Marine soft clay with weak engineering properties, is widely distributed in Southeast China. As the most developed area in China, Zhejiang has a vast transportation infrastructure including highways, roads, railways and airport runways which have been constructed on the marine clay. With long-term vehicle loading, excess settlement tends to occur on the existing infrastructure. In order to reveal these effects on the marine clay caused by vehicle loading, and to predict future settlement, research was undertaken.
Vehicle loading is not only a long-term cyclic loading, it is unique in the shape of stress path’s during each cycle. Along with the wheels, approaching and then leaving, the stress components of the soil change in both magnitude and direction (see Fig 1.1). Moreover, the angle of major principal stress σ rotates during each cycle. When plotted together in the 2τzθ (σz - σθ) space, the stress paths form the shape seen in Fig 1.4.
According to the finite element analyses by previous researchers, the ratio of shear stress to axial stress decreases as the depth increases, instead of remaining constant, leading to the change in shape of stress paths.
To simulate the stress path of a vehicle loading, accurate control of each stress component is required (as shown in Fig 1.2). It further necessitates the redefined waveforms according to the shape of loading.
Fig 1. Stress components of the soil element in soft subsoil induced by vehicle loading