Abstract
According to the strain-softening characteristics of rock mass, an ideal elastic strain-softening model is developed, and the surrounding rock of tunnels is subdivided into the plastic broken zone, plastic strain-softening zone, and elastic zone. Based on the generalized spatially mobilized plane criterion, an elastic-plastic analytical solution of a circular tunnel is derived. The effects of intermediate principal stress, strain softening, and dilatancy are considered in the unified solution. The stress, displacement, and plastic zone radius of surrounding rock based on the SMP criterion are compared with those based on the Mohr–Coulomb criterion. Furthermore, the effects of parameters such as the softening modulus, dilatancy angle, and internal friction angle on the deformation and stress of tunnels are discussed. It has been found that the larger the dilatancy angle is, the larger the plastic zone displacement and the radius of the broken zone are. The larger the internal friction angle, the smaller the sizes of the plastic zone, the strain-softening zone, and the broken zone are. The deformation of surrounding rock in the broken zone is more sensitive to the internal friction angle than that in the strain-softening zone. The unified solution based on the SMP criterion provides a well understanding for the elastic-plastic state of tunnels, which can be the guidance for tunnel excavations and support designs.
Highlights
Rock tunnels are common underground constructions for mining engineering, traffic engineering, diversion engineering, and nuclear waste disposal engineering. e stress around tunnels redistributes due to the excavation disturbance. e concentrated stress usually exceeds ultimate strengths of the surrounding rock, which make the rock properties transform from elastic state to plastic state
Based on the generalized SMP criterion, a rational analytical solution of the circular tunnel is derived in consideration of the effects of the intermediate principal stress, strain softening, and dilatancy. e stress distribution, displacement distribution, and plastic zone radius of surrounding rock calculated by the solution based on the SMP criterion are compared with those based on the Mohr– Coulomb criterion
E circular tunnel surrounding rock is subdivided into plastic broken zone, plastic strain-softening zone, and elastic zone
Summary
Rock tunnels are common underground constructions for mining engineering, traffic engineering, diversion engineering, and nuclear waste disposal engineering. e stress around tunnels redistributes due to the excavation disturbance. e concentrated stress usually exceeds ultimate strengths of the surrounding rock, which make the rock properties transform from elastic state to plastic state. Erefore, the strain-softening characteristics of the surrounding rock must be considered in the elastic-plastic analysis of tunnels. Traditional elastic-plastic analytical solutions of tunnels are generally based on the Mohr–Coulomb criterion or the Hoek–Brown criterion, in which the effect of the intermediate principal stress is not considered. Erefore, in the elastic-plastic analysis of tunnels, the effects of intermediate principal stress, strain softening, and dilatancy should be considered comprehensively. Based on the generalized SMP (i.e., spatially mobilized plane) criterion, a rational analytical solution of the circular tunnel is derived in consideration of the effects of the intermediate principal stress, strain softening, and dilatancy. When the general clay soil is destroyed in the plane strain state, the common tangent of the Mohr circle of limit stress on the τ-σ σ1 Mohr–Coulomb criterion.
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