Statistical Constitutive Model of Loess Damage and Its Application in Tunnel Stability Analysis

In order to judge the stability of surrounding rock in loess tunnel construction more correctly and reasonably, a statistical constitutive model of loess damage is proposed, and a limit strain method is proposed to judge the stability of tunnel construction. In this paper, it is assumed that the strength of loess micro elements is subject to composite power function, and the continuum damage mechanics theory and equivalent strain theory are used as the modeling basis. Meanwhile, considering the influence of confining pressure and water content on the deformation modulus of loess, a new constitutive model which can reflect the stress-strain relationship of loess under different water content and different confining pressure is established by using statistical method. The results show that the model established in this paper can well reflect the strain hardening characteristics of loess during the whole loading process, especially the strain softening characteristics under low confining pressure. Based on the statistical constitutive model of loess damage established in this paper, the formula for determining the limit strain of surrounding rock is modified on the basis of the original method for determining the limit strain of surrounding rock. Finally, a method for determining the stability of tunnel construction in loess stratum is proposed and applied to practical engineering.