The most common soil reinforcement method used in tunnelling, such as jet grouting, fiberglass reinforcement and ground freezing, leave spoils into the ground and have high costs of implementation. On the other hand, preloading methods for soils improvement require long construction periods and limit the enhancement of the undrained shear strength to the applied surcharge load or vacuum load. This paper presents the concept of suction drain as an innovative technique for temporary stabilisation of geo structures in soft clayey soils, which overcomes the inconvenience of current soil reinforcement techniques and the limitation of the preloading. Based on suction generated into the ground by the evaporation from pre-drilled holes, the suction drain enables the enhancement of the undrained shear strength in soft clayey soils. The concept and its validation at mock-up scale level are presented in this study. The experimental investigation assessed the capacity of the suction drain to reduce the soil water content via soil water evaporation induced by forced ventilation. The mock-up scale test was then validated numerically via FEM modelling. Finally, the suction drain modelling was extended to an ideal case of tunnelling for assessing the potential impact of the suction drain on undrained shear strength and, hence, on tunnel face stability.
- undrained shear strength
- tunnel face stability