Instability Analysis of Anchorage Supporting in Soft Rock Roadways based on Strain Softening

Abstract

In view of the problems such as spray layer peeling-off, reduced anchoring force and serious floor heave in the weakly cemented soft rock roadway in the west region, we took samples from the sandy mudstone formation in the main haulage roadway of Luxin Coal Mine in Inner Mongolia and performed triaxial compression tests at different confining pressure in the lab. The test data show that the post-peak strain behaviour of the mudstone is obviously softened and there exists residual deformation, thus the tri-linear strain-softening model is more suitable for analysis. We made fish corrections to the bi-linear strain-softening model in FLAC to achieve the numerical application of the model. The verification model shows that the tri-linear strain-softening model better describes the deformation features of mudstone. We analyzed the construction stability of the mudstone roadway and conducted evaluation based on the softening index. The results show that due to the increasing softening degree and softening depth of the mudstone roadway, the shotcreting support system has no obvious effect in controlling the deformation of the surrounding rock, and that the bolt axial force first increases and later decreases, losing its retaining effect.