Explore the vast range of titles available.

The overlying rock in the weathering and oxidation zone has well-developed micro-fissures, making roadway roof control highly challenging. Ordinary cement slurry is hard to inject, failing to achieve effective reinforcement. By introducing admixtures like ultrafine fly ash and polyvinyl alcohol (PVA) to modify ultrafine cement, this paper developed a PVA-modified ultrafine cement-based grouting material (PVAM-UFCG). It systematically investigated the influences of various factors on the slurry’s setting time, fluidity, water separation rate, viscosity, and 28-day uniaxial compressive strength, determining the optimal mix ratio through comprehensive analysis. The results show that the water–cement ratio is the dominant factor affecting slurry viscosity, strength, and setting time; the polycarboxylate superplasticizer concentration has the most significant influence on fluidity and water separation rate; a 20% ultrafine fly ash replacement rate can optimize particle gradation and enhance long-term strength; and a 1.0% polyvinyl alcohol concentration can effectively control the water separation rate (≤5%) and improve slurry cohesiveness. Through range analysis and multi-indicator comprehensive evaluation based on the entropy weight method, the performance-balanced optimal mix ratio meeting the grouting requirements for the Weathering and Oxidation Zone was determined: a water–cement ratio of 0.6, an ultrafine fly ash replacement rate of 20%, a polyvinyl alcohol concentration of 1.0%, and a polycarboxylate superplasticizer concentration of 0.4%. This mix ratio material exhibits good permeability, stability, and appropriate reinforcement strength. The research results can provide a new material choice and theoretical basis for controlling the surrounding rock of roadways under similar geological conditions.

Significant risk of water and sand inrushes is commonly encountered during coal seam mining when thin bedrock is directly overlain by thick, water-bearing, unconsolidated layers. Achieving effective strata control and establishing reliable water-isolating mechanisms under these conditions represent critical scientific and technological challenges for safe mining operations. Furthermore, this is a vital research direction for advancing the extraction limit (or recovery height) in coal seams. Initially, drawing on key stratum theory, ground pressure behavior patterns, and mining operation characteristics, the weathered zone was identified as the critical grouting horizon. During the initial mining stage, the first two periodic weighting intervals (approximately 60 m) were identified as the key area. Subsequently, a strategy of high-pressure grouting was proposed to modify the weathered stratum. Numerical simulation methods were employed to optimize the grouting parameters, with the core specifications determined as follows: grouting pressure ≥30 MPa, water–cement ratio of 0.7:1, and grouting hole spacing ≤30 m. Ultimately, a grouting system was designed that used directional drilling from the surface to access the weathered zone, followed by branched horizontal boreholes for staged high-pressure grouting. The borehole trajectory was predominantly L-shaped. Field implementation demonstrated that the grouting intervention increased the first weighting span by an average of 17.3%. Critically, no water inflow was observed throughout the initial caving period, and significant roof falls or rib spalling were effectively mitigated. This confirmed a substantial improvement in key stratum stability, ensuring the safe and efficient advancement of the mining face. This study provides essential technical support and a practical model for safely and efficiently extracting coal seams under thin bedrock under similar complex hydrogeological conditions.

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.

Vertical electrical sounding is widely used as information essential to governing the subsurface geological character, structural and hydrogeological conditions to delineate the sustainable development of groundwater potential zone. The structural reliability of this setup is concerned with Electrical resistivity method insights into the resistivity distribution in the subsurface fracture of groundwater resource conditions. This study is an objective framed for evaluating the groundwater potential and aquifer protective capacity. It is important to assure groundwater supplies to fulfill the requirements for society’s water requirements. Surface recharge structures have enhanced the groundwater resource to identify subsurface characters using resistivity surveys. In this investigation, an endeavor has been made to outline distinctive lithological conditions by the use of this survey technique to determine the suitable areas of artificial groundwater recharge. The VES profile indicates that in this area, results show the distribution and variability of resistivity layers as depth wise, at point 1 gives ρ2 > ρ 3 > ρ1 and point 2 as ρ1 < ρ2 > ρ3 > ρ4. An obtained VES results are interpreted in the watershed which showed maximum current penetration. Point 1 is good for locating bore wells whereas point 2 is greater than 600 hence it is the best suitable site for recommendation. Groundwater potential are good that was observed at closer to well point 1 and aquifer protective capacity has been determined by Longitudinal Conductance (S), which was found good protective aquifer capacity in the study area indicates low vulnerability area. Hence, protective capacity renders the aquifer a good resource in this study area.

Changing climate in Northern Ghana has led to erratic rainfall patterns which have affected agricultural practice over the years. This research interrogates various factors which affect the success of agriculture in the area, specifically the Nasia sub-basin, to suggest prudent water management strategies which will be required to adequately adapt to the impacts of climate change. The research evaluates the irrigation water requirements of the major staple crops in the area in the context of a changing climate, and the implications on available groundwater resources to support small-scale irrigation. The study then proceeds to use a robust geostatistical technique to estimate the spatial variations in the thickness and characteristics of the regolith in the Nasia sub-basin since the latter plays an important role in the hydrogeological characteristics and the groundwater resources potential of the rocks of the Neoproterozoic Voltaian Supergroup. The variography conducted on the regolith thicknesses in the area suggests a high level of spatial variability within short distances, consistent with the nature of the underlying geology. The models suggest that the older, sandstone formations in the north of the terrain are associated with thicker regolith compared to the finer grained, younger formations in the south. Locations of thick regolith are generally regarded as areas of high promise in terms of shallow groundwater-based irrigation. Based on local conditions which dictate the crop types cultivated during the major cropping season, this research has computed crop coefficients for four crops (i.e., millet, maize, groundnut, and rice). The analysis suggests that the crop water requirements for the various staple crops are sensitive to variations in climatic conditions and will respond to increasing temperatures and evapotranspiration rates as predicted by climate models over the sub-region. This research recommends further detailed hydrogeological research which builds on the predicted variations in regolith thickness and characteristics already identified here. This will facilitate a proper delineation of prolific groundwater-bearing units within shallow, easily accessible depths to support smallholder irrigation in the area.

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 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 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 2+ –Mg 2+ –HCO 3 − , Na + –K + –HCO 3 − and Na + –K + –Cl − –SO 3 2− . The Na + –K + –HCO −3 has the highest percentage of occurrence (70%) followed by Na + –K + –Cl − –SO −3 (20%) and the least, Ca 2+ –Mg 2+ –HCO −3 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).

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.

Once a coal seam has been weathered and oxidized, the quality of the coal is lost and the coal resources are wasted. At the same time, new risks are introduced to the safe operation of the coal mine. Therefore, it is critical to determine the extent of the weathered and oxidized zone in the coal seam. This paper depicts the electromagnetic characteristics of the weathered and oxidized zone of coal seams, briefly introduces the method of detection by transient electromagnetic method (TEM) and the data processing steps, and performs the numerical simulation for the simplified resistivity model of weathered and oxidized zone in a coal seam. It is observed that after the coal seam has been weathered and oxidized, the electromagnetic characteristics (secondary field potential and resistivity) will be dramatically affected, namely high secondary field potential and low resistivity. For experimental verification purposes, this study selects the test project of the Shixin Minefield in Shanxi, China as an example, and the accuracy for the detection of the weathered and oxidized zone of the coal seam using TEM is successfully verified.