黄土隧道网喷支护结构中锚杆的作用

Function of Rock Bolt of Lattice Girder and Shotcrete Support Structure in Loess Tunnel

为了检验锚杆在黄土隧道中的作用,在某黄土隧道中设置有系统锚杆和无系统锚杆2个长为30 m的试验段,对隧道初期支护的净空收敛、拱部下沉、围岩压力、钢架应力、喷射混凝土应力、锚杆轴力和纵向连接筋应力进行监控量测。研究表明:2个试验段无论从变形还是受力上讲,同类数据均处于同一量级,说明系统锚杆对结构的稳定性作用不大;网络钢架、喷射混凝土、钢筋网共同组成的支护结构是合理的黄土隧道初期支护结构;取消系统锚杆,可以及时喷射混凝土,有利于围岩稳定,从而大大缩短工期;以Ⅳ级围岩为例,取消系统锚杆可降低工程造价10.6%。

Two test sections with the length of 30 in were disposed in the loess tunnel to take the measure on the structure of tunnel, in order to prove the function of the rock bolt in loess tunnel. Convergence, crown settlement, surrounding rock pressure, lattice girder stress, shotcrete stress, rock bolt axial stress and profile collar brace stress during initial support of tunnel were monitored. Comparative analysis shows that the stresses of the same item of the two test sections are in the same class. It shows that the system rock bolts have little effect on the stability of the tunnel structure; support structure composed of lattice girder, shotcrete and grillage is reasonable in the loess tunnel. If the system rock bolts are retracted, construction of shotcrete can be taken in time. It is beneficial to the stability of surrounding rock and the construction period can be reduced. If the system rock bolts are retracted in Ⅳ class surrounding rock, the construction expenditure can be reduced at 10.6 %.