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Water–sand mixture inrush generally poses a significant threat to the safe operation of the quarry of coal mines. Therefore, proactive management initiatives are essential to enhance the impact resulting from mining operations. A novel approach involving grouting into the unconsolidated sand aquifer and the weathered zone was initially executed in the 1010-1 panel of the Wugou coal mine in Anhui Province, China. Considering the hydrogeological conditions of the study area, over 70 thousand tons of cement and fly ash were injected through 42 boreholes. Sampling, laboratory tests, similar materials model simulations, and numerical simulations of the trending and dipping profiles were all employed to elucidate the evolution and characteristics during the progression of the No. 10 coal seam. The outcomes illustrated that the grouting execution had transformed the structure of the porous media, weakened the watery media, and intensified the mechanical strength of the No. 4 aquifer and the weathering zone. This transformation proved beneficial in reducing the heights of the caving zone and water-conductive fracture zone, leaving more coal–rock pillars for safety. Twenty-seven underground detection drill holes and whole-space 3D resistivity exploration were adopted to verify its transformed property of low water content. During the mining process, the height of the caving zone at 19.70 m was measured through inter-hole parallel electrical detection. The pressure of hydraulic supports in the grouted area did not exceed the rated working pressure during mining. All of these findings highlight the significant impact of grouting in this study area. The successive safe mining of the 1010-1 panel demonstrates that grouting can be used to prevent water–sand mixture inrush during mining operations. [ABSTRACT FROM AUTHOR]

Coal mining in North China is widely threatened by underlying Ordovician karstic limestone groundwater. This study focused on the top portion of the Ordovician limestone and its water resisting properties at a mine in North China, where the total thickness of the Ordovician limestone ranges between 300 and 1600 m. A packer pump test showed the average permeability coefficient for the top portion of the limestone to be 0.57 × 10–3 m/day; laboratory tests showed that the strength of this segment was 175 Mpa. Meanwhile, the water pressure was 0 Mpa for the top 40 m of the aquifer, and only 6.7 × 10–3 Mpa for the top 41–46 m; it increased considerably between 46 and 55 m, to an average value of 0.47 Mpa, and remained stable after 55 m, with a water pressure of 0.71 Mpa. The top of the Ordovician limestone was therefore divided into weathered, transition, and karst fracture zones. Each zone has different hydrogeological characteristics (water pressure, permeability, and drilling fluid leakage). The thickness of the weathered zone was determined to be ≈ 20–70 m in most of the study area. Overall, the water resistance of the top portion of the Ordovician strata allows it to be treated as an aquifuge, preventing Ordovician groundwater from flowing into the mining face. [ABSTRACT FROM AUTHOR]

In terms of the problems of instability and sand inrush of coal and rock pillar in working face of wedge area under special geological conditions，such as thick loose aquifer，thin bedrock，and so on，taking the water inrush and sand inrush disaster from No.11071 working face of Zhaogu No.1 Coal Mine as an example，combined with geological drilling data，a geological model of wedge shape preserving water pressure mining-sand inrush is established. Through clay liquid plastic limit test，dried and saturated water absorption and disintegration test，it is concluded that bottom clay and weathered mudstone has a good water-proof performance，and can form a “wedge protect pressure” structure. On this basis，through the experiment of weathered mudstone mining crack extension under water pressure，the inherent disaster-causing mechanism of instability of coal and rock pillars of sand layer that is affected by mining damage under water pressure is studied. The results show that under a high water pressure，the mined crack in weathered mudstone extends to pipeline，thus the sand-proof properties of the protective layer fail. Considering the damage thickness of weathered zone of coal pillar，the method of setting up the sand-prevention safety coal and rock pillar under water pressure was put forward，and an engineering application was carried out in No.11191 working face and achieved the expected results. Research results complement the design method of sand prevention safety coal and rock pillars in China，and can reduce the coal mine collapse sand disasters and accidents. [ABSTRACT FROM AUTHOR]

The static corrections are a necessary step in the sequence of the seismic processing. This paper presents a study of these corrections in the Essaouira basin. The main objective of this study is to calculate the static corrections by exploiting the seismic data acquired in the field to improve the deep structures imaging. It is to determine the roof and the basis of the superficial layers which constitute the weathered zone while calculating the delays of seismic wave’s arrivals in these layers. The purpose is to cancel the effect of the topography and the weathered zone, in order to avoid any confusion when the seismic and geological interpretation. The results obtained show the average values of the static corrections varying between - 127 and 282 ms (double time), with existence of high values by location, particularly in the Eastern and North-Eastern of the basin, which meant the presence of altered zone with irregular topography and whose thickness and speeds vary laterally. In effect the variations of velocities in the fifty meters from the surface may introduce significant anomalies in seismic refraction, with heavy consequences when the interpretation or the drilling establishment. These variations are mainly due to lateral changes in facies and variations in the formations thickness. The calculation of the static corrections, revealed high values at certain areas (East and North-East), which will enable us to better orient the future campaigns in these zones. It is therefore necessary to concentrate the seismic cores drillings and the small refraction seismic profiles by tightening the seismic lines meshes in order to have the maximum values of static corrections and thereafter a better imaging of the reflectors.

The electromagnetic profiling and Vertical Electrical Sounding (VES) data were acquired from some communities in the Twifo - Hemang Lower Denkyira District of the Central region of Ghana, in order to determine zones of high groundwater potentials and to recommend suitable sites to drill boreholes for community water supply. The research reported here covered three communities namely; Esukese Ekyire, Kwanyarko. First the electromagnetic measurements were carried out, qualitative interpretations of the data were carried out and weathered rock zones were identified. Then the VES measurements using Schlumberger array were conducted at points on the electromagnetic traverse that displayed weathered zones. ZONDIP1D software was used in creating 1D sounding curve models of geological subsurface structures beneath the sounding points. Results of the modelling suggest that the communities are underlain by three to four geological layers. Interpretations of the 1D inversion of the VES data provide the resistivities and thicknesses of subsurface layers. On the basis of resistivity values and thicknesses of the layers in the 1D models, sites were recommended to drill boreholes for community water supply. [ABSTRACT FROM AUTHOR]

The present study discusses a technique of locating high-discharging dugwells in Precambrian metamorphic rocks in Balarampur, Purulia district, West Bengal, India and describes the hydrodynamic properties of hardrock aquifers using bedrock joints/fractures, lineaments and weathered zone. Dugwells with higher discharges are mainly concentrated in metapelites, rich in biotite. In groups of dugwells, high-discharging wells exhibit linear spatial distribution, denoted as 'well-line,' and consistently show high well discharge along each well-line in every dugwell group. The spatial distributions of high-discharging wells are associated with thick weathered-zones. Well-lines, comprising abruptly high-discharging wells, are spatially correlated to the lithostratigraphic contacts and lower elevation zones. [ABSTRACT FROM AUTHOR]

The quality of groundwater from the Egbe-Mopa area of the Basement Complex of Nigeria has been assessed. Hydro-geochemical analyses and evaluation studies were conducted on twenty water samples, three from boreholes and seventeen from hand-dug wells. The evaluation involved correlation matrix, multivariate analysis (principal component analysis), and comparing the hydro-geochemical data with various standards. The descriptive statistical tests revealed that the principal controlling processes of the groundwater chemistry are hydrolysis of silicate and sulphide minerals and anthropogenic processes. The anthropogenic sources include domestic wastes, and agricultural activities. Based on the hydro-geochemical data, three hydro-geochemical facies were identified, namely: Ca-Mg-HCO, Na-K-HCO and Na-K-Cl-SO. The Na-K-HCO has the highest percentage of occurrence (70%) followed by Na-K-Cl-SO (20%) and the least, Ca-Mg-HCO with 10%. The facies analyses indicate that the groundwater in the area is predominantly recharged by infiltration from precipitation and high occurrence of water-rock interactions. The geochemical data also reveal that the groundwater from the area did not satisfy the standard for drinking purposes; it, however, satisfied the standard for agricultural purposes (especially for irrigation and livestock farming). [ABSTRACT FROM AUTHOR]