Strain Softening Properties And Engineering Applications Of Rock In Post-peak

With the development of underground excavation, the tunnel projects undergroundare increasing depth. After the tunnel excavation, the surrounding rock in the originalthree-dimensional stress state is in a two-dimensional stress, and even in single axial stressstate. This makes the surrounding rock destroyed. The surrounding rock in the three or twodimensional stress is almost in the post-peak, but the rock still has the support of rockstrength. Research in this part of rock can contribute to supporting the work ofunderground, and somehow the research work can reduce the costs and strength that fromthe outside of the tunnel supporting, thereby the work can enhance the economic efficiency.Based on previous research, a new model of stress-strain curve of rock in post-peak.From the view of the evolution of the strength parameters, the article determines the strainsoftening parameters and the strength criterion, than the article makes sure the relationshipbetween the strength parameters and the strain softening parameters. Using the Mohr-Coulomb strength criterion, the article makes the axial plastic strain as the strain softeningparameter, and makes the cohesion and internal friction angle expressed as the function ofthe strain softening parameters, And finally the axial plastic strain is transformed to theaxial strain, which gives the deformation modulus expression and stress andstrain relationship of the post-peak rock.Comparing with the experimental data and the rock post-peak curve which detainedby using the above method, the result shows that the variation trend is consistent and theyhave the very good fitting. And with the increasing confining pressure on three-axial tests,the post-peak stress-strain curve trends to flat.And then the paper uses the FLAC3Dsoftware to simulate the false three-axialcompression of the rock specimen. Observing the plasticity of the model, with thecontinuous axial compression, the side of the rock specimen turns elastic state to plasticstate after a period of time from the beginning. And then the plastic zone becomes bigger. Finally the side of the rock specimen appears two rupture areas which are cross. Finally thespecimen reaches to residual strength.Then the paper uses the new constitutive and the conventional Mohr-Coulomb modelinto the full section excavation of the underground tunnel. For the two models, after thetunnel excavation, the plastic zone of the tunnel in the vertical direction is smaller than thehorizontal direction.Comparing with the ordinary Mohr-Coulomb model, the new model inthis paper has the larger plastic zone when simulating with FLAC3D, the vault settlementand the horizontal displacement of the tunnel are bigger than the ordinary model. But afterthe tunnel excavation, the trend of the tunnel vault settlement and the horizontaldisplacement of the two models tends to be consistent.