Study On Jointed Rock Mechanic Characteristics And Mechanic Behaviors During Tunnel Construction

Abstract:In recent years, with the accelerating pace of mountain area’s traffic construction in our country, geological conditions faced in the construction process become more and more complicated. Particularly, tunnel excavation under the condition of jointed surrounding rocks has caused great difficulties to construction. Based on discrete element theory, combined with China Railway25th Bureau Group Co., Ltd. science and technology research plan project"the key techniques for construction of extra-long tunnel under complicated conditions of security ", and on the reference of Hengchaji railway’s longest Eling tunnel, jointed rock mechanic characteristics and tunnel construction mechanic behaviors have been studied, the main research contents are as follows:(1) From jointed rock’s geometrical and mechanical characteristics, and on the basis of jointed rock fissures’permeability coefficient and seepage deformation characteristics, the deformation equation of jointed rock fissures under the action of seepage water pressure was put forward.(2) the basic principle of discrete element particle flow numerical calculation was expounded, and the modeling methods and calculation steps of discrete element software PFC3D for numerical analysis of geotechnical engineering were introduced systematically.(3) According to discrete element theory, from granular medium’s motion equations and force/displacement equations, the particle flow calculation software PFC3D was used to carry out three-axis numerical experiments on jointed rock materials to analyze jointed rock’s microcosmic parameter selection and macroscopic mechanic property responses, and the general rules of jointed fissure rock’s mechanic parameter selection were studied.(4) On the reference of Eling Tunnel engineering, jointed rock’s fluid-solid coupling analysis model was established, and the disturbance effect of surrounding rock during tunnel excavation and seepage stability of tunnel face were studied and comparatively analyzed with field monitoring data, which provide technical support for tunnel’s safety construction.