Study On The Loading Deformation And Settlement Calculation Method Of Composite Foundation With Mixing Piles

The accuracy of settlement calculation of composite foundation with mixing piles depends on the additional stress distribution in the foundation, especially in the subjacent bed. Based on the previous research results, the deformation mechanism of mixing piles is studied and a proper method of settlement calculation is discussed and proposed.First, the elastic analysis of composite foundation with mixing piles is carried out by application of Boussinesq method and Boussinesq and Mindlin united method. In the united method, the influence of the acting position of skin friction of piles on the additional stress distribution is analyzed. It is pointed out that the simplified mode of skin friction of piles in some present literature papers results in the overvaluation of additional stress of the foundation. Compared the calculating results with the observation ones, it is found that the additional stress calculated is overvalued in Boussinesq method, resulting overvaluation of calculation settlement. Because the interaction between piles and soil is considered in the united method, so its calculation results accord with the true value. Then, elastic-plastic finite element method is applied on homogeneous ground and composite foundation with mixing piles. The regulation of additional stress distribution in the foundation especially on the top surface of subjacent bed is studied. The calculation results indicate there is great stress concentration in the bottom of mixing piles, and the degree of stress concentration decreases with the depth and disappears rapidly. Hence, the calculation of additional stress on the top surface of subjacent bed using the united method should be considered in layerwise summation method, the stress difference between the bottom of piles and the soil around the piles and the area weighted average value is proposed. Further more, some influencing factors on additional stress distribution, such as the length, radius and spacing of piles,...