Nondestructive Testing Of Existing Structural Piles By Low Strain Torsional Shear Wave Method

Pile foundation is widely used because of its reliable bearing capacity and seismic performance,but it is a kind of underground concealed engineering.It is easy to be affected by the construction or natural factors,such as necking,expanding,segregation,broken pile and so on.The formation of defects in service both the structure of pile will be collision,typhoons,earthquakes and other force majeure effect,serious security risks to the project,so the detection of both the structure of pile reinforcement is an urgent problem to be solved.Low strain reflected wave method is the most economical,convenient and fast detection method,and belongs to the field of nondestructive testing.The method has been developed in the integrity testing of free single pile,and is mainly focused on the traditional longitudinal wave method,but the integrity of the existing pile foundation is still a major problem in the engineering field.The sensitivity of the shear wave to the superstructure is much less than that of the longitudinal wave,and it also has the advantages of accurate defect location and sensitivity to minor defects.Based on the traveling wave theory,this paper studies the method of detecting the integrity of the existing structural piles by using the two methods of model test and numerical simulation:(1)the feasibility of model test to study the torsional shear wave method,and compared with the longitudinal wave detection,summed up the torsional shear wave method is more suitable for the existing structure of pile integrity testing;and the whole pile,necking pile,broken pile dynamic test curve has a deep understanding,understanding to the reflection of the waveform characteristics of different defects.(2)by using the finite element software ANSYS/LS-DYNA numerical simulation,discussed the torsional shear vibration wave method and the best receiver position,and analyzed the soil pile,pile,impulse width,impulse effect on the peak time domain curve,is deduced considering the hysteresis of the first wave velocity correction and the defects of calculation formula,and the use of double speed method of formula.(3)continue to use the finite element analysis of the existing structure of pile necking,expanding and segregation of different types of defects and waveform characteristics,and the comparative analysis of the waveform characteristics of different degree defects,defects of different axial length,different defect depth etc.,at the end of the broken pile are described.