Earth pressure and deformation of cut-and-cover and trenchless flexible pipes under different soil properties and groundwater conditions

Abstract

A field case was first studied to verify the reliability of PLAXIS 2D and the accuracy of the modeling and calculation methods, in terms of calculating the radial earth pressure and vertical deformation on the cut-and-cover and trenchless pipes. Then, four types of classical soils were considered to compare the effects of cut-and-cover and trenchless construction methods on the installed flexible pipes. Besides, groundwater conditions and main physical properties of soils were also considered. Results demonstrate that deviations among the simulation calculated and the field measured value on earth pressure and deformation are all within 5%, showing a high accuracy and reliability. The maximum earth pressure and deformation on the cut-and-cover flexible pipe are 2.66–11.65 times and 3.96–11.95 times larger than that on the trenchless pipe, which is mainly due to the passive earth pressure caused by the deformation of the trenchless pipe. As the groundwater level increases from the bottom to 5.5 m above the top of pipes, the maximum earth pressure and deformation of the cut-and-cover pipe increase by 18.74% and 13.38%, while that on the trenchless pipe increased by 6 times and 3 times, because of the difference of reduction in effective stress. Density, cohesion, and friction angle are positively related to the earth pressure and deformation on the cut-and-cover pipe, and Poisson’s ratio and density are positively related to that on the trenchless pipe, while the others are the opposite. Density and cohesion are respectively the most significant factors affecting the cut-and-cover pipe and trenchless pipes.