Study On Ultimate Bearing Capacity And The Failure Mechanism Of Rigid Footings Near Slopes

Foundations(e.g.foundations of retaining walls,power transmission towers and piers)constructed near a slope are common in engineering practice in order to meet the engineering demand.With the rapid development of city,the issues of stratum deformation and reduction of bearing capacity of ground are raised by the excavation of foundation surrounding foundations of existing buildings.It is necessary to study the stability and bearing capacity of foundation near a slope.Previous researches about rigid foundation mainly focused on the bearing capacity of ground of a footing on a purely cohesive and frictional soil rather than c-?,which is more common in engineering practice.More work should be done to investigate the collapse mechanism of a vertically loaded strip footing,because it is in relation to both the bearing capacity and stability.Researches about bearing mechanism influenced by soil parameters and groundwater and seismic loads have not considered the effect of gravity of soil and other associated parameters.Therefore,the main focuses of this paper are to identify the change of ultimate bearing capacity and failure mode considering the influence of the gravity of soil,and to analyze the reason why formula raised by Terzaghi over estimate the bearing capacity.A numerical model is developed to analyze the ultimate bearing capacity of the rigid strip foundation near a c-?soil slope under static loadings.The study demonstrates the bearing capacity and stability of foundation,and points out the errors in the calculation of the bearing capacity on the basis of Terzaghi formula to overcome the problem of slope.The influence of slope height,slope angle,distance from foundation to slope shoulder and soil strength parameters on ultimate bearing capacity are discussed.Based on numerical results,the calculation method of China Code for design of building footing and AASHTO code are evaluated.N_c and N_?,in existing research,were calculated separately and linear superposition under the horizontal seismic action.Didn't take into account the complexity of slope project,thus underestimated the bearing capacity of c-?slope.In this study,results show difference from horizontal foundation,the c,?and?of foundation soil will produce coupling actions for this problem.In addition,a rigorous analysis in the framework of upper-bound limit state plasticity,was adopted to investigate the performance of footings placed on the top of slopes considering the horizontal seismic action by pseudo-static method.A set of design charts containing the horizontal seismic acceleration is presented for preliminary estimates.The ultimate bearing capacity of ground near a slope influenced by groundwater was estimated in three cases(i.e.,the rapid drawdown of reservoir water level,the drop inside a slope after reservoir emptying and the gradual drawdown).This study evaluates the effects of these threecases of water level and several failure modes of a slope on ultimate bearing capacity,as shown in a set of line charts involving the change of ultimate bearing capacity.