| Blocky rock is a kind of common enginerring rock mass, which’s internal has various joints, bedding and other weak plane. Those defects have a great influence on rock mass structure stability and engineering safety. Bolt support is main control means of surrounding rock stability now. It has important significance of bolt support design to study strength characteristic and deformation behavior of blocky rock anchorage unit under various factors and analysis action mechanism of bolt and stress distribution of model. With research object of blocky rock of mine tunnel roof, this article studies anchoring characters of blocky rock under different rock mass conditions and anchoring factors through physical model test and numerical simulation calculation. This article analyzes the influence of various factors to strength characteristic, deformation behavior, bolt axial force and stress distribution of anchorage unit model. Based on those, this article also studies anchoring mechanism of block rock unit. The main resuls are as follows:(1) Based on simplify mechanical model of tunnel rock anchorage unit, testing simulation system is designed to simulate and control boundary conditions of model in the process of blocky rock anchorage unit compression tests. Based on similarity criterion, similar materials of rock, structural plane and bolt, which are mainly considered, are tested to get essential mechanical properties. Blocky rock samples are prepared on the basis of testing program which has been designed.(2) The models with different rock mass conditions and anchoring factors, are compressed. Those test results show that various factors have evident effect on mechanics properties and deformation behavior of models. Compared with models without anchoring, peak stress and elastic modulus of anchoring models increase obviously. And following the increase of blocky size, anchorage length, bolt density and bolt pretension, peak stress and elastic modulus of anchoring model show a trend of increase. The primary and secondary sequence of effect of different factors to unit strength with reference value is that blocky size, anchoring type, bolt density, bolt pretension in sequence through analysis of factors sensitivity.(3) Bolt axial force mainly experiences slowly increase period, rapid growth period, stable period or decrease period, invalidation period. Failure forms of modes mainly include shear and slip failure, X-type shear failure, shear and splitting failure with different rock mass and anchoring condition, which show that main function of bolt is to increase shear strength of structural plane.(4) Based on physical model tests, numerical simulation models, which agree well with test results, are built by using discrete element numerical inversion. Through numerical simulation research, angles of joint and bedding have obvious influence on model peak strength, and angles of joint 1 and bedding also have evident effect on elastic modulus of models, but angles of joint 2 have a little impact on model elastic modulus.(5) Bolts have a great influence on displancement and stress field. Because of bolts, coneshaped compression zones develop in models, which overlay mutually in neighboring areas and develop to anchorage area. Blockys glide distinctly along weakness plane, in which stress change obviously. Anchoring mechanism of blocky mass is to increase strength characteristics of structural palne and mechanical behavior of rock mass, and improve bearing capacity of unit. |
