Large deformation mechanism and concrete-filled steel tubular support control technology of soft rock roadway-A case study

Large deformation control of soft rock roadway is a major challenge for the safety of mining production. Herein, a well-documented case study of a soft rock roadway is presented regarding its large deformation mechanism and the corresponding control technology. The failure characteristics of the studied roadway under the original support scheme were analyzed in detail, and the large deformation mechanism was discussed combining the geological conditions, rock mass properties and the original support scheme. A reasonable numerical method for concrete-filled steel tubular (CFST) support was proposed, and the bearing performance of the inclined-wall arc arch CFST support was analyzed. Then, a modified combined support scheme composed of ‘bolt-cable + mesh + shotcrete’ and CFST support was proposed and validated by numerical analysis and field application. The results show that there are three main reasons resulting in the large deformation of the background roadway, which are: the contradiction between high in situ stress and broken surrounding rock, the contradiction between high clay mineral composition and poor disintegration resistance, and unreasonable original support scheme with low bearing capacity. The monitoring data obtained from both numerical analysis and field application show that the modified combined support scheme was effective for controlling the large deformation of the studied roadway. This work can provide some helpful guidance for similar projects.