Mechanical Analysis Of Weak Loess Tunnel Conctruction

With the implementation of develop-the-west strategy, another round of intense traffic construction is carried on in western China by holding the basic principles of "building the road is the first step to become rich". The particularity of western region makes loess tunnel into traffic builders'hot topic. In this paper, supported by a large loess tunnel project in Xining Qinghai province and combined with geological conditions of the tunnel site area, the basic idea of monitoring and measuring which is one of New Austrian Tunneling Method'three central parts is carried out firmly in construction. The deformation characteristics and law of loess tunnel are revealed by long-term canonical and timed measurements to the surface subsidence, crown settlement and perimeter convergence. Large geotechnical finite element analysis software is used in this paper to have a numerical simulation on the construction process of loess tunnel, studying respectively the deformation law of wall rock at different depths and different construction methods:center cross-diagram(CRD) method, center diagram(CD) method and circle-digging preserved core method are used respectively under the depth condition of 20m and 40m.through contrasting and analyzing the final data of surface subsidence. By the comparative analysis of the surface subsidence, crown settlement and perimeter convergence values, it is found that circle-digging preserved core method is better than CD method which is superior to CRD method at the same depth of excavation and corresponding construction methods are also recommended in this paper.According to a good many engineering characteristics of loess and the phenomena that it is easy to cause uneven settlement at the fresh-old bonding interface, the values of add-on crown settlement and inverted arch settlement of reinforced foundation at the three work conditions are primary calculated by using finite element analysis software, all that is compliant with rule by contrasting construction code.