Stability Analysis of Tunnel Driven in Stratified Anisotropic Rockmass

In present engineering design, rock mass is simply treated as an isotropic material and their strength parameters are given by decreasing those of intact rock through joint connectivity, which is introduced to reflect the integrity of rock mass separated by joints. This method may be acceptable for most jointed rockmass. But for some sedimentary or metamorphic rocks, such as shales, sandstones, slates, phyllites and schists, are characterized by inherent anisotropy due to the existence of the preferentially oriented weakness plane. In this study, the influences of the anisotropic properties of rockmass on the deformation and stability of tunnel are analyzed by the site monitoring and numerical calculation. A detailed investigation on the engineering geological conditions of the horizontal stratified strata in Queerxi Highway Tunnel was carried out. The deformation and the surrounding rock pressure are monitored, and then field measuring results and distributing law are summarized. The results show that anisotropy of rockmass has remarkable influence on the deformation properties and stability of tunnel in stratified jointed rockmass.