The traffic loading is a typical cyclic loading with variable confining pressure and always lasts long, and is believed to have a significant effect on the subgrade soil, especially for the subgrade filled with soft clay. However, the mechanics have yet to be fully understood. Given that the duration of traffic loading lasts long enough, the partially drained conditions should be considered for the soft clay under the long-term cyclic loading, rather than the undrained conditions adopted commonly by most previous researches. In this study, 28 cyclic tests were conducted on the remolded saturated soft clay, utilizing both constant confining pressure and variable confining pressure under partially drained and undrained conditions. The effect of cyclic confining pressure and different drainage conditions is analyzed in relation to the evolution of pore pressure and deformation behaviors. Incorporating both the cyclic confining pressure and cyclic stress ratio, a concise pre-diction model of permanent strain is proposed and validated by the experimental results.

Traffic-induced cyclic loading generates repetitive stresses and cumulative deformations on the GRS abutments, which affect the serviceability of GRS abutments. To evaluate the stress distribution of GRS abutments under cyclic traffic loading, this paper presents reduced-scale GRS abutment models constructed with sand backfill and geogrid reinforcements. The GRS abutment models were subjected to staged cyclic loading with different cyclic loading amplitudes to investigate the influences of cyclic loading amplitude, bridge superstructure load, and reinforcement vertical spacing on the dynamic soil stress distributions. The results indicate that the increase in residual stresses due to stress redistribution induced by cyclic loading is most pronounced at the top of the abutment, while there is little stress redistribution down to the foundation level. Increasing the static load of bridge superstructure or the amplitude of cyclic loading results in an increase in the incremental dynamic vertical soil stresses. Reinforcement vertical spacing does not significantly impact the incremental dynamic vertical soil stresses under cyclic loading, while the cyclic load has the most significant influence. Closer reinforcement vertical spacing could provide stronger lateral confinement, resulting in larger dynamic lateral soil stresses behind wall facing.

Road embankments along irrigation canals, constructed on soft Bangkok clay, have always been unstable. Numerous studies have shown that rapid drawdown of water level may be one of the main causes, while vehicle cyclic loading may also contribute to embankment failure. This study aims to investigate the impact of vehicle loading on the failure of embankments built on Bangkok soft clay. The behavior of soft Bangkok clay under vehicle load has been investigated by employing conventional and dynamic triaxial techniques, and finite element method (FEM). This study also examined the effects of soft clay thickness and cyclic loading with different magnitudes and frequencies. The laboratory testing results indicate that the threshold stress of the soft clay is estimated to be approximately three-fourths of the undrained shear strength of the soil. The reduction in effective stress in the soft clay is caused by varied frequencies and thicknesses of the clay. Based on the analysis results, it has been proven that the cyclic loads exerted by vehicles solely are insufficient to cause the embankment to collapse. Nevertheless, the repetitive loading of vehicles may result in a one-quarter decrease in the embankment's factor of safety.

Traffic cyclic loading is the key factor that leads to the deterioration of the long-term service behavior of subgrade. A series of cyclic triaxial tests was carried out by the large-scale dynamic and static triaxial apparatus (LSDSTA) to study the dynamic behaviors of coal gangue subgrade filler (CGSF) under multi-step cyclic loading using the morphological characteristics of hysteretic curves (MCHC). MCHC was quantitatively characterized by four parameters, i.e., the unclosed degree (epsilon phl ), inclination of long axis degree (k hl ), area (S hl ) and fullness degree (alpha hl ). With the increase of dynamic strain, epsilon phl increases exponentially. k hl of the coal gangue sample first decreases and then shows an increasing trend with the increasing dynamic strain. The values of S hl are close to each other, and the energy dissipation in the sample is small. However, with the increase of dynamic strain, the specimen failure degree is increased, S hl increases exponentially, and the damping ratio increases. With the increase of dynamic strain, alpha hl increases approximately linearly. Confining pressure has a certain effect on the four parameters. There parameters can be recommended and used for quantitative analysis the dynamic behaviors of subgrade filler under traffic cyclic loading.

Calcareous sand is a favored unbound granular fill-in island project where complicated stresses are often applied. Traffic and ocean loadings are frequent in praxis, but poorly understood about the normalization of the pore pressure for both. This paper deals with an experimental simulation study on the pore pressure of calcareous sand subjected to ocean waves, traffic, and cyclic loading. Particular attention is devoted to the effect of the initial shear stress and the dynamic stress ratio (CSR). Results showed that, owing to the features of traffic loading and initial shear stress, the soil skeleton can still withstand partial external loading when reaching the failure criterion, hence the pore pressure at failure(ruf) is much smaller than liquefaction. In terms of the influence mechanism, unlike the initial shear stress, the increase in CSR accelerates the destruction of the soil skeleton, reducing the ruf, but having less effect on the critical pore pressure. Expressions for the number of cycles at failure (Nf) and ruf were obtained and the exponential model was simplified by changing N/Nf to epsilon 1/0.05 to reflect the characteristics of traffic loading. To normalize the pore pressure under different loadings, each stress component on Nf and ruf has been analyzed and the noteworthy finding is that torque has a very minor impact on the soil skeleton. Based on this finding, a new normalization method was proposed in which Nf needs to combine all loads including torque, while ruf only needs to consider axial forces. Hence, a pore pressure equation under three different loadings was established, taking into account the role of CSR and the initial shear stress.

Although the cardioid-shaped traffic loading path can be implemented using hollow cylinder apparatus, the preparation of inherently anisotropic sand with different bedding plane angles could be difficult. Consequently, the macro-scale response of inherently anisotropic sand under traffic loading has not been adequately investigated to reveal the underlying microscopic mechanism. In this paper, elongated particles with various aspect ratios were used to approximate the natural sand particles, and uniform three-dimensional specimens with different bedding plane angles were generated using discrete element method based on a modified version of under-compaction method. The cardioid-shaped loading path was implemented using an advanced servomechanism that can apply arbitrary loading paths. The internal structure of specimen was quantified through a contact-normal-based fabric tensor, which could describe the load-bearing structure of granular specimens. The interplay between the macro-scale observations and the fabric evolutions was elucidated. The influences of both bedding plane angle and aspect ratio on the accumulations of volumetric strain and generalized shear strain are not monotonic, with the largest strains at the bedding plane angle of 45 degrees and the aspect ratio of 1.4. Results provide useful insights into the underlying mechanism of the deformation behavior of inherently anisotropic granular materials under traffic loading.

In road engineering, the applications of piezoelectric ceramics on road energy harvesting or electronic sensing have drawn many attentions. However, the application potential of piezoelectric sensor on UGMs (unbound granular materials) in road is unclear. The main problem is the applicability of piezoelectric equation considering that the soil structure of UGMs and the working environment that the transducer may suffer may influence the transferred stress on the piezoelectric transducer and then the electricity generation. In this study, a twodimensional piezoelectric transducer made by PZT-5H piezoelectric ceramics was installed in the sample of UGMs, and a series of cyclic tests were performed on the UGMs samples by a large-scale triaxial apparatus. This test method is specially designed for the case that the piezoelectric transducer is installed in UGMs of pavement base/subbase layers and then undergo traffic loading under complex working environment. Test results show that the electricity generation is primarily dependent on the magnitude and frequency of cyclic loading, while the influences of other factors are limited. The piezoelectric equation to calculate the open-circuit voltage is deduced and verified under the complex working environment. This indicates that the piezoelectric equation is applicable to the case that the applied stress on the piezoelectric transducer is transferred from the soil medium, and the two-dimensional piezoelectric transducer has a sensor potential to monitor the dynamic vertical and horizontal soil stresses under traffic loading.