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In order to clarify the suction characteristics of unsaturated clay under different conditions of water and salt, taking soil in western Jilin province, China as the research object, the suctions (matrix suction and osmotic suction) of samples with different water content, salt type, and salt content were determined by filter paper method. The results indicate that salt type and content have insignificant influence on the matrix suction. With the increase of water content, the matrix suction decreases at different rates in different suction regimes. When water content is constant, the osmotic suction increases with the increase of salt content, and under the condition of a constant salt content, the osmotic suction first increases and then decreases with the increase of ion concentration of the pore water, and can reach tens of MPa. The concept of suction equilibrium water content is proposed. When water content of sample is higher than this value, the magnitude of osmotic suction will always be greater than that of matrix suction. This indicates the necessity to consider osmotic suction in the presence or change of salt in soil. The applicability of the traditional models of matrix suction and osmotic suction in the full suction range of clay is discussed, and it is found that the traditional models cannot make a full explanation to the variation in suction. Based on the experimental data, an improved van Genuchten matrix suction model and an osmotic suction model, transformed by the Planck blackbody radiation formula, are proposed. [ABSTRACT FROM AUTHOR]

Underground mining has the potential to trigger wide-area surface subsidence, and it is crucial to identify and investigate mining-induced subsidence to reduce potential damages. In recent years, the development of remote sensing and deep learning has brought a novel direction to the automatic identification of mining-induced subsidence. In this paper, we present a comprehensive solution for the automatic identification of mining-induced subsidence using deep convolutional networks based on time-series interferometric synthetic aperture radar (InSAR) data. First, we obtain a surface deformation rate map of the Huodong mining area based on SBAS-InSAR technology. Second, we automatically identify mining-induced subsidence areas from the InSAR deformation map based on a convolutional neural network (CNN) deep learning model. Finally, we summarize the potential risk of surface subsidence to roads in the Huodong mining area. The InSAR results show the detailed characteristics of surface deformation with a maximum subsidence rate of 112.1 mm/year, where the surface deformation is distinctly different between the urban, forest, and mining areas. The deep learning results show 202 identified mining-induced subsidence areas, including the subsidence areas located in the forest which were difficult to distinguish in the InSAR monitored deformation map. This paper demonstrates the potential and capability of deep learning models for more automatic and accurate identification of mining-induced subsidence and provides a comprehensive solution for improving the efficiency of interpreting surface deformation monitoring information. [ABSTRACT FROM AUTHOR]

One of the main products of the mining industry is crushed stone, which is an essential material in structure construction, such as concrete aggregate, asphalt aggregate in road construction, ballast aggregate in railway construction, etc. Due to the application fields, evaluating the durability of these aggregates is required. An economical and durable design cannot be achieved without knowing the resisting capacity of the used stone materials to abrasion, crushing, impact, and disintegration – collectively known as mechanical weathering or degradation. In addition to presenting different forms of mechanical weathering of aggregates, the paper summarizes the most frequently used laboratory tests developed to determine the resistance to these stresses. It introduces various national standards emphasizing their differences and examines the possibility of test result comparability with respect to geology and practical application. The research also presents several empirical relations from the literature between the different degradation parameters. Besides that, the paper aims to give an overview of the international literature that deals with the mechanical weathering of aggregate materials by using organizing tables and comparative graphs; it tries to contribute to the organization and comparability of the existing knowledge and the results found in the literature. [ABSTRACT FROM AUTHOR]

Accurate landslide displacement prediction is an important component to realize landslide warning. For the displacement prediction of landslides, how to improve the prediction accuracy has been the focus on such research problems. Therefore, in this paper, the TS-SSA-LSTM landslide displacement prediction model is proposed as an example for landslides in Anxi County, Quanzhou City, Fujian Province. First, the cumulative displacement is decomposed into trend and period terms by time series. Then, the MIC coefficients are utilized for correlation test to screen the input terms of the prediction model. Then, the prediction models of trend and period terms are established by LSTM model, and SSA algorithm is introduced in this process for optimization. Finally, after obtaining the prediction results of the trend and period terms, the displacement data are reconstructed according to the basic theory of time series to obtain the final displacement prediction results. By comparing the RMSE, MAE and R 2 of the TS-SSA-LSTM landslide displacement model with those of the traditional RNN and LSTM landslide displacement models, it is shown that the established landslide displacement prediction models have higher accuracy and stability. From the prediction results of TS-SSA-LSTM, the deviation from it and the real monitoring value is small and the fitting degree is high, which indicates that the TS-SSA-LSTM types proposed to this paper can effectively predict the displacement change of the landslide in the study case. [ABSTRACT FROM AUTHOR]

In the process of coal mining, the original state of rock strata is seriously damaged and a large number of fractures are produced. If the fracture is connected to the overlying natural water body, leakage of surface water and ground water will cause serious mine water damage and lack of regional water resources. If the fracture is connected with gob water containing harmful gases and substances, in addition to the occurrence of mine water damage, it will pollute the water body. In the process of mining extra-thick coal seams, water inrush accidents caused by the development of large-space overburden fracture are more frequent, which causes more serious loss and pollution of water, and even desertification of land. In this paper, digital panoramic imaging technology is used to monitor the movement of overburden rock during the mining process. A reasonable time for fracture grouting sealing was proposed based on the similar simulation experiment and the evolution characteristics of fracture fractal dimension and a reasonable ground grouting sealing scheme was designed. The field monitoring results show the grouting effectively seals the fractures and reduce air leakage and solve the risk of gob water leakage above the working face. The research in this paper reveals the evolution characteristics of large-space overburden fractures in extra-thick coal seam mining with hard roofs. It shows that ground grouting sealing is an effective means to reduce the secondary disasters of fracture development, which has practical value and practical significance for environmental protection and coal safety development. [ABSTRACT FROM AUTHOR]

Studying the disturbance patterns of surrounding rock and soil during TBM excavation holds great significance in ensuring the safe construction of tunnels. Geomechanical model testing serves as an effective approach for such research. However, the current model tests suffer from lengthy curing times of rock similar materials and the simplification of tunneling simulation devices. To address these issues, this paper presents an innovative approach by preparing a rock similar material with early strength and good brittleness and utilizing a self-developed scaled TBM testing machine for rock breaking simulations. The conducted tests demonstrate that an increased content of sulphoaluminate cement significantly enhances the compressive-tensile ratio of the rock-like similar materials, thus indicating the excellent performance of the developed materials. The impact zone of TBM tunneling primarily encompasses the surrounding rock within 0.5D in front of the tunnel face and 2D at the rear. The proposed method for similar material preparation and the model test device put forward in this paper can serve as valuable references for similar tunneling experiments. [ABSTRACT FROM AUTHOR]

The platforms of old landslides triggered by historical earthquakes have often been important residential and agricultural places in active tectonic regions. In recent years, many old landslides have been reactivated due to various causes. Previous studies have shown that the hydrodynamic effect is an important triggering factor for landslide reactivation. However, as an old landslide has undergone a long consolidation period, the permeability of deposits is generally very low, and surface water can hardly infiltrate into deep zones of landslide deposits. Through field investigation, it is found that many old landslides are reactivated due to the coupled action of water infiltration and cracks in the east Tibetan Plateau. The cracks are controlled by fault creep in the initial formation process. In this paper, taking the Chashushan old landslide in the upstream of Jinsha River as a case study, field investigation, experimental study, numerical simulation, and PS-InSAR technique are performed to investigate the reactivation mechanism of the old landslide. The influences of cracks, rainfall, and canal leakage on old landslide reactivation are discussed. The cracks controlled by fault creep provide channels or media for the rapid infiltration of surface water, which is the triggering factor of landslide reactivation. The results in this paper can provide an important reference for research on the reactivation mechanism and risk control of old landslides in the east Tibetan Plateau and even in active tectonic areas around the world. [ABSTRACT FROM AUTHOR]

The bearing characteristics of random lumpiness gangue formed by rock fragmentation in gob roofs are important to ensure roadway stability in the new nonpillar mining approach. In this paper, the bearing characteristics of gangue are divided into bulking and compaction characteristics. Bulking characteristics mainly depend on the lumpiness and bulking coefficient of randomly lumpy gangue (KRAFT). This paper proposes a method to invert KRAFT of gangue samples with a small amount of lumpiness, and a random subset of 30% of an experimental sample of broken rocks is selected for analysis. The lumpiness distributions of the subset of samples and all the samples are normal, and the average lumpiness error of the subset is 0.54–2.86%. The ratio of average lumpiness to rock before breakage (KASB) is introduced as a parameter for analysis. The results show that KASB and KRAFT have a log-normal functional relationship, and KASB can be used to infer KRAFT from laboratory and field monitoring data. Compaction characteristics show that the relationship between KRAFT and the supporting force of gangue (σGB) is a power function, and σGB in gangue during different stages of compression in a gob can be obtained from the value of KRAFT obtained from experiments or field monitoring. [ABSTRACT FROM AUTHOR]

The strength reduction method (SRM) is widely used in calculating the factor of safety (FOS) of a slope, and the key of this method is to select the appropriate instability criterion. At present, the commonly used instability criteria include displacement mutation, plastic zone penetration, calculation program nonconvergence, and energy mutation. To avoid human error in these criteria and find a unified mechanical explanation for slope instability, a new criterion, the variational criterion, is proposed in this paper. With this criterion, the slope stability is determined by identifying the positive or negative of the variational value. This criterion avoids the human error of other criteria and provides a unified and definite index for judging slope instability. The FOSs of two-dimensional and three-dimensional slopes calculated by this criterion are compared with those calculated by other criteria and classical papers, which verifies that this criterion is applicable and accurate. The effect of the mesh size on the accuracy of the results is analyzed, and the newly proposed criterion is applied to a variety of common slopes. It is further demonstrated that the proposed criterion is not an accident of numerical calculation and some examples but is universally applicable and accurate. [ABSTRACT FROM AUTHOR]

Grouting process in shield construction plays an important role in controlling surface deformation and ensuring structural stability. The soil in water-rich areas has large water content and strong self-stability, and inappropriate grouting parameters will result in surface settlement and slurry dilution. The purpose of this paper is to propose a calculation method for grouting parameters in water-rich areas to ensure grouting effect and reduce deformation. Firstly, based on the maximum balance condition of soil, this paper derived a calculation equation for optimum grouting pressure considering the self-stability of soil by introducing the safety factor. Then, it analyzed the cause of the slurry loss, and the method for determining each expansion coefficient taking into account the time-varying nature was given. Finally, it put forward a method for modifying the mix ratio of grouting slurry in water-rich areas. In addition, it analyzed the relationship between grouting parameters and surface settlement through an engineering example. The study shows that the stability of the tunnel is related to the nature of the soil and the size and depth of the tunnel. The grout loss caused by the slurry infiltration is the most serious, and the slurry with modified mix ratio has excellent and stable performance. The grouting parameter determination method proposed in this paper improves the accuracy of parameter selection and has smaller surface settlement, which provides theoretical guidance for grouting construction in water-rich areas. [ABSTRACT FROM AUTHOR]

Brittle failure of rock masses poses a great threat to safety and property in underground engineering and slope engineering. It is necessary to develop effective methods to evaluate the damage degree of rock masses and make predictions of sudden failure. In this paper, a new method is proposed to extract damage information about rocks from acoustic emission (AE) data, and three indicators are obtained: the average local maxima of the frequency response along the propagation path (ALM), the average correlation value (ACV), and the standard deviation of the main frequencies of different signals (SD). Lead break tests and uniaxial compression tests are conducted to verify the applicability and effectiveness of the indicators. The results show that the frequency of the elastic wave will change after the elastic wave propagates along a path. When final failure state is approached, the ACV often decreases, while the ALM and SD increase. The p value based on a comprehensive analysis of the three indicators is convenient for estimating the damage degree, and it performs better than the traditional b value in predicting final failure when experimental conditions are suitable. The method proposed in this paper provides a new way to analyze AE data by focusing on the differences in waves from different sensors instead of the rupture sources. The indicators can provide precursor information for the failure and damage degree of rock masses. [ABSTRACT FROM AUTHOR]

An unbalanced rockburst dataset will restrict the accuracy and reliability of rockburst prediction based on machine learning. Therefore, a new oversampling algorithm was proposed based on Copula theory and Monte Carlo simulation to balance the dataset. This paper collected 243 rockburst cases worldwide. The predictors of rockburst used in this paper include the maximum tangential stress of the surrounding rock, the uniaxial compressive strength of rock, the tensile strength of rock, and the elastic energy index. During oversampling, Copula theory determined the predictors' joint distribution function by considering the correlation among predictors. Then Monte Carlo simulation was performed to generate enough data for oversampling according to rockburst classification standard. Six common machine learning methods with tenfold cross-validation were adopted to establish nonlinear models between predictors and rockburst grades. The accuracy rate of rockburst prediction has increased by 9.3–15.5% after oversampling. The prediction performance is better than the commonly used synthetic minority oversampling technique. Finally, rockburst predictors' importance was evaluated with the initial dataset, and the elastic energy index got the maximum value of 0.41. The proposed oversampling algorithm in this paper can reasonably overcome class imbalance and improve the prediction performance for rockburst. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the distribution of various types of debris flows along the traffic artery. By examining the distribution of debris flows, the study found that the most conducive geological and tectonic conditions for debris flow formation are located 5–30 km from the main fault and experience peak ground motion acceleration of 0.15 g or 0.20 g. In the study area, debris flows are primarily concentrated in the plateau mountainous region, where the annual average temperature ranges from 4 to 8 ℃ and the annual average rainfall is less than 1000 mm. The paper further examines four key factors contributing to the hazard tendency of debris flows. It discusses in detail the underlying trends in tectonic activity and climate change and how these factors may impact the hazard tendency of debris flows in the study area. By using fuzzy synthesis method, the paper presents the distribution of debris flow hazard tendency within the study area. The study found that 11.9%, 30.8%, 31.0%, 10.4%, and 15.9% of the total area have very high, high, medium, low, and very low risk of debris flows, respectively. Of the 575 debris flow gullies identified by field investigations, 8%, 39%, 49%, 4%, and 0% were classified as having an extremely high, high, medium, low, and extremely low risk of debris flows, respectively. This indicates that the Sichuan–Tibet traffic corridor will remain a high-risk area for debris flows in the future due to the influence of active faults and climate change. [ABSTRACT FROM AUTHOR]

Water retention is an important soil property affecting the hydro-mechanical behavior of unsaturated soils. This study investigated the water retention property and the microstructure of lime-treated Ili loess from Xinjiang in China. Such material is a typical central Asian loess characterized by high salt content and strong collapsibility. The matric suction and total suction were measured by the filter paper method and saturated salt solution method. The microstructure characteristics of untreated and lime-treated loess were analyzed by scanning electron microscopy and mercury intrusion porosimetry, and the influence of the microstructure variation on the macroscopic water retention property was analyzed by introducing the parameter of fractal dimension, which is commonly used to describe the characteristic of pore shape and size. Results showed that, along the curing time, the lime treatment induced a change of the soil microstructure in terms of pore distribution with a consequent increase of the matric suction and overall water retention capacity. However, the osmotic suction decreased during curing. During curing, the lime treatment reduced the percentage of macro-pores and increased the nano-pores. Then, the soil microstructure was characterized by the fractal dimension, which increased with the curing times. Finally, the proposed fitting model of water retention consisting in introducing the fractal dimension into the Van-Genuchten model appeared adequate with good accuracy. [ABSTRACT FROM AUTHOR]

The use of instrumentation in monitoring or evaluating geodynamic phenomena such as landslide, ground subsidence, earthquake, as well as engineering structures such as dams, foundations, deep excavations, landfills, tunnels and underground openings is widespread. The data of common instruments including piezometers, load/pressure cells, settlement-meters, extensometers, inclinometers, tiltmeters, etc. accumulates over time and forms a huge volume which, without having a proper database and application, causes many problems for users. Therefore, it is essential to create a database/application to store and analyze such periodic datasets in an integrated environment. ArcGIS as a good geospatial platform was used to store, retrieve, analyze, and visualize the instrumentation data. Being one of the most complex types of projects in terms of spatial arrangement of instruments, the embankment dam was chosen, the data of which was used to develop a geodatabase/application. For the purposes of this paper, a relational geodatabase is designed based on data from instruments installed in a dam in NW Iran. Then, a new Dam Data Analysis Application (DDAA) Toolbox was developed using ArcGIS ModelBuilder. DDAA provides valuable custom maps/charts in cross and longitudinal sections of the dam for parameters of pore-pressure, pore-pressure ratio, total stress, arching ratio, and displacement. Also, the toolbox was carefully evaluated and a complete correlation of observations with model-driven results was obtained. It is emphasized that the main purpose of this paper is to develop a geodatabase/application to manage instrumentation data rather than to analyze the behavior of a specific structure. [ABSTRACT FROM AUTHOR]

The amount and variety of waste materials used in civil engineering are steadily increasing due to the depletion of natural resources and the implementation of environmental policies. A new mixture of colliery spoils and fluidized bed bottom ash was recently developed in Poland, which proved to be prone to excessive, long-term swelling, potentially damaging structures such as road embankments. Numerous papers discuss the heaving mechanisms in spoils or fluidized bed ash. However, no reports analyzing the expansion of their mixture seem to be available. The purpose of this paper is to fill this void. The experiment involved measurements of linear swelling of mixture samples stored inside CBR test molds and isolated from moisture loss/gain. Material expansion is caused by the reactivity of the fluidized bed ash; its content in the mix correlates positively with the final swelling strain. At the same time, colliery spoils provide an environment particularly conducive to the phenomenon’s occurrence. A linear swelling strain of 0.3–3.2% was observed after 6 months (disregarding the first 24 h of rapid volume growth). The expansion of mixtures was also measured under constant compressive stress of 0–100 kPa to better represent their actual working conditions. Based on the results, it is proposed to adapt a mathematical model developed for anhydrite-rich rock to describe the load-swelling relationship in mixtures of colliery spoils with fluidized bed bottom ash. Such a model can be potentially used, e.g., in numerical analyses, to assess the impact of the material’s expansion on embankments. [ABSTRACT FROM AUTHOR]

Landslides and ground subsidence resulting from changes in soil-water characteristics during drying and wetting cycles present a severe hazard to the environment and human life in the Loess Plateau region of China. In this study, the soil-water characteristic curve (SWCC) evolution mechanism during drying and wetting cycles was carried out on compacted loess with various dry densities. The samples were subjected to three cycles of drying-wetting, and the change of matric suction was measured using the filter paper method. Additionally, nuclear magnetic resonance (NMR) technology was used to study the change in the pore size distribution (PSD) before and after the drying-wetting cycles. The results reveal that as the dry density increased, the saturated volumetric water content decreased, the SWCC slope gradually decreased, and the air entry value increased. Furthermore, the drying-wetting cycles increased the aggregated volume and macropore diameter, and their effect on SWCC intensified with dry density. Based on experimental observation, a simple method to calculate the surface relaxivity ( ρ 2 ) was proposed. Finally, the Weibull distribution function was innovatively applied to predict the PSD, achieving highly satisfactory accuracy. These results have practical implications for the construction and protection of loess engineering in the Loess Plateau region. [ABSTRACT FROM AUTHOR]

Freeze–thaw cycle is one of the primary rock physical weathering agents which causes the deterioration and softening of rocks in cold regions. The frost-weathered rocks are prone to damage and destruction under loading. Determining the deterioration and stress–strain behavior of rocks following cyclic freezing and thawing is of crucial importance for evaluating the stability of rock excavation engineering in cold regions. A long-term artificial freeze–thaw cycles test on fresh sandstone samples was designed in this paper. The saturated condition was selected to accelerate the effect of freeze–thaw weathering. The mechanical behavior of the specimens undergoing different freeze–thaw cycles was further investigated through the uniaxial compression test. Experimental results indicate that the cycling of freezing and thawing causes a gradual decline in uniaxial compression strength followed by a rapid fall. An obvious beginning compaction stage can be observed in the stress–strain curve and the strain of the compaction stage increases during the freezing and thawing process. The deterioration of the sandstone was expressed by uniaxial compression strength, elastic modulus, and frost resistance coefficient in a piecewise decay model. A damage critical point can be distinguished in the model. Then, piecewise damage strain equations under the combination of freeze–thaw action and loading were derived by introducing the damage mechanics theory. The presented model was validated by the test results in this paper and a published article. It demonstrates that the simulated data agree well with the test results, indicating the effectiveness of the presented model in describing the stress–strain behavior of sandstone suffering long-term freeze–thaw weathering. [ABSTRACT FROM AUTHOR]

Landslide-induced waves often result in severe casualties, economic losses, and even catastrophic consequences, which are far more destructive than the landslide itself. In this paper, accurate geomorphological and geological characteristics of the Wangjiashan landslide in Baihetan Reservoir, southwest China, were obtained through field investigations, and a three-dimensional model was built for numerical calculation. Through the time series curve of cumulative deformation, the water level variation of the reservoir was found to be the major factor causing the landslide deformation and eventual failure. The generation and propagation progress of water waves induced by the Wangjiashan landslide was simulated by coupling the granular flow model and renormalization group turbulence model in FLOW3D. The results show that a large sliding mass silts up the channel, forming a landslide dam with a maximum height of 21.5 m. Nevertheless, it does not block the channel and will not affect standard navigation on account of the wide channel in this area. The maximum run-up wave height of waves spreading to the Xiangbiling resettlement area on the opposite bank is 3.7 m. As the resettlement area is only 1.3 km away from the landslide, and its elevation is only 2.5 m higher than the normal water level of the reservoir, landslide-induced waves should be considered a potential threat. The most vulnerable area affected by landslide-induced waves is about 8 km long along the river, where wave run-up heights are more than 1 m. The results in this paper have important reference values for the early warning and prevention of potential disasters caused by landslides and landslide-induced waves. [ABSTRACT FROM AUTHOR]

Landslides are a major cause of losses and damages in railways and roadways which cross hilly regions. Some landslides may cause traffic interruption for several days, leading to severe prejudice to cargo flow in busy transportation systems. Landslide studies are essential to identify potentially unstable areas, and their consequent impact on infrastructure, and prioritize critical areas to implement failure prevention measures. This paper presents the results of a Landslide Hazard Analysis Program (LHAP) developed to evaluate failure-prone slopes along a 41-km rail that crosses the “Serra do Mar” mountain range, located in the southeastern region of Brazil. This railway was built in the late 1920s and is still vital to transport commodities from the Brazilian countryside to the major port in Brazil, located in the city of Santos. The paper shows how local geological-geotechnical conditions, associated with construction peculiarities, resulted in a very fragile infrastructure. Recent failures caused severe losses and damages to the railway system, leading to traffic interruption for several days and prejudice to cargo flow. The Landslide Hazard Analysis Program was developed to identify and understand the main causes of slope failures and prioritize intervention with basis on failure susceptibility and consequences to the railway. A failure prevention program was developed with basis on the results and consisted in stabilizing slopes with both temporary and permanent retaining structures as well as restoring and implementing a new drainage system. The methodology presented in this paper could be validated with basis on data from five slope failures that occurred in cut slopes after the ranking had been defined, demonstrating the suitability of the analysis. With some adaptations, the methodology may be used in similar linear structures such as roadways, pipelines, and others. [ABSTRACT FROM AUTHOR]

Data-driven stability prediction of slopes on the basis of survey data plays a vital role in geohazard prevention. A critical issue in data-driven stability prediction is that many factors can affect slope stability and have varied influences. Exploring the influence of different factors on the prediction model is helpful to improve its accuracy. In this paper, we used machine learning methods to predict soil slope stability based on soil slope survey data from four cities in Hunan Province, and evaluated the effects of groundwater and lithology on soil slope stability prediction. First, we analyzed and selected features using machine learning methods, i.e., random forest combined with SHapley Additive exPlanation (SHAP) values. Second, we constructed four machine learning models and compared the performance of the models. Finally, the best machine learning model was selected, and the influence of groundwater and lithology on the prediction of soil slope stability in the study area was explored using the SHAP method. The results show that the prediction accuracy and recall rate of the model decrease when only lithology is considered, while the prediction accuracy cannot be improved when only groundwater is considered. However, when combined with lithology, the prediction performance can be improved, and the accuracy and recall rate of the model are both improved by 0.01, and F-measure is improved by 0.02. The results of this paper can help improve the prediction accuracy of soil slopes in geohazard prevention. [ABSTRACT FROM AUTHOR]

Separation grouting filling technology is widely used in surface subsidence management because of its simple process and good overburden control effect, while the changing pattern of overburden off-layer space (OS) during the mining process plays a key role in the selection of grouting timing and rock control effect. In this paper, the law of OS development and the mechanism of rock movement control by gangue slurry filling is studied by combining numerical simulation and physically similar simulation experiments with the engineering background of the 3−1801 working face of Hongqinghe coal mine. The results of the study indicate that the OS undergoes a slow growth period, an accelerated expansion period, a slow decrease period, and an accelerated decay period during the development process. The change of OS is closely related to the form of key layer bending and sinking, and the change of key layer from V-type sinking to basin-type sinking during the mining process is the turning point when the OS starts to decay faster, and timely grouting and filling before the turning point can effectively control the key layer breaking and sinking, reduce the stress concentration, and the effect of rock layer sinking reduction is obvious. The research results of this paper have certain theoretical value and practical significance for the technical scheme design of OS grouting and gangue filling treatment. [ABSTRACT FROM AUTHOR]

Heterogeneity is an essential feature of rock, while most rock mechanics models only adopt conventional rock physical properties and ignore the influence of heterogeneity. Quantifying rock heterogeneity is of great significance for accurately predicting rock mechanical properties. This paper introduced homogeneous coefficient to quantify rock heterogeneity and designed a model for automatically evaluating rock homogeneous coefficients by combining computer tomography and image recognition technology. In addition, this paper optimized the model parameters by correlation analysis and sensitivity analysis to predict various rock mechanical properties. When using rock homogeneity coefficient as a model parameter, the predicted loss value of rock strength is 2.95%, which is 25.7% lower than that of the model without rock homogeneity coefficient. The predicted loss value of elastic modulus is reduced by 3.9%, while it is almost unchanged for Poisson’s ratio. Empirical equations are also proposed adopting optimized model parameters, providing reliable predicted results as accurate as artificial neural network model. The Pearson correlation coefficient for rock strength could reach 0.9537. In this paper, the mature technology combination in the computer field is applied to predict rock mechanical properties, which shows great application prospects. [ABSTRACT FROM AUTHOR]

Rockburst is a common geological disaster in the process of deep rock excavation, and stress gradient is an important factor affecting rockburst. In this paper, the concept of “stress concentration” was proposed. The relevant data of a large number of engineering rockburst cases were statistically analyzed, and a new rockburst criterion of stress–strength ratio considering stress gradient of surrounding rock was established. The research results revealed that the rockburst criterion considering the stress gradient distribution of surrounding rock could effectively overcome the problem of non-uniform division of rockburst criteria in the traditional strength-to-stress ratio. It can fully reflect the influence of tunnel size effect on rockburst. There was a significant correlation between rockburst strength and stress gradient, and different rockburst strengths showed obvious zoning concentration phenomenon on the two-dimensional plane. The established rockburst criterion considering the stress intensity ratio of surrounding rock had strong applicability, and the prediction accuracy could reach more than 90%. The proposed rockburst criterion in this paper has certain theoretical and engineering guiding value for the early warning of underground engineering disasters. [ABSTRACT FROM AUTHOR]

The design of various components of underground trenchless constructions requires geotechnical parameters as inputs. Currently, determination of geotechnical parameters for application in the design of trenchless constructions relies heavily on the standard penetration test (SPT) and corresponding N-value. However, N-values are often misinterpreted in practices, resulting extracted geotechnical parameters poorly representing the true soil conditions. Especially among the numerous empirical methods available related to N-value, it is challenging for practitioners to find an appropriate empirical correlation for their projects. This paper summarizes ten geotechnical parameters that are often required for trenchless design, including internal friction angle, modulus of elasticity, shear modulus, undrained shear strength, modulus of soil reaction, constrained soil modulus, preconsolidation stress, overconsolidation ratio, relative density, and porosity. Empirical methods based on SPT for determining the geotechnical parameters required in trenchless design are reviewed with ninety-eight correlations between the geotechnical parameters and N-value. Furthermore, comparisons between the SPT correlations are made to provide insight on determining the geotechnical parameters. Four laboratory examples from literature sources related to the design of horizontal directional drilling (HDD) are studied to demonstrate the usefulness of the systematic determination of geotechnical parameters using SPT correlations. Compared to geotechnical parameters provided by researchers that conducted the laboratory experiments, geotechnical parameters determined using SPT correlations resulted improvement in precision by 17% for the estimation of maximum allowable annular pressure in HDD. With application of a correction factor that is commonly used among practitioners, the maximum allowable annular pressure estimated using SPT correlations are found nearly equal to the measurements of annular pressure at hydraulic fracture, confirming that SPT-based empirical methods reviewed herein are reasonably reliable for trenchless design. [ABSTRACT FROM AUTHOR]

The quality and cost-effectiveness of rock core samples and rapid rock coring are main issues that need to be considered in the special operations of oil and gas fields and coal mines, such as opening coal seams with gas outburst, detecting fault distance or lithologic pinch out. Soft rock coring technology has a lot of work to do to improve coring quality and coring speed. In this study, pressure maintaining continuous coring technology (PHCCT) and equipment was developed, and the new coring method was compared with traditional coring method in terms of coring speed, core quality, and rock quality index (RQD). Compared with traditional coring method, the coring speed of PHCCT was almost doubled, and the RQD value of rock stratum was increased; however, the PHCCT method had little effect on the RQD value of coal bed. In this paper, the process parameters and technological measures of PHCCT were also discussed, the drilling fluid pressure of 6 MPa and the drill bit outer diameter of 94 mm were reasonable, and the drilling fluid pressure-holding of PHCCT was realized through the sealing device of drill pipe and sealing fixing borehole. The PHCCT method has great significance for the coring of coal seam and soft rock stratum. [ABSTRACT FROM AUTHOR]

Rock mass integrity is related to rock mass quality and strength. It can be characterized by a single index, or a combination of multiple indices. In this paper, the rock mass integrity classification index and corresponding classification scheme are described. The relationship between intactness index and rock mass structure index in the RMR89 system is examined, and the relationship between Kv and Q′, representing the rock mass structure index in the Q system, was determined. Results of the case study show that there is a good correlation between Kv and the sum of the RQD ratings, joint spacing D, and the joint conditions in the RMR89 system. A better correlation exists between Kv and GSI|2013, a quantitative expression of GSI proposed by Hoek et al. (2013). Based on the above correlations, if a certain rock mass integrity index is unavailable in an engineering project, other indices can be used as alternative to complete the rock mass quality evaluation; however, because the data employed in this paper are from only two projects, the similarity of rock mass conditions should be thoroughly considered. More research is needed to supplement, validate, and revise the results of this study in the future. [ABSTRACT FROM AUTHOR]

In previous research concerned on mercury intrusion porosimetry (MIP), the fractal curves of six fractal models tended to have segmentation characteristics. However, most of these models are rarely applied to loess pores and often have inconsistent results. Therefore, this paper used a combination of techniques to study the loess pore structure and permeability properties, including routine tests, MIP analysis, and scanning electron microscope (SEM) image analysis. The results indicate that different models have various goodness of fit and fractal dimensions. Among them, the Zhang-Li model had the best fractal features. However, there are certain similar segmentation diameters between different fractal curves, suggesting that the segmentation diameters are determined by the pore structure, rather than by the fractal models. By using a new modeling detection method, the paper determined that the segmentation diameters are centrally distributed around two diameters: d1 (7.08 μm) and d2 (0.035 μm). The pore structure is divided into three regions based on these two diameters. Furthermore, the paper proposes a new parameter λ, the relative content for pores with diameters larger than d2 (0.035 μm), which is used to correct effective porosity and permeability prediction. The traditional K-C equation is only 68.41% of the goodness of fit in predicted and measured values. After correcting the porosity, it rises to 77.99%, while the correcting prediction equation based on the pore-size distribution function is 80.46%. These results prove that our new segmentation method for loess pore structure and effective porosity correction is reasonable for permeability estimation. [ABSTRACT FROM AUTHOR]

The destruction of mountain landform by forest fire often leads to the outbreak of catastrophic debris flow. In March 2020, a huge forest fire broke out in Xiangjiao Gully, seriously damaging the mountain landform and leading to the outbreak of a catastrophic debris flow on July 5th, 2021. To mitigate such disasters more scientifically, this paper analyzes the disaster characteristics of the “7·05” catastrophic debris flow and studies the cause mechanism and mitigation countermeasures. The results show that the debris flow density ranges from 1.831 g/cm3 to 1.930 g/cm3, belonging to viscous debris flow. The velocity of each section point is between 7.22 and 9.78 m/s, with huge kinetic energy. Forest fire, torrential rainfall, and gully terrain conditions combined to cause the outbreak of the debris flow. The rainfall intensity of the maximum rainfall point reached 77.84 mm, corresponding to a recurrence period of more than 200 years. The forest fire severely damaged the landform, and the high-intensity burned area reached 59.97%, which led to a surge in loose materials and wood debris. Combined with steep terrain, channel erosion and the blocking-bursting effect are prominent, leading to the scale amplification of debris flow. The peak flow of the upstream section D1 and the downstream section D6 are 308.21 m3/s and 759.08 m3/s, with the scale expanded by 2.46 times. To mitigate the harm of Xiangjiao Gully debris flow, this paper deduced the determination method of the optimal hydraulic section of a Rectangle-V-shaped drainage canal under the limited conditions. The calculated characteristic parameter of the section is m = 11.75, h2 = 0.60 m. [ABSTRACT FROM AUTHOR]

Large deformation and support failure of a tunnel with poor lithology, which significantly threaten the stability of the tunnel, have always been major difficulties in underground engineering construction. This paper describes a case study of the failure mechanisms and support design for tailrace tunnels that cross a wide fracture zone in the Wuyue pumped storage power station in Henan Province, China. Geological investigation and mechanical experiments, including large-scale triaxial tests, X-ray diffraction, and free swell tests, were performed to reveal the failure mechanism of the tailrace tunnel. It was observed that the surrounding rock of the tunnel is a completely weathered granite that is characterized by extremely poor rock mass quality, severe deformation, and significant expansibility. Based on the failure mechanism and combined with the concept of “inner and outer load-bearing structures”, a multilevel support system with “long anchor bolts + anchor bolts + rigid arch” as a core is proposed with consideration of the rotation of the principal stress axis. Numerical simulation was adopted to verify the rationality of the proposed support system compared with other support conditions, i.e. no support and uniform support. The results indicate that the proposed support system effectively improves the principal stress state of a tunnel with poor lithology and controls the large deformation of the surrounding rock, especially in the floor and inclined sidewall. Additionally, three successful application cases were introduced to promote the utilization of the proposed support, and possible improvements in enhancing engineering applications were evaluated. The support methodology presented in this paper can support the design of other engineering projects in complex geological environments. [ABSTRACT FROM AUTHOR]

With the resource exploitation from the shallow to the deep, how to effectively control the deformation and floor heave of roadway in soft rocks has become an important factor affecting the safe mining of resources. For deep mining, the serious supporting problems and destruction of the surrounding rock are widespread. This paper takes a testing gallery in China’s Huainan mining area as an example to study the deformation and failure behavior for deep roadway in soft rocks. Combining the geological environment characteristics of the roadway, the indoor creep test of soft rock and the large-scale triaxial creep tests on site are carried out, and the nonlinear creep constitutive model of soft rock and its numerical realization method are proposed. Then, the nonlinear creep model is applied to a particular case of the testing gallery in soft rocks. According to the long-term deformation monitoring data of surrounding rock, the mechanical parameters of loose zone are determined by the orthogonal design method. The results show that the deformation and floor heave of the roadway is mainly due to the obvious creep deformation caused by the weak surrounding rock under the high ground stress level. The model proposed in this paper can better reflect the creep characteristics and nonlinear characteristics of soft rock under different stress levels. The research results have important reference value for long-term deformation prediction and supporting system optimization of deep roadways in soft rocks. [ABSTRACT FROM AUTHOR]

In addition to the high stress, hard rocks around deep mine entries are also subject to the disturbed stress by mining activities nearby, which increases the risk of rockburst incidents. One preventative measure is the employment of drilling pressure relief (DPR) on hard rocks. This paper analyzes the borehole parameters effects on strength weakening of red sandstone through numerical simulation based on the finite difference method. Input parameters for the numerical simulation were determined by the calibration with laboratory test results. A series of uniaxial compression tests were conducted on red sandstone specimens (100 mm × 50 mm × 50 mm). The mechanical properties and strain energy characteristics of red sandstone were analyzed under different drilling schemes (borehole number, borehole diameter, borehole depth, borehole position, and borehole arrangement angle). The results show that the uniaxial compressive strength (UCS) and strain energy storage capacity of red sandstone decrease by 1.60-39.20% and 35.84-92.77%, respectively after DPR. Moreover, there is a positive correlation between the UCS and elastic strain energy. Further sensitivity analysis of borehole parameters has concluded that the UCS of the specimens is significantly affected by the number of boreholes. In contrast, the borehole diameter prominently affects the strain energy storage capacity. This study verified that DPR has a substantial strength-weakening effect on hard rock, providing a theoretical foundation for further improving the mechanism of DPR in rockburst prevention. [ABSTRACT FROM AUTHOR]

Stronger soil layer within a layered slope is of no concern as the stronger soil layer provides extra stability. But if the relatively stronger soil layer has less permeability, it will cause hindrance to the natural infiltration processes and makes the slope vulnerable. This paper presents the results of a series of laboratory tests and numerical analyses on 45º inclined homogeneous and non-homogeneous unsaturated sandy slopes subjected to continuous rainfall. The non-homogeneous slopes consist of less permeable but stronger silty-sand (NH) layers located at different locations of an otherwise homogeneous sandy soil slope. It is observed that the inclusions of NH layers within the homogeneous sandy slopes trigger a failure during continuous rainfall. The NH layers prevent the seepage of the infiltrated rainwater through the slope. As a result, the water content increases rapidly just above the NH layers and consequently the suction pressures in the soil and its shear strength just above the NH layers decrease. With the rainfall duration, the positive pore water pressures buildup just above the NH layers. This induces a slope failure with the failure plane passing above the NH layer. A discontinuity of the shear plane is also observed in the case of a multiple NH layered soil slope. [ABSTRACT FROM AUTHOR]

This paper investigates the use of a protective pile row barrier to mitigate the risk due to a deep excavation in soft soils adjacent to an existing tunnel. The study includes two reduced-scale 1 g model tests with and without the barrier, along with monitoring data from a case history in Wuhan, the Huazhong Science and Technology Industrial Park basement; physical testing and numerical sensitivity study results are compared to the case history to evaluate the barrier efficiency. The monitoring data show successful excavation and basement construction within allowable displacement thresholds in the presence of the barrier. The entire tunnel settled and translated towards the excavation, although different types of ovalization of the tunnel cross-sections were recorded depending on their alignment to the excavation (centre and corners). Experimental results indicate that the pile row barrier can withstand a portion of the soil pressure on the diaphragm wall, leading to a substantial reduction in tunnel bending moments and displacements; in particular, experimental results showed a greater percentage reduction in settlements than horizontal movements of the existing tunnel. When a pile row barrier is constructed in proximity to the retaining wall, it can help to minimise the detrimental effects of the deep excavation on the existing tunnel, similar to twin retaining wall scenarios. [ABSTRACT FROM AUTHOR]

For reservoir landslide, in addition to hydrological conditions, creep properties of soils play an important role in explaining the mechanisms behind landslide movement. When studying the creep characteristics of geotechnical materials in reservoir area, most of them only consider the influence of a single factor (i.e. confining pressure, water content or osmotic pressure) on the creep behavior at present. In order to better describe the creep behavior of clay–gravel composite, this paper considers the effects of the initial water content and the saturation-undersaturation cycle together on the creep properties, and introduces the time-damage function to establish a novel creep-damage constitutive model. Compared with the classical Burgers model, this model can well characterize the creep experimental data with high accuracy, especially in the accelerated creep stage. Then, FLAC3D software is used as a platform to realize the proposed model applied to the long-term stability analysis of Woshaxi landslide by using C + + language. Comparing the Burgers model by the calculation, the proposed model shows a better reflection of the effect of initial water content and the number of saturation-undersaturation cycles on creep as well as being able to describe the accelerated creep phase. It is hoped that this research can provide scientific and engineering application value for the mitigation of the disasters on the reservoir bank slope. [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]

This paper aims to comprehensively update seismic hazard assessments for Sudan and South Sudan using the Probabilistic Seismic Hazard Analysis (PSHA) method. To achieve this goal, a new and up-to-date earthquake database was developed, which includes a newly unified and updated declustered catalog, earthquake sources, and focal mechanism database. Different magnitudes were homogenized to the moment magnitude (Mw) using region-specific conversion relationships based on orthogonal regression. In addition, two types of seismotectonic idealization were considered in the seismicity assessment: the area source model and the linear (fault) source model. Focal mechanisms were used to refine the stress regime for seismicity sources derived from formal inversion analysis. To handle uncertainty, the logic-tree framework is employed, with three different Ground Motion Prediction Equations (GMPEs). The results are obtained in terms of the PGA and for the first time the spectral accelerations at two vibration periods of 0.1 s and 1 s for 475 and 975 years return periods, respectively. Hazard curves and Uniform Hazard Spectra were obtained for three considerably vulnerable cities, and PSHA disaggregation was performed in the highest risk regions with nearby seismic sources. The highest PGA values were 0.195 g and 0.285 g, with a 10% and 2% chance of exceeding these values in 50 years, respectively, in South Sudan along the western branch of the East African Rift System (EARS). In view of the increase in population and infrastructure development in the region, these results will be invaluable for seismic safety and design. [ABSTRACT FROM AUTHOR]

The saturation line serves as the foundation for the safety analysis and seepage control design of tailings dams. The primary cause of the saturation line formation in dry-stack tailings dams is the cumulative infiltration of years of rainfall. Previous studies have indicated that, under the cumulative infiltration of years of rainfall, a relatively stable seepage field eventually forms within dry-stack tailings dams, but there is a lack of theoretical research on this seepage field. This paper aims to establish a theoretical solution for the saturation line of dry-stack tailings dams under the accumulation of rainfall over many years. Based on this, the gradual seepage differential equations of the saturation line in dry-stack tailings dams were derived using Darcy's law and the energy equation. By incorporating downstream boundary conditions and rainfall boundary conditions, an analytical solution for the saturation line of dry-stack tailings dams under multi-years rainfall conditions was derived. A comparison between the analytical solution and numerical simulation results was conducted, indicating that the analytical solution closely matches the numerical solution, with a maximum difference of 5.17%. The findings of study can fill the gap in the theoretical study of seepage fields in dry-stack tailings dams under the accumulation of rainfall over many years, which is of significant importance in enriching the theoretical framework of seepage in dry tailings dams. It can serve as the basis for drainage design and slope stability analysis of dry-stack tailings dams, and is crucial for designing safer and more efficient waste management practices in mining and construction. [ABSTRACT FROM AUTHOR]

This paper presents a new and innovative methodology for the investigation of karst systems using spring discharge. The behaviour of springs in phase space is investigated by plotting the measurements of spring discharge versus the measurements of the water level at the spring’s outlet. Such a diagram reveals new features of the function of the karst system and the discharge pattern of the spring that are not captured by common research methods. The application of this method to the Azmak Spring in southwestern Türkiye revealed the existence of five distinct discharge subsystems that operate alternately and never simultaneously. They have a specific connection between them, while the transition from one to another is not random but follows a pattern. An attempt was made to interpret these features using concepts from percolation theory. [ABSTRACT FROM AUTHOR]

Rock abrasiveness is a vital parameter affecting cutter wear, tunneling efficiency, and cost budgeting during mechanical excavation. The Cerchar abrasivity index (CAI), a suggested standard parameter to characterize the rock abrasiveness, can be obtained through the laboratory test. Understanding the correlations between the CAI and physical, mechanical, and mineralogical properties helps to precisely evaluate the cutter wear and improve the excavation efficiency. In this paper, correlations between CAI and 17 commonly used rock parameters were established for 27 groups of rock samples collected from China using simple and multiple regression methods. Based on the Pearson correlation coefficient (PCC) results, the possibility of linear relationships between CAI and physical, mechanical, and mineralogical parameters of rock samples was analyzed for determining the appropriate model. Subsequently, simple linear regression and Boltzmann models were developed based on physical and mechanical parameters. The model based on porosity showed excellent forecasting performance over other models. Through the analysis on the coefficient of determination (R2) value, a better multiregression model (R2 = 0.92) based on the mechanical parameters was obtained. However, a more feasible model (R2 = 0.91) based on the thermal conductivity, diffusion coefficient, elastic modulus, and Rock Abrasivity Index (RAI) was also suggested, considering the simplicity and period of parameter measurement. After the classification of rock types, the linear correlations strengthened significantly, especially for the mineralogical properties. The CAI showed a linear correlation with equivalent quartz content (EQC) and RAI for the granite and sandstone, while the quartz content (Q) still showed no relation with CAI. The results can provide a reference for evaluating the abrasive properties of rock during the mechanical excavation process. [ABSTRACT FROM AUTHOR]

Erosion behavior at the interface of different layers is a critical consideration in pavement design and construction. Especially, this issue poses a particular challenge in dispersive clays, which are prone to excessive erosion. The current paper focuses on evaluating the effectiveness of nanoclay in stabilizing and mitigating the contact erosion behavior of dispersive clays. To do so, a range of experimental testing, including double hydrometer, pinhole, contact erosion and unconfined compressive strength (UCS) tests was employed. The findings revealed that incorporating 0.75% nanoclay content yielded significant results, leading to a remarkable 391% increase in the UCS, a notable 58% reduction in dispersivity potential (DP), a 53% decrease in eroded soil mass, and a 29% decrease in the dispersive clay settlement after a 28-day curing period. Additionally, new exponential correlations were successfully developed between soil dispersivity and contact erosion parameters (CEPs) with high coefficients of determination using over 50 contact erosion test results. To facilitate the estimation of CEPs, the values were made dimensionless including the ratios of eroded soil mass (m/m0), settlement (S/H), and void ratio (ef-e0/e0). Finally, scanning electron microscopy (SEM) and microstructural image processing (MIP) confirmed the filling between soil particles and the reduction of the number of voids due to nanoclay incorporation into dispersive clays. [ABSTRACT FROM AUTHOR]

The stability of a slope at a hydropower station is closely related to variations in water storage levels. At China's Yellow River Laxiwa Hydropower Station, although operations have been at normal water level since 2015, slope deformation intensified and local instability occurred during the impoundment process. Therefore, it is important to research the mechanism of landslides, predict possible landslide phenomena and introduce treatment measures. The Guobu slope, situated on the right bank of the Laxiwa Hydropower Station, was chosen as the research object in this paper. The three-dimensional distinct element method (DEM) was used to investigate and calculate the slope deformation and stability under different water levels. The numerical results accurately simulate the in-situ toppling deformation of the Guobu slope instability and demonstrate that impoundment and geological structures are the dominant factors contributing to the slope's significant deformation. Based on slope stability analysis, slope-cutting measures were proposed, and the modified strength reduction method was applied to the factor of safety (FOS) calculation. We use 3DEC to analyze the control factors of deformation and failure of Guobu slope instability accurately. Our findings contribute significantly to the understanding of toppling mechanisms in steep slopes, revealing how complex geological structure and reservoir level fluctuation interact to trigger instability. [ABSTRACT FROM AUTHOR]

Characteristics of a rainfall event (e.g., rainfall duration D and intensity I) have a significant influence on the probabilistic stability analysis of the rainfall-induced landslides. However, most previous probabilistic stability analyses of rainfall-induced landslides have been performed under a given rainfall pattern without considering the uncertainty of the rainfall characteristics. The Monte Carlo simulation method, which takes a lot of computing resources and time, has been widely used in previous studies. In this paper, a fully analytical method is proposed to estimate the slope failure probability induced by a random rainfall event (PF1) and the annual slope failure probability (PFA), which considers both rainfall uncertainty and the variability of saturated hydraulic conductivity Ks. Triple integration is used by the analytical method to avoid repeated sampling and calculation. Compared with the Monte Carlo simulation method, the analytical method greatly improves the calculating efficiency. The outcomes based on the analytical method are consistent with those obtained by the Monte Carlo simulation method, which verifies the accuracy of the analytical method. When the mean of the saturated hydraulic conductivity (μKs) is large, PF1 decreases with the increase in the coefficient of variation (COV) of Ks. When μKs is small, PF1 and PFA increase with the increase in COV of Ks (COVKs). [ABSTRACT FROM AUTHOR]

Tunnel boring machines (TBMs) have been increasingly applied in extreme regions such as "Three highs" (high confining pressure, high rock hardness and high quartz content), researchers have introduced laser technology to the TBM field to improve cutting efficiency. The aim of this study is to investigate the effect of laser power, laser moving speed, blade width, distance between the cutter and laser-induced groove (DCLG), and edge angle on rock breakage after coupling the laser with TBM cutter-head, and obtain the optimal combination of these parameters. Two sets of indentation tests were conducted: one with the assistance of laser-induced grooves (LG) based on a L18(37) orthogonal design table; the other was a controlled trial without the laser. The corrected indentation hardness index (CIHI), specific energy (SE) and penetration force were utilized as performance indicators to comprehensively evaluate the experimental results. Additionally, a new method proposed in this paper allowed for accurate measurement of the volume of rock debris, avoiding the difficulties associated with the traditional weighing method, which requires collecting rock fragments caused by rock bursts. Finally, variance analysis, range analysis, and comprehensive evaluation analysis were performed on the three performance indicators. Results show that LG can greatly reduce the penetration force of the cutter and improve cutting efficiency. The primary and secondary factors affecting the rock breaking performance of a laser-assisted cutter are: blade width, DCLG, laser moving speed, laser power and edge angle, and the optimal combination of rock-breaking parameters: The blade width is equal to 3 mm, the DCLG is equal to 5 mm, the laser moving speed is equal to 2 mm/s, the laser power is equal to 20 W, and the edge angle is equal to 12°. [ABSTRACT FROM AUTHOR]

This paper aims to reveal the effect of lithology assembly on the seismic performance of steep consequent-layered slopes composed of strong and interbedded rock strata. These slopes exhibit failure during intense seismic events but typically remain stable under natural conditions. A large-scale centrifugal shaking table test is conducted with various seismic excitations to examine the dynamic response of these slopes. The test results comprise crack propagation observation, acceleration responses, and spectral characteristics. Additionally, a simplified analytical approach is introduced to determine the transient safety factors for the two slopes at any given time, considering the type of seismic failure the slope may experience. The failure mode of a steep consequent-layered slope closely associates with the lithology. Two distinct failure modes, namely buckling and rockfall, are identified and replicated through the centrifugal model test. In both slopes, there exists a critical height beyond which acceleration amplification significantly increases toward the slope surface. For a steep slope composed of strong rock, this critical height is situated near the upper-front slope surface, whereas for an interbedded steep slope with the same inclination, it is located at 1/4 of the slope height from the toe. Furthermore, the interpolated distribution of the transient safety factor field reveals that the most critical location varies with the seismic Peak Ground Acceleration (PGA) for assessing potential buckling failure, while it remains constant for evaluating potential rockfall failure. [ABSTRACT FROM AUTHOR]

In the reliability analysis of the landslide-stabilizing piles system (LSP), the most commonly used uncertainty models of geotechnical parameters mainly include the homogeneity model (HM) and unconditional random field (UCRF). However, neither of these models considers the existence of borehole data, which may lead to overestimation of the degree of site uncertainty. Based on borehole data in situ, the conditional random field (CRF) of the shear strength of the sliding surface was established through random field theory and the Kriging estimation method. By combining the limit equilibrium method (LEM) and Monte Carlo simulation (MCS), a novel procedure was introduced that can calculate the stability coefficient and design thrust of pile stabilization at the same time. By considering multiple failure modes comprehensively, a calculation flowchart for the failure probability of the LSP was proposed. The spatial layout parameters of pile stabilization, including the pile location, pile spacing, and pile length, significantly impact the calculation results. Compared with using HM and UCRF, the failure probability of the LSP may be lower when using CRF. Based on the allowable failure probability, feasible design solutions were provided. Further comparisons were made on the number of feasible solutions under these three uncertainty models. The research results in this paper might provide some assistance for the optimization of pile stabilization. [ABSTRACT FROM AUTHOR]

Compound large deformation in tunnel has been a challenging issue influenced by complex geological conditions such as weak surrounding rock, high ground stress and groundwater. This paper summarizes the characteristics of compound large deformation in Gaopo tunnel, which passes through a weak coal-bearing stratum. Mechanical and swelling tests were conducted, alongside in-situ stress tests, to analyze the potential for squeezing and swelling deformations. A numerical simulation using an elastoplastic damage model, coupled with a method that calculates the humidity field based on the temperature field, was carried out to quantitatively analyze the mechanisms of compound large deformation. It was found that ground stress emerges as the primary determinant of the compound large deformation in Gaopo tunnel, followed by weakened surrounding rock and the humidity field. To address these problems, a new support scheme primarily based on double primary support was proposed. Field monitoring was conducted to evaluate the mechanical and deformation characteristics of support structure during the construction process. The results indicate that the new support scheme effectively controlled the compound large deformation, and the timing of the second primary support installation was found to be satisfactory. The treatment experience provides valuable insights for support design in tunnels experiencing compound large deformation issues. [ABSTRACT FROM AUTHOR]

This paper proposes a novel treatment scheme for expansive soil slopes, incorporating a flexible facing, steel cables, and soil nails. Based on completed practical engineering projects, a series of high-precision numerical models for differently supported expansive soil slopes were established. These include hard facing with soil nails, flexible facing with soil nails, and the newly proposed flexible facing with steel cables and soil nails. By comparing safety coefficients, soil displacement patterns, slope surface strain distributions, soil nail force diagrams, and steel cable force distributions under different conditions with or without considering expansion forces, the study thoroughly elucidates the working mechanisms of various support schemes in addressing expansive soil slopes. A comprehensive comparative analysis reveals the irreplaceable advantages of the proposed flexible facing incorporating steel cables incorporating soil nail support (flexible-cable-nail support, FCN support) scheme in the treatment of expansive soil slopes. [ABSTRACT FROM AUTHOR]

The rationality of rockfall path analysis results is closely related to the resolution of the slope shape model. With the emergence of unmanned aerial vehicle (UAV) photogrammetry technology, which is suitable for engineering geological surveys, the modeling resolution for unstable rock slopes has gradually increased. In this paper, the process of constructing a model of unstable rock slopes based on UAV photogrammetry is improved. A method to obtain the geometric parameters of unstable rock masses by using the model is proposed. The movement characteristics required for rockfall analysis are summarized. Based on the analytical results of rockfalls, a method for setting up passive protective nets is suggested. A quantitative evaluation method is proposed for the protective effect of each protective scheme. Through a practical engineering case, two passive protective schemes (the original design and the optimized design based on the proposed method) are compared and evaluated by numerical simulation, and the actual site layout scheme is more similar to the optimized design scheme. The results show that the proposed method has a positive effect on the design and improvement of protective nets. [ABSTRACT FROM AUTHOR]

The causes of ground fissure formation are closely related to the change in the stress state in a loose layer, but many researchers often ignore the dynamic processes of mining when studying mining-induced damage mechanisms. The study of stress evolution in a loose layer during mining can help to reveal the causes of surface damage and its self-healing mechanism. This paper establishes a numerical model to study a loose layer’s stress evolution and its causes during mining. The discriminative conditions of the potential dynamic fissure formation cycles and self-healing are given. The vertical and horizontal stresses in the loose layer at the mining boundary increase and then decrease under the mining disturbance, and the vertical stresses in the loose layer above the comprehensive mining surface undergo two increasing and decreasing stages, while the horizontal stresses increase and decrease and then increase again. The permanent fissures at the mining boundary form because of the decompression- and compression-related damage caused by horizontal unloading, while the dynamic fissures in the loose layer at the mining surface form due to the first horizontal unloading effect; the shear damage is caused by the second increase in vertical stress. Additionally, the soil Mohr‒Coulomb strength criterion and the linear elastic stress‒strain relationship are used to discriminate the single- and double-cycle development patterns of the dynamic fissures on the ground surface. [ABSTRACT FROM AUTHOR]