类矩形盾构隧道下穿引起既有隧道竖向位移计算方法研究

为探究类矩形盾构隧道施工对既有隧道造成的影响，得到既有隧道竖向变形规律，基于随机介质理论并结合累积概率曲线计算土体损失造成的土体竖向位移，再通过转动错台协同变形模型计算既有隧道竖向位移；针对新建类矩形盾构隧道下穿既有隧道，以土体损失作为造成既有隧道沉降的唯一因素开展室内模型试验，并对拱顶位移进行施工全过程测量，将实测值与理论计算结果进行对比验证。研究结果表明： 1）理论计算结果与实测值较为吻合，证明了理论计算方法的可靠性； 2）类矩形盾构隧道下穿既有隧道造成既有隧道沉降的规律与圆形隧道一致； 3）由于土体损失，新建隧道下穿会导致既有隧道发生沉降，在新旧隧道投影交汇处的既有隧道拱顶变形最大； 4）既有隧道拱顶沉降变形随着开挖面的掘进逐渐增大，且存在一个快速变形的阶段。

Determination of Vertical Displacement of an Existing Tunnel Caused by Underpass of Quasi Rectangular Shield Tunnel

The effect of quasi rectangular shield tunneling on an existing tunnel is investigated, and the vertical deformation law of the existing tunnel is determined by estimating the vertical displacement of soil caused by soil loss. This calculation is based on the random medium theory combined with the cumulative probability curve, and the vertical displacement of the tunnel is calculated using the cooperative deformation model of rotation and abutment dislocation. Furthermore, an indoor model test is conducted for the newlybuilt quasi rectangular shield tunnel underpassing the existing tunnel. The soil loss is monitored, as it is the only factor causing the settlement of the existing tunnel and displacement of the crown during the entire construction process. Moreover, to validate the reliability of the theoretical calculation method, the measured values are compared with the calculated values. The results reveal the following: (1) The theoretically calculated results concur with the measured values, thereby confirming the reliability of the method. (2) The settlement law of the existing tunnel caused by the quasi rectangular shield tunnel is consistent with that of a circular tunnel. (3) Due to soil loss, the underpass of the new tunnel leads to the settlement of the existing tunnel. Furthermore, the crown deformation of the existing tunnel is largest at the intersection with the new tunnel. (4) The crown settlement deformation of the existing tunnel increases gradually with the excavation of the tunneling face. Additionally, a stage of rapid deformation is observed.