Safety Control Theory And Application On The Stability Of Surrounding Rock Mass In Deep Mine Roadways

Correct safety control theory in surrounding rock need to be solved while the safety control problem in deep roadway becomes more and more apparent along with the increase of mining depth. Thus, according to the research status at home and abroad as well as geological conditions in Xiezhuang coal mine in Xinwen mining area, based on the analysis of deformation and failure mechanism in surrounding rock in deep roadway, the initial and long-term stability mechanism were explored theoretically, and the first and second support parameters were confirmed and the research results are applied to engineering practice successfully.According to the characteristics of severe defomation at initial time and rheology in long-term, and through the analysis of test block post-peak volumetric strain experiment as well as pre-peak and post-peak rheology experiment, two main aspects of deformation failure in surrounding rock in deep roadway were figured out as follows:one is the broken expansion character of surrounding rock under high stress, the main cause for severe deformation at initial time in deep roadway, the first bolt support control object is the fracture deformation of surrounding rock post-peak rupture status; the second one is long-term rheology character of post-peak surrounding rock directly influencing the long-term stability of deep roadway.Based on the analysis of first support objective and control object in deep roadway, the surrounding rock strength reforcement theory was used as theoretical basis to analyze the bolt support effect in deep roadway, and the initial stability mechanism in deep roadway was put forward by the establishment and analysis of the first support elastic-plastic mechanical model: Control the development of plastic area in surrounding area, which means support strength should satisfy the needed support strength at initial stability, maintain the rock integrity, reduce the decrease of surrounding rock strength, and limit the post-peak broken expansion deformation.The surrounding rock post-peak stress relaxation and the resulting sustainable creep and accelerated creep, which is the main reason for long-term rheology and failure in deep roadway. The elastic-viscoplasty stress relaxation mechanical model in deep roadway was thus established. The effect of bolt support to deep roadway stability was analyzed by using this model and the long-term stability condition was put forward:the surrounding rock creep will stop in non-stability area and the roadway could be in a state of long-term stability when the radial stability stressσrmn (t=∞) supported by bolt support in the outer boundary of anchorage zone r=Rm is greater than the needed radial stressσrpn(t=∞); conversely, the surrounding rock will be in a state of continuous creep, increasing non-stability area, and the roadway could not remain stable.The second support time, bolt support parameters and grouting consolidate radius in deep roadway were confirmed by using the FLAC numerical calculation software, and the veracity of initial and long-term stability mechanical models were verified by the contrast analysis between theory and numerical calculation.The first and the second bolt support and grounting consolidate parameters obtained from theory and numerical analysis can safely control long-term deformation in deep roadway, construction works well, rock creep ceased, and long-term stability of the roadway can be maintained.