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采用泥水平衡盾构进行过江越海隧道施工时,重要的技术难点就是特殊小覆土区间盾构掘进保证开挖面稳定以及防止泥水劈裂的发生。对于泥水劈裂现象的室内试验研究,有一定的基础资料。但是,由于尺寸和边界条件限制,使其研究成果不能直接应用到工程中去。在理论分析的基础上,研制了现场泥水劈裂仪,确定了劈裂试验的具体实施步骤和劈裂压力的断定方法。并在南京某在建过江隧道工程中进行了现场劈裂试验。(1)试验结果表明:由于劈裂过程为突变过程,采用总应力法时,地层劈裂模型能很好的预测地层劈裂压力,也更符合实际工况;由理论分析得出,掘进模式模型的地层劈裂压力更小,几乎与地层静止侧向土压力相当;增加泥水黏度能够增加地层劈裂压力,但增加量有限。(2)运用现场劈裂试验结果给出了防止泥水劈裂的泥水压力设定上限值,并运用盾构机在始发不远处进行了原位泥水劈裂试验,在一定程度上验证了预测模型的准确性。
When using the mud-water balance shield to carry out the construction of the Jiang-Ho-Hohai Tunnel, the important technical difficulty is that the shield tunneling in the special small enclosed area ensures the stability of the excavation surface and prevents the occurrence of the mud splitting. There are some basic data for the laboratory test of mud splitting phenomenon. However, due to the limitation of size and boundary conditions, the research results can not be directly applied to the project. On the basis of theoretical analysis, an on-site mud-water splitting instrument was developed, and the concrete implementation steps and determination methods of splitting pressure were determined. In Nanjing and a construction of the tunnel project in the field split test. (1) The experimental results show that the formation splitting model can predict the splitting pressure well, which is more in line with the actual working condition when the total stress method is used because of the splitting process. According to the theoretical analysis, The stratigraphic splitting pressure of the model is smaller and almost equal to the lateral lateral earth pressure in the stratum. Increasing the muddy water viscosity can increase the splitting pressure of the strata, but the increase amount is limited. (2) The upper limit of the set pressure of muddy water to prevent the muddy water splitting is given by using the field splitting test results, and the in-situ muddy water splitting test is carried out with the shield machine not far from the starting point, to a certain extent, The accuracy of the prediction model.