Analysis Of Roadway Surrounding Rock Stability And Research Of Bolting Effect Evaluation

With mineral resources reduced, geological conditions become more and more complex, mining depth and degree of difficulty become bigger and bigger, Especially in high stress and soft rock roadways that the surrounding rock have larger damage range,it’s difficult to design and construction with the traditional bolt support theory. The project based on the Hecaogou No.5 coal seam auxiliary transport Roadway, analyzing the stability of the surrounding rock and evaluatting the support effect the bolt by reinforcement area supporting design. The main conclusions are as follows:(1) The reinforcement range of traditional bolt support theory is the plastic zone, suitable for roadway of small disturbance and smaller plastic zone, support resistance not less than the plastic deformation pressure calculate by Kastner formula, so the tunnel surrounding rock can keep stable. District branch support theory only need to reinforce the surroundding rock in the shallow broken surrounding rock, anchoring in stable rock mass, do not have to strengthen the whole plastic zone, not affected by the width of plastic zone. The surrounding rock stability need to meet two conditions:Firstly,the outside area of anchor reinforcement not less than the result calculated by Kastner formula.Secondly, any point in the reinforced area need to meet the Mohr coulomb strength criterion. With the increase of the reinforcement area thickness, the decreases of the plastic area width, when the outer surface of the reinforced zone and the elastic plastic interface coincide,the surrounding rock supporting resistance equal to the traditional supporting design by Kastner formula of plastic deformation pressure, it obtained that the reinforced zone theory bolting force algorithm method is reasonable.(2) The roadway support design follow the regular of ‘Long and thin,Short and thick’,the pretension apply by anchor and the support resistance to keep surrounding rock in stability conditions have a positive correlation relationship. proposed a concept of surrounding rock supporting strength coefficient, the physical meaning is the supporting force for producing a unit displacement of the tunnel wall, it reflects the ability to resist deformation of surrounding rock. applying of unified strength theory to get the displacement analytic solutions of tunnel wall, with the increase of the anchor length. the roadway wall rock displacement decreases, and the slope of the curve showed a decreasing trend, indicating selecting reasonable bolt parameter is conducive to enhance economic efficiency. Through analysis of surrounding rock supporting strength coefficient, indicated that for the same tunnel, the change of surrounding rock supporting strength coefficient is small, it can be thought of as constant; but the surrounding rock supporting strength coefficient is different for different depth roadways, it increased with the original rock stress increase.(3) Combined with engineering example, using the surrounding rock support strength coefficient extremum of the working conditions, combined with measured displacement solution and evaluate the anchoring effect of roadway surrounding rock, effective evaluation of the anchor effect, improve the work efficiency and economic benefits. If surrounding rock supporting strength coefficient is satisfied with the condition of extreme value, anchor spacing meet support request, the anchoring effect better and the stability of surrounding rock; conversely, the surrounding rock instability, need to reduce the bolt spacing and improve bolt strength.