Softening Character Of Bearing Capacity Of Pile Foundations Under Cyclic Loading

In addition to the vertical load,the wharf structure also bears load of earthquake,wave,ice,and impact of ships. These loads generally are cyclic,and the soil around pile will experience a fatigue effect, especially for soft clay. Soil will suffer damage of structure, softening of strength as a result of cyclic loads. At the same time, the pore pressure of soft clay will accumulate,while the effective stress will decrease. The combined effect of the two circumstances will reduce strength of soil, thus reduce bearing capacity and pullout capacity of the pile.1. In this paper, dynamic triaxial test was employed to simulate vibration of earthquake, wave and ice load to study the loss of strength during vibration of soil under different depth. According to which the strength compensation can be determined, and provide references for estimation of bearing capacity of pile.2. Employing large-scale finite element soft, Abaqus, to make dynamic analysis of large diameter concrete pile in Tianjin port. Determine the interaction relationship of pile vs. soil under earthquake, wave and ice load by applying cyclic dynamic stress on the model, and finally obtain the compensation curve of undrained strength along the depth of pile according to the dynamic triaxial test.3. On account of three conditions of the pile, lateral load, vertical load and vertical pullout, analyze ultimate bearing capacity of themselves respectively. Select ultimate bearing capacity formulation under static conditions, plot undrained shear strength curve of the foundation soil around the pile according to geology data, and calculate ultimate bearing capacity of the pile under static conditions. Thus provide theoretical basis for reduction of bearing capacity of pile under cyclic load.4. Utilize coefficient-reducing method to analyze pile under cyclic load, and then get the reduction regularity of bearing capacity of the pile according to undrained shear strength.