软弱围岩隧道管棚预支护开挖土压分布模型试验

 针对软弱围岩隧道管棚预支护体系的开挖土压分布展开研究，自主设计36组正交模型试验。得到以下结论：(1) 试验体系条件下，管棚预支护体系能有效防止覆跨比H/D = 1时的坍塌，采用120°布置管棚预支护能减少59.5%(H/D = 2)和64.8%(H/D = 3)的地表最大沉降值，采用150°布置管棚预支护能减少63.2%(H/D = 2)和76.8%(H/D = 3)的地表最大沉降值；(2) 通过试验数据拟合给出Peck公式沉降槽宽度参数K的建议区间，区间内K值随管棚密布增大，施加120°管棚预支护的K值平均增大约0.13，施加150°管棚预支护的K值平均增大约0.19；(3) 伴随隧道开挖及加载中的围岩破坏过程，受管棚系统支护力 作用的围岩在破坏试验中承受的极限荷载值提高约1倍，破坏形式由拱顶坍塌转变为侧壁挤扩。

Model test to earth pressure distribution on pipe roof of tunnels#br# as pre-supporting system in weak surrounding rock

36 sets of orthogonal model tests on the ultimate bearing capacity of the pre-support system of tunnels with pipe roof in soft surrounding rock were carried out. The pre-supporting system with pipe roof was found to effectively prevent the collapse when cross-cover ratio H/D = 1. The 120° arrangement of pipe shed advanced support reduced 59.5%(H/D = 2) and 64.8%(H/D = 3) of the maximum surface settlement. The 150° arranged pipe roof reduced 63.2%(H/D = 2) and 76.8%(H/D = 3) surface maximum settlement. The recommended range of width parameter K of Peck formula was given by fitting the experimental data. K increased with the density of pipe roof，and increased about 0.13 in 120° pipe arrangement，about 0.19 in 150° pipe arrangement. The limit bearing capacity of supported surrounding rocks was approximately doubled in the ultimate load tests，and the destruction form was changed from the dome collapse into the sidewall squeezing in the process of the tunneling and loading.