Experimental Study On Generalized Relaxation Of Rock Under Triaxial Compressive Loading Condition

The rheological properties of rocks are the properties of the stress-strain relation and time of the rock.Studying the rheological properties of rocks is helpful to improve the stability and safety of geotechnical engineering.As the understanding of complexity of stress state of surrounding rock of underground space,more and more engineering phenomena cannot be explained by pure creep or stress relaxation pure,rock may be between pure creep and stress relaxation alone another rheological state,in this state of rheological rock stress and strain may change at the same time,this phenomenon is called generalized stress relaxation.Based on the field of tuff and wellhead sandstone as test object,and carry out rock under triaxial stress state,the generalized stress relaxation characteristic test research,this paper discusses the evolution of the generalized stress relaxation properties of rocks and axial axial stress,confining pressure,the lithology on the experimental research on the influence of the generalized stress relaxation properties of rocks,the research results to assess long-term stability of surrounding rock of underground space analysis and evaluation.The main research work of this paper and its research results are as follows:(1)Rocks in various regions to carry on the generalized stress relaxation process can be according to the change of stress and strain of the generalized stress relaxation stage division,in regional ?,creep and ? rocks under the condition of low confining pressure and high stress level prone to complete changes slow,uniform and accelerated destruction 3 phase;However,in the stress relaxation and in more cases in the region,only the deceleration change and the uniform velocity change stage,the acceleration failure stage is not easy to occur.(2)When the rock specimens are subjected to generalized stress relaxation in different regions,the external(testing machine)is different in doing work on the rock specimens.In the case of rock specimen strain(regional ?,? and creep direction),testing machine for rock specimens do positive work;In the direction of stress relaxation,the test machine does not work on the rock specimens,and the rock specimens are rearranged through the internal fabric to consume internal energy.Decreases in rock specimen strain ?(area),under the condition of rock specimen on the outside(tester)doing positive work and release energy process.(3)Stress level of influence of the generalized stress relaxation properties of rocks is relatively uniform,the higher the stress level,rock internal damage accumulation,the more its axial deformation is more intense,it mainly for rock axial strain increment,the absolute value of axial stress increment,the initial axial strain increment rate and initial axial stress increment rate with the increase of stress level decreases.(4)The effect of confining pressure on the generalized stress relaxation characteristics of rocks in different regions is not very similar.The axial strain increment and axial stress increment of the rock specimens decrease with the increase of confining pressure in the direction of region,internal and creep,and the confining pressure inhibits the deformation of rock.There is no obvious law between confining pressure and rock axial stress increment in stress relaxation test.And within the regional ?,the existence of confining pressure obviously promoted the axial deformation of rock specimen,and regional ?,? and creep law of direction is not the same.