Study on the Evolution of Fault Permeability and the Retention of Coal (Rock) Pillar under the Mining Conditions of Thick Coal Seam in the Footwall of Large Normal Fault.

As a typical geological structure, the fault often threatens the safe mining of coal mines. In order to investigate the permeability evolution of the significant normal fault under the mining disturbance of the thick coal seam of the fault footwall and to propose a scientific and reasonable coal (rock) pillar retention plan, this paper took the YinJiaWa Fault (YJW Fa), a large normal fault, in Fucun Coal Mine, Shandong Province, China, as a research object, conducted a coupled fluid and solid simulation study on permeability evolution of the fault using COMSOL Multiphysics, based on the revealed geological data and rock mechanical parameters, and combined the theoretical calculation results to determine the width of the waterproof coal (rock) pillar. The results show that the width of the waterproof coal (rock) pillar of YJW Fa is negatively correlated with the porosity, permeability, and flow velocity of each monitoring point. With the width of 60 m as the dividing point, as the width left less than 60 m and gradually reduced to 30 m, its water-blocking capacity is destroyed, increasing the seepage velocity in the water-flowing fractured zone, forming a water channel, causing water inrush accidents. The formula and numerical simulation results are used to determine the width of the waterproof coal (rock) pillar of the YJW Fa to be 74.44-84.08 m, to ensure the safe mining of the fault footwall. This paper provides a theoretical basis for further understanding of the fault permeability development rules and safety guidance for coal seam mining of the fault footwall.

Research on the Genetic Mechanism of High-Temperature Groundwater in the Geothermal Anomalous Area of Gold Deposit-Application to the Copper Mine Area of Yinan Gold Mine.

Geothermal energy is new, environmentally friendly, and clean energy, which is of great significance to realize energy saving and emission reduction. The study of the genesis mechanism of geothermal water is the key to its rational development and utilization. In this study, based on 14 sets of water samples from the eastern section of the copper well mining area of Yinan Gold Mine, mineral saturation index, isotope analysis (δ18O, δD), Si-enthalpy mixing equation, and geochemical geothermal temperature scale were used to analyze the thermal storage temperature, recharge characteristics, mixing ratio, circulation depth, and fluid passage to reveal the geothermal water fugitive transmission pattern and genesis mechanism in the study area and to propose a geothermal water genesis model. The study shows that the water supply elevation in the area is between 687.22 and 1164.15 m and a large amount of cold water recharged it. It is inferred that the recharge area is the precipitation in the Northwest Mountain range and surrounding atmosphere. Groundwater flows along the fracture zone in a south-easterly direction. It receives heating from the surrounding rocks, where the water level rises at the fracture zone intersection and is stored in the lower and middle Cambrian thermal reservoirs and continues to receive heating from deeper heat sources. Based on this study and previous regional research data, the fault structure in this area is within the influence range of the energy field of the Yishu fault zone. Yishu fault zone becomes the heating source under the background of cold water. It is inferred that the east-east Yishu fault zone in the study area may also be the recharge area.

Improved Combination Weighted Prediction Model of Aquifer Water Abundance Based on a Cloud Model.

The sandstone aquifer is an important underground water storage space, and the study of its water abundance is of great significance to ensure the safety of underground engineering and to explore the occurrence mechanism of groundwater sources. Based on the correlation between geological characteristics and aquifer water abundance, this paper proposed an aquifer water abundance prediction model based on a cloud model that improved combination weighting. The model took the roof sandstone aquifer of the Qingshuiying Coalfield as an example and selected five basic geological indicators that are closely related to the water-rich influence degree of the aquifer as evaluation indicators. The model was based on the idea of game theory, combined the analytic hierarchy process (AHP) and the entropy weight method, and introduced the cloud model evaluation method. The establishment of the model was based on the idea of game theory, combining the AHP and the entropy weight method and introducing the cloud model evaluation method. The results show that most of the study areas are located in weak or relatively weak water abundance areas; relatively strong water abundance areas are mainly distributed in the central, western, and southeastern parts of the study; strong water abundance areas are scattered in parts of the northeast, southwest, and southeast. The unit water inflow data of the actual pumping test is consistent with the water-rich prediction partition, which proves the accuracy and scientificity of the method. The model provides a new idea for the study of groundwater geology and a new method for predicting the water abundance of the roof aquifer in coal mines.