Experimental Study And Theoretical Analysis On Creep Properties Of Anchored Rock Mass With Cracks

The creep characteristics of jointed rock masses are the current research hotspots.The ever-changing cracks in rock mass not only bring certain difficulties to the research objects and research methods,but also make the creep mechanics of anchored rock mass more complicated and the anchoring effect is not up to expected.However,the occurrence of creep disasters is mostly due to the generation and expansion of hidden cracks inside the rock mass.Therefore,it is of great practical significance to study the creep properties of crack-bearing anchors.In this paper,the combination of indoor model test,theoretical analysis and numerical simulation is used to systematically study the creep properties of anchors with cracks and bonded anchors.First,the crack characteristics were quantified into three kinds of characteristic variables: quantity,discontinuity and inclination,and orthogonal test design was performed.Secondly,the orthogonal experiment with the crack characteristic variable as the main factor,the anchor compressive strength and the creep strain as the main indicators is carried out,and the influence of the crack characteristic variable on the test index is studied by statistical means.Then,the crack-anchor-rock creep constitutive model is established and the relevant parameters are inverted.Finally,the numerical simulation experiment of bolt pull creep is carried out to enrich the research object and further verify the conclusions of the indoor model test.The results show that(1)The significance order of the crack characteristics to the compressive strength of anchors is the inclination angle,the number and the degree of discontinuity,and there is a linear relationship between the seamless anchor and the seamed anchor compressive strength with the characteristics of crack 3 as parameters.Relationship,and for different kinds of strains of anchor creep effect,the degree of crack discontinuity plays a major control role.(2)Considering the deformation angle of anchor,there is the most favorable crack content and the most unfavorable crack inclination angle.The optimum crack content can be obtained by the “three-line intersection” method obtained by numerical method.(3)Based on the above conclusion,the crack elastic modulus is expressed by the quadratic function of the crack characteristic variable as the parameter,and the joint-anchor-rock coupled creep constitutive model can better describe the creep of the fractured anchored rock mass.Change process.(4)Propose the microscopic discontinuous energy step theory of macroscopic continuous creep strain growth.From the energy point of view,the creep process is a process in which the stress potential energy accumulates continuously,through strain release,re-accumulation,and then release,and the crack can be effectively released.Stress potential energy,slowing creep strain.The research results further enrich the relevant theories of rock mass creep field and provide reference for the prevention of creep damage of fractured rock mass.