaining walls. A series of conservative solutions for the passive earth pressure coefficient in the presence of negative wall friction is obtained, shedding light on the load transfer mechanism of cohesionless backfill materials. While focusing on the passive earth pressure coefficient, the study further identifies the stress state transition zone in the backfill and the influence of wall inclination on passive earth pressure. In addition, the load transfer mechanism of cohesionless backfill material in a retaining wall is affected by various factors, including wall geometry, degree of negative wall friction, the direction of the major principal stress at the wall, and the position and orientation of the transition zone and line of stress discontinuity. It follows that comprehensive design charts involving various rigid wall geometry and negative wall-soil friction are provided for engineering practice. Overall, the study successfully characterizes the admissible stress field in the backfill of rigid retaining walls, contributing to the knowledge of retaining wall design under the effect of negative wall friction. [ABSTRACT FROM AUTHOR]

Piled raft foundations (PRFs) below stepped high rise towers are often subjected to non-uniform loads with eccentricities. In this study, twenty five cases of rectangular rafts with different pile configurations and orientations embedded in sand are analyzed using nonlinear three-dimensional finite element analysis. These PRFs are subjected to different triangularly distributed loads and uniformly distributed loads with and without eccentricities. The piled raft responses investigated are the maximum and differential settlements, angular distortion, tilt, load sharing between the raft and the piles, the load carried by the individual piles, and the subgrade modulus (spring constant) at the raft-soil and pile-soil interfaces. The PRF responses are greatly influenced by the distribution of the applied loads and the magnitudes of the load eccentricities. The study provides insights into the PRF behavior under nonuniform and eccentric loads and may help practitioners in making informed design decisions. [ABSTRACT FROM AUTHOR]

Depending on the characteristics of soil particles and external load, natural soils often undergo particle breakage which may significantly influence their mechanical behavior. In this study, a hypoplastic model is proposed to describe the sand behavior over a wide range of stress levels, especially those sufficient to cause particle breakage. The characterized void ratios and granulate hardness of the model are related to the plastic work to reflect the impact of particle breakage on the strength and deformation properties of sand. The influence of confining pressure on the extent of particle breakage is properly considered. The model is demonstrated to be capable of simulating the response of crushable sand under various test conditions. The simulation results of the original hypoplastic model are also presented, which indicates that neglecting the particle breakage may cause unreasonable predictions at high stress state. [ABSTRACT FROM AUTHOR]

Background and aims: Windblown sand movements, i.e., wind denudation and sand burial, pose a strong selective pressure on dune vegetation. Dune plants commonly receive repeated wind denudation or sand burial. Therefore, simultaneously examining the role of sand movement intensity and frequency in shaping dune vegetation is critical for dune biodiversity conservation and ecological restoration. However, studies of this nature are rare. Methods: We studied the integrated effects of sand movement intensity and frequency on the seedling performance of a dominant semi-shrub, Artemisia ordosica, in the Mu Us sandland. We subjected A. ordosica seedlings to a total intensity of 10 cm wind denudation or sand burial treatments conducted once, twice or four times. Key results: We found, given that the total intensity of sand movement remains the same, increasing frequency and decreasing intensity per time largely improved seedling survival. Furthermore, increasing frequency and decreasing intensity per time significantly alleviated the negative effects of wind denudation, although such alleviation effect was not detected for sand burial. Seedlings of A. ordosica increased specific leaf area, root length, and biomass allocation to root to adapt to wind denudation, while they developed adventitious roots to adapt to sand burial. Conclusions: Our results demonstrate that a single heavy sand movement is more detrimental than multiple light ones to the performance of A. ordosica seedlings. Our findings suggest that windproof measures to prevent severe sand movements is necessary to allow the establishment of A. ordosica during the dune restoration process. [ABSTRACT FROM AUTHOR]

The aim of this study is to improve and simplify the measurement of radon exhalation rate using the closed-loop accumulation method. Based on the 222Rn concentration data obtained from reference the standard module of uranium ore sands and cement, this work simplifies the 222Rn concentration growth model for calculating radon exhalation rate using the least squares method and proves its accuracy. Through fitting residual analysis, anomalies are screened at the significance level of α = 0.05 to enhance fitting precision. Herein, the influence of the starting point on the fitting effect and the calculation of radon exhalation rate is explored. The results indicate that after screening anomalous data, the fitting effects of the two sets of experimental data are further improved, and the relative errors in radon exhalation rate measurements are reduced from 1.77 to 1.41% and 13.08 to less than 10% respectively. [ABSTRACT FROM AUTHOR]

The bearing capacity of shallow foundations on geocell-reinforced sand (GRS) depends not only on the soil characteristics but also on the geometries and properties of geocell. The geometry characteristics of GRS comprise height, length and cell aperture size of geocell as well as the sand layer thickness engaged between footing and GRS layer. Using the design-of-experiments (DOE) method the trends of bearing capacity ratio (BCR) as a function of selected geometry parameters of geocell are systematically visualized. Furthermore, trends of BCR as a function of geocell-selected geometry parameters are analysed. To this end, the study deploys the response surface methodology (RSM) to identify several configurations of geocell by conducting only twenty-seven laboratory tests. The results show that the DOE-RSM method gives an efficient interpretation of the variable's interaction while it lessens the number of tests. In addition, it has been found that the geocell height is the most influential parameter on BCR of footings on GRS. Moreover, an interaction between geocell aperture size and geocell height is recognised. The results are formulated and compared with the literature, resulting in good agreement. [ABSTRACT FROM AUTHOR]

This study investigates the effect of non-plastic fines content of sand–silt mixtures on excess pore water pressure generation using an energy-based approach. For this purpose, an experimental program was designed and conducted on mixtures of Firoozkuh sand No. 161 and Firoozkuh silt. A total of 35 undrained strain-controlled cyclic triaxial tests were performed on the reconstituted specimens of sand–silt mixtures, with a wide range of effective parameters such as relative density, effective confining stress, and fines content. Also, to present a more generalized and precise model, 37 undrained cyclic tests were collected from previous studies. Then, using nonlinear regression analysis and the results of these 72 tests, a model, relating residual excess pore water pressure ratio ( r u ) to the ratio of dissipated energy to capacity energy ( W / W liq ), is proposed. The results indicated that initial effective confining stress has a negligible effect on the r u - W / W liq trend and so, the calibration parameter of the model only depends on the relative density and fines content. Convincingly, the accuracy of the proposed model was verified using the results of a series of centrifuge tests, reported by others, and the recorded data of wildlife downhole array site during the Superstition Hills 1987 earthquake. The proposed model is practical, applicable to various sands and sand–silt mixtures with nonplastic fines contents, and able to be calibrated using convenient parameters (i.e., relative density and fines content). Finally, the model can be easily implemented in site response analysis for energy-based liquefaction potential evaluation. [ABSTRACT FROM AUTHOR]

The effect of electrokinetic sodium silicate injection into sand formation containing fine grains was studied in this research. A soil was grouted by Na-silicate in a 160 mm length electrokinetic cell with a 1 V/cm potential gradient for 1 week. Silicate solutions of 5% and 10% concentrations were injected through the reservoir next to the anode electrode, while 10% phosphoric acid or 30 mg/l bicarbonate solutions were used in the cathode chamber. When comparing the results, it was evident that the electrokinetic (EK) process without additives does not significantly enhance soil strength, except in the vicinity of the cathode electrode. Specifically, the most notable increase in strength was observed in the section proximal to the cathode, which demonstrated approximately 3.1 times higher strength than the control sample (i.e., without EK application). The obtained results indicate that injecting 5% and 10% Na-silicate solutions significantly increase the strength of soil all over the sample. Significant improvement in soil strength was observed when Na-Si was injected with bicarbonate as a catholyte during the EK process. Strength at the anode increased by 82% and 107% at 5% and 10% Na-Si concentrations, respectively. Resistance in the middle of the cell samples remained consistent for both concentrations. Immediate application of bicarbonate catholyte and silicate injection notably enhanced soil strength, while efficiency decreased when Na-Si was injected with phosphoric acid catholyte, especially near the cathode. Higher silicate concentrations resulted in reduced penetration length in both acid and bicarbonate catholytes. It can also be concluded that adding silicate to the anode chamber meaningfully reduces the electro-osmotic flow after 2 or 3 days. [ABSTRACT FROM AUTHOR]

Researchers have developed numerous breakage indices, predominantly relying on comparisons between pre- and post-test Grain Size Distribution (GSD) curves determined through conventional sieve analysis. Although these indices enable a precise estimation of particle breakage extent, a significant limitation arises when attempting to integrate them into constitutive models, especially when those models cannot consider GSD as an input. This paper addresses the need for tailored breakage indices designed to suit the specific requirements of different families of constitutive models. The new indices have been developed based on stress and strain tensor invariants or combinations thereof, ensuring the future ease of implementation into various constitutive models. The proposed equations have been validated using five different sets of experiments performed on rockfill material, calcareous, and quartz sands. The comparison between the available experimental data and the estimated degree of particle breakage using the suggested indices demonstrates their adequate performance. The novel indices can be integrated into different constitutive models, including hypoplastic, elastoplastic, and thermodynamically consistent approaches, as well as tested for their practical applicability for boundary value problems. [ABSTRACT FROM AUTHOR]

Purpose: Permeability is one of the primary concerns in geotechnical engineering research. The permeability coefficient, the most significant parameter defining permeability, has a significant impact on the mechanical and physical properties of the soil by virtue of its value. Because soil is a bulk material and its internal seepage channels are intricate, it is challenging to accurately describe those using straightforward physical parameters. As a result, the models currently in use for calculating the coefficient of permeability of soils are mostly skewed towards empirical statistics and have issues with uneven magnitude and ambiguous physical significance. Thus, one of the key scientific issues in the field of geotechnical engineering is the development of a permeability coefficient estimate model that can characterize the seepage channel. Methods: Based on the idea of hydraulic radius in circular pipe flow, this paper establishes the calculation method of the equivalent hydraulic diameter by analyzing the microstructure of the soil body and proposes the idea of equivalent hydraulic force inside the soil body, taking into account factors such as granular gradation, dry density, and specific gravity of solid particle. Furthermore, a theoretical model based on the equivalent hydraulic diameter has been constructed for the permeability coefficient of the soil body, by introducing the coefficient of fluid dynamic viscous and the water gravity. In order to assess the accuracy and validity of the equivalent hydraulic diameter and the model of soil permeability coefficient estimation, permeability tests were designed and the results of undisturbed loess, single particle size quartz sand, and multi-grain-size quartz sand combinations were obtained. The results of the estimated model, the traditional estimated model, and the permeability coefficient of the tests were compared and analyzed. Results and conclusions: The findings indicate a square relationship between the permeability coefficient and the equivalent hydraulic diameter and a correlation coefficient of more than 97% between the equivalent hydraulic diameter calculation results and the measured permeability coefficient results; the error analysis results demonstrate that the equivalent hydraulic diameter calculation results can meet the permeability test error range. This paper presents an estimation model for the soil permeability coefficient that is universally applicable to a wide range of particle sizes (0.002 to 2 mm). It is compared with experimental test results, Terzaghi formula, Hazen formula, and Amer formula. The results demonstrate that the model developed in this paper has a higher degree of agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Most natural sandy deposits contain low amounts of fine content (< 10%), which is usually anisotropic and characterized by complex microstructures. The present study investigates the influence of low silt content on the anisotropic behaviour of sand. For this purpose, 30 undrained tests were performed using a hollow cylindrical apparatus with constant α° and b values on Firoozkuh sand. The specimens had silt contents of 0, 3, 5, 7 and 10%, and the inclination angle (α°) was varied from 15° to 60°. The specimens were prepared with the dry deposition method and subjected to confining pressures of 100 and 200 kPa. The equivalent intergranular relative density parameter was then introduced in order to create a comparative basis for the specimens. The experimental results show that increasing α leads to more contractive behaviour in the pure sand. By adding silt particles to the host sand up to 5%, the peak strength of the specimen is increased (18.5%, 12% and 7.7% for α = 15°, 30° and 60°, respectively), and the strength of the specimen is decreased. It should be noted that with a silt content of 10%, the strength of the specimen was lower than that of the host sand (about 12%). On the other hand, it can be seen that with the increase of α, the influence of fine grains as an important parameter in sand-fine mixtures is decreased. [ABSTRACT FROM AUTHOR]

The microbial induced partial saturation (MIPS) technique is the new environmentally friendly, cost-effective technique applicable under existing structures for mitigating sand liquefaction. The current study investigated the effectiveness of MIPS for mitigating sand liquefaction under undrained static loading. A series of undrained static triaxial tests were conducted to examine the influence of biogenic gas production through microbial denitrification on poorly graded sand at various relative densities. Initial batch experiments revealed that increased nitrate concentrations resulted in a decreased degree of saturation. Loosely and medium-dense saturated samples exhibited positive pore pressure during loading, which was reduced through biological desaturation, resulting in increased undrained shear strength ratios. Dense saturated and desaturated samples produced negative excess pore pressure, decreasing the undrained strength of treated samples due to dilative behavior. The undrained stress–strain behavior of loose and medium-dense sand transitioned from strain softening to strain hardening as the degree of saturation decreased from 100 to 90%. However, dense sand exhibited strain-hardening behavior with decreased saturation from 100 to 95%. Decreasing saturation levels reduced instability susceptibility, resulting in more stable soil behavior and decreasing the potential for large strains and instability. The study demonstrated a reduction in the Liquefaction Potential Index (LPI) for both loose and medium-dense sand as the degree of saturation decreased from 100 to 90%. These findings highlight the potential of MIPS as an effective technique for mitigating sand liquefaction and offer insights into its underlying mechanisms. [ABSTRACT FROM AUTHOR]

Particle breakage plays a pivotal role in shaping the deformation behavior of granular soils when subjected to compression. To comprehensively assess the influence of particle breakage on the evolution of particle size distribution and the compression characteristics of calcareous sand, this study conducted 63 sets of confined compression tests on calcareous sand, specifically under high-pressure conditions. The results indicated that the compression behavior of calcareous sand can be classified into three distinct stages within the logarithmic coordinate system of void ratio (e) and vertical pressure (σv): (1) σv < 2.18 MPa, (2) 2.18 MPa < σv < 4.35 MPa, and (3) σv > 4.35 MPa, with the first and third stages representing linear relationships. Furthermore, the concept of yield stress ascertained within the e–logσv coordinate system proves invaluable in assessing the effects of the initial void ratio (e0) and particle size (d) on particle breakage. Notably, when σv exceeds 2.18 MPa, the relative breakage index experiences a substantial increase. The characteristic particle sizes (d10, d30, d50, and d60) of calcareous sands exhibit a consistent decrease with an increase in the relative breakage index (Br); however, this relationship is independent of e0 but is closely related to the particle size (d) of calcareous sands. The one-dimensional compression characteristics of calcareous sand are effectively represented using a power function relationship, and a formula for calculating the compression modulus (Es) of calcareous sand is theoretically derived. The deformation (Δs) of calcareous sand can be calculated using the index parameters obtained through the Es–σv curve method. In addition, a method for computing the preconsolidation pressure (pc) of calcareous sand is introduced. This method uses the parameter (eb) as an indicator of particle breakage and has been experimentally validated. [ABSTRACT FROM AUTHOR]

In order to further promote the application of cementitious sand gravel (CSG), the mechanical properties and variation rules of CSG material under triaxial test were studied. Considering the influence of fly ash content, water-binder ratio, sand rate and lateral confining pressure, 81 cylinder specimens were designed and made for conventional triaxial test, and the influence laws of stress–strain curve, failure pattern, elastic modulus, energy dissipation and damage evolution of specimens were analyzed. The results showed that the peak of stress–strain curve increased with the increase of confining pressure, and the peak stress, peak strain and energy dissipation all increased significantly, but the damage variable D decreased with the increase of confining pressure. Under triaxial compression, the specimen was basically sheared failure from the bonding surface, and the aggregate generally did not break. Sand rate had a significant effect on the peak stress of CSG, and decreased with the increase of sand rate. Under the conditions of the same cement content, fly ash content and confining pressure, the optimal water-binder ratio 1.2 existed when the sand rate was 0.2 and 0.3. After analyzing and processing the stress–strain curve of triaxial test, a Cuckoo Search-eXtreme Gradient Boosting (CS-XGBoost) curve prediction model was established, and the model was evaluated by evaluation indexes R2, RMSE and MAE. The average R2 of the XGBoost model based on initial parameters under 18 different output features was 0.8573, and the average R2 of the CS-XGBoost model was 0.9516, an increase of 10.10%. Moreover, the prediction curve was highly consistent with the test curve, indicating that the CS algorithm had significant advantages. The CS-XGBoost model could accurately predict the triaxial stress–strain curve of CSG. [ABSTRACT FROM AUTHOR]

Understanding the geometric dimensions of pipes formed during backward erosion piping (BEP) is crucial for comprehending the BEP mechanism and conducting numerical simulations. However, current research primarily focuses on the two-dimensional morphology of pipes, with a lack of sufficient understanding regarding their three-dimensional (3D) characteristics. To study the 3D geometric characteristics of the pipe, the 3D size of the pipe was measured and analyzed using the gypsum injection method and 3D laser scanning method in this study. The variations in pipe depth, width, and the ratio of width to depth were investigated in detail. And the influence of cover plate roughness and sand compactness on the 3D geometry of the pipe was clarified. It is found that the cross-section shape of the pipe is approximately rectangular, with the horizontal scale being significantly larger than the vertical scale. With increasing distance from the outlet hole, there is a gradual decrease in both the depth and width of the pipe. The relationship between the pipe's depth and width with respect to its length can be described using linear functions. As the compactness of sand layer increased, the depth and width of the pipe decreased to a certain extent. [ABSTRACT FROM AUTHOR]

In order to promote the development and utilization of desert sand, this study is based on researching the most suitable ratio of bio-cement, analyzing the shear strength and permeability of improved desert sand by combining bio-cement and fly ash, and clarifying the applicability of tap water in bio-cement. The relationship between the two and the microstructural properties was investigated using the results of the straight shear test and the permeability test. The results showed that the urease solution prepared with tap water had a more pronounced temperature resistance. The urea concentration and the corresponding pH environment had a direct effect on the urease activity. The calcium carbonate yield was positively correlated with the calcium concentration, and the urea concentration was higher in the ranges of 1.0–1.5 mol/L. As the enzyme-to-gel ratio decreased, the calcium carbonate precipitate produced per unit volume of urease solution gradually converged to a certain value. The shear strength (increased by 37.9%) and permeability (decreased by about 8.9–68.5%) of the modified desert sand peaked with the increase in fly ash content. The microscopic test results indicated that the fly ash could provide nucleation sites for the bio-cement, effectively improving the mechanical properties of the desert sand. The crystal types of calcium carbonate in the modified desert sand were calcite and aragonite, which were the most stable crystal types. This study provides innovative ideas for interdisciplinary research in the fields of bioengineering, ecology and civil engineering. [ABSTRACT FROM AUTHOR]

The Mu Us Sandy Land is a region characterized by wind-blown sand and soil erosion in northern China. To enhance the soil quality of this area, various organic materials were incorporated into the mixed soil at a volume ratio of 1:2 for feldspathic sandstone to sand. Culture was conducted in the field and under constant temperature conditions in laboratory culture chambers. Four treatments were established in the experiment, each calculated based on weight ratio and controlled (with no organic material added, CK); single application of straw (5% straw, P1); single application of biochar (5% biochar, P2); combined application of biochar and straw (5% biochar + 5% straw, P3). After 90 days of culture, soil samples were collected for analysis of various indicators such as soil aggregate particle size distribution, water stability of soil aggregates, mean weight diameter, mean geometric diameter, and fractal dimension using dry sieving and wet sieving methods. The objective is to establish a scientific basis and provide technical support for addressing the challenges associated with compound soil and implementing rational fertilization measures. The research results indicate that: (1) The quantity of aggregates > 0.25 mm under different treatments follows the order CK < P1 < P2 < P3, and the differences between treatments are significant (P < 0.05); (2) Soil water stability, mean weight diameter (MWD), mean geometric diameter (GMD), and fractal dimension of soil aggregates in compound soil with different organic material additions are superior to the control, and the effect of biochar on improving soil aggregates is better than that of corn straw. The combined application of both significantly improves the effect compared to single applications. In both culture modes, under wet sieving, the P3 treatment shows the highest MWD and GMD of soil aggregates, with an increase ranging from 3.45% to 85% and 4.55% to 38.46%, respectively, compared to other treatments. (3) The trend of fractal dimension among treatments is consistent: P3 < P2 < P1 < CK, and the differences between treatments are significant (P < 0.05). Moreover, there is a good negative correlation linear equation relationship between the fractal dimension (y) and WR > 0.25 (x) of compound soil, with a correlation coefficient of up to 0.9851. In conclusion, the incorporation of organic materials can effectively enhance the proportion of macroaggregates in compound soil consisting of Feldspathic sandstone and sand, thereby improving soil stability and erosion resistance. The optimal outcome is achieved through the combined application of biochar and straw. Indoor culture proves to be more effective than field culture, while wet sieving accurately reflects the structural characteristics of compound soil under both dry and wet sieving treatments. [ABSTRACT FROM AUTHOR]