Shanghai, a typical coastal soft-soil area, is characterised by thick soft layers with high compressibility and low permeability. Together with five confined aquifers, these layers form a complex multi-aquifer system. Historically, excessive deep groundwater extraction caused severe land subsidence. However, after years of extraction restrictions and artificial recharge, subsidence has been controlled and groundwater levels have risen, creating possibilities for groundwater extraction in emergency situations. Focusing on Shanghai's third confined aquifer (Layer ⑪) and the adjacent aquitard (Layer ⑫), this study first employed high-pressure consolidation tests to verify the over-consolidated state of the deep soils, followed by high-pressure triaxial tests and numerical simulations to investigate their deformation behaviour under staged pore pressure changes. The triaxial tests indicated that during staged dewatering, the deformation modulus (E) dropped sharply once the effective stress exceeded the preconsolidation stress, falling to 1/2 to 1/4 of its initial value and marking the elastic-elastoplastic transition. Moreover, the void ratio change was strongly negatively correlated with the over-consolidation ratio (OCR), and a higher OCR significantly suppressed compression during pore pressure changes. Numerical simulations based on the Modified Cam-Clay model agreed well with the experiments. These findings provide a scientific basis for predicting safe drawdown thresholds in emergency groundwater extraction.
The overburden extra-thick sandstone confined aquifer in underground coal mines also functions as a key stratum. Its failure and the associated confined water migration have a substantial impact on mine safety. A field case involving an overburden extra-thick Luohe confined aquifer (LHA) was introduced, and long-term ground monitoring up to 6 years of water level in LHA was conducted. A comprehensive analysis was carried out on the failure process of the overburden extra-thick LHA and its relationship with confined water migration. The influence of the confined water drainage in the extra-thick LHA on the mining-induced stress field and the reasonable panel size under the extra-thick LHA were discussed. The results indicate that water-level variations in LHA exhibit a phased pattern and significant changes in LHA water level and goaf water inflow occur when the panel goaf reaches the square stages, especially when the LHA breaks. The mining-induced drainage of confined water in the LHA transfers a greater portion of the roof load to the surrounding rock, intensifying stress concentration and the risk of dynamic disasters. For mine water conservation and dynamic disaster prevention, panel dimensions beneath the extra-thick LHA should be scientifically predetermined.
Unknown authors· Canadian geotechnical journa...· 0 citations
Rainfall-induced instability of highway slopes with a soil–rock binary structure may be strongly influenced by the hydraulic barrier effect of low-permeability shale. This study investigated the right-side slope along the D-ramp section from DK0+230 to DK0+660 at Deze Interchange on the Zhanhui Expressway, China. A two-dimensional coupled seepage–stress model was developed based on the engineering geological conditions and rainfall records to simulate the slope response under a 72 h extreme rainfall scenario with an intensity of 175.6 mm/d. Field displacement monitoring data were used to validate the modeled deformation pattern under natural conditions. Under natural conditions, the reinforced toe zone remained stable, deformation was concentrated along the interface between the block-stone layer and strongly weathered limestone in the middle and rear portions of the slope, and the factor of safety was 1.1344, indicating a basically stable state. During prolonged rainfall, infiltrating water accumulated near the interface between the strongly weathered shale and the underlying shale owing to the hydraulic barrier effect of the low-permeability shale, forming a continuous transient saturated zone. The plastic zone progressively extended from the upper shallow weak interface to the lower deep interface and eventually became fully connected, while the factor of safety decreased to 0.9886, indicating overall instability. The results reveal a coupled mechanism involving interfacial water accumulation, increased pore-water pressure, the formation of a transient saturated zone, and a shift in the controlling zone of slope deformation and failure from shallow to deeper layers. These findings provide a reference for disaster prevention and mitigation of similar soil–rock binary-structure slopes.
Zhang Luo, F. A, Shiqiang He et al.· Engineer· 0 citations
An excavation-induced clayey landslide in Jianshui County, Yunnan Province, China, threatens a national refined oil pipeline near the rear slope. Field investigation, borehole logging, laboratory testing, and three-dimensional finite-element analyses were integrated to investigate the excavation–rainstorm instability mechanism and evaluate circular anti-slide piles with toe backfilling. Under natural excavation, the reported factor of safety was 1.39, and the maximum displacement was 2.35 mm. Under a 60 mm/day rainstorm, increased pore-water pressure and saturation in the shallow sliding mass and strongly weathered claystone, together with saturated-state strength parameters, reduced the shear-strength reserve. The deformation and stability analyses yielded a maximum computed displacement of 1.36 m and a factor of safety of 0.95, respectively, indicating pronounced pre-failure deformation and loss of stability. After mitigation, the factor of safety increased to 1.41, while the maximum slope and pile-head displacements were both approximately 6.90 mm. The pile row redistributed nonuniform landslide thrust and reduced deformation transfer toward the pipeline. The results are site-specific engineering estimates for the investigated rainfall and parameter conditions.
Haifeng Jia, F. A, Ruo-Xi Lin et al.· Engineer· 0 citations
Rainfall infiltration frequently triggers slope failures by elevating pore water pressure and compromising the shear strength of unsaturated soil layers. Modeling these severe geological events remains computationally challenging. Standard grid-based techniques, such as the Finite Element Method (FEM), typically fail due to severe mesh distortion under large deformations, whereas the Discrete Element Method (DEM) demands excessive computational resources. Addressing this gap, we develop an advanced theoretical framework utilizing the Material Point Method (MPM) integrated with a liquid-solid-gas three-phase mechanics model. We first verify the algorithmic accuracy using a 1D unsaturated soil column test. Subsequently, the framework is deployed to capture the dynamic displacement and mechanical responses of a 2D rainfall-induced landslide. Benchmarking against FEM data confirms that our multiphase MPM accurately models the infiltration process and subsequent structural collapse. Ultimately, this approach offers a highly robust computational strategy for analyzing large-scale landslide deformations and improving predictive assessments.
Long Zhu, Lele Wang, Xiao Liu et al.· E3S Web of Conferences· 0 citations
Groundwater forms the primary source of freshwater in the basaltic hard-rock regions of central India; however, rising agricultural demand and increasing dependency on deeper aquifers have resulted in growing stress on groundwater resources in parts of Dhar District, Madhya Pradesh. To address this concern, an integrated hydrogeological and hydrochemical investigation was carried out in the district, underlain predominantly by Deccan Trap basalts. The study identifies a multi-layered aquifer system comprising a shallow weathered zone (5–30 m depth) and deeper vesicular and fractured basalt aquifers (30–150 m depth), where secondary porosity plays a dominant role in groundwater storage and movement in deeper aquifer. Pumping-test results indicate highly variable aquifer productivity, with transmissivity values ranging from 3 to 593 m2/day and yields from 0.10 to 24 L/s, reflecting strong spatial heterogeneity. Seasonal and long-term water-level behavior highlights monsoonal-controlled recharge, with localized decline observed in southern parts of the district due to excessive extraction. Hydrochemical analysis revealed dominant Ca–Na–HCO3–Cl and Na–HCO3 facies, with localized fluoride and nitrate contamination. Elevated fluoride (up to 2.5 mg/L) and nitrate (up to 142 mg/L) concentrations in specific pockets pose risks for drinking-water use, while irrigation suitability varies from medium to high salinity hazard. The study recommends a combination of supply-side measures, including artificial recharge structures in fractured zones, and demand-side measures such as water-use efficiency, regulated pumping, and improved fertilizer management. The findings offer a scientific basis for sustainable groundwater development and can serve as a reference for similar basaltic terrains in India.
