Study On Ultimate Bearing Capacity Of Large Diameter Bucket Foundation In Soft Clay

Large diameter bucket foundation is a new kind of foundation to adapt to China’scoastal geological conditions and environment loads. Upper structures are typicallysubjected to significant horizontal. As a result, combined vertical, horizontal, andmoment loading is a common scenario for their footings. The classical bearingcapacity design approach is difficult to determine the bearing capacity of largediameter bucket foundation. A more accurate approach is to express a footing’sbearing capacity under general loading explicitly in terms of a surface written directlyin combined loading space. Load combinations inside the surface are considered safe,whereas those outside the surface cause footing failure. According to the ultimatebearing capacity of foundation under combined loading mode, the failure pattern andthe ultimate bearing capacity of clay foundation are analyzed and investigated in thispaper. The main results of this study are as follows:1. Based on the limit analysis principle, and on the assumption of Mohr failuretheory and soil rigid-plasticity model, the kinematic allowing variable velocity fieldare given, and then the upper bound solution of ultimate bearing capacity of largediameter bucket foundations are given.2. The result of finite element method indicates that the value of soil elasticmodulus has an effect on the value of accuracy of ultimate bearing capacity andconvergence rate. The skirt length of bucket foundation improves the ultimate bearingcapacity of clay ground obviously.3. The failure envelope under combined loads is investigated by adopting thefinite element method. There is much difference between the failure envelope ofundrained saturated foundation and the clay foundation. The failure envelopes ofundrained saturated foundation contract with the increasing of vertical load. Thefailure envelopes of clay foundation expand and then contract.4. The failure mechanism of foundation are analyzed in this paper usingnumerical calculation method. The results are as follows:(1) the failure patterns ofsurface sliping failure, superficial sliding failure and deep sliding failure arecontrolled by vertical loading.(2) the horizontal loading makes the failure pattern offoundation asymmetry.(3) the moment loading changes the effective width of footing.