Bulletin of Engineering Geology and the Environment最新文献

Radon release rate is one of the most important indicators to assess the environmental radon hazard. In the loess-covered area of northern China, the decay of uranium ore associated with the coal seams has caused elevated radon concentrations in overlying soil layers, significantly increasing the risk of various respiratory diseases to residents. In this paper, the effects of burial depth and soil type on radon release rate were investigated by X-ray diffraction (XRD) analysis, low-temperature nitrogen adsorption (LTNA) experiments, and measurement of radon concentrations in the soil based on the pore structure characteristics of soil layers. The results showed that all N₂ adsorption isotherms in the soil were inverse-S shaped with well-developed mesopores. The number of mesoporous materials was positively correlated with the radon release rate of the soil. The overall tendency of the radon release rate was to firstly increase and then decrease with increasing depth. The relative degree of variation in radon exhalation rate between adjacent soil layers was in the order as follows: red clay > paleosoil > loess > pedocal. The results of this study can help to understand the release pattern of radon in different soils and provide valuable references in reflecting the characteristics of radon release in regional soils.

Catastrophic landslides often occur along the southeastern margin of the Tibetan Plateau because of strong earthquake/faults and heavy rains. In this study, 26 large-scale landslides were collected from the middle segment of the Yalong River to analyze landslide features and possible formation mechanism. The investigation results revealed that landslides featuring a linear distribution along the riverbanks can be classified into three failure types: tensile cracking-sliding, sliding-bending (crushing and buckling), and toppling. Among them, the Xiamajidian landslide at the junction area between the river and the Qianbo fault is being dangerous with obvious deformation, including different subzones and different failure types. The landslide body is delineated into three distinct zones (A, B, and C) based on different deformation features and material compositions. Among them, the Zone A with the largest deformation is dangerous, the front of which is obviously moving toward the river channel. The deformation monitoring data indicated that the 2008 Ms 8.0 Wenchuan earthquake caused only slight disturbances to the Xiamajidian landslide body, but the subsequent 2008 Ms 6.1 Huili earthquake caused the deformation to increase quickly. The distinct-element method is then used to determine the importance of strong earthquakes and heavy rainfall during landslide failure. The results suggest that the landslide may have been broken to form a large landslide event, and finally to form a large landslide dam to block the Yalong River. The results presented in this paper are helpful for disaster prevention and risk evaluation.

The aim of this study is to investigate the rockfall potential of the steep rock slope above the Sumela Monastery (Trabzon, Türkiye) by using Ground Penetrating Radar (GPR) and surface fracture analysis on discontinuity. In this context, studies were carried out on 10 risky blocks determined after the investigations made by a team of industrial mountaineering and observations on the orthophotos. The discontinuity analysis data on the rock masses containing of mainly andesites and basalts were combined with discontinuities observed in the ground penetrating radar sections (radargrams) and the risk status of the blocks was revealed by using the location and characteristics of the dominant discontinuities. By using GPR data, discontinuities with 4 main sets were detected in 3 blocks at a depth of 2.0–2.5 m from the surface and the loose rocks were removed from the slopes using a combination of manual and mechanical techniques, including the use of lifting jacks and jackhammers, as well as explosives. In another block where GPR measurements were taken, a main fracture was detected from the surface to a depth of 2 m, but the continuity of the fracture to a deeper depth was not observed. Thus, this block was reinforced together by wrapping them with steel nets. Ground penetrating radar measurements could not be taken from the other six blocks because they did not have smooth surfaces. The stability of these blocks, which are smaller than the others, was assessed using observational data collected in situ by industrial climbers. In addition, the monastery was opened to visitors after the other small blocks on the slope that were at risk of falling were dropped. It has been demonstrated that fracture-crack systems of rocks on steep and weathered rock slopes, which are difficult to apply in rock engineering studies, can be successfully visualized using GPR measurement.

This study comprehensively investigates the hygric performance of two commonly used types of granite in masonry, each characterized by distinct porosity levels. A series of experimental tests, including capillary absorption, one-dimensional drying, cup methods, vacuum saturation, sorption/desorption isotherms, mercury intrusion porosimetry, and ultrasonic pulse velocity, was conducted in different directions and by using both pure water and NaCl solutions. The results highlight pronounced anisotropy in the granite’s hygric response, with significant directional differences in liquid and vapor moisture movement, as well as ultrasonic wave propagation. Granite with lower porosity and a finer pore structure exhibited hysteresis effects and more pronounced hygroscopic behavior, while granite with higher porosity showed greater capillary activity. The presence of salt crystals within the pore network significantly influences vapor and liquid transport properties, porosity, and moisture storage capacity. The gradual formation of sodium chloride crystals on drying surfaces noticeably altered drying kinetics, influenced by salt concentration and pore characteristics. These findings provide valuable insights into the hygric properties of granite, essential for understanding its durability and informing moisture transfer numerical models.

Geothermal heating and cooling is a new type of building energy-saving technology that utilizes surface geothermal energy, which causes temperature changes in the surrounding geotechnical bodies when it works, and affects the strength characteristics of loess when it is applied in loess areas. To investigate the change in the strength of intact loess under the effect of temperature, this study uses loess in the Xi'an area of China as the main research object and conducts consolidated undrained triaxial shear tests on intact loess at four different temperatures (5 ℃, 20 ℃, 50 ℃ and 70 ℃) to analyze the change law of shear strength of intact loess specimens under varying temperatures. The results show that the stress‒strain curves of loess specimens show strain softening under the effect of different temperatures, while the stress‒strain curves of remodeled loess show strain hardening, and the strength of loess gradually decreases with increasing temperature under the same confining pressure. Based on the binary medium modeling of a geotechnical body, the shear sharing ratio is modified by considering the effect of temperature and confining pressure. The variation in the shear sharing ratio with temperature (T), confining pressure (sigma), parameter m, and structural yield strength (sigma_{s}) is investigated. The strength criterion of intact loess is modified to establish a strength criterion applicable to intact loess under high temperatures, and the strength criterion is verified by indoor test data, which show that the strength criterion has good applicability to intact loess under high-temperature conditions.

Landslide susceptibility evaluation is pivotal for mitigating landslide risk and enhancing early warning systems. Current practices in developing Landslide Susceptibility Mapping (LSM) often overlook the diverse mechanisms of landslides, and traditional machine learning (ML) models lack the capability for autonomous feature learning in landslide contexts. This study proposes a methodology that precedes the application of deep learning algorithms for LSM by classifying landslides and selecting relevant factors based on their deformation mechanisms. In the Zigui-Badong section of the Three Gorges Reservoir area (TGRA), landslides are classified into rock landslides (RL) and soil landslides (SL) based on the geological conditions and historical landslide inventory. A comprehensive evaluation index system, comprising thirteen factors is established. To identify the most pertinent factors for each type of landslide, these factors are ranked according to their contribution to landslide occurrence. For susceptibility assessment, this study introduces a Convolutional Neural Network (CNN) model and benchmarks its performance to traditional ML models including Classification and Regression Trees (CART) and Multilayer Perceptrons (MLP). The efficacy of these models is evaluated using the Receiver Operating Characteristic (ROC) curve and various statistical analysis methods. The findings indicate that LSMs that consider different types of landslides yield more accurate and realistic outcomes. The CNN model outperformes its counterparts, with MLP being the second most effective and CART the least effective. Overall, this study demonstrates the superiority of an LSM approach that accounts for landslide diversity over traditional, monolithic methods.

Bentonite is utilized as a barrier material in high-level nuclear waste repositories due to its superior low permeability and swelling properties. However, its engineering properties are influenced by the chemical composition of the infiltrating pore water during operation. Understanding the effect of salt solution on the mechanical properties of bentonite is crucial for evaluating the performance of buffer and backfill barriers in deep geological repositories for nuclear waste. In this study, various concentrations and types of salt solutions were used to treat Na-bentonite samples, which were then subjected to free swell test, no loading swelling ratio test, Atterberg limits test, compaction test, and analysis of the content of exchangeable cations. The results showed that the content of counterbalance cations changed significantly after the addition of salt solution, and the decrease in free swelling rate increased gradually with the increase of solution concentration. The effect of different types of salt solutions on swelling was primarily determined by the type of cation that governs charge level and hydration capacity. The inhibition of the free swelling rate was stronger for high-concentration low-valence salt solution than that for low-concentration high-valence one. Bentonites undergoing cation exchange exhibited a decreased plasticity index, a decreased maximum dry density, and an increased optimum water content. This was mainly due to the cation exchange that occurred between bentonite layers under the action of the salt solution, which affected the crystal layer structure, double electric layer structure, and intergranular stress. Finally, the van’t Hoff equation was used to quantitatively characterize the differences in swelling in the test results.

Shield tunneling can cause deformation of the interlayer soil. Traditional static methods do not consider the shield dynamic load and the construction influence on the dynamic performance of interlayer soil, resulting in inaccurate results. Therefore, this paper proposes a dynamic analysis method to assess soil deformation. Firstly, the composition and stress state of interlayer soil were monitored on site. Secondly, the dynamic triaxial tests were conducted based on the monitoring results to analyze the soil dynamic characteristics. Then, a dynamic constitutive model of the interlayer soil was constructed, which considers the change of the dynamic performance. Finally, the dynamic effect of shield on soil is simulated based on viscoelastic mechanics, and the dynamic analysis of interlayer soil deformation is realized by three-dimensional finite element method. The results indicate that the interlayer soil near the excavation face is more significantly affected during the crossing stage. Shield construction increases the dynamic strength and dynamic modulus of the interlayer soil, while reducing the damping ratio. The Hardin-Drnevich model and the logarithmic-linear model can well describe the evolution laws of dynamic modulus and dynamic strength. The dynamic analysis method is closer to real construction and has higher prediction accuracy.

A quantitative assessment of the seismic stability of anchored anti-dip slopes is of great importance for the safety of residents and infrastructure in seismically active regions. However, the subject has received relatively little scientific attention globally. This study aims to analyze the dynamic stability of an anchored anti-dip slope during the Ludian earthquake in Yunnan Province, China, a region characterized by active faults and frequent strong earthquakes. The Manhekuan slope located near the Lancang River fault, an active fault in Yunnan Province, was chosen as a case study to propose a method that integrates engineering geological investigations with the discrete element method (DEM). To validate its effectiveness, the proposed method is compared with the pseudo-static method and subsequently applied to optimize the anchorage parameters of the Manhekuan slope. The results indicate that the stability factor achieved by the proposed method is slightly higher than that of the pseudo-static method, showing a 3.6% increase. The proposed method effectively describes the shear evolution characteristics of the anchor cable and its influence on the seismic dynamic stability of the anchored anti-dip slope. The dynamic stability of the Manhekuan slope under the Ludian earthquake is reasonably analyzed using three indices: stability factor, geological body displacement, and anchorage force. This analysis leads to the determination of optimal anchorage parameters for the Manhekuan slope. The findings provide a valuable reference for evaluating the seismic stability of anchored slope engineering in seismically active regions, including the Himalayas.