初期支护组合形式有效性现场试验研究

Study of Field Test on Effectiveness of Composition Mode of Primary Support

初期支护组合形式的有效性一直存在较多争议。依托蒙华铁路在建隧道,针对初期支护不同组合形式有效性问题开展大量现场试验,量测内容包括拱顶沉降、水平收敛、系统锚杆轴力、喷射混凝土应力及钢架应力。通过对花岗岩、板岩、砂泥岩、黄土4种地层进行试验,分析具有代表性的Ⅲ、Ⅳ、Ⅴ级花岗岩和Ⅴ级黄土试验段数据,研究深埋岩质和土质隧道初期支护中钢筋网喷射混凝土、钢架及系统锚杆不同组合形式的有效性。结果表明:1)现阶段"网喷+钢架+系统锚杆"的初期支护组合形式未充分发挥其作用效果,有效性差,措施过于保守,存在很大优化空间;2)在土质或浅埋破碎岩质隧道初期支护中,系统锚杆无明显作用,可以取消,而只采用"网喷+钢架"组合形式;3)在深埋岩质隧道初期支护中,采用"网喷+钢架"或"网喷+系统锚杆"2类组合形式之一即可。考虑到目前现场系统锚杆施作机具和施工质量,采用"网喷+钢架"的组合形式是合理和可行的。

The effectiveness of composition mode of primary support has been controversial. A large number of field testes have been carried out on the effectiveness of the different composition modes of primary support of Menghua Railway Tunnel under construction. The measurement items include crown top subsidence,horizontal convergence,axial force of anchor bolt and stress of shotcrete and steel frame. Tests are carried out on granite,slate, sand mudstone and loess strata; the representative data of granite of Grade IE, IV and V and loess of Grade V are analyzed, and the effectivenesses of different compositions of steel mesh shotcrete, steel frame and systematic anchor bolt in primary support of deep rock and soil tunnel are studied. The results show that ： 1） The composition mode of steel mesh shotcrete ＋ steel frame ＋ systematic anchor bolt of primary support can not work effectively at present,and can be improved. 2） The anchor bolt can be canceled for its useless in soil or shallow broken rock tunnel primary support; and steel mesh shotcrete ＋ steel frame mode can be adopted. 3 ） The composition mode of steel mesh shotcrete ＋ steel frame and steel mesh shotcrete ＋ systematic anchor can be adopted selectively in deep rock tunnel primary support. The composition mode of steel mesh shotcrete ＋ steel frame of primary support is rational and feasible considering the uncontrollable present quality of construction machinery and systematic anchor bolt.