Laboratory Test And Calculating Method Research On The Settlement Of Roadbed Caused By Lateral Deformation

The settlement of roadbed was always an important resourceful topic in the Geotechnical Engineering. Whether its' calculation was right or not was a matter which affected the design,construction and safety of the project. Now, the common methods for calculation were all based on one-dimensional compression test and one-dimensional consolidation theory in which we only considered the deformation under vertical stress. However, the embankment load belonged to partial load and would bring shear stress in the foundation. Since the sub grade was under plane—strain condition, So the deformation of the soil happened in two-dimension. But these methods used now always neglected the effect of shear stress and the associated settlement resulted in the lateral deformation. In many literatures, they only considered the immediately settlement caused by shear stress, which were always based on the elastic theory and different from the term we discussed here.In this paper, we first did lots of experiments to study the mechanism of the lateral deformation and the factors which effected the lateral deformation. Beyond the former study, we found a method to consider the effect of lateral deformation to the settlement. The main works of this paper was as follows:Firstly, we put forward the necessary to study this subject and introduced all the reference about the lateral deformation and settlement in the domestic and foreign literatures. Especially we demonstrated that the effect of lateral deformation to the settlement was along the whole course of settlement and the shear stress has influence on the curve of settlement, which was much more different to the traditional viewpoint.Secondly, we have done plenty of laboratory tests, such as the three-dimensional undrained or drained creep test,plain-strain drained creep test and so on, in order to study the relationship between lateral deformation and time and the factors which influenced the lateral deformation. Then we got some important conclusions: the relationship between the initial stress and strain was non-linear; the lateral deformation expanded all the time under the un-drained condition, while it not only squeezed out but also shrink under the drained condition, the rate of loading has not obvious effect on the development of lateral deformation, there were corresponding relationships between the shear stress level and the shape of lateral deformation, when the shear stress level was low, the influence of lateral deformation to the settlement of roadbed was not so distinct, when it was high, this influence should not be neglected and it appeared along the whole course of settlement.Thirdly, we summarized nearly all the method which used to calculate the settlement nowadays and developed a new method to consider the effect of shear stress. We proposed two coefficients to correct layer-wise summation method: correctional coefficient of volumetric strain m_sv and correctional coefficient of lateral deformation m_sl. m_sv was calculated in the Skempton's method while m_sv was calculated in this article's method. Besides, for the different pattern of the shear stress under the narrow and wide embankment, we deduced the calculated method respectively.At last, though the analysis of the filed monitoring data of several transects about the constructed or constructing road, we learned these relationships such as the max lateral deformation and settlement,the lateral deformation and time and so on. Also we got the empirical value of m_sl in the eastern region of Guang-Dong province. Beyond this, wededuced the m_sl of the eastern area in the Guang-Dong province, which was 1.1. The curve of max lateral deformation and settlement was constituted by 3 lines. The pattern of the curve of the lateral deformation and time was depended on the shear stress level. The lateral deformation was effected by these factors, such as v , non-linear of the soil, the stiffness of the embankment, the characteristic of soil that shrink in the consolidate process and expanded in the creep process.