Study On Behaviour And Application Of Cast In Situ Concrete Large Diameter Tubular Piles

The cast in situ concrete large diameter tubular pile (CTP) now has been widely used in our country’s construction projects, such as sea dike, retaining and protecting for foundation excavation and composite foundation of highway and building. But as all new construction technologies, the behindhand in theoretical research hampered its applications, particularly in the behavior of laterally loaded CTP piles. So based on the previous research work of others, the main works of this dissertation are shown as follows:1) The field test of Guangdong highway CTP pile composite foundation was introduced. According to field test and in-situ observation, the bearing and settlement law of Geosynthetic-reinforced CTP pile-supported embankments was analyzed.2) Based on the earth pressure theory and interface friction theory considering the displacement effects, the supporting force of soil to the CTP pile (H(z,y))was deduced. Then the effects of pile and soil parameters including the pile diameter, the depth and the internal friction angle, the cohesive strength and the bulk density of soil were analyzed.3) Based on the supporting force formula deduced in this dissertation, effects of parameters piles and soil on lateral bearing capacity of rigid piles were studied. It was found that the lateral bearing capacities of rigid piles have important relation with the cohesion and internal friction angle of soil. But the effects of friction coefficient of pile-soil interface on the lateral bearing capacities of rigid piles were negligible.4) The deflection differential equation of elastic beams was introduced, considering the soil supporting force, the horizontal displacement and internal force of CTP pile could be solved by Finite Difference Method and MATLAB. Further discipline on mechanical characteristics of laterally loaded piles probed by changing the pile diameter, pile length and soil parameters.5) The design and construction of sea dikes using CTP piles were discussed. Using the program based on the method of this dissertation, the horizontal displacement and internal force of CTP piles of sea dikes were calculated, and the effects of soil reinforcement were analyzed.6) The using on CTP piles on building foundation pits was discussed, and the analyze method based on the earth pressure theory considering the displacement effects was deduced. After comparing the calculated results with the measured values, the results were close to the measured values. Meanwhile, the influences of many factors, such as the soil reinforcement, the stiffness and position of the brace on the horizontal displacement of pile-brace support system were investigated thoroughly.