This paper presents observed arching-induced ground deformation and stress redistribution behind braced excavation using the top-down construction method. The soil properties around the excavation were determined by laboratory and field tests. The ground deformation, soil displacement vector, strain path, principal strain, maximum shear strain, lateral earth pressure, pore water pressure, and effective stress path are presented based on the measured data. The majority of soil behind the wall is under volumetric expansion, indicating consolidation, creep behavior, or a combination of both. Besides, two periods of increases in pore pressure are observed, due to stress transfer from the lower to the upper parts (i.e., soil arching effect). The deep inward movement of the wall and the nearby soil accounts for the distribution of lateral earth pressure acting on the wall. The soil located behind the area of maximum wall deformation and adjacent to the wall, as well as the soil below the excavation base intersected by the shear plane, is in an active stress state. The lateral earth pressure at 5 m from the left excavation wall showed minimal changes, due to the combined effects of soil arching from lateral excavation and shield tunneling.

This study investigated active and passive lateral earth pressure in the presence of anisotropic seepage conditions. The soil was assumed to be granular and fully saturated. Three methods were used to solve the problem: (1) the upper bound limit analysis method (UBM); (2) upper and lower bound solutions of finite-element limit analysis (FELA); and (3) the stress characteristic method (SCM). The proposed analytical solution for the UBM employed the logarithmic spiral slip surface. The lateral earth pressure coefficients for the active and passive cases were calculated and presented, considering variations in the vertical-to-horizontal hydraulic conductivity ratio, friction angle, and soil-wall interface friction angle. The obtained results for the active and passive cases agree with those of previous studies. The results of the SCM showed that in the presence of seepage, the distribution of stress on the soil-wall interface is nonlinear. In addition, the failure zone obtained from different methods was compared and examined. The failure patterns obtained from the SCM and FELA were almost identical.

The coefficient of lateral earth pressure at rest, K-0, is an essential parameter for analyzing earth pressure distribution and the safe reliability of structures in geotechnical engineering. This paper presents a series of numerical one-dimensional compression tests on granular soils with particle size distribution (PSD) and rolling resistance (RR) effects using a real-particle 3D discrete element model. The corresponding macro-micro behaviors are investigated in a parallel way. Both PSD and RR affect K-0 and the related compression characteristics. A higher coefficient of uniformity (C-u) or rolling resistance coefficient (mu(r)) results in a monotonic decrease in the mean coordination number, and too much consideration of RR makes the mean coordination number less realistic in a particle system. The influence of PSD is more sensitive to the local-ordering structure and contact force network than the RR. The inhomogeneity of normal contact forces enhances as C-u increases and slightly reduces as mu(r) increases. The strong contacts are much more anisotropic than the weak ones. Specimen with lower C-u or higher mu(r) induces higher anisotropy and more strong contacts during compression, in which a lower K-0 is measured. A unique macro-micro relationship exists between K-0 and deviatoric fabric when strong contacts are considered only.

This paper presents experimental studies on a compacted expansive soil, from Nanyang, China for investigating the at-rest lateral earth pressure sigma(L) of expansive soils. The key studies include (i) relationships between the aL and the vertical stress sigma(V) during soaking and consolidation, (ii) the influences of initial dry density p(d0) and moisture content w(0) on the vertical and lateral swelling pressures at no swelling strain (i.e. sigma(V0) and sigma(L0)), and (iii) evolution of the sigma(L) during five long-term wetting-drying cycles. Experimental results demonstrated that the post-soaking sigma(L)-sigma(V) relationships are piecewise linear and their slopes in the passive state (sigma(L) > sigma(V)) and active state (sigma(L) < sigma(V)) are similar to that of the consolidation sigma(L)-sigma(V) relationships in the normal- and over-consolidated states, respectively. The soaking sigma(L)-sigma(V) relationships converge to the consolidation sigma(L)-sigma(V) relationships at a threshold aV where the interparticle swelling is restrained. The sigma(L0) and sigma(V0) increase monotonically with p(d0); however, they show increasingthen-decreasing trends with the w(0). The extent of compaction-induced swelling anisotropy, which is evaluated by sigma(L0)/sigma(V0), reduces with an increase in the compaction energy and molding water content. The sigma(L) reduces over moisture cycles and the stress relaxation in the sigma(L) during soaking is observed. An approach was developed to predict the at-rest soaking sigma(L)-sigma(V) relationships, which requires conventional consolidation and shear strength properties and one measurement of the sigma(L)-sigma(V) relationships during soaking. The proposed approach was validated using the results of three different expansive soils available in the literature. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).