| Segmentally variable cross-section pile-net composite foundation is a new technique of foundation treatment.On the one hand,it has the features of pile-net composite foundation—shorter construction period,good stability and slight influence on the environment.On the other hand,it has the advantages of segmentally variable cross-section pile—high bearing capacity,little settlement,low fabricating cost.In order to better reveal the working properties of the new technology under the embankment load,this thesis,which relies on the project supported by Natural Science Foundation of Hunan Province,discussed and compared the working properties between the segmentally variable cross-section pile-net composite foundation and the cylindrical pile-net composite foundation under the embankment load through the methods of indoor model test and numerical simulation.The main work and conclusions are as follows:1.By the indoor model test,through comparing load settlement,axial force of pile shaft,skin friction of pile and pile-soil load sharing ratio of composite foundation,the study comprehensively analyzes the differences of working properties between the segmentally variable cross-section pile-net composite foundation and the cylindrical pile-net composite foundation under the embankment load.Results show that: as vertical reinforcement body,the segmentally variable cross-section pile can make most use of the bearing capacity of pile and shallow foundation to reduce the settlement of the composite foundation,so as to improve the composite foundation bearing capacity and the working properties of the pile-net composite foundation under the embankment load.2.The load-settlement relationship,distribution of shaft axial force and pile-soil load sharing ratio of composite foundation under the embankment load are comparative analyzed by using the FLAC3 D numerical simulation software to establish the full-scale numerical simulation model of the segmentally variable cross-section PC pipe pile-net composite foundation and the cylindrical PC pipe pile-net composite foundation.The effects of pile spacing,cushion modulus,cushion thickness on the working properties of the segmentally variable cross-section PC pipe pile-net composite foundation are also discussed.The results show that: pile settlement,axial force of pile shaft and pile-soil load sharing ratio of the segmentally variable cross-section PC pipe pile-net composite foundation under the embankment load are all better than the cylindrical PC pipe pile-net composite foundation under the same condition.Load sharing ratio and settlement of the pile decrease nonlinearly with pile spacing increasing;moderate increasing the modulus of cushion or improving the cushion thickness are beneficial to reduce the settlement of pile,soil between piles and the load sharing ratio of soil in the segmentally variable cross-section PC pipe pile-net composite foundation. |
