Identification Of Water Inrush Source And Water Intensity Prediction In Deep Mining Of Jiaojia Gold Mine Area,Shandong Province

The deep resources of the gold mines have great potential to be the leading area of the national gold industry,Jiaodong gold mine area is the most important gold deposit concentration area in China,and the Jiaojia gold mine area located in the northwest of Jiaodong,as a typical"Jiaojia type" gold mine,has lacked systematic hydrogeological research for a long time.As the gold deposits are mainly distributed along the footwall of the Jiaojia main fault,the fractures in the stopes are developed with unstable surrounding rock.With the increase of mining depth,the mining and hydrogeological conditions become more complex,surrounding rock stress increases continuously,the space structure is destroyed,the temporal and spatial distribution of surrounding rock stress field and underground flow field become more complex,the composition of mine water is complex with unknown source,which seriously affects the further mining of gold deposits.Therefore,the identification of the source of water inflow(inrush),the prediction of water inflow,and the comprehensive evaluation of water inrush risk can not only provide a theoretical basis for the prevention and control of mine water disaster,but also provide applicable results for avoiding water inrush accidents.Taking the transformation from shallow to deep mining in Jiaojia gold mine area as the background,and established the PCA(principal component analysis)-EWM(entropy weight method)-HCA(cluster analysis method)water source identification model based on isotope analysing and correlation degree analysis,et al.Based on GMS software,a three-dimensional numerical model of groundwater flow was established to study the characteristics of groundwater flow field,water inflow and water chemistry.Based on FLAC3D software,a three-dimensional geomechanical model was established to study the characteristics of surrounding rock migration,stress field change,plastic zone failure and fault slide in the process of gold mining.Combined with the above analysis and research,the multi-source information fusion technology was used to make a quantitative evaluation of the water inrush risk in the study area by integrating the water abundance,structural complexity,permeability,hydrodynamic conditions,aquifer thickness and water pressure influence factors.The main research results are as follows:(1)By means of isotope and water chemical characteristic tracer analysis,it can be concluded that the main water inflow(inrush)source of deep mining is the structural fracture water in fault footwall,followed by the structural fracture water in fault hanging wall,however,it is difficult for bedrock weathered fracture water and Quaternary pore water to enter the stope.With the increase of mining depth,the hydraulic connection between mine water and the structural fracture water in fault footwall and hanging wall is more close,the recharge of seawater infiltration is stronger.(2)A groundwater numerical model was established based on topographical,stratigraphic and hydrogeological data,and it was concluded that the mine drainage was the main discharge method,obvious depression cone had appeared in the mining area,and groundwater was in a negative equilibrium state.With the increase of mining depth,the water inflow increases and had a stable trend at the same level.The general direction of groundwater in fracture aquifer was from southeast to northwest,and the fault has a certain blocking effect on groundwater flow.(3)A three-dimensional geomechanical model was established based on the mechanical properties of rock mass,and concluded that the vertical displacement of the middle stope was large but the displacement of both sides was small,and the displacement of the hanging wall of fault was significantly greater than that of the footwall.Generally,when mining at the beginning of a new level,the displacement of the shear direction of the fault was the largest.A stress concentration zone is formed in the front and rear of the stope,and compressive stress at one end near the fault is less than that far away from the fault.The plastic area is banded along the footwall of the fault.According to the characteristics of overburden failure,fracture development and stress variation,the overlying strata in stope are divided into four zones,that is,ground pressure crushing zone,fracture expansion zone,fracture disturbance zone and original rock stress zone.(4)Aquifer water abundance,structural complexity,permeability,hydrodynamic conditions,aquifer thickness and water pressure influence factors were selected for multi-source information fusion.Then,according to the threshold value of water inrush intensity index,the study area is divided into three areas,that is,strong water inrush area,medium water inrush area and weak water inrush area.The intensity index of water inrush gradually increases from east to west,and it is the largest in the central and western regions of the study area.When the mining level is-700 m to-900 m,the stope is in the strong water inrush area.