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Groundwater resource plays a central role in every sector of life globally. Unfortunately, the roles of groundwater are often unappreciated in many parts of the world, especially in developing nations. The paper applied a combined geo-electrical method and hydrochemical analysis alongside physical surveys to investigate aquifer promising zones, the quality and the source of water supply in the selected regions. The geo-electric resistivity data were used to select the most aquifer-promising zone for groundwater development with a key interest in groundwater potential and aquifer overburden protective capacity overlying the water-bearing unit. Seventeen (17) vertical electrical sounding (VES) acquired in four regions reveals that the regional weathered/fractured unit which constitutes the aquifer unity extends from 13.4 m to 41.3 m in depth with the subsurface resistivity value varying between 53 Ωm–1013 Ωm in terms of resistivity values. The overburdened thickness (protective soil layers) stretches from 2.5 m to 13 m with a resistive layer of resistivity values ranging from 111 Ωm to 2877 Ωm, which could provide high aquifer protective cover for the regional groundwater systems. The computed aquifer transmissivity and hydraulic conductivity range from 0.54 m 2 / h –15.85 m 2 / h , and 0.95 m/day–9.19 m/day, respectively. The estimated average longitudinal conductance (0.2 moh) reveals that the regional groundwater systems are moderately protective against surface contaminants. In addition, the physicochemical water analysis was examined, which exposes the level of heavy metals (HMs) compositions in the regional groundwater systems and the possible public health risks compared to WHO permissible drinking water limits. The sample water from the Rivers had the highest concentration of HMs (0.089 mg/I–2.012 mg/l), followed by the hand-dug wells (HWDs) (0.033 mg/l–1.555 mg/l) and the lowest in the borehole (0.011 mg/l–0.511 mg/l). In contrast, the borehole water sample shows a moderation where the HMs presence falls within the WHO standard for drinking water. The outcomes of the study show that 63% of the investigated region consumed water with a high concentration of HMs above the WHO permissible standard allowance for drinking water, while only 37% took water that falls within the WHO permissible standard. In conclusion, the study showed significant impacts of anthropogenic activities on the regional water quality, which provides vital information about the regional groundwater systems and the quality of water supply for adequate groundwater development and sustainability. [ABSTRACT FROM AUTHOR]

Boreholes excavated in porous rocks exhibit a variety of inelastic deformation patterns. This paper investigates how nucleation, propagation, and coalescence of compaction zones, including those resulting from compaction localization, affect the mechanics of excavated boreholes in high-porosity rock formations. For this purpose, a recently developed controllability framework able to differentiate among multiple modes of compaction banding is used to guide the interpretation of numerical simulations for boreholes excavated in porous rock. The goal is to explain the link between heterogeneous deformation patterns forming around the excavated zone and in situ stress conditions. To carry out the analyses, the theory is combined with a strain-hardening constitutive law calibrated against Berea sandstone laboratory evidence, thus capturing the stress-dependence of both homogeneous and heterogeneous compaction. The resulting simulations of idealized boreholes show that the inelastic compaction around the excavated zone depends dramatically on the far-field stress state, leading to transitions from isotropic-distributed plastic deformation modes under in-plane isotropic stress states, to dog-ear-, slot-, and/or butterfly-shaped inelasticity in the presence of strongly anisotropic in situ stress. It was found that each of these scenarios can be explained in terms of controllability indices computed at locations exhibiting inelastic response, thus establishing a link between the computed modes of global borehole deformation and multiple types of compaction localization processes (e.g., compactive shear bands, shear-enhanced compaction bands, and pure compaction bands). [ABSTRACT FROM AUTHOR]

The load transfer mechanism of laterally loaded pile groups is very complicated, and the analysis method is affected by many factors. This paper presents a field test study on lateral responses of large diameter cast-in-place isolated single piles with free head and pile groups with fixed head to investigate the pile group effect. Boreholes are drilled, and relevant field and laboratory tests are carried out to obtain main physical mechanical parameters and the soil profile of the site. Results of lateral loads, lateral displacements and bending moments measured in the field are reported and discussed. A group efficiency factor-based calculation method applicable to laterally loaded pile groups is derived according to a series of full scale and centrifuge tests. An existing group efficiency factor-based calculation method is compared with the proposed method. And three other measured test results are used to verify the calculated results. The comparison results show that the proposed method provides good predictions of load–displacement responses of pile groups. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine how to evaluate the engineering geological suitability of large-scale infrastructure site quantitatively. This paper presents a borehole engineering geological suitability index (BEGSI) model based on the rock engineering system. This model was designed to define the principal causative factors responsible for engineering geological suitability, quantify their interactions, obtain their weighted coefficients, and calculate the suitability index. Recently, the BEGSI model has been applied successfully in the site evaluation for the China initiative Accelerator Driven System (CiADS) and the High Intensity heavy-ion Accelerator Facility (HIAF). Firstly, lithology, structural surface inclination, rock quality designation (RQD), topographic elevation difference, fault influence, groundwater depth, and weathering crust thickness were selected as influencing factors and classified into different categories. Afterwards, the interaction matrix was constructed, and the weighted coefficients of each factor were calculated by considering the relationship among these seven factors comprehensively. Finally, the BEGSI for 222 boreholes were computed, and then the site zoning was accomplished. The result was adopted by the Chinese government, and the CIADS and HIAF site layout was adjusted accordingly. This study shows that the BEGSI model is scientific, reasonable, and applicable as a reference for similar large-scale infrastructure site evaluation. [ABSTRACT FROM AUTHOR]

Radial borehole fracturing is a production method that combines ultrashort radius radial boreholes with hydraulic fracturing, which is expected to effectively improve the drainage and transformation effect of tight oil and gas reservoirs. In view of the problem that radial boreholes cannot be fully fractured when high-pressure liquids are injected into them simultaneously, this paper proposes a new method of fracturing the radial boreholes step by step, and this method is verified by the laboratory fracturing experiments. It designed and processed wellbores with both internal and external pipes, conducted 24 sets of radial boreholes step-by-step experiments of double-layer radial boreholes, analyzed the reproducibility of the experimental results, and compared the results of fracturing radial boreholes simultaneously and fracturing radial boreholes step-by-step experiments. The results show that this method can fracture two sets of radial boreholes distributed in different vertical planes. The results demonstrate that this method is feasible and can solve the problem that not all the radial boreholes are fractured when fracturing fluids are simultaneously injected into them. Besides, the azimuth is the key factor affecting fracture geometries. When the azimuths are 0° and 30°, the fractures can cut through radial boreholes in different layers within the rock samples. If the radial boreholes with larger azimuths are fractured, it will generate higher breakdown pressures. Fracturing radial boreholes with smaller azimuths first and then radial boreholes with larger azimuths should be selected. This study provides a theoretical basis for the field application of radial borehole fracturing technology. Highlights: A new method of fracturing the radial boreholes step by step is proposed. The azimuth is the key factor affecting fracture geometries. If the radial boreholes with larger azimuths are fractured, it will generate higher breakdown pressures. [ABSTRACT FROM AUTHOR]

The Osaka Bay is situated at a seismically active region north of the Median Tectonic Line and east of Awaji Island in western Japan, known as part of the Kinki Triangle and the Niigata–Kobe Tectonic Zone. Dense distribution of active faults and high geodetic strain rates characterize the region, posing a major seismic hazard potential to the coastal and metropolitan areas of the Kansai region. To investigate the shallow structure and recent deformation history of active faults in the Osaka Bay, we acquired 15 high-resolution seismic profiles using a Mini-GI airgun and a Boomer as active sources, together with multi-beam bathymetry data across the Osaka Bay Fault. Our seismic sections image a ~ 0.1 to 3.7 km-wide asymmetric anticline forelimb above the Osaka Bay Fault at shallow depths, coupled with a ~ 2.6 km-wide syncline to the west, and a broad, ~ 11 km-wide syncline in the footwall to the east. The synclinal axial surface at shallow depths measured in this study ranges 75°–89°. We observe the vertical displacement of the Osaka Bay Fault increasing northwards along strike. The sediment thickness on the hanging wall, however, is variable, modified by non-tectonic processes such as by tidal currents, affecting the geometry of growth strata. The most recent deformation by the Osaka Bay Fault reaches to near the seafloor by active folding, with large vertical offsets of 8–14 m over the last ~ 11 ka, and 5–11 m over the last ~ 5 ka. By combining with previously reported borehole age data, the average uplift rate on the Osaka Bay Fault is estimated to be ~ 1.0 to 1.7 m/ka during the Latest Pleistocene to Holocene. The inferred slip of the Osaka Bay Fault during the Holocene is likely to account for > 5% of the regional geodetic strain accumulation within the Kinki Triangle. Further studies to evaluate the Holocene slip rates of regional faults are necessary to assess the seismic hazards and the internal strain budgets within the Kinki Triangle and the Niigata–Kobe Tectonic Zone. [ABSTRACT FROM AUTHOR]

The South Jingyang tableland, located in Shaanxi Province, China, is composed of loess deposits. Agricultural irrigation in this area has caused the continuous rise of the groundwater table, which triggered a series of loess landslides. Although extensive research has been conducted on the effect of rising groundwater tables on induced loess landslides, less is known about the groundwater table distribution. This study jointly investigated the distribution of the groundwater table in the South Jingyang tableland using boreholes, electrical resistivity tomography (ERT), and laboratory tests. A qualitative analysis between the apparent resistivity and the water content was estimated at different depths, using the borehole data and ERT inversion data. A quantitative relationship between the resistivity and the water content was established in the laboratory tests. A combination of the qualitative analysis of the inversion results and the quantitative relationship was used to determine the distribution of the groundwater table. The groundwater table is present at the depth where the water content of the loess is 30% (liquid limit of loess) and the resistivity is 28.35 Ω m. The groundwater table elevation in the southern study area is higher than that of the northern study area and decreases in a stepwise gradient from south to north. This study not only identified the distribution of the groundwater table in the South Jingyang tableland, but also makes up for the limitation and inaccuracy in determining groundwater tables by relying solely on the borehole information or inversion results of ERT. The ascertained distribution characteristics of the groundwater table provides a basis for the analysis of the formation mechanism of landslides. [ABSTRACT FROM AUTHOR]