Study on mechanical strength and deformation characteristics of tuff rock in deep formation of Xushen gas field

The volcanic tuff in the deep of Xushen gas field is the most development volcanic rock. Through the conventional triaxial compression experiments, the stress-strain curve of tuff rock was obtained under the different confining pressures. The strength characteristic, deformation characteristics, expansion characteristics and the basic deformation parameters were also obtained. The results show that with the increase of confining pressure, the strength and deformation ability of tuff increase significantly. The rock experiences the transition from plasticity to elasticity, elasticity to elasticity-plasticity in break forepart. After break, the strain softening characteristic is weakened gradually. It presents the ideal plastic characteristics. Taking the linear strength envelope as a special case, the rock's critical confining pressure of achieving the ideal plastic state prediction method was established. The above research results provide the foundation for the various engineering problems' analysis and calculation in this kind of formation.