现场泥水劈裂试验及应用研究

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。

Test and application of in-situ slurry fracturing

For constructing slurry shield tunnels under rivers or seas, it's a difficult technical problem to maintain the stability of the excavation face while preventing slurry fracturing. There are some laboratory investigations of slurry fracturing. But, due to small sizes and different boundary conditions, the results cannot be directly applied to the projects. In-situ slurry fracturing instrument is developed on the basis of theoretical analysis, and the test procedures of fracturing and the relevant method of confirming fracturing pressure are introduced. The in-situ slurry fracturing test is carried out on the rive-crossing tunnel under construction in Nanjing. The results indicate that: (1) as the fracturing process is a mutation process, the stratum fracturing model can predict fracturing pressure by means of the total stress method, which agrees with actual working condition. The theoretical results show that the fracturing pressure of tunneling model, which is almost equal to the lateral earth pressure, is smaller than that of the in-situ slurry fracturing test. It's efficient to increase fracturing pressure by increasing the slurry viscosity, however, the effect is limited; and (2) the upper limit value of slurry pressure set for preventing slurry fracturing is given according to the results of the in-situ slurry fracturing test. The in-situ slurry fracturing test is performed by shield machine after originating, and it may verify the accuracy of the prediction model to some extent.