Experimental study of similar simulation of locked-in stress in rock based on simplified mechanical model

Abstract

In the environment of deep earth, the “locked-in” stress is widely distributed and considered to be the main cause of rock engineering disaster. But when the rock sample is brought back to the laboratory from deep rock mass of high stress, temperature, and hydraulic pressure, the locked-in stress is dissipated over time. In this paper, similar materials are used to simulate the locked-in stress in the rock. Assuming that “locked-in” stresses in the rock are randomly distributed in the form of spherical inclusions, a simplified geometric model is proposed. By making the “locked-in” stress in rock equivalent to the thermal stress caused by the uncoordinated deformation of inclusion in the rock-like material, the elastic theory formula which expresses the relationship among temperature increment, mechanical parameters of rock-like materials, mechanical parameters of inclusions, and equivalent locked-in stress is deduced. According to the thermodynamic properties of various materials, nitrile rubber is selected as inclusion material. On the basis of the relationship among the temperature increment, the mechanical parameters of the rock-like material and that of the mechanical parameters of the inclusions, and the equivalent “locked-in” stress, an appropriate rock-like material is selected as the matrix material. The “locked-in” stress produced by the inclusions in different ambient temperatures was tested by self-designed method. By comparing and revising, the empirical equation to quantify the locked-in stress is obtained.