Enhanced Geothermal Systems (EGS) improve geothermal energy extraction but can rapidly cool high-temperature rocks, leading to internal fractures that weaken mechanical properties and pose risks such as well collapses and seismic events. Understanding the physico-mechanical changes in dry hot rocks, particularly sandstone, when high-temperature water cooling cycles is essential. This study examines the dynamic behavior of sandstone through impact tests at varying temperatures and cycles. Results show that as temperature and cycle count increased, peak dynamic stress decreased while dynamic strain increased. A critical temperature range of 500-600 ​°C was identified, beyond which significant changes in dynamic stress and strain occurred, indicating severe damage to the specimens’ stability. High-temperature water cooling cycles enhanced energy reflectivity and dissipated energy, reducing transmittance. The study revealed that between 200 and 400 ​°C, tensile damage predominated, while between 500 and 600 ​°C, compression-shear damage was dominant. Increasing temperature and cycles led to more extensive cracking and increased rock fragmentation. These findings provide a basis for assessing the stability of sandstone and offer theoretical insights into mechanical properties, energy transfer, and crack propagation in geothermal energy extraction, aiding in the prevention of geological disasters.

Aiming at the technical problems of regional rock burst control and disaster reduction, the indoor comparative tests of three kinds of variables are designed, involving water content, borehole diameter and borehole filling materials. This research analyzed the characteristics of the whole process of energy evolution of rock impacted by different regulation methods, and revealed the differences and applicable conditions of different regulation methods in reducing the impact mechanism. The results show that different control methods can effectively change the mechanical parameters of the target object. There are significant stage differences in the energy evolution of impact rocks. By constructing the energy conversion efficiency model, the study further elaborated on the water injection softening mechanism of "release first and then weaken", the drilling pressure relief mechanism of "guide first and then release" and the filling strengthening regulation mechanism of "release first and then absorb". The study of the optimal application conditions of different control measures provides an important basis for the regulation and disaster reduction of rock burst.

Unloading failure of the coal-rock (CR) system is the key factor leading to rock burst disaster. Therefore, it is very important to explore the failure mechanism of the CR system by laboratory test. Initially, CR composite samples underwent laboratory tests with unloading pressure at various rates (0.03-0.12 ​MPa/s). However, due to the limitations of the available monitoring equipment, the recorded deformation data were restricted to the coal mass, which may lead to inaccurate conclusions as potential rock deformation was not captured. Subsequently, coal and rock mass deformations were separately monitored by simulating corresponding unloading pressure tests using PFC2D numerical software. Simulation results suggested that the peak of the AE event during the critical stage before sample failure could serve as an indicator of imminent sample destabilization. Post-failure observation revealed a higher degree of damage in the coal mass (35.02%) compared to the rock mass (12.17%), indicating that coal mass destabilization triggers destabilization in CR composite samples. Moreover, faster unloading rates corresponded to deeper damage in the coal mass. Additionally, macroscopic tensile and tensile-shear cracks were observed in the rock mass, while macroscopic shear cracks were present in the coal mass, providing insights into the unloading confining failure mode of CR samples. Finally, the study established a relationship between unloading rate and bursting liability by introducing the elastic energy density difference index. The research results can provide a theoretical basis for the prevention and control of rock burst disasters.

Flooding is one of the most devastating quasi-natural hazards in Southeast Asian monsoon region. The recent study aims to define the flood risk zones (FRZ) by using the multi criteria evaluation (MCE) method with the help of the Geographical Information System (GIS) of the lower Keleghai River Basin in West Bengal. For this purpose, post-monsoon multi-temporal Landsat-8 satellite imagery, topographical maps and Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) data have been used to identify the severity level of the flood risk area. To perform this study, different thematic raster layers of nine flood-conditioning factors like elevation, slope, rainfall, geomorphology, drainage density, distance from the river, LULC, SPI and TWI integrated to prepare a flood-zoning map using Weighted Overlay Linear Sum Model (WLSM) in GIS environment. The method of training set and validation in different locations in the study area of existing flood and prepared flood-prone zone has been tested to validate the study. The results depicted that in general very low (0.00-0.25), moderate (0.50-0.25), high (0.75-0.50) and severe (1-0.75)) flood risk zones found in the study area and the proposed multi-criteria approach of spatial layers in GIS environs provides a better assessment of flood risk zone. The outcomes of the study guide in developing comprehensive flood management strategies for efficient management on a priority basis of present and future flood hazards in the area.

This study investigates the phenomenon of slope failure in shale, particularly in the context of heavy rainfall events. Despite the critical role that water plays in influencing the stability of shale slopes, the effects of hydrological conditions on their structural integrity remain inadequately understood. To address this gap, the research integrates field observations with controlled laboratory experiments aimed at elucidating the relationship between water infiltration and shale stability under varying boundary conditions. Shale blocks without silt layers (SNSL) and those with horizontal (H-SSL) and vertical (V-SSL) silt layers were considered. Vertical tensile fractures were observed in SNSL blocks, while H-SSL blocks displayed horizontal fractures along the silt layers, particularly at failed corners in the BFC. Fractures along the silt layers and diagonal fractures were more pronounced under the BCC. V-SSL blocks exhibited the formation of vertical rock columns along the silt layers, which were more common in the BFC. Inclined small fractures were commonly observed under the BCC. In a wet environment, shale demonstrates high responsiveness, and its behavior in the presence of water is complex. Water interaction with shale blocks leads to fracture formation, influenced by the clay matrix and silt layers. The introduction of water alters the clay matrix, resulting in tensile fractures. Silt layers act as weak planes, facilitating fracture propagation. Notably, shale is vulnerable under the BCC, with increased vulnerability under the BFC, particularly due to silt layers with outward-facing dips. The study recommends constructing retaining walls and applying polymers to enhance local and regional stability, mitigating the risks associated with slope failure.

To thoroughly investigate the damage evolution of anchorage structures under corrosive conditions, laboratory simulations of corrosive environments were conducted, including corrosion tests and mechanical performance evaluations on anchorage systems. Based on experimental results, relationships were analyzed between factors (prestress, pH value, and anti-corrosion methods) and the corrosion degree, macro-micro characteristics, and mechanical performance degradation patterns of specimens. The results of the test indicated that: (1) the corrosion of coal bodies increases over time, and lower pH environments correspond to lower uniaxial compressive strength of coal bodies; (2) the corrosion of the rock bolts increases over time, the maximum mechanical performance in the rock bolts loss occurs at pH ​= ​5.0, and higher prestress of the rock bolts leads to greater mechanical degradation, and galvanization effectively reduces corrosion in functional rock bolts; (3) the degree of corrosion in the anchorage bodies has increases over time, pH ​= ​5.0 causes maximum bond strength of the anchorage bodies property loss and increases the prestress in the anchorage bodies exacerbates bond strength degradation, and double anti-protected anchorage bodies show less bond strength loss than ordinary ones. The corrosion-induced structural deterioration of underground anchorage systems leads to significant mechanical performance degradation, potentially causing support failure, surrounding rock instability, and roof fall disasters. Greater attention therefore needs to be paid to this area.