开挖卸荷引起下卧已建盾构隧道的纵向变形研究

开挖卸荷引起的下卧已建盾构隧道纵向变形是城市基础设施建设面临的热点和难点问题。将已建盾构隧道视为三参数Kerr弹性地基上的无限长梁，采用两阶段法研究基坑开挖卸荷引起下卧盾构隧道的纵向变形。对简化弹性空间法获得的地基参数进行讨论，通过与有限元模拟结果对比确定了合适的Kerr地基模型参数选取，并对Winkler、Pasternak与Kerr 3种地基模型的模拟结果进行了对比。为获得更合理的上方卸荷引起的隧道响应，推导并求解了考虑隧道侧向土体对隧道作用的平衡微分方程，解析结果与有限元结果基本吻合，与工程实例监测数据对比，验证了方法的有效性。研究表明：相对于Winkler与Pasternak模型，Kerr地基模型更具优越性；对通过简化弹性空间法得到的地基参数进行适当修正可以使弹性地基模型的模拟结果更理想；隧道侧向土体对隧道的作用比较显著，应在计算中考虑。

Longitudinal deflection of existing shield tunnels due to deep excavation

In the area of infrastructure construction,increasing attention has been paid to the deflection of existing shield tunnels due to deep excavation unloading.The simple two-stage method is adopted to study this problem.The existing shield tunnel is simplified as an infinite beam on a Kerr-type three-parameter elastic foundation.Its governing differential equations are formulated and analytically solved.The parameters of the Kerr model from the simplified elastic continuum method are adjusted by comparing the results with those of finite element models,and comparisons are carried out among Winkler,Pasternak and Kerr models.To obtain more reasonable results,the effects of the lateral soil beside the tunnel are considered and the governing equations are modified and solved accordingly.A good agreement is achieved between the analytical results and finite element ones after considering the lateral effects.The study indicates the superiority of the Kerr foundation model.The effects from the lateral soil are remarkable and should be considered in the analysis.