Applied Study On The Quantitative Analysis Of Pile Defects With The Shear Wave Velocity Of Soils

It was a problem unsolved how to do the quantitative analysis of defects in piles so far. In order to resolve the problem, following researches had been done:The relationship between the incident and reflected velocity amplitudes ratio at the top of pile and the damping coefficients of soil was obtained based on the analytical solutions of velocity response on the arbitrary point caused by transient exciting force in the friction pile surrounded by homogenous soils. Then the attenuation rule of stress wave in friction pile was obtained. The characteristic of the stress wave's reflection and transmission caused by the impedance changes was researched. At last the relationship between the defective degree of single defection in friction pile and the incident and reflected velocity amplitudes ratio at the top of pile was established.The shear wave velocities of five kinds of soils used in the model tests of integrated piles were tested in order to analyze the changing rule between the damping coefficients and the shear wave velocities considering the damping coefficients of the soils obtained from the model tests. Results showed that the damping coefficients of five kinds of soils increased with the increase of the shear wave velocities and the changing rule was consistent; when the shear wave velocities were less than 250m/s, the damping coefficients of five kinds of soils were very similar as long as their shear wave velocities were the same; when the shear wave velocities were more than 250m/s, the damping coefficients of five kinds of soils were some difference when their shear wave velocities were the same. Finally the relationship between the damping coefficients and the shear wave velocities was established and applied on the quantitative analysis of single defection in friction piles.The attenuation rule of stress wave in the friction pile was showed to be reasonable based on the model tests. At the same time, the results showed that: when the overburden effective pressures on the soils were less than 250kPa, the relationship between the damping coefficients and the shear wave velocity was reasonable basically; the errors between the actual defective degree in the piles (expanding pile and necking pile) 3 meters long and the calculated values obtained from the quantitative analysis of single defect were less than 5%, So the quantitative analysis of single defect in friction piles surrounded by homogenous soils was considered to be reasonable basically.