Study On The Failure Mode And Ultimate Bearing Capacity Determination Method Of Ground Foundation Adjacent To Slope

The foundation adjacent to slope is the common foundation or embankment type widely in all kinds of engineering structures which should be ensured the enough bearing capacity and stability. The engineering design method modified from flat foundation bearing capacity formula is relative hysteretic. Moreover, the calculating formula of the current specification is not clearly. Therefore, it has important theoretical significance and engin eering practical significance to carry out research failure mode and bearing capacity calculation method suited to the engineering characteristics.In order to study the sliding deformation, earth pressure distribution characteristics, failure mode and ult imate bearing capacity, the special geosyncline in filling the soil-rock foundation was adopted.The slope foundation model was tested under vertical static load. Then, the failure mode and ultimate bearing capacity were analyzed in the numerical simulation by using the finite element analysis software ABAQUS. Compared with the test results,the analysis result was a good reference to study the failure mode and the ultimate bearing capacity.The failure mode and ultimate bearing capacity of strip footing adja cent to slope was studied with limit equilibrium analysis method. Combining with the engineering characteristics of strip footing near slope, the failure mechanism was deeply analyzed. Meanwhile, reference for the experiment analysis result and the existing experience,the reasonable sliding failure mode which was considering the bilateral and asymmetry characteristics of strip footing adjacent to slope was constructed; Following the previous study, the ultimate bearing capacity analysis model of strip footing adjacent to slope was derived by the rigid body limit equilibrium analysis method; Then, a new method to determine the ultimate bearing capacity of strip footing adjacent to slope is put forward by use of the sequential quadratic programming optimization algorithm, considering the foundation geometric model uncertainty of strip foundation adjacent to slope caused by the bilateral and asymmetry failure mode.In the existing research methods for determining the ultimate bearing capacity of foundation, the vertical uniform force instead of embedded depth of foundationwere adopted which were not considering the contribution of the soil shear strength in depth enough. In view of such a problem, the Meyerhof Theory was introduced. Based on the experimental study, the new unilateral failure mode considering the soil shear strength was established.The ultimate bearing capacity analysis model of strip footing adjacent to slope was derived by the rigid body limit equilibrium analysis method, to solve the impact of the soil shear strength in depth on the Meyerhof theory basis. The method not only reflects the soil shear strength, the distance effect, and different embedment depth on both sides of the footing, but also the friction effects between the wall of s trip footing and the soil in depth.Furthermore, the failure mode and ultimate bearing capacity of strip footing and rectangular footing adjacent to slope were studied by upper limit analysis method. The unilateral sliding failure mode should be the security model and more suitable for the small distance from the top, the bilateral failure mode could more reflect the double asymmetric characteristics of sliding block size and geometry. The new unilateral and bilateral failure mode considering the asymmetry characteristics were established. The mobile permissible velocity field and the ultimate bearing capacity calculation formula were developed with the upper limit analysis theory and optimization algorithm. There was a sliding between the foundation base a nd soil considering the limited friction. In view of the problem, the bearing capacity calculation formula was included in energy dissipation of the foundation base friction. A three-dimensional and bilateral failure mode of rectangular footing adjacent to slope was established, which fully considered the influence of the shear strength of inside soil of the foundation and the double asymmetrical features. Moreover, a simplified method of the rigid-motion blocks collapse mechanism was proposed, which could effectively reflect the three-dimensional end effect. Then, a new analysis approach for determining ultimate bearing capacity was put forward. Bearing capacity of foundation is conventionally calculated based on the linear Mohr-Coulomb failure criterion. In view of the problem, in this paper, a nonlinear failure criterion and a multi-tangential technique method were employed to evaluate the bearing capacity of strip footing adjacent to slope using the upper bound theorem of limit analysis. Finally, the unilateral rigid blocks sliding mode of strip footing adjacent to slope was built up, according to the characteristics of the asymmetry failure mode, a new method for determining ultimate bearing capacity was established.In addition, the failure mode and ultimate bearing capacity of the two-layer clay foundations adjacent to slope was studied. Combined with the characteristics of the asymmetry failure mode and layered properties, the unilateral sliding failure mode of two-layer foundations under strip footing adjacent to slope was buil t up based on the existing concerned researches. The failure mechanism was made up by many slider s. According to speed compatible relationships and triangle closed condition, the corresponding planar kinematically admissible veloc ity field was constructed. Introduced the upper limit analysis theory, the ultimate bearing capacity calculation model and determination method were derived.In the end, the failure mode and ultimate bearing capacity of strip footing adjacent to slope was studied based on the theory of slip line. First, the Hill failure mechanism and its slip line solution for the ultimate bearing capacity of flat ground foundation and slope foundation were put forward no considering foundation soil gravity. The failure mechanism of strip footing near slope was a continuous variation mode. It should be between flat ground foundation failure mode and slope foundation failure mode. The bilateral asymmetric Hill failure mode of strip footing near slope was put forward on the previous research basis. In the same foundation and boundary conditions, the bearing capacity slip line solution was a continuous function between the two critical foundation states as the distance from the top of slope was variable. Then, the basal pressur e zone was divided into two uniform compressive areas by introducing the wi dth ratio coefficient. The stress influence on the slope slider was simplified by using the equivalent free surface. The limit pressure on the slope slide could be calculated by sli p line solution for slope foundation. The function of the width ratio coefficient was settled, by analyzing the relationship among the width ratio coefficient, the distance from the top of slope and the failure mode. So a new method to determine ultimate b earing capacity of strip footing adjacent to slope was put forward based on the theory of slip line.