The Study On Post-Peak Strain Softening Constitutuerit Equation And Numerical Simulation Of Rock

In the21st century, rock engineering is developing rapidly at home and abroad, and involved energy, transportation, mine, water conservancy and national defense project more and more. China engineering construction developing at unprecedented speed, rock and underground engineering space has become the focus of our country’s economic construction. At present, these engineerings are facing a lot of rock excavation problem, which involves lots of rock engineering properties. And the strength of the rock mass influence the characteristic and the post-peak mechanical properties. Through the numerical simulation method, this paper researched the process of the surrounding rock tunnel and the laws of the gradual to provide the guidance for the tunnel construction.(1) Firstly, The stress-strain curves of rocks are composed of two parts, which are pre-peak region and post-peak region. In the pre-peak region of stress-strain curve, rocks are usually regarded as elastomer. At this stage, the constitutive relationship is linearly elastic. However, in the post-peak region, the curve could not be determined by classical theory because the fracture morphology and the stress drop of the rocks are hard to describe. Thus, the post-peak modulus is the key of the mechanical behavior research. Based on Mohr-Coulomb strength criterion, the paper uses internal friction angle as intermediate variable to propose post-peak modulus with stain. The nonlinear post-peak stress-strain relationship of rock is established.(2)In numerical cases, the stress-strain curves under different confining pressures are obtained and it agrees well with the test data. It is concluded that the fit curve model proposed by this paper is reasonable and the model could describe the post-peak mechanical behavior of marbles under various confining pressures preferably.(3) On the basics of the theory in the above, develop rock’s two-dimensional calculation program by the FISH language in the FLAC. And the program is applied to the simulation of Cubic Samples and Circle Tunnel by static load-controled mode. Then on the basics of two-dimension, develop rock’s three-dimensional calculation program by FLAC3D. Then the three-dimensional damage and failure numerical simulation of cylinder samples and the tunnel over-loading test of the geomechanical model. The results show that the new consititutive model is feasible to simulate the tunnel surrounding rock’s damage and failure process.(4) Lastly, based on the Liangshui tunnel, the developed rock damage and failure model is used to have the three-dimensional damage and failure numerical simulation of five-grade rock mass’s whole section excavation and steps method excavation. Then this paper studies the tunnel surrounding rockmass’s damage and failure space-time evolution characteristics under the two methods during tunnel excavation. The analytical results could provide usefull guiding views for engineering construction.