The Soft Rock Tunnel Analysis Of The Characteristic And Study Of Construction Control Measures

The surrounding rock lithology of Guanyazi Tunnel is weak. There are no obvious laws on the degree of weathering and fragmentation as the distance changes. There are large amounts of weak consolidated minerals and developed joints between layers of surrounding rock. After excavation the surrounding rock scarcely have the ability of self-stability. When it is revealed, the strength degrades soon. The surrounding rock has the expansive and loose characteristics exposed to air and the softening characteristics exposed to water, which has obvious continuous deformation of soft rock. Therefore, in order to ensure the safety of tunnel construction, the research is carried on aiming to the foregoing problems. The relevant research results can provide guidance for tunnel construction and also offer reference for similar tunnel design and construction. The main research work and achievements are as follows:(1) Through the observation of the microstructure and the lithofacies identification of rock samples, the samples are identified as phyllite that is filled with sericite. In the mechanical characteristics experiments of rock, physical properties, hydro-physical properties and strength are tested.(2) According to the testing experiment data of rock mechanics characteristics, the large deformation mechanism of Guanyazi Tunnel is analyzed. The results shows that the expansion has little effect on the early deformation, the deformation is mainly resulted from the plastic flow of surrounding rock, and the influence of expansion on the deformation starts after a while. Rock pressure includes deformation pressure and expansion pressure at the same time, which is the cause that large deformation happens and the tunnel is badly damaged.(3) Based on the test results, tunnel construction is simulated with the software FLAC3 D. The calculation contents include three bench method, CRD method, CRD method whose support parameters are improved and double-side-drift method. According to the calculation results and practical monitoring measurement data, reasonable support parameters and construction methods are proposed.