Study on creep constitutive model of stratified siltstone and its application to instability analysis in mining

The main objective of this research is to propose scheme to solve creep hazards caused by mining. Rock is the main body of underground coal mining, and among them stratified siltstone is very common. Creep of underground stratified siltstone is one of the main inducing factors of ground fissures and ground surface settlement. In this study, the VCM of stratified siltstone was built and theoretically analyzed. Creep tests under multi stress were conducted, also, numerical simulation was carried out with 3DEC. Numerical simulation results under high, medium and low stress were consistent with the creep test results, it made up for the deficiency of traditional creep models in predicting plastic deformation at low stress level. Numerical simulation results showed that under different boundary conditions, the proposed model had advantage to more accurately simulate creep behavior of stratified siltstone compared to traditional models. Also, the numerical simulation results reveled creep characteristics of underground roadway surrounding rock, based on which a supporting scheme was put forward. In the stress adjustment stage, the strain rate dropped significantly from 14.6 mm/day to 10.3 mm/day. Then, it entered the deceleration creep stage. Creep of roadway surrounding rock and ground surface settlement stopped. The creep hazards were solved to a great extent.