针对复合地层条件下的先下后上重叠隧道施工工况引起的土体变形进行了理论推导,在类随机介质理论和三维统一解的基础上,建立了可以考虑开挖面上存在多种土层情况的计算模型,并考虑了下线隧道对上线隧道变形的遮拦效应,推导得出土体变形的计算公式。将本文理论方法代入多组实测案例进行验算,研究表明:计算结果有较好的拟合度,证明了该方法的可行性;通过单因素分析发现,在重叠隧道中上线隧道附近的土质条件对地表土体变形的影响较大;相较于单线施工,先下后上重叠隧道中的上线隧道引起的土体变形由于受到下线遮拦效应的影响,变形曲线会更浅更窄,而本文提出的遮拦效应系数能较好地体现下线隧道对上线隧道土体变形的影响,遮拦效应系数的大小与隧道轴线间距离成反比例关系,隧道间距越小,遮拦效应系数越大。
Theoretical research is conducted on the soil deformation caused by the construction of overlapping tunnels under composite geological conditions. Based on the theoretical method of combining analogous considering the shielding effect of the stochastic medium theory and the three-dimensional unified solution, a computational model was established considering the shielding effect of theunderground tunnel on the deformation of the upper tunnel is taken into account. The calculation formula for soil deformation was derived. The theoretical method in this article was applied to multiple sets of measured cases for verification. Research indicates that: The calculation results have a good degree of fit, proving the feasibility of this method. Through single factor analysis, it is found that the soil conditions near the upper tunnel in overlapping tunnels have a significant impact on the deformation of surface soil. Compared to single line construction, the soil deformation caused by the upper tunnel in the overlapping tunnel from bottom to top is shallower and narrower due to the influence of the lower line shielding effect. The shielding effect coefficient proposed in this article can better reflect the influence of the lower line tunnel on the soil deformation of the upper tunnel. The magnitude of the shielding effect coefficient is inversely proportional to the distance between the tunnel axes, and the smaller the tunnel spacing, the greater the shielding effect coefficient.
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