偏压连拱隧道优化施工的研究

针对多数连拱隧道修建中存在浅埋地形偏压结构受力状况，结合金丽温高速公路二期工程20多座隧道实际情况，选取有一定代表性浅埋地形偏压覆土厚度，对不同坡度1：1～1：1．5情况下（Ⅱ类取7种、Ⅲ类取3种）偏压连拱隧道结构受力及围岩屈服破坏等进行了施工步骤优化研究。结果表明，一般情况下，连拱隧道施工存在两种偏压效应：一种是因地形偏压引起，称之为“地形偏压”；而另一种则因连拱隧道的分部施工所引起，称之为“施工偏压”。这两种偏压有明确作用方向，产生结果也不相同。对连拱隧道左右洞，按“先外后里”工序施工，能够利用“施工偏压”来部分程度地“抵消”因地形偏压产生的结构偏压受力的不利情况。因此，采用“先外后里”工序施工，实为浅埋偏压情况下连拱隧道最优施工工序。

Research on optimized construction procedure for double-arched tunnel in unsymmetrical pressure

Based on mechanical analysis of construction progress of double-arched tunnel under unsymmetrical pressure, the two kinds of partial pressures effects are put forward, which influence together the loaded state of double-arched tunnel. One of them is result from shallow depth ground partial pressure, named ‘terrain partial pressure’, the other is caused by construction order of the two bore of double-arched tunnel, named ‘construction progress partial pressure’. The result demonstrates that the direction of oblique load in ‘terrain partial pressure’ is definite and unchangeable, i.e. the direction of oblique load is from the inside of hill to the outside of hill-slope; the direction of oblique load caused by ‘construction progress’ depends on the early and late construction order of the two bore of double-arched tunnel; the study shows that the direction of oblique load is from the early excavated bore side to the late bore side. As a result, the procedure of the early excavation of external bore closed to the hill-slope is considered as the optimized construction procedure for double-arched tunnel under unsymmetrical pressure, since the oblique load caused by construction progress can be applied to balance out partial load in ‘terrain partial pressure’. The above conclusion is made use of the modification design and construction of double-arched tunnels under unsymmetrical pressure of Jinhua to Lishui highway in Zhe jiang province.