Because it is difficult to monitor the quality of gravel pile (the length, the diameter) in composite foundation, the method of radar is put forward. Numerical simulations of radar monitoring on flexural pile are processed. The results show that the method of radar monitoring can be used to check the quality of gravel piles (length, diameter) accurately. Then this technology is applied in some highway project. By comparing with the results of another company, the characteristics including high precision and speed are found. So the technology can be far and wide used.

In this paper, , the combination of antenna array detection method of ground penetrating radar is put forward to solve the actual engineering problem that is difficult to monitor the integrity of the flexural pile composite foundation. The experiments of defects of six tamping soil cement piles find that the relative error of the pile position of defects is 5.25%. The result indicates that it is enough reliability to determine the pile defects by using the GPR method and can meet the engineering needs. Furthermore, the effect of age of cement, the ration between soil and cement, depth and types of defects on the monitoring quality is obtained.