| With the rapid development of China's Infrastructure,the high-rise buildings, heavy plant, bridges, ports, offshore oil platforms,nuclear power plants and other projects use pile foundation extensively.The pile foundation increaseingly developed into high bearing capacity.so,the detection of large diameter piles foundation engineering has become an important part.This article relies on a test pile detection engineering of Shenyang New World Convention & Exhibition Center. The pile diameter is 0.85m, its length is 52.0m, and length-diameter ratio is between 56 and 62, which belongs to the large diameter long pile. As there is no similar projects in this region, lacking of the experience of Construction and Detection, the design need to be verified by experiments, so that the engineering quality can be assured.At present, the most direct and reliable detection method is foundation pile static load test. According to this test, the Q-s curve is Slow variant, and it did not show any great fluctuation with the length Change of the pile, which reveal that increasing length of the pile can not increase bearing capacity Significantly, and it Is not conducive to settlement control. So if the design need to be improved, the pile length and diameter should be considered comprehensively, and choose a proper length-diameter ratio. In order to exert the end-friction effects and lower cost, the pile length can be properly shorten to 44m with the changing of length-diameter ratio. And in connection with the stratum structure of the region, the sand foundation of the region can be approximately regarded as the Same medium foundation. By regression analysis, the formula are obtain as follows, Y=A+BX and A=C+DL;B=C+DL, it can effectively describe the relationship between axial force of pile shaft and depth variation under conditions of the similar soil medium in the region, which has some reference for the similar projects of this region.In the course of pile-forming, defective piles can be showed as broken or segregation. Compared with other Integrity detection, low-strain reflected wave method is the most suitable method for this project. The method has the following characteristics, such as rapid, economic, and can survey a large area. As the complexity of the field test conditions and many influencing factors, the Pretty standard Full test waveform can be hard to obtained. This article has determined the pile Integrity class through the method of contacting Geological conditions to analysis the measured waveform, which is identified as class I pile.As the Field experimental piles are all the piles for work, it can not be impossible to conduct destructive test. The destructive Simulation analysis of the pile is carried out with FLAC 3D(Fast Langrangian Analysis of Continua 3 Dimensions), and the ultimate bearing capacity of the pile was obtained, proposing the post grouting and enlarged base optimal design. At the same time, Numerical Simulation is conducted for the Program. The result shows that the length of Pile can be shortened,so that the steel consumption and project cost can be decreased,and it can provide a certain frame of reference for the similar design and construction of pile foundation engineering in the region. |
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