Examination of the treatment quality of filling mined-out voids using super-high-water material by the TEM technique

Abstract

Many mined-out voids pose a great threat to engineering construction in China. To prevent the potential surface deformation caused by mined-out voids collapse, filling material treatment methods such as liquid cement slurry, mixture with different proportion of cement and fly ash, mixture with different proportion of cement and clay are used. In recent years, the super-high-water material has been widely adopted. However, few studies have been carried out to examine the treatment quality using super-high-water material. In this study, a case of the application of super-high-water material in treatment of mined-out voids was firstly presented and then the treatment quality was examined by geophysical transient electromagnetic method (TEM). In order to study the feasibility of TEM, 1D forward modeling was used to obtain the TEM response curves before and after filling and obvious differences were observed. After filling, the max amplification of secondary field-induced voltage would be about 40 or 100% depending on whether underground mined-out voids had been water-accumulating or not before; the corresponding apparent resistivity would decrease more than 20% after filling. The practice at a coalmine located in northern China showed that the change features of apparent resistivity between before and after filling coincided with the modeling; the effective filled area inferred by the boundary whose apparent resistivity had decreased more than 20% was basically accurate, which clearly indicates that the filling mined-out voids using super-high-water material was feasible and effective.