Study on mechanism of disaster reduction under extremely-thick igneous rock by isolated grouting in Huaibei Mining Area

In order to solve the problem of disaster prevention and control under the overlying thick and hard strata in Huaibei Mining Area, grouting for disaster red uction was tested below an extremely-thick igneous rock in the No. 1102 mining district of Haizi Mine. The mechanism of mining-induced disaster by the igneous rock W as revealed.The thick rock overlying the No. 1102 mining district had a thickness of 120 ~ 170 m and an uniaxial compressive strength of 120 MPa.During the mining, th is rock roof yielded the overburden load to solid coal due to the underlying bedding separation under igneous rock. Because of the stress concentration and the large d epth, this rock roof became the key issue for this area.A technical measure of isolated grouting was then proposed for disaster reduction.An isolated coal pillar was arra nged between the mined area and non-mined longwall panels. Grouting was first conducted for the mined panels, which was followed by the grouting of the subsequent panel during its extraction. Support was then produced for the overburden. Nine boreholes were drilled for the grouting of bedding plane separation zones and the cave d zones.A total volume of 471 994 m3 fly ash was injected with an extraction of 563 000 tons of coal.The risks for the disasters were eliminated for the mining area.