Influence of stone content on face stability for tunnels in sandy cobble strata

As a result of the complex geological conditions sand-cobble stratum, various types problems may arise during construction tunnels crossing most prominent which is stability problem face. In order to study tunnel face in first, continuous medium model sandstone soil established, and numerical simulation carried out on three-axis compression test analyze its micro-mechanical characteristics. Second, calculation simulated strata excavation established by FLAC3D finite difference software. Then, safety factor K calculated strength reduction method introduced as evaluation index stability, with series stone content, burial depth diameter are analyzed. The results show that macro stress-strain curve can be divided into linear stage, elastic-plastic stage ideal plastic shear increases increase content. process excavation, content stratum; while buried increase, decreases. These provide reference for predicting instability failure tunnels, critical stratum.