Application Study On Long-short-piled Raft For Deep Soft Ground Of High-rise Building

As an unusual kind of pile foundation, long-short-piled raft foundation combines long pile with short pile. The bearing capacity of pile foundation is improved and less settlement is expected. It can achieve the reinforcement requirements, save cost and shorten construction period while being applied to pile foundation reinforcement of existing buildings. Since this method has so many obvious advantages, it is recommended in the extension project of reinforcement design of piled raft foundation of an existing building in Tianjin. The engineering characteristics of long-short-piled raft foundation was studied. The main work are as follows:(1) The quality level of pile and foundation of an existing building in Tianjin was evaluated. The design of long-short-piled raft foundation of this project was introduced.(2) Based on the study of several researchers, a kind of simplified theoretical method for settlement calculation of long-short-piled raft foundation was introduced. The correction coefficient for calculation of settlement was studied.(3) On the basis of FEA software ABAQUS, the bearing capacity of single piles of the extension project of an existing building in Tianjin was analyzed. The results show that FEA software ABAQUS can be used as a good tool in the numerical analysis of geotechnical engineering problems.(4) A great amount of elastic-plastic analysis were performed on the behavior of long-short-piled raft foundation, the effects of some factors such as pile spacing, layout of the piles,length of the piles, the thickness of raft and bearing conditions were carefully studied.