To explore the variation behaviour of anchor jointed rock subject to high in situ stress states, a coupling effect calculation model based on stress equality was established based on the original rheological model of rock by combining element combination theory and experiment, and the model was verified. The coupling effect between rock mass creep and bolt prestress loss is established by setting the deterioration function of bolt prestress loss. The uniaxial creep test is performed on specimens with different joint angles, and the results show that the prestress loss time in anchor rods decreases linearly with increasing stress level. With increasing stress level, the time of prestress loss decreases linearly with the increase in stress level. With increasing axial load, the deformation caused by the transverse expansion stress of the specimen can offset the compression deformation of the prestressed anchor rod. The relationship between prestress loss in anchors and creep of rock is solved theoretically, and the stability criterion for anchor jointed rock is proposed. The results of this study provide a scientific reference for anchor design of deep jointed rock mass.
This paper aims to study the deformational behaviour of tensile-type viscoelastic dampers under different earthquake excitation directions. A method for calculating the corresponding equivalent additional stiffness and damping of a self-centring-segment bridge pier is derived. Using the displacement-based seismic design method, a design method for self-centring-segment bridge piers with tensile-type viscoelastic dampers is proposed. Using the proposed method, a self-centring-segment bridge pier is designed. Based on dynamic analysis of the finite element model by OpenSees, the effectiveness of the proposed seismic design method is validated.
The tunnel excavation destroys rock stress state and when concentrated stress exceeds the strength of surrounding rock, the tunnel periphery rocks will be destroyed. And the effective bearing ring will be soon instable and it needs to be supported. Blot-grouting support is an active support method which organically combines shotcreting support and grouting consolidation and its theoretical research achievements are less. This paper, starting from catastrophe theory, established catastrophe instability model of blot-grouting support body and it also obtained the mechanic judgment criterion of blot-grouting support body damage and the regular pattern of the point (N, q)’s motion tract in the controlling space, of which the influence to the rock stability. And the paper also judged the minimum thickness of blot-grouting support body in the point of catastrophe stability model to provide the basis for theoretical calculation and engineering application.
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