Bulletin of Engineering Geology and the Environment最新文献

Landslides formed in rock with bedding and weak layers threaten the environmental safety of the Yellow River Basin in China. Further study of the creep mechanism of such landslides will help to evaluate their stability. In this study, field investigation, data monitoring, basic parameter tests, and expansion pressure test are combined. The failure characteristics and mechanism of the Luoquan (LQ) landslide in Zezhou, Shanxi, China, under natural rainfall conditions are analyzed in detail. The creep deformation of the LQ landslide occurred continuously during the period of meteorological rainfall concentration. Natural rainfall was the main triggering factor of the long-term creep deformation of the LQ landslide. With increasing saturation degree and time of the slide zones, the creep deformation of the LQ landslide was caused by weakening of the shear strength and expansion of the slide zones, causing cracks in roads and houses built on surfaces. When the natural rainfall decreased, the weakening, softening, and expansion mechanism of the slide zones weakened. The stability of the LQ landslide increased, and the creep deformation gradually stopped. As of now, the creep deformation rate of the LQ landslide, currently increasing, is likely to develop into complete destabilization. Therefore, the on-site monitoring of the LQ landslide needs to be continued.

Dramatic changes in temperature and rainfall with global warming can significantly alter the moisture status of topsoil, thereby inducing soil structure degradation. However, few studies have reported the variation in permeability of saline soils during drying, which contributes to further refining the mechanism of wetting‒drying effect on soil properties. In this study, the permeability and microstructure of sodic-saline loessal soil with different initial water contents (IWCs) and salt contents (ISCs) obtained from pre-saturation and subsequent drying were explored using constant head permeability tests and SEM observations. The results show that the permeability coefficient decreases exponentially with time. The maximum permeability coefficient (K_max) of the samples decreases with decreasing IWC and ISC, while the relatively stable permeability coefficient (K_rs) is less affected. The microscopic results show that during the seepage process, the porosity and pore diameter of samples with low IWC gradually decrease, accompanied by a weakening of pore directionality and an increase in fractal dimension. In contrast, samples with high IWC show an initial increase followed by a decrease in porosity, pore diameter and pore directionality, alongside a gradual decrease in fractal dimension. The drying process promotes the formation of inter-aggregate pores and weakens aggregate stability, leading to significant microstructural disturbances in low IWC samples upon rewetting. The increase in salt content enhances particle cementation but also creates additional channels for rapid permeability. These findings carry practical implications for the prevention and control of soil erosion and engineering geohazards in saline soil regions under the impact of climate change.

The mechanical behavior and deformation characteristics of gray sandstone greatly affect the stability and safety of large-scale structural engineering on the rock stratum. A series of tests for sandstone collected from Jinping hydropower stations in southwest China under complex stress paths were carried out, including hydrostatic pressure test, conventional triaxial test, cyclic loading and unloading of deviatoric stress, confining pressure and pore pressure test. Meanwhile, a fractional elastoplastic damage model was proposed. The results show that the crack closure stress, crack initiation stress, and crack damage stress under conventional triaxial compression path are 0.189~0.217, 0.475~0.615, and 0.730~0.856 of peak stress, respectively. The influence of cyclic loading and unloading on mechanical behavior and deformation of gray sandstone has a significant strengthening effect. Under deviatoric stress cyclic loading and unloading, with increasing cycle number, axial and lateral strain increment curves tend to coincide, and the volumetric strain increment decreases. Under confining and pore pressure cyclic loading and unloading, the lateral strain increment is much larger than the axial strain increment. The axial elastic modulus and lateral elastic modulus show great discretization and irregularity. Moreover, a modulus-like axial coupling parameter is analyzed and discussed. The established constitutive model can accurately reflect the hardening and plastic dilatancy behavior of gray sandstone. Meanwhile, the staggered iterative return mapping algorithm is improved to ensure the convergence of the model.

Landslide-generated impulse waves (LGIWs) in mountain reservoirs pose serious threats to dam safety. In this paper, the potential LGIWs hazard induced by the ZJ landslide is studied by combining a hybrid SPH-SWEs method and LSTM networks. The hybrid SPH-SWEs method is used to investigate the evolution process of LGIWs, including landslide sliding, impulse wave generation, wave propagation, and running up on the dam. The map of the maximum water level is obtained. Subsequently, 49 calculation samples with different sliding velocities and failure volumes are established using the hybrid model. Based on the numerical samples, the sensitivity of sliding velocities and failure volume on the runup height on the dam is studied, and a LSTM surrogate model is trained to conduct the probabilistic analysis. The results show that the LGIWs is significantly influenced by topography. The influence of sliding velocity on the runup height on the dam surface is greater than that of the failure volume in this case study. The runup height on the dam surface is concentrated between 5.9 m and 7.5 m with a percentage of 84%. The results demonstrate that the combination of the SPH-SWEs method and the LSTM surrogate model can effectively carry out the probabilistic estimation of LGIWs in mountain reservoirs. This study provides technical support for disaster prevention associated with the ZJ landslide and presents a valuable method for assessing the risk of LGIWs.

Accurate and reliable displacement prediction is crucial for landslide monitoring and early warning. Landslide displacement data is complex nonlinear time series. Although some studies have employed dynamic models to predict landslide displacement, they have only focused on point displacement prediction, inevitably compromising the prediction credibility due to the inherent uncertainties in landslide prediction. This paper proposes a novel hybrid intelligent prediction model to enhance the prediction accuracy of point displacement in reservoir landslides and construct reliable displacement prediction intervals. Specifically, PSO-SVM is adopted to predict the trend displacement, while CNN-GRU-Attention is designed to predict the periodic displacement. Furthermore, the hybrid model allows for the direct construction of required displacement prediction intervals based on the landslide time series. The superior performance of the proposed model is proven by using the Baishuihe and Shuping landslides as case studies. The results demonstrate that the developed model achieves higher prediction accuracy and enables the construction of reliable displacement prediction intervals. Additionally, the proposed model can predict the time series of unknown displacement and provide an early warning of landslides at the early stage of displacement mutation. This research contributes to the improvement of landslide risk assessment and disaster early warning capabilities, providing reliable scientific guidance for landslide disaster prevention and mitigation.

The Jiaodong Peninsula in China is rich in metal deposits, but its geological setting is very complex. To ensure the stability of metal mining-induced excavations of the study area, it is necessary to understand the development of regional structures and the distribution of stress fields. Considering the multi-scale characteristics of geological objects, we conducted multi-scale 3D geological modeling and in situ stress inversion from regional large-scale (100km), regional medium-scale (10km), and engineering scale (km) to obtain the in situ stress distribution of several mine areas (Xincheng, Tengjia, and Hongbu mining areas) at the Xincheng Gold Mine, in the Jiaodong Peninsula region and guide engineering practice. The Hermite Radial Basis Function (HRBF) is adopted to obtain multi-scale geological models including small faults, surrounding rocks, and ore bodies by using regional field survey data, exploration profiles, and boreholes. Then, through several groups of measured in situ stress data, multi-scale in situ stress field inversion is carried out by adopting the multiple linear regression method. Then, the distribution of the in situ stress field is analyzed. In this paper, each smaller-scale 3D modeling and in situ stress inversion is refined and corrected based on the larger-scale modeling and inversion. The results show that the calculated in situ stress of multi-scale inversions is more accurate, which verifies the practicability and effectiveness of the multi-scale modeling and in situ stress inversion. Therefore, compared with the single-scale geological model and inversion, the multi-scale model and inversion can predict the in situ stress distribution of rock engineering more accurately.

This study examines the influence of sub-zero temperatures on the mechanical behavior and failure prediction of black sandstone. For this, quasi-static compression tests were conducted on black sandstone specimens under various temperatures, 5 °C, -5 °C, -10 °C, and − 20 °C. An acoustic emission (AE) monitoring technique was utilized to reveal the damage features of the rock at negative temperatures. The autocorrelation coefficient (AC) and variance of AE counts were assessed using the critical slowing down (CSD) theory to examine the precursor characteristics of rock failure under sub-zero temperatures. Further, the analysis of correlation dimension (CD) evolution was conducted to validate the results of CSD theory. The results indicate that as the temperature decreased from 5 °C to -20 °C, the uniaxial compressive strength (UCS) of the black sandstone increased by 43.09%. The AE counts, and cumulative counts effectively reflect the damage progression in the rock under compressive loading. The AE counts, and AE cumulative counts gradually rise with decreasing temperatures, indicating a more intense AE response. The AE signals associated with rock failure demonstrate CSD phenomena, where abrupt increases in the AC and variance curves of AE counts can be used to predict the ferocious failure. Furthermore, the findings show that the precursory time lag in black sandstone samples increases as the temperature decreases. Compared to CD and AC curves, the variance curve of AE counts provides a more distinct early warning feature for predicting rock failure under sub-zero temperatures. Consequently, this research holds significant implications for the prediction of rock failure in cold regions.

During pulsating hydraulic fracturing (PHF), the reservoir generates dynamic stress response and fatigue damage under the excitation of fluctuating fluid pressure. However, it remains to be determined which is the primary factor affecting fracturing effectiveness, particularly for tight sandstone reservoirs. Identifying the critical factors that govern the effectiveness can help optimize the fracturing scheme and increase production. The present study employed laboratory experiments and numerical simulations to investigate its mechanism. Specifically, the rock triaxial loading test system was utilized to conduct the PHF experiments. It was analyzed that the effect of maximum pressure and frequency on breakdown pressure, acoustic emission signals, and fracture morphology. Subsequently, a three-dimensional numerical simulation model of dynamic stress response was established using ABAQUS. The influence of the maximum pressure and frequency on the stress response amplitude was also discussed. The experimental results revealed that PHF can cause fatigue damage to the specimens. Interestingly, compared to conventional hydraulic fracturing (CHF), PHF can reduce the breakdown pressure. Additionally, it is beneficial to reduce the fatigue life by increasing the maximum pressure or decreasing the frequency. From the simulation results, enhancing the maximum pressure can notably improve the stress response amplitude. However, in the low-frequency range, the frequency variation has a minor impact on the amplitude. To conclude, the fracturing effect primarily relies on the fatigue damage effect rather than the dynamic stress in the low-frequency range. The results are significant for comprehending the PHF mechanism and determining parameters in engineering applications.

Red stratum soft rock, which is prevalent in the deep backfill regions of southwest China, exhibits water-induced disintegration characteristics that significantly impact the bearing capacity and deformation behaviours of the foundation. To further examine its damage evolution after encountering water, a numerical simulation study was conducted utilising the particle discrete element method, based on immersion testing. The water-induced disintegration of soft rock is characterised by the expansion of clay mineral particles and a reduction in breaking force and residual strength coefficient. The findings indicate that the disintegration of red stratum soft rock can be categorised into three stages: Surface Erosion, Crack Development, and Crack Penetration. Natural cracks enhances permeability, while any increase in clay mineral content heightens hydration sensitivity. These factors decrease the slaking durability index, exacerbating failure and potentially altering the disintegration mode. The excellent simulation outcomes in this case indicate that the discrete element method effectively simulates the disintegration process of red stratum soft rock. The work thus enhances understanding of disintegration mechanisms and paves the way for further elucidation of the complex behaviours of soft rock.

Many reservoir landslides have started undergoing rapid deformation in the Baihetan Reservoir region (BRR) by the complex structural background and initial impoundment, posing a significant risk to human life and infrastructure. In order to understand the intrinsic relationships between the geological structure, reservoir water, and landslide deformation, a detailed analysis of the Gengdi landslide along fault zones during the first water level circulation fluctuation in the BBR was conducted. The investigation was conducted systematically by means of comprehensive in situ monitoring, drilled cores, adit, high-density resistivity method, field investigations and engineering mapping, and aerial photographs. The Gengdi landslide showed a characteristic type of bending flowing and fracturing. The shear outlets of the landslide are the top and bottom of the fault gouge respectively. Hydrodynamic pressure and fault gouge softening are the trigger factors of the landslide. The main deformation of the landslide was along a deep fault zone. The maximum rate of landslide deformation occurred during the period when the reservoir water level fluctuation between the top and bottom of fault gouge. The findings revealed that the reservoir water level fluctuation caused the compression of the fault gouge and dragged the upper rock mass of fault zone. This study provided a detailed geological model for the formation of the landslide in fault zone. The likelihood of large-scale landslides is significantly high with the current deformation rate of the Gengdi landslide. Therefore, the analysis of reactivation mechanism and control of this type of landslide should be strengthened.