Offering a New Computational Relationship to Evaluate the Bearing Capacity of the Strip Footing on the Two Frictional -Cohesive Layered Ground

In this study, in order to provide a new analytical relationship for evaluating the bearing capacity of a two layered cohesive- frictional soil mass, 12 sets loading tests of physical model for three types of upper layers with different thicknesses and compactions. In continuation, a series of parametric studies were performed to evaluate the accuracy of the proposed relationship using PLAXIS 2D finite element software. In order to study the results of numerical modeling and control of the accuracy of the modeling, results of these analyzes were compared with the experimental results of corresponding physical models by considering the effect of different parameters)relative thickness, compaction ratio and different shear strength parameters of  soil layers) on the failure mechanism and the ultimate bearing capacity of the soil. Considering the appropriate fit of the load-displacement curves, the failure pattern and the average difference of the bearing capacity about 3.3% between the physical and numerical models, show that finite element models have good accuracy in predicting the actual behavior of laboratory samples and the results of numerical simulations can be trusted. After the verifying of the numerical analysis results, the values of the bearing capacity obtained from both numerical and analytical methods for 88 different modes of the strip foundation with dimensions B = 1 and 2 meter and soil mass with different layering, depth and shear strength parameters were compared and a difference of about 7 and 12.5% were observed for foundations with dimensions of 1 and 2 meters, respectively. The results showed that there is a relatively good agreement between all three experimental, numerical and analytical methods in the evaluation of the ultimate bearing capacity and the analytical relationship can predict the process of limit pressure changes in terms of the relative thickness of the layers and the evaluation of the ultimate bearing capacity for various states of the strip footing resting on two layeres ground with relatively good accuracy.