The reflected signal caused by bottom sediment beneath a socketed pile may not be observed with the conventional low-strain reflected wave method

and the reflected signal caused by soft interlayer (or cave) would be undetected if its dip angle of the top surface close to 45º or not less than 45o. In order to make up these insufficiencies

the combination of low-strain reflected wave method

frequency-initial velocity method and core drilling method should be used to do the end-bearing piles and reinforcement effect testing so that they can verify mutually and the reliability of the testing can be enhanced. The abnormalities of the reflected curve of pile bottom or of obvious low dynamic stiffness would be considered too thick bottom sediment or abnormal characters of pile bearing stratum; and then it would be validated with core drilling method. Besides

a formula for the average velocity of defects in the lower section of the pile is set up; and the severity of the defect can be estimated according to the velocity. Through deeply investigating the reflected curves and the dynamic stiffness before and after reinforcement and comparing with those of the perfect piles under the same conditions

the reinforcement effect can be inspected.