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The seismic effect of well water level is complex and variable, and even if both wells are located in an area with similar tectonic and hydrogeological conditions, they exhibit slightly varying response characteristics to the same earthquake. Wells BB and RC, located about 100 km apart in the southwest of the Huayingshan fault zone in the Sichuan and Chongqing regions, exhibited obvious similarities and differences in their co-seismically response and sustained recovery characteristics during the Wenchuan Ms8.0 earthquake. Based on the dislocation theory and fluid–solid coupling theory, this study developed the seismic stress–strain model and the response model of pore pressure to seismic stress using Coulomb 3.3 and COMSOL 6.3, respectively. Simulation findings indicate that both BB and RC are located in the expansion zone, where their water levels show a co-seismic step-down. The amplitudes of BB and RC water levels are 83 cm and 81 cm, which are approximately 10 cm smaller than the actual values. The recovery times are 60 d for BB and 3 h for RC, closely resembling the actual values. Furthermore, the numerical results from different scenarios show that the recovery time of pore pressure is reduced by several times when the permeability of the confining layer overlying the observed aquifer increases by one order of magnitude or the thickness decreases, and this change is more sensitive to the permeability. It is clear that the confining condition has an important impact in the response time of sustained changes in well water levels, which may also help to explain the variations in the characteristics of sustained changes in wells BB and RC. [ABSTRACT FROM AUTHOR]

Active fault zones are critical pathways for the migration of deep fluids to the Earth's surface, carrying gases such as He, Rn, and CO2 that provide evidence for the physical and chemical dynamics of the Earth's interior. This review examines the geochemical characteristics of fault zone gases and their implications for understanding fault activity and seismic events. Fault zones with high activity levels exhibit significant gas release, and variations in soil and hot spring gas concentrations can serve as indicators of seismic activity. Changes in gas concentrations and isotopic ratios, particularly before and after earthquakes, reflect the dynamic interplay between deep-sourced and shallow-sourced fluids. Seismic-induced stress alterations enhance gas release along fault zones, leading to observable anomalies that can aid in earthquake monitoring and prediction. The study underscores the importance of isotope tracing in deciphering fluid sources, migration pathways, and the evolution of fault zones, providing valuable information for assessing tectonic activity and mitigating seismic risks. [ABSTRACT FROM AUTHOR]

In subway construction, the presence of boulders can significantly impact excavation and tunneling processes. However, despite these challenges, an effective and reliable method for detecting boulders in advance has not yet been established. This paper presents a novel method for detecting and characterizing boulders using 3D cross-hole electrical resistivity tomography (ERT). The proposed technique involves the strategic deployment of multiple borehole electrodes, which work together to create a comprehensive three-dimensional resistivity model of the subsurface. This model allows for the identification and characterization of boulders, providing crucial information about their location and size. We demonstrate the efficacy of this approach in a physical flume experiment and a case study of subway construction, The findings from both the laboratory and field studies indicate that the 3D cross-hole ERT method is not only effective in detecting boulders and providing detailed information about their size and spatial distribution but also optimizes construction planning, reduces unexpected disruptions and additional costs, and enhances overall construction safety. The results highlight the potential of 3D cross-hole ERT as a valuable tool for geological assessments during infrastructure development. [ABSTRACT FROM AUTHOR]

Because of its long processing time, low operating cost, simultaneous processing of multiple pollutants, PRB (permeable reactive barrier) is a commonly used technique for groundwater pollution remediation in western countries. But relative research about the PRB technology in China is still in its infancy. We reviewed the PRB structure, PRB repair mechanism and application progress at home and abroad. Aiming at the problems of PRB technology at reaction material selection, pollutant repair mechanism, removal of various pollution components and site installation design, development direction of the PRB technology was prospected. [ABSTRACT FROM AUTHOR]

Liujiang basin is located in a typical rural mountain area dominated by agriculture and mining industry in Qinhuangdao, Hebei Province of China. Groundwater plays significant role for socioeconomic development in the area. 78 well samples and 11 spring samples showed great variation of chemical compositions and groundwater quality class across the study basin. Groundwater hydrochemical type in Liujiang basin is mainly dominated by the typical Ca Mg-HCO SO or Ca Mg-SO HCO. The relative abundance of constituents is in the following order: Ca > Mg > Na > K for cations and HCO > SO > Cl for anions. Spring water quality is all good for drinking and irrigation, whereas about 33.00 % of the well water samples were not suitable for drinking and the exceeding indices included NO, total hardness, total dissolved solids and SO, and seven well samples were not suitable for agriculture use. The control of sodium and salinity hazard is required for irrigation. Natural processes include weathering-dominated, mineral weathering and ion exchange controlling groundwater chemistry. Principal component analysis and Pearson correlation matrices were used to identify groundwater contaminant sources and can be categorized as follows: (1) natural minerals dissolution and mine water mixing (2) domestic sewage and septic tank contamination and (3) agricultural fertilizer contamination. This study suggested that both natural and anthropogenic processes contributed to chemical composition of groundwater in Liujiang basin, especially the NO concentration is more than the acceptable limits in groundwater used for drinking purposes, indicating that anthropogenic nitrogen pollution is currently serious. [ABSTRACT FROM AUTHOR]