Study On Undrained Slope Foundation Ultimate Bearing Capacity

With the speeding up of the economic development, an increasing number of highways, railway, low-rise building and port engineering are built on the saturated layer, such as the layer near the seaside, riverside and levees. However, the stability evaluations of low-medium slopes near the foundation need to be carried out during and after construction. Considering to the influence of slopes, the bearing capacity of the slope foundation is reduced compared to that of the horizontal foundation. The stability of the slope foundation will directly affect the reliability of construction foundation. Though certain achievements and progress have been achieved in the understanding of failure mechanism for the slope foundation, until now few criteria have been definitely proposed for the distinguishing of the failure mode of slope foundation.With the ideal elastic-plastic finite element method, the paper mainly focused on the bearing capacity of the undrained-homogeneous slope foundation under strip load. After 1040 times of simulation, the relationship between the ultimate bearing capacity of slope foundation and the stability of the slope, the gradient, the ratio of width of basis to the height of slope, the ratio of the distance from foundation to slope shoulder to the width of basis were analyzed. The failure mode of slope foundation was also studied, and the maximum range of the impact of the slope on the bearing capacity of foundation was put forward. The main results are as follows:(1) Terzaghi’s calculation formula that proposed for horizontal foundation can still be ised for the analysis of ultimate bearing capacity of undrained slope foundation: Ru= cuNc(2) If the foundation is on the top of slope, the stress field will be affected by the coupling action of slope and foundation. The failure modes can be divided into three types: the slope failure mode (with circular slip surface), foundation failure mode (with streamline failure surface) or the transition mode (The failure surface is the combination of circular and streamline modes).(3) The difference between Taylor’s stability number with load on the slope and that without load (△N) can be the index to identify the failure mode of slope foundation. When the △N is small (the stability of the slope is low), the failure of slope occurs; when the AN is large (the stability of the slope is high), the failure of the foundation occurs. The values of △N corresponding to the two failure modes can be obtained the basis of the slope β and the ratio of width to height of the slope (B/H).The formula of bearing capacity factor was proposed and the ways to achieve the parameter M were described in detail.(4) The ratio of the distance between the edge and shoulder of the slope to the width of the foundation was defined as the coefficient of the effect of distance from the slope to foundation on the bearing capacity of foundation (λ).The smaller the safety margin of slope and the larger of the slope gradient, the greater the maximum value of λ0 can be.The relationship formula of the stability factor of the slope without load and the parameter was obtained. When λ is greater than 10, the slope has little effect on the reduction of bearing capacity.(5) The reduction ratio of Nc (NcRR) was also defined. If the evaded distance is larger than 3.5 B which is required in the Code for design of building foundation (GB50007-2011), The NcRR can be estimated by the formula:...