Experimental Study On Creep Mechanical Properties Of Water-bearing Rocks Under Different Initial Damage Conditions

Before the creep failure occurs in deep rock mass engineering under the action of long-term in-situ stress,it is often subjected to strong disturbances such as blasting excavation and coal driving,which cause different initial damages.Coupled with the groundwater environment and other factors,the surrounding rock mass generally shows instability problems such as brittle extension transformation and large deformation,which seriously affects the safety and stability of rock mass engineering.In view of this,the rock-like specimen is selected as the research object in this paper.According to the prefabricated loading damage of 40% ～ 80% of its uniaxial compressive strength,the specimens with different water content are prepared by drying and soaking.The effects of initial damage and water content on the basic mechanical properties of rocklike were studied by uniaxial compression tests.The effects of different initial damage and water content on the mechanical properties of rock-like creep were studied by the creep test under graded loading.The main contents are as follows:(1)Through the experimental study of the basic mechanical properties of rock-like,it is found that with the increase of damage degree,the uniaxial compressive strength and elastic modulus of rock-like significantly decrease,while the peak strain increases.With the increase of water content,the uniaxial compressive strength and elastic modulus decreased,while the peak strain increased.By observing the appearance of the damaged specimen,it is found that there are main cracks through the specimen under natural and dry conditions,and there are a large number of small cracks at the end of the specimen after soaking in water,with obvious compression phenomenon.(2)Through the uniaxial graded loading creep tests of rock-like specimens under different initial damages,it is found that the creep characteristics of damaged specimens are similar,including three processes of decay creep,steady creep and accelerated creep,and the change of creep velocity has a certain regularity.The larger the initial damage is,the larger the creep deformation is and the lower the long-term strength is.In terms of the failure modes of specimens,there are mainly shear failure and tensile failure.The damage is relatively small,and after creep,there are several small cracks on the surface of specimens,but the specimens remain intact.However,with the aggravation of the initial damage,a main crack runs through the surface of specimens.(3)Through the uniaxial graded loading creep test of water-bearing rocks under different initial damages,it is found that the increase of water content reduces the strength of specimens and increases the creep deformation.Some specimens fail in advance before reaching the preset stress.In addition,the increase of water content will lead to the increase of steady-state creep rate,which affects the time to reach the stable creep stage.The time to reach the stable creep stage is the slowest in the saturated state.In the late stage of stress loading,the steady-state creep rate presents an obvious doubling trend,and the higher the water content,the lower the long-term strength.According to the failure morphology of the specimen,the end of the water-bearing specimen has obvious compression phenomenon,small cracks are derived from the surrounding area,and small fragments fall off.Figure 45 Table 25 Reference 86...