Experimental Research On The Failure Characteristics And Support Mechanism Of Surrounding Rock Under High Ground Stress

As production technology level increased steadily and the constant expansion of human activity, the scale and amount of underground engineering is increased increasingly. Underground deep construction has become the inevitable choice of engineering project activities. But deep large underground engineering construction will bring a series of technical problems of high ground stress. Especially, high ground stress brought to difficult bracing problem which is becoming an important subject that deep underground engineering face to be researched and solved. It also limited the scale and speed of deep underground engineering construction to some extent. In present, we still cannot understand and analyze these phenomena adequately. According to the stress complexity and failure characteristics of depth surrounding rock, present research is still not mature. So, research of the failure characteristics and stability control of roadway surrounding rock has become a problem which needed to be discussed of the engineering construction under high ground stress.In this paper, "Study on the Comprehensive Control Technology of Complex Stress and Large Deformation Chamber Group in Xiandewang Coal Mine" as the blueprint, the experimental technique of self developed CM60/10 plane strain test-bed combined with triaxial servo tester and CM250/18 plane stress test-bed was used to research failure characteristics and supporting effect. FLAC3D numerical simulation was used to make contrast verification with the physical experiment simulation. Experimental research on the failure characteristics and support mechanism of surrounding rock under high ground stress was accomplished by the above technical means. The surrounding rock stress distribution, failure characteristics and displacement deformation of the single roadway without support was analyzed. Supporting effect of bolt-mesh- injection+ base angle anchor support and simple support was compared, and the former was used into industrial test.The main research contents and conclusion are as follows:(1) The concept of stress concentration structure of surrounding rock was proposed, which is that the stress in roadway surrounding rock concentrated on the outer ring of destroyed zone to form the three-dimensional stress concentration structure of surrounding rock which is consist of "stress concentration circle", "stress concentration shell", "stress concentration ring" and "stress concentration bubble". The transformation law of each other among each branch of surrounding rock stress structure was analyzed, and the main damage root of surrounding rock is the instability of stress concentration shell was revealed.(2) The CM60/10 plane strain test-bed was self developed which can combine with the triaxial servo test-bed simply and conveniently. Its size design, manufacture method and working principle were introduced. The site actual operation showed that the CM60/10 plane strain test-bed can more easily obtain the failure characteristics of the surrounding rock.(3) Failure process partition of surrounding rock inλ< 1 state was divided. The first fracture zone: sidewall exfoliation occurs during the initial stage of roadway destruction, and then gradually formed a wedge failure, the roadway span was increased. (Wedge failure zone); The second fracture zone: when the wedge failure zone was fully cut and lost the supporting function, the skewbacks and base angles will gradually lose stability (Second failure zone); The third fracture zone: due to the instability of skewbacks and base angles and slip line of the sidewall transfer to the roof, the roof lose supporting gradually, then the roof lose its stability. (Transfixion instability zone)(4) The evolution of stress and partition failure modes under different stress state and the disturbance law were studied by numerical simulation.