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The forces on TBM druing tunnelling are analyzed in detail based on the characteristics of mixed face strata. Suitable parameters of TBM are choosed according to the characteristics of the strata ahead. The studies are focused on both the acting posture of TBM and the points of the main forces. A systemic model is consequently set up, which can provide ones with analysis of TBM stability, parameter calculation and tunnelling design in mixed strata. Two cases are finally analyzed of TBM tunnelling in different mixed strata by using this model. Then some of countermeasures is given as reference for TBM tunnelling in such mixed strata in the further.

Earth Pressure Balance shield machines are used to construct metro tunnel in Shenzhen mixed ground. The ground condition is full of water and the diversity of two grounds in juncture is drastic. The risk mechanism of this ground is studied, and the main risks are found out. The main risks are assessed and classified employing the method of P=R×C, then the risk classification is determined. These studies ensure the projects in Shenzhen metro advance successfully.