Abstract
The evaluation of local stability of the tunnel surrounding rock mass with weak rock layer is very important for the economy and security of the tunnel construction. Based on the rock tunnel geological conditions in the construction, the finite element model of the tunnel surrounding rock mass stability analysis with weak rock layer is established in the article by selecting the ABAQUS program linear D-P materials model as the gneiss yield criterion. The computation result indicates that the explicit dynamic analysis program could simulate the whole process of the instabilization and failure of the weak rock layer, and avoid the convergence existing in the general finite element computation, and the analysis model and program could offer effective measure for the analysis of local stability of the tunnel surrounding rock mass with weak rock layer.
Highlights
Instabilization criteria of tunnel surrounding rock massThe criterion that the finite element method is adopted to compute extreme status of instabilization and collapsed of rock-soil mass includes following kinds
December, 2009 the weak rock layer is failured, and the local supporting opportunity, and the supporting effect
In general finite element analysis, there are three methods to simulate the tunnelling, i.e. (1) gradually reducing the elasticity modulus of the excavating rock mass, (2) adopting the killing element or removing element method, (3) substituting the rock mass in excavating tunnels by the fixed boundary conditions, and first computing the initial stress to balance the reverse stress of above borderlines, and in subsequent computation, putting the borderline reverse function on the responding nodes, and removing corresponding fixed borderline conditions on the tunnelling plane, and computing the ground stress balance, and in subsequent computation, gradually reduce the reverse stress on the tunnelling face to simulate the stress release in tunnelling according to certain proportion
Summary
The criterion that the finite element method is adopted to compute extreme status of instabilization and collapsed of rock-soil mass includes following kinds. In the finite element simulation analysis of tunnelling, the result of the general finite element program is not convergent often, so the further change of the surrounding rock mass status after local destroying can not be known. If the numerical method can compute the deformation of surrounding rock mass, and follow the whole process of the deformation and instability of surrounding rock mass, so this rule is very good. It can monitor various points of the surrounding rock mass of different classes in different parts of the tunnel, which can know the local instability, but know the total instability induced by the local instability. It specially suits for the analysis and judgment of the local stability of tunnel surrounding rock mass with weak rock layer
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