Method for separating viscosity-elasticity-plasticity characteristic parameters in triaxial rheological test on rocks

Abstract

The invention discloses a method for separating viscosity-elasticity-plasticity characteristic parameters in a triaxial rheological test on a rock. The method comprises the following steps: making a sampled rock body into a standard cylindrical test sample, firstly applying a static water pressure state to the cylindrical test sample to load initial confining pressure of the test sample to reach a rheological test designed value sigma 3, keeping the confining pressure unchanged, performing the triaxial rheological test on the rock in a multistage increment circulated loading and unloading mode till the test sample is damaged, recording deformation characteristics, including an instant strain value epsilon 1, a loading stable strain value epsilon 2, an unloading instant strain value epsilon 3 and an unloading rheology stable value epsilon 4, of the test sample in each stage of axial deviatoric stress level, and identifying according to an elastic-plastic theory to obtain the instant elasticity strain valve epsilon me, the instant plasticity strain value epsilon mp, the viscoelasticity strain value epsilon ce and the viscoplasticity strain value epsilon cp of the test sample. By the viscosity-elasticity-plasticity parameter separation method, the viscosity-elasticity-plasticity rheological characteristics of the rock under different deviatoric stress levels can be identified, and corresponding technical measures are provided for reinforcement of surrounding rock bodies under high ground stress conditions in deep underground engineering.

Description

technical field [0001] The invention relates to a method for separating elastic-plastic properties of rocks, in particular to a method for separating visco-elastic-plastic properties in triaxial rheological tests of rocks. Background technique [0002] A large number of engineering practices have shown that the instability and failure of rock engineering does not occur instantaneously, but develops slowly over time. After the rock mass is excavated and unloaded, the internal stress of the rock mass is readjusted, and the deformation develops with the progress of practice until instability and failure occur, that is, rheological damage occurs, especially in soft rock engineering. more common. Therefore, it is of great significance to study the rheological properties of rocks under high stress conditions for the deformation and stability control of rock engineering. [0003] At present, the rheological properties of rocks are mostly obtained by using conventional multi-stage...

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Problems solved by technology

In 1998, J.Jin and N.D.Cristescu introduced the progressively changing single yield surface and plastic potential function determined by the true triaxial rheological test into the Cristescu constitutive model, and established an elastic-viscosity model that can reflect the first-stage rheology of rock salt. Plastic constitutive equation; In 2001, E.Maranini and T.Yamaguchi introduced the viscoplastic strain direction tensor N(σ) on the basis of the Cristescu model to replace the plastic potential function in the original formula, and proposed a new rheological rate equation In 2009, Xia Caichu et al. introduced the influence of confining pressure unloading into the Cristescu model, and established a three-dimensional elastoviscoplastic rheological model for describing the unloading stress path of marble; but the above models are all experiments with incremental loading The method obtained the rheological test results and established the elasto-viscoplastic rheological constitutive model without effective elasto-viscoplastic strain separation; in 2005, M.C. Weng et al. used cyclic loading and unloading tests to conduct triaxial tests under pure shear stress paths , and separated the elastic-plastic strain of the rock sample through experiments; in 2008, L.S.Tsai et al. carried out elasto-plastic separation on the deformation of sandstone rock samples based on the experimental results of M.C. Weng et al., but the above results were all based on triaxial shear flow strain test without considering the effect of viscous strain

[0005] To sum up, the triaxial compression rheological test of rock is carried out by cyclic loading and unloading, and the elasto-viscoplastic strain separation is carried out on the test results at the same time. -Elasto-plastic rheological constitutive model, currently less researched, in-depth research on the visco-elastic-plastic rheological properties in the rock rheological process is still an important content in the study of rock mechanical properties, especially rheological properties

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