The transfer process of vertical stress of strata is affected by local soil arching effect, to address the limitation of differential soil layer method in overestimating the transferred stress, a method for calculating average vertical stress based on stress transfer ratio was proposed. This approach integrates numerical simulation results on the relationship between the rotation angle of principal stress and the average vertical compressive and shear stresses. Additionally, the shear stress distribution and the transmission behavior of vertical stress in both the equal settlement zone and the arching zone were verified. The results indicate that the stress transfer ratio can be used to define the boundary between the equal settlement plane and the soil arching zone of the tunnel. As the final stress transfer ratio increases, the path of principle stress gradually evolves into a closed arch trace, the proportion of transition before the peak of the average vertical stress curve decreases, while both the inflection point of the stress curve and the boundary of the equal settlement zone shift upward, and the transferred stress of strata with unit thickness increases accordingly. The transferred stress increases with gradual rotation of the principal stress, once the principal stress path forms a closed arch, the stress transfer function exhibits a sharp rise. The rate of change of the stress transfer ratio also increases in tandem with the rotation angle of the principal stress. These findings reveal the vertical stress transfer mechanism in the local soil arching zone and clarify the influence of the principal stress path on this process.

This paper aims to investigate the role of bi-directional shear in the mechanical behaviour of granular materials and macro-micro relations by conducting experiments and discrete element method (DEM) modelling. The bi-directional shear consists of a static shear consolidation and subsequent shear under constant vertical stress and constant volume conditions. A side wall node loading method is used to exert bi-directional shear of various angles. The results show that bi-directional shear can significantly influence the mechanical behaviour of granular materials. However, the relationship between bidirectional shear and mechanical responses relies on loading conditions, i.e. constant vertical stress or constant volume conditions. The stress states induced by static shear consolidation are affected by loading angles, which are enlarged by subsequent shear, consistent with the relationship between bidirectional shear and principal stresses. It provides evidence for the dissipation of stresses accompanying static liquefaction of granular materials. The presence of bi-directional principal stress rotation (PSR) is demonstrated, which evidences why the bi-directional shear of loading angles with components in two directions results in faster dissipations of stresses with static liquefaction. Contant volume shearing leads to cross-anisotropic stress and fabric at micro-contacts, but constant vertical stress shearing leads to complete anisotropic stress and fabric at micro-contacts. It explains the differentiating relationship between stress-strain responses and fabric anisotropy under these two conditions. Micromechanical signatures such as the slip state of micro-contacts and coordination number are also examined, providing further insights into understanding granular behaviour under bi-directional shear. (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/).

For deep-filled building site, it is not acceptable to neglect water seepage and land settlement caused by the coupling effect of wetting and loading. However, previous soil column tests employed in investigating the water seepage always failed to consider the vertical stress. In this article, a stress-controlled soil column test was conducted to investigate the effect of vertical stress on water seepage and deformation of the compacted soil. The soil column was equipped with a vertical loading device and a water-recharge device to control the boundary conditions and water sensors, tensiometers, dial indicators and a data collector to monitor the displacement and water movement. The soil column test was utilised to perform seepage tests on compacted loess with vertical stresses of 0 and 400 kPa. The time-history data of wetting front depth, volumetric water content (VWC), suction and vertical displacement have been monitored directly. The VWC and suction profiles, soil-water characteristic curves and hydraulic conductivity curves were then obtained with the monitored data. The test results demonstrated that the vertical stress affected the water seepage and consolidation of the compacted soil, but this effect gradually decreased as the depth of the soil column increased. Moreover, the reliability of the proposed test method was verified by the comparison of some available test results. The findings of this study contribute to a better understanding of water seepage and consolidation characteristics of the compacted soil subjected to vertical stress. A stress-controlled soil column test equipment is developed for investigating soil water migration and deformation characteristics.The time-history curves about wetting front depth, volumetric water content (VWC), suction and vertical deformation are measured directly using a developed stress-controlled soil column test equipment.The VWC and suction profiles, soil-water characteristic curves and hydraulic conductivity curves are obtained.The validity of the test method and developed soil column is verified by the comparison of partial test results.

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/).