| The Zaozigou gold deposit in Gansu Province is located in the northeastern margin of the Qinghai-Tibet Plateau and belongs to the Xiahe-Hezuo iron-copper-gold metallogenic belt.The geological structure is complex and the fault structure is very developed.It is roughly composed of five groups of faults in NE,NW,near SN,near EW and NNE directions,and the metallogenic conditions are superior.The mining area is rich in water resources.As a result of the structural influence on the groundwater system,the hydrogeological conditions are notably intricate.Therefore,the analysis covers the characteristics of geological structure development and the hydrogeological conditions within the mining area.,and the control effect of the fault structure on the groundwater system is analyzed.In order to study the regularity of structural water control,and establish the structural water control model of the mining area,it provides a reference for the safe mining of gold deposits in the mining area,and also provides a theoretical basis and guidance for the mine to formulate corresponding water control measures.This study takes the Zaozigou gold mining area in Gansu Province as the object,and comprehensively uses the theory of structural geology,hydrogeology and structural water control.Firstly,the study focuses on the regional geological structure and hydrogeological features.Secondly,the hydrogeological units are divided and the structural characteristics are analyzed to understand the hydrogeological conditions and groundwater dynamic characteristics.Based on this,the control effect of structure on groundwater in the mining area is studied,including the control characteristics of structure on water-rich zoning and the control characteristics of structure on groundwater dynamics.Finally,the fault structures within the mining area are classified into water-conducting,water-blocking,and water-storing types,with each type’s structural water-controlling mode being investigated individually.Using FLAC.3D mathematical simulation method,taking the water-conducting fault structure which is most closely related to mineralization as an example,the influence of water control characteristics of fault structure on mining effect in Zaozigou mining area is discussed.The study draws the following conclusions :(1)The mining area is generally presented as a nearly north-south monocline structure,which tends to the west.In some areas,strata are affected by magmatic intrusion and fault activity,forming small folds between layers.The fault structures in this area are very rich,mainly including NE,NW,near SN,near EW and NNE five groups of faults.The first four groups of faults control and form four groups of gold ore belts.These structures have tensile shear properties and large extension.In terms of scale,NE and near SN faults are the most significant,followed by near EW and NW faults.In terms of formation time,from early to late,it is NW,near SN,NE,near EW and NNE.(2)The water filling factors of the deposit are mainly atmospheric precipitation and structural fracture zone vein water.(3)The recharge source of groundwater in the study area is mainly from atmospheric precipitation and the seepage of the Zaozi River.The groundwater types can be divided into three types : Quaternary gully loose rock pore water,bedrock fissure water and fault zone vein water.(4)Fault structure can not only affect the water yield of aquifer,but also is an important factor affecting the depth of groundwater circulation.Through calculation,the groundwater recharge circulation depth of Quaternary gully is relatively shallow and basically stable.Under the influence of bedrock fissures that are well developed in the mining area,the spring recharge circulation depth is relatively shallow.The supply circulation depth of mine water is relatively deep,and the corresponding fracture is also a favorable channel for ore conduction.(5)The Zaozigou gold mining area’s structural water control mode can be classified into three categories: water-blocking,water-conducting,and water-storing types.The water-conducting fault is the largest fault group in the mining area.There are 28 faults in SN,NE and nearly NW directions.The water-blocking faults mainly include NW and NNW faults and the water-blocking boundary of the mining area.The water-storing faults mainly include weathering faults in the shallow part of the mining area and nearly EW faults.As a result,the research focused on the F24 water-conducting fracture located in the central part of main shaft 12 for mathematical modeling and comparative examination.The findings from the simulation highlight a considerable impact of water-conducting faults on gold extraction.Compared with the mining without faults,the plastic failure degree of the roof and floor of the goaf is more serious and the deformation displacement is larger in the presence of water-conducting faults.At the same time,the vertical stress of rock is significantly higher than that of non-fault mining,and the deformation of roof also forms a good water channel.This significantly increases the risk of mine water inrush and reduces the safety of gold mining. |
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