A large number of laboratory triaxial experiments were performed to evaluate the likely cumulative settlement of a low embankment road on soft subsoil due to the traffic loads, for the purpose of determining the undrained cumulative strain and cumulative pore-water pressure for different loading conditions. A cumulative settlement model of soft subsoil was then derived with the provision for dynamic stress, confining pressure, initial static deviatoric stress, number of load cycles, and loading frequency. Based on a particular vehicle-road-ground coupling model, the dynamic stress induced by traffic loads, which has a great influence on the cumulative settlement of soft subsoil, is given in explicit form. The cumulative settlement of a road with a low embankment was evaluated, and the results were compared with the field data. The calculated results agreed well with those from the field, which implies that the method proposed in this paper can give precise predictions of the likely cumulative settlement of low embankment roads on soft subsoils due to traffic loads. Moreover, a parametric study was conducted using numerical computation, and the results show that the vehicle types and the pavement unevenness parameters have a major influence on the settlement caused by traffic loads. The influences of the pavement and embankment properties on the cumulative settlement also are significant.

The study of dynamic responses of a layered road system under heavy duty vehicle is one of the most important areas in the field of transportation. This paper introduced a field testing programme of traffic-induced road vibration in Guangxi, China and investigated the subgrade vibration induced by a heavy duty truck with various axle weights and speeds through a series of field tests. The vertical stress and acceleration of the road subgrade at different depths from the tests were presented and analysed. According to the test road, a semi-analytical model of the layered road was established via the stiffness matrix method and the heavy duty vehicle was simulated by ten moving rectangular load pressures. Numerical results in the space domain were derived by performing Fast Fourier Transform and were used to compare its results with the field measurements. The agreement between the numerical and the field results was good, which indicates that the proposed method is useful in predicting the dynamic stress and acceleration of a multi-layered road structure.

Soil slope diseases in seasonally frozen regions are mostly related to water migration and frost heave deformation of the soil. Based on the partial differential equation defined using the COMSOL Multiphysics software, a thermo‐hydromechanical coupling model considering water migration, ice‐water phase change, ice impedance, and frost heave is constructed, and the variations in the temperature field, migration of liquid water, accumulation of solid ice, and deformation of frost heave in frozen soil slopes are analysed. The results show that the ambient temperature has a significant effect on the temperature and moisture field of the slope in the shallow area. In addition, the degree of influence gradually weakens from the outside to the inside of the slope, and the number of freeze‐thaw cycles in deep soil is less than that in shallow soil. During the freezing period, water in the unfrozen area rapidly migrates to the frozen area, and the total moisture content abruptly changes at the vicinity of the freezing front. The maximum frozen depth is the largest at the slope top and the smallest at the slope foot. During the melting period, water is enriched at the melting front with the frozen layer melting; the slope is prone to shallow instability at this stage. The melting of the frozen layer is bidirectional, so the duration of slope melting is shorter than that of the freezing process. The slope displacement is closely related to the change in temperature—a relation that is in agreement with the phenomenon of thermal expansion and contraction in unfrozen areas and reflects the phenomenon of frost heave and thaw settlement in frozen areas.

The swelling properties of expansive soil at different depths were investigated by the laboratory model test. It was experimentally found that the swelling deformation of different expansive soil layers was obviously different under unidirectional seepage. Pore solution collection boxes were designed to collect the pore solution of different soil layer interfaces during the saturation process. Cation concentration tests were then used to analyze the migration regulation of cations in these soil layers. Results showed that the divalent cations in the surface soil layer migrated downward along with water molecules and aggregated around clay particles to form the electrical environment in expansive soil. Additionally, swelling tests were performed to compare with their initial values to research the variation of swelling behavior of expansive soil at different depths after completion of the model test. It was observed that the swelling potential of the surface expansive soil layer at a depth of 0–30 mm was released while that of the middle and bottom ones at depths of 90–120 mm and 180–210 mm was inhibited. An analysis on the above results was used to clarify the mechanism controlling the swelling difference of different expansive soil layers. This swelling difference may be explained by the joint effect of two factors that can be treated as an electric charge effect, namely (i) the modification effect, (ii) the electrical environment.

In this paper, a full vehicle–track–ground coupling model is presented to evaluate the dynamic response of the subgrade due to high-speed trains. The vehicle was modeled as a multibody. The track was considered as an Euler beam. The ground soil was regarded as two elastic layers and a poroelastic half-space, taking into account a complete subgrade/subsoil system. The wheel–track interaction was considered by using the linear Hertzian contact theorem. The stiffness matrix method and the Fourier transform were introduced to deal with formulations of the coupling model in a transformed domain, and the time-domain solutions were derived by using the fast Fourier transform algorithm. The wheel–track contact forces and the dynamic responses of the subgrade were studied, and the effects of the rail irregularity and the properties of the subgrade bed were then investigated. It was concluded that the dynamic responses of the subgrade are significant compared with responses induced by the axle load and are influenced greatly by rail irregularity and parameters of the subgrade bed.