Impact of underground mining on permafrost environment

During underground coal mining in permafrost area, the stability of frozen soil is the constraint factor for coal mining. The paper attempts to investigate the status of permafrost environment after underground mining. We therefore forecast permafrost environment under certain conditions of the initial temperature and different boundary conditions by using the numerical simulation method. The study analyzes the change of the maximum thaw depth (freezing depth) with time at different depth around wall of a well and the space continuity of the maximum thaw-depth (freezing-depth) change with time at different locations of the wall profile. The results show that the maximum freezing depth tends to increase over time. The maximum thaw depth increases along wall of a well year by year and the maximum thaw depth increases faster near the junction of the permafrost and seasonal frozen soil. The cross-section of the mining laneway is smaller, so the increasing range of permafrost temperature is not too large around wall of a well under the effective protection measures. The underground mining thus brings up some certain impact to the surrounding permafrost around wall of a well, but it will not cause a large area of the permafrost thawing deformation.