The Research On Creep Of Surrounding Rock And Soil Softening In Tunnel Excavation

Rock shows not only the elastic and plastic mechanical properties, but also time-related properties, this is rock rheology. In the engineering construction, there are often encountered in construction development of deformation of rock increasing with time, it has brought a very negative impact to the project long-term stability. In recent years, study on rock rheology research especially surrounding rock roadway with viscoelastic rheological analysis in particular needed theoretical methods and research levels of support, to meet the needs of engineering practice. Shield tunnel have obvious strain-softening characteristics in the bulk soils, the research on soil strain-softening of shield tunnel excavation face stability has very important significance. Based on the mentioned above, this article has mainly carried on the following research work:1. First described the commonly used rheological model of creep curve characteristics and applicable scope. Based on the stress-strain relationship of rock creep experimental analysis, using a reasonable model for fitting analysis, combined with the traditional empirical method and the least square method, has established a way to calculate creep model parameters, the creep curve fitting is good, at the same time obtain the experimental creep constitutive model parameters, give a guidance to select creep constitutive model in practical engineering.2. Carried on the viscoelastic analysis of surrounding rock to rock creep properties in tunnel excavation, explore the radial displacement with time deformation relation, and compared with elastic analytical results. The creep characteristics of rock tunnel shows the necessity in considering viscoelastic analytical. This article has predicted the reasonable tunnel excavation volume. it also gives a reasonable explanation that geological disasters due to creep phenomena in construction.3. Analysis of soil strain-softening effect on stability of shield tunnel face stability, Use FLAC3D to explain the principle in soil strain softening and realization of key techniques for solving procedures, and select reasonable soil constitutive model, then developed numerical simulation scheme, and showed the importance of soil strain-softening in shield tunnel excavation.4. With Shenyang heavy industry shield tunnel for numerical simulation experiments to study the face stability in shield tunnel excavation, monitor the ground settlement to obtain the excavation shoring pressure ratio, then calculate the face excavation shoring pressure, it can give the reasonable scope during excavate process.