Study on Surface Stability and Residual Deformation of Old Goaf in Dongjiagou Mine, China

Old goaf under the overpass becomes serious hidden trouble of subgrade-pavement and bridge engineering. Based on geological survey, geophysical survey and theoretical analysis, this paper studies on formation mechanism and distribution characteristics of the surface residual deformation in old goaf in No.9 Line Overpass across Rapid Rail Transit Line No.3 in Dalian city. A comprehensive analysis and evaluation has been made on the stability of old goaf. Based on the calculation principle of the probability integration method, the conception of ground residual subsidence coefficient and the predicted model of residual deformation are proposed, ground residual deformation of old goaf under the overpass is predicted. According to the zonal principles of ground stability, the stabilities of areas are divided. The results indicated that, new overpass has an important effect on the old goaf overburden rock activation in study area that the surface will be instability uneven settlement and the ground residual deformation values will exceed allowable values. Some treatment should be done to the old goaf because of the poor stability of goaf and non-goaf within influence zone in study area.