Microseismic Source Location Method Research Based On Ground-underground Layout In Coal Mine

Due to the high-intensity mining of coal resources,the coal resources in the old mining areas in the central and eastern regions are rapidly depleted.The recovery of shallow remaining resources and the development of deep coal resources are facing the "three under and one above" problems.Although the coal seams in the western mining areas are shallowly buried and the mining conditions are simple,the environment is very fragile,and"water-preserved coal mining" has become an important issue to ensure sustainable development in western mining areas.How to use microseismic monitoring technology to achieve high-precision observation of mining fractures in coal mines has become a research hot topic.Microseismic source location accuracy is limited by multiple factors such as travel time calculation method,monitoring network layout,velocity model,source location method and so forth.In this paper,the main factors affecting the accuracy of source location are taken as research objects.Theoretical analysis,numerical simulation,and field tests are used to carry out research on high-precision methods for microseismic location.The main research results and conclusions obtained are as follows:(1)Aiming at the problem of low calculation accuracy of travel time near the microseismic source point during calculation of the fast marching method,a grid encryption method near the microseismic source point is optimized,which has a significant effect on reducing the travel time error near the focal point and diagonally.(2)The objective function of the multi-seismic joint speed model is constructed,and the DIRECT fast search method with global optimization characteristics is used to solve the objective function,which makes the inversion of the microseismic layered velocity model to realize and the inversion accuracy of "Ground-Underground" microseismic velocity model to improve.(3)Based on the layered velocity model inversion method and the fast marching method of the grid encryption method improved near the focal point,a microseismic source location inversion method is constructed.The source location method has high positioning accuracy in both the horizontal and vertical directions.(4)Five kinds of microseismic monitoring network layouts are designed,and a comparative study of the microseismic monitoring network layouts is carried out.The results show that the "Ground-Underground" microseismic monitoring network layout method is significantly superior to other monitoring network layout methods in the horizontal and vertical directions.(5)By taking advantage of the "Ground-Underground" microseismic monitoring system in the coal mining process,the development height of the water flowing fracture zone is delineated and the abutment pressure distribution characteristics of the first mining face is analyzed.The three have higher consistency through comparing with the field measurement results and numerical simulation results.