Abstract: To reduce the negative impact of the underlying goaf on the stability of the roadway surrounding rock, this paper adopts the method of adjusting the supporting time to realize the purpose of actively regulating the surrounding rock deformation. Based on the theory of virtual supporting force method, three influencing variables, namely zone insecurity, stress release coefficient and displacement completion coefficient, are introduced, the relationship curves of the three variables are constructed to solve the optimal supporting time, and the comprehensive evaluation is carried out from the two aspects of displacement and supporting force. The results show that the distribution pattern of zone insecurity at the tunnel wall changes from circular to oval and finally to circular. The smaller the spacing between roadway and goaf, the shorter the optimal supporting distance. When the spacing is 0.5D (D is the tunnel diameter), the optimal supporting distance is advanced by 91.866%, and when the spacing is above 2.0D, the influence of goaf basically disappears. The research results can provide reference for related engineering.
Keywords: underlying goaf; supporting time; virtual supporting force method; zone insecurity