承压拱在隧道喷锚支护参数优化设计中的应用

国内隧道施工中对于Ⅲ类围岩喷锚支护的参数设计多数是根据围岩位移监测结果,经工程类比确定,没有考虑围岩主体对支护参数的影响。根据锚杆加固机理,从理论上阐述了系统布置锚杆时,由于锚杆和喷射混凝土与围岩的共同作用,在锚杆互相作用影响范围之内将形成一个加固后的承压拱。承压拱的厚度与锚杆的长度、间距、围岩的力学性质等因素有关。给出了锚杆加固影响范围系数K_l的计算方法,并根据围岩稳定所必须形成的承压拱最小厚度、锚杆加固影响范围系数K_l和锚杆的间距来确定锚杆长度的方法。优化后喷锚支护成本可降低30％。

Application of bearing arch to optimumization of tunnel combined bolting and shotcreting parameters

During the construction of a tunnel, most of a the parameter designs of the third short of adjacent rocks combined bolting and shotcreting are analogical designs based upon the observation of displacements and without any of the effect of surrounding rocks taken into consideration. According to the anchor bar strengthe- ning theory, there will be a strengthened bearing arch in the action area of anchor bars as a result of the com- bined actions between these bars and shotcrete. This bearing arch's depth is in accordance with many factors such as the length, distance of the anchor bars and surrounding rocks' mechanic behaviors. This provides the method to calculate the anchor strengthening action area coefficient K_l and design the length of an anchor bar considering the minimum depth of the bearing bar permitted by the stability of the base rocks, K_l and the dis- tance between anchor bars. The cost of combined bolting and shotcreting can be reduced by 30%.