Abstract
The performance of geotechnical structures in unsaturated soils is affected significantly by the hydraulic conditions. In the present paper, a unified computational upper bound limit analysis method is applied to study the stability of dual circular tunnels located in unsaturated soils. The linings are substituted by an equivalent uniform pressure exerted on the periphery of the tunnel. The main focus is put on the effect of ground water table and surface water infiltration on the required supporting pressure and collapse mechanisms of dual tunnels. The critical center-to-center spacing above which the interaction of the tunnels disappears is also discussed.
Highlights
Most available studies mainly dealt with the surrounding soils as single-phased materials, and their shear strengths are kept constant
Unsaturated soils are frequently encountered in geotechnical engineering, and a large portion of their strengths is contributed by the matric suction. e matric suction is affected by the external hydraulic conditions such as rainfall, irrigation, and ground water level fluctuation. erefore, the stability of dual tunnels in unsaturated soils will be varying with the hydraulic states of surrounding soils, which will be the main focus of the present study
One of the most important contributions in the authors’ work is to consider the saturation variation of unsaturated soils by the incorporation of equivalent forces, whereas the strength parameters are specified in advance. e proposed upper bound theory in Yuan and Du [21] will be combined with the finite element method in the present paper to make use of the seepage analysis programs of available commercial software
Summary
Most available studies mainly dealt with the surrounding soils as single-phased materials, and their shear strengths are kept constant. CLA is very appropriate to compute the required supporting pressure and if unsaturated seepage analysis is combined, the impact of hydraulic conditions such as ground water table fluctuation and surface water infiltration can be studied efficiently.
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