Effects Of Spatial Variability On The Bearing Capacity And Failure Mechanism Of Footings In Clay

The vertical bearing capacity of a shallow foundation is a classical geotechnical problem. The majority of the previous studies on the bearing capacity problem of buried footings have been limited to homogeneous soil or uniform soil of strength increasing linearly with depth. Natural soil is one of the most variable materials as a result of physical and chemical changes. Research have shown that the variation in soil properties significantly affects the failure mechanism and bearing capacity of a footing. This effect is further complicated by considering the spatial correlation of the soil properties.Combing random field theory with non-linear finite element analysis, this study develops random finite element to analyze the vertical ultimate bearing capacity of a foundation. The sensitivity of the bearing capacity of the footing to the degree of local average of random field are explored. The reas on of this sensitivity is further illustrated. The safety factor and failure probability of the foundations with different dimensions are examined by investigating the failure mechanism of the footings.In this paper, the finite element model of the footing bearing capacity in homogeneous soil is established, and the validation of the model is done by comparing with theoretical solutions. The generated random field is mapped to the finite element model, and the correctness of the stochastic finite element model is verified later.Monte Carlo simulation method is adapted to analyze the influence of local average random field degree on the vertical bearing capacity and failure mechanism. So as to obtain the basic failure probability in the local average random field degree. Results in this paper indicates that footing bearing capacity will be overestimated using larger local average with fixed the spatial correlation length.Based on the research on bearing capacity and failure mechanism of different widths of footing in a typical spatial variability of soil, this paper obtained the influence of soil spatial variability on safety factor and the failure probability of different widths of footing. The results show that the bearing capacity is the smallest when the footing width is in the range of 1-10 times spatial correlation length. And the variation of the bearing capacity increases with the decrease of the footing width. The safety factor of the 50 m width footing is 1.21 when the failure probability is below 10-3, while the safety factor of the 2.5 m width foundation is increasing to 2.44.