Experimental Study On Triaxial Time-Dependent Behaviour And Strain Localization Of Rock Under Water-Rock Interaction

In the process of tunnel excavation and support,the surrounding rock shows obvious time-dependent behaviour.The dissolution and erosion of surface water and groundwater lead to the deterioration of time-dependent characteristics of surrounding rock.Therefore,the study of the time-dependent characteristics of surrounding rock under the action of water environment is of great significance to the long-term stability control of the tunnel.Based on this engineering background,this paper uses an improved three-axis visual servo control test system and combined with a 3D-DIC system,and takes sandstone as the research object to carry out the experimental research on the time-dependent behaviour of rock under the conditions of different water environment(water bearing,seepage pressure),different loading rate,different direction of generalized stress relaxation.The temporal and spatial evolution of the three-dimensional strain field on the rock surface under water-rock interaction and the time-dependent characteristics of deformation and damage are revealed.The deformation localization characteristics of sandstone surface under different time-dependent characteristics are quantitatively characterized.The micro-mechanism of the deterioration of rock time-dependent caused by water-rock interaction is clarified.The main research work and results of this paper are as follows:By adding the axial seepage channel,introducing the high-precision plunger pump,and combined with 3D-DIC system,the visual triaxial servo control test system is upgraded and improved.The whole process observation of three-dimensional deformation field evolution in the process of rock deformation and failure under water-rock interaction is realized,which provides an experimental method for the visualization of rock deformation and failure under water-rock interaction.The experimental study on the loading rate dependence of rock with different water content and different seepage pressure were carried out.The influence law of loading rate on the spatio-temporal evolution process of three-dimensional strain field on rock surface under water rock interaction is revealed.The loading rate dependence of rock deformation characteristics and its mechanical characteristic parameters under water-rock interaction is analyzed,and the functional relationship between the loading rate dependence and water content is constructed of rock strength.The influence mechanism of water-rock interaction and loading rate on rock microstructure is analyzed.The generalized stress relaxation tests of rocks under different water content conditions,different seepage pressures,different directional coefficients and different stress levels were carried out.The time history evolution of the initiation,growth and interpenetration of surface microcracks in the process of generalized stress relaxation under water-rock interaction is revealed.The influence of water-rock interaction on the generalized stress relaxation of rock is discussed.The difference of the effect of water-rock interaction on the generalized stress relaxation of rocks at different starting stress levels is studied,and explored the degradation mechanism of water-rock interaction on the time-dependent characteristics of rocks.Based on the analysis of the strain evolution characteristics inside and outside the deformation localization band,the starting time of deformation localization,the width and inclination angle of the deformation localization band in the loading rate dependence and generalized stress relaxation test of rock,the influence of water-rock interaction on the characteristic parameters of rock deformation localization under different loading rates and different generalized stress relaxation conditions is clarified.The strain localization factor and damage factor of rock surface strain under water-rock interaction are established.The spatial distribution characteristics and damage degree process of rock surface microcrack damage evolution under different time-dependent behaviour are quantitatively characterized.