Research Into The Large Deformation Of Surrounding Rock And Control Measurement In Compressed Fragmentized Zone

The large deformation of compressed fragmentized surrounding rock has been attracted many attentions in underground engineering. It caused many problems during tunnel excavation, such as exceeding clearance limit, protruding steel arch, falling primary support concrete, collapse, and so on. Due to the complexity of deformation form different effect factors in compressed fragmentized zone, the corresponding engineering measures must be used to prevent the occurrence of the large deformation accident. In this paper, based on the background of Xiangshan tunnel of Ten-Day Highway, the large deformation mechanism and control measure of soft fractured surrounding rock are studied at high geostress. The study methods of theoretical analysis, site investigation, site monitoring and numerical simulation are adopted. The main research results are as follows:(1) The hydrogeological and surrounding rock conditions are surveyed in the construction site. The prominent problems of primary support concrete falling and arch bending deflection are easily caused in the large deformation tunnel section. The deformation and pressure of surrounding rock are studied by using monitoring method. The results of vault settlement, level convergence, surrounding rock pressure are analyzed, the space- time effect is studied during construction of tunnel.(2) Based on the practical construction case of tunnel, the model is established by FLAC3 D software. The rationality of model is verified by comparing monitoring data. The effects of the depth and the level of the surrounding rock on the large deformation of surrounding rock are studied by numerical simulation.(3) Effect of site grouting is simulated and evaluated by using the model box. The reasonable water cement ratio of single and dual liquid grouting was acquired. The deformations of surrounding rock are analyzed under different construction methods, the reasonable excavation step and cyclic length of tunnel and support opportunity of second liner are obtained. The conclusion can provide a reference for tunnel construction at fraction zones and similar projects.