Research On The Detecting Technology Of Reflection Wave For Cement-Soil Mixing Pile

For the advantages of low cost, convenient construction, environmental pollution, Cement-Soil Mixing Pile has been widely used in reinforcing weak foundation such as silt and soft clay, clayey silt. However, it has higher construction technology requirements, the water cement ratio and uniform mixing is difficult to control in the actual process and the quality problems are Likely to occur. Therefore, the detection of the pile quality is especially important. Common quality inspection methods include open-cut inspection, core-pulling, portable penetration test, standard penetration. penetration test etc., which is specified by standard. But these ways has many problems, such as high cost, low efficiency, slow speed etc. In this reason, this paper makes some research of the reflected wave method on cement-soil mixing pile detection.First of all, this paper carried out tests of model piles, in order to prove the reflected wave method is effective for the Cement-Soil Mixing Pile, it made different model piles according to the actual projects' cement content. The main research is on ways of excitation, different defects' reflection waveform and the capture effect of different channels. Then with the help of numerical model this do some research on phenomenon of the model pile test can't simulate just like the reflection characteristics of different defects and the Surrounding soil's Influence to the detection. Finally, it applied this reflected wave method to actual project, the comparison result of the core drilling and the detection proved this reflected wave method is effective for Cement-Soil Mixing Pile.The main results and conclusions are as follows:(1) In this paper, it applied multi-channel reflection detection technique to detect the Cement-Soil Mixing Pile's quality and the channels' main frequency are 38,60,100,1100Hz. By analysis the detection result of the model pile and actual project, it found the low frequency is more effective, it's just meeting the Cement-Soil Mixing Pile's characteristics of low intensity and uniformity.(2) In this paper, it used different ways of excitation to detect the Cement-Soil Mixing Pile, it found the rubber hammer' effect is the best. It also found that put the detector at the location of 0.7R from the pile heart can get the best test results and can effectively avoid disturbance. (3) The nature of the piles'surrounding soil has some Influence to the stress wave velocity of the Cement-Soil Mixing Pile, the stress wave velocity of layered soil is lower than a single layer soil. When determined the defects'location and the length of pile,it must do experimental study on the actual piles'stress wave velocity.(4) In the actual detection, Wavelet Analysis is a good tool to make sure the defects'location, when can't get the information from the original waveform. Wavelet Analysis can improve the detection accuracy.