偏压错台小净距隧道力学性态相似模型试验

Model Test on Mechanical Behavior of Two Shallow-buried Closely-spaced Tunnels at Different Elevations Under Unsymmetrical Load

试验研究了浅埋、偏压、错台条件下的小净距隧道力学性态相似模型，模拟不同的施工顺序（先开挖左洞和先开挖右洞）对隧道围岩及中间岩柱应力和沉降的影响．试验结果表明，在浅埋、偏压尤其是错台条件下，左洞和右洞开挖对中间岩柱的应力和位移均产生较大的影响；右洞先开挖引起整个上覆岩体的地表和深层沉降量比左洞大3％～48％，引起的两线隧道围岩中的应力释放量比左洞大3％～46％．左洞先开挖对隧道安全有利，应先开挖左洞．因此，针对平行的偏压小净距隧道应先开挖浅埋侧隧道的经验方法，对于错台不完全适用．数值分析和现场监测数据有力地验证了模型试验结果的合理性．

Reduced scale model tests of two parallel shallowburied closely-spaced tunnels at different elevations under unsymmetrical load were carried out to simulate the interaction effects of different excavation sequences （excavation of the right tunnel first and excavation of the left tunnel first）, and variations of stresses and settlements in the wall rock especially in the rock pillar were obtained. The results of tests show that, for the shallow-buried closelyspaced tunnels, especially when the two tunnels are at different elevations, the excavation of both the right tunnel and left tunnel has significant effects on the pillar; moreover, the final surface and subsurface settlements caused by the former excavation sequence are 3% to 48% larger than those caused by the later; and the release of stresses in the rock caused by the former excavation sequence is 3% to 46% higher than those of the later. So, it is believed that excavating the left tunnel first can improne the stability of the two tunnels. The empirical method is not suitable as it suggests the outer tunnel （the right tunnel in this paper） should be excavated first when the closely-spaced tunnels are at a same elevation under unsymmetrical load. Furthermore, the results of numerical simulation and field investigation verify the rationality of model tests.