施工期同步注浆影响下盾构隧道管片纵向上浮特征分析与应用
Analysis and application of longitudinal uplift characteristics of segments of shield tunnels affected by synchronous grouting during construction period
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摘要: 同步注浆是盾构施工中的关键工序,浆液压力产生的上浮力是导致施工期管片上浮的重要因素。在未凝固区长度范围内,上浮力逐渐衰减,上覆土体基床系数逐渐增加。针对该类复杂力学问题,基于弹性地基梁矩阵传递法理论,综合考虑了浆液黏度时变性、上覆土体基床系数各异性以及施工荷载步叠加效应的影响,提出了一种施工期盾构隧道管片上浮预测方法。将现场实测数据和模型计算结果进行比较,验证了计算模型的合理性。研究表明:在施工过程中,同步注浆引起的隧道上浮量最大处一般在距盾尾6~7环附近,远离盾构机40环以后影响较小;浆液黏度随时间增加使浆液流动性和周围土体渗透性降低,浆液压力衰减幅值减小,导致浆液未凝固区更长和上浮力更大。主要解决了复杂变基床系数条件下两类弹性地基梁计算方法耦合和考虑多因素影响下上浮量精细化预测的问题,其研究成果可为后续类似盾构隧道上浮量的控制提供参考。Abstract: The synchronous grouting is a key procedure during the construction of shield tunnels, and the uplift pressure generated by the grout is an important factor leading to the uplift of segments. Within the length of unconsolidated zone, the uplift pressure decreases and the foundation coefficient of the overlying soil increases gradually. Aiming at this kind of complex mechanical problem, a method for predicting the uplift of segments of shield tunnels during the construction period is proposed based on the theory of the matrix transfer method for elastic foundation beams. The influences of the time-varying property of grout viscosity, the variety of the foundation coefficient and the superimposed effect of construction load step are considered. The proposed model is well verified by the comparison between the theoretical results and the field test data. The results show that the maximum uplift of segments caused by the synchronous grouting is generally 6~7 rings away from the shield tail, and the influences are small beyond 40 rings. The time-varying property of grout viscosity affects the longitudinal distribution of unconsolidated zone and the uplift pressure. The grout viscosity increasing with time will decrease the grout fluidity and the permeability of surrounding soil. Therefore, it leads to the decrease of grout pressure which causes a larger uplift pressure and a longer length of unconsolidated zone. The coupling calculation of two kinds of elastic foundation beams under the complex variable foundation coefficient and the fine prediction for uplift of segments under the influences of multiple factors are solved. The research results can provide a reference for the subsequent control for the uplift of segments of the similar shield tunnels.