新建双线隧道下穿对既有盾构隧道影响研究

Effects of twin tunneling underneath on existing shield tunnels

新建双线隧道下穿施工会引发上部既有盾构隧道产生纵向沉降,并可能进一步影响隧道正常运营。采用Pasternak弹性地基梁模型和Loganathan-Polous解,提出双线隧道下穿作用下既有隧道纵向变形的简化计算方法,利用指数曲线公式量化双线隧道开挖引发土体损失之间的差异。利用工程实测数据进行对比分析,验证了方法的有效性。结合参数分析研究双线隧道水平距离、土体损失、竖向净距对隧道沉降和弯矩的影响。研究结果表明,考虑双线隧道之间土体损失差异的理论计算结果更符合实测数据;增加双线隧道距离,减小土体损失,增加竖向净距均有利于既有隧道沉降和弯矩控制,并会使隧道纵向沉降和弯矩曲线形态产生明显变化。研究成果可为合理预测双线隧道下穿施工对既有隧道的影响提供一定的理论依据。

The twin tunneling may induce settlements of the overlying tunnels and lead to adverse influences on the operation of the existing tunnels.The Pasternak elastic foundation beam theory and Loganathan-Polous solution are used to propose a simplified analysis method for evaluating the responses of existing tunnels to new twin tunneling underneath.The relationship between the ground losses induced by the first and second tunnel excavation is described by an exponential equation.The effectiveness of the proposed method is verified by measurement data from a case study.Based on the verified method,a parametric analysis is performed to investigate the influences of the horizontal distance between the twin tunnels,the ground loss and the pillar depth on the tunnel responses.The results show that the proposed method considering the ground loss differences between twin tunnels can derive more accurate calculation results.Increasing the horizontal distances between the twin tunnels and the pillar depth and reducing the ground loss are able to alleviate the tunnel settlements caused by twin tunneling underneath.These parameters have apparent effects on the settlements and bending moments of existing tunnels.The proposed method can provide a theoretical basis for predicting the influences of new twin tunnels excavation on the existing tunnel in relevant engineering practice.