Method for calculating collapsible compressive stress of loess tunnel foundation

The differential settlement produced by collapsible deformation of loess tunnel foundation is an important factor to cause failure of lining structures. Firstly, two methods for calculating base pressure of the lining structures are derived based on the Terzaghi formula from loose medium surrounding rock pressure and the loose rock pillar formula considering the dead load of lining structures. Then, the analytical solution of vertical compressive stress of tunnel foundation is got when that elastic half-space answer is applied and the base pressure of lining structures and the self-weight stress of at both sides of tunnel overburden soil are considered. Thereby an analytic method for collapsible compressive stress of loess tunnel foundation is proposed. The difference between different buried depths of tunnel foundation pressure and self-weight stress is analyzed by using the two methods for tunnel base pressure, and the difference between the vertical compressive stress of tunnel foundation and the field self-weight stress is analyzed by using the proposed method. The distribution variation laws of foundation compressive stress of vertical and field self-weight stress with the increase of depth are obtained. Compared with the numerical results, the proposed method is proved to be more reliable and safer. It may provide the compressive stress condition for reasonable evaluation of the collapsibility of loess tunnel foundation.