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Abstract: When performing a slurry shield excavation in the shallow earth cover under a waterway, the support pressure is difficult to calibrate. If not carefully monitored, slurry fracturing or even slurry breakout can occur; water from the river can rush into the slurry circulating system, threatening the security of the project. In this study, an in-situ slurry fracturing apparatus was created to analyze the phenomena of slurry fracturing and fracture propagation. First, the fracturing test procedures and the method of identifying slurry fracturing are introduced. Then, mechanical models of the slurry fracturing and fracture propagation are described and validated with in-situ tests. The models provide fairly good predictions: the driving pressure is related to the properties of both the soil and slurry. Slurry with large parameters for bulk density and viscosity is beneficial for preventing slurry fracturing propagation. However, such parameters have little influence and can be neglected when determining the initial fracturing pressure. Preventing slurry fracturing and breakout is important for not only shield tunnel preparation, but also shield tunneling under dangerous conditions. A crucial factor is setting and limiting the maximum support pressure values. These pressures can be obtained through the in-situ tests and mechanical models described here. These results provide useful references for the Weisan Road Tunnel to be built under the Yangtze River in Nanjing, China.

泥水盾构掘进过程中的泥水劈裂现象现场试验研究

研究目的：本文通过研究泥水在地层中的劈裂和伸展现象，给出一种地层劈裂抗力的测定方法，从而为泥水盾构掘进过程中泥水压力设定提供参考，防止盾构掘进过程中泥水喷发现象的发生。
创新要点：1.给出了地层劈裂抗力的测定方法，并通过现场试验和理论分析得出该方法是可靠的；2.建立了考虑泥水粘性和比重的地层劈裂伸展模型，该模型对现场试验结果有较好的预测；3.结合地层劈裂抗力和泥水劈裂伸展特性给出了盾构掘进过程中泥水压力的设定上限。
研究方法：基于现场泥水劈裂试验，通过试验结果分析和理论分析，建立了劈裂压力和劈裂伸展压力的计算模型。通过泥水和地层参数对计算模型的影响分析，给出泥水盾构掘进过程中泥水配比和压力设定选择建议。
重要结论：1.本文描述的现场泥水劈裂仪可以用于地层劈裂抗力的测定；2.使用总应力法的劈裂模型能够很好的预测地层的初始劈裂压力；3.考虑泥水粘性和比重的地层劈裂伸展模型对现场试验结果有较好的预测；4.在劈裂伸展的过程中，具有更大比重和粘性的泥水有利于阻止劈裂的进一步伸展，但是对初始劈裂压力的影响不大。5.在实际盾构掘进过程中，泥水劈裂发生后很难阻止其伸展。因此，防止泥水喷发的关键措施在于设定泥水压力上限防止泥水劈裂。

关键词：现场泥水劈裂试验；初始劈裂压力；劈裂伸展；劈裂伸展压力；泥水盾构隧道施工

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