Three-dimensional consolidation deformation analysis of porous layered soft soils considering asymmetric effects

ZHANG Zhi-guo(张治国)^{1, 2, 3}, HUANG Mao-song(黄茂松)^{2, 4}, Wang Wei-dong(王卫东)⁵

(1. School of Environment and Architecture, University of Shanghai for Science and Technology,
Shanghai 200093, China;
2. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education
(Tongji University), Shanghai 200092, China;
3. State Key Laboratory for Geomechanics and Deep Underground Engineering
(China University of Mining and Technology), Xuzhou 221116, China;
4. Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China;
5. East China Architecture Design Institute, Shanghai 200002, China)

Abstract:Long-term settlements for underground structures, such as tunnels and pipelines, are generally observed after the completion of construction in soft clay. The soil consolidation characteristic has great influences on the long-term deformation for underground structures. A three-dimensional consolidation analysis method under the asymmetric loads is developed for porous layered soil based on Biot’s classical theory. Time-displacement effects can be fully considered in this work and the analytical solutions are obtained by the state space approach in the Cartesian coordinate. The Laplace and double Fourier integral transform are applied to the state variables in order to reduce the partial differential equations into algebraic differential equations and easily obtain the state space solution. Starting from the governing equations of saturated porous soil, the basic relationship of state space variables is established between the ground surface and the arbitrary depth in the integral transform domain. Based on the continuity conditions and boundary conditions of the multi-layered pore soil model, the multi-layered pore half-space solutions are obtained by means of the transfer matrix method and the inverse integral transforms. The accuracy of proposed method is demonstrated with existing classical solutions. The results indicate that the porous homogenous soils as well as the porous non-homogenous layered soils can be considered in this proposed method. When the consolidation time factor is 0.01, the value of immediate consolidation settlement coefficient calculated by the weighted homogenous solution is 27.4% bigger than the one calculated by the non-homogeneity solution. When the consolidation time factor is 0.05, the value of excess pore water pressure for the weighted homogenous solution is 27.2% bigger than the one for the non-homogeneity solution. It is shown that the material non-homogeneity has a great influence on the long-term settlements and the dissipation process of excess pore water pressure.

Key words:three-dimensional consolidation deformation; porous layered soils; asymmetric loads; long-term deformation prediction; transfer matrix method