Deep hole geophones and installing techniques used in microseismic monitoring underground

Two kinds of geophones and their installing techniques used in microseismic monitoring underground coal mines were introduced. The method of installation with hydraulic expander can be used in middle hard and hard strata while the depth of drilling holes should be less than 50 m and geophones can be recycled. The method of installation with cement pouch can be used in soft strata and the depth of drilling holes can reach 50-100 m. These geophones and their installing techniques were investigated by field tests and have successfully applied in underground coal mines.