Study On Mechanical Behavior Of The State-Changeable Interface Between Soil And Underground Structure

In the long-distance pipe jacking or box culvert projects, the thixotropic slurry is usually injected between the soil and structure, in order to reduce the friction acting on the outside surface of the structure. The slurry injecting technique is also used in shield tunnel projects to reduce the soil deformation caused by the shield-end structural spacing. The grouting interface is existed in these projects. The grouting interface is a kind of interface whose state is always changing in the constructing process. It continues varying, from the initial liquid state gradually to the grumous state, or from the grumous state to the liquid state, such as the thixotropic mud injected in the pipe jacking projects.This paper studies on the grouting interface with its state varying. There is analysis about the features of the grouting interface, including the material properties of the interface and the interaction mechanism between the structure and soil around. The slurry performances and the effecting factors of slurry injecting are also investigated. Based on the study about the features of the state- changeable interface, a reasonable interface model has been chosen for simulation. The model test about the grouting and contacting problems in box culvert project has been done with the results of the friction coefficient to the different slurry ratio interface. According to the analysis of the propulsion in box culvert project, the transformation rule of the friction coefficient about the state-changeable interface is concluded. A numerical simulation method about the grouting-interface is presented based on the study. Considering the different state of interface, the construction process can be divided into several different phases. The interface parameters value should be in accordance with the state of slurry in different phases. Finally, the finite element simulation has been done with considering of the construction process of the box culvert project between the Hongxu Road and Beihong Road.