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Simulation Analysis of the Low Strain Reflected Wave Method in Pile Integrity Testing and Fuzzy Evaluation of Defects

Author: XiaWei
Tutor: ZhangHong
School: Changsha University of Science and Technology
Course: Geotechnical Engineering
Keywords: finite element simulate wave theory low strain reflected wave method fuzzy comprehensive evaluation
CLC: TU473.16
Type: Master's thesis
Year: 2009
Downloads: 175
Quote: 4
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Abstract

To study on the influence of the parameter change on the reflect wave of time domain -speed curve, finite element analyze program was adopted in this paper. Basing on that, this paper discussed the regularity on stress curve of reflect wave as changing the exciting force pulse width, stake diameter and receive point of the intact stake; also discussed the regularity on stress curve of reflect wave ranging from the flaw location on expand diameter stake and shrink diameter stake, severity degree and flaw thickness variation, thereby, draw some valuable conclusion as following:①No matter what the stake is, the expand diameter stake or shrink diameter stake, alone with the flaw degree accretion, the arriving time of reflect wave would be delay and the amplitude decreased relatively.②Multi-reflect on the same interface have the isochronous characteristic.③As for the expand diameter stake, the positive and negative pulse would detach as the diameter thickness accretion.④No matter what the stake is, the expand diameter stake or shrink diameter stake, the friction of the stake and soil would increase as the depth of the flaw location grow, bring about the reduce amplitude of the reflect wave. Therefore, using low frequency exciting force relatively to make the reflect signal of the flaw characteristic more clearly.As to the high frequency interfere problem, the interfere degree under different receive point was analyzed, through calculate the width of 10 different exciting force, gain the conclusion that interfere degree was low when the sampling 2R/3 away from stake top.Using the finite element method, a large sum of calculation which simulate different flaw was done, and sample data was picked up to statistical analyze the result. At the same time, combining the test method of low strain reflect wave and fuzzy decision-making in the fuzzy mathematics theory, this paper primary discussed the comprehensive evaluation of shrinkage influence on the flaw degree, and tentatively put forward a 5 sampling points testing method. By contrasting the estimate result with simulate result, with reference to relative norm, finally draw the conclusion that both of two could coincide with each other, and that using finite element method to simulate can gain a good result.

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Foundation > Pile foundation and deep foundation > Pile > Pile test
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