The Research And Application Of Pile Foundation Detection Method

With China’s sustained and rapid development of national economy, the improvement of the infrastructure construction further, pile foundation is widely used in high-rise buildings, highway bridge, railway bridge, wharf and so on in the foundation engineering. In recent years, the growing demand for high-rise buildings in our country, more and more deep foundation pit engineering, pile foundation engineering quality is not only involved in building the safety stability of the upper structure, and is related to people’s life and property security, so our country to the pile foundation engineering quality requirements more stringent, not only requires high construction quality, and strive for a more scientific and rigorous pile foundation detection technology. Due to the pile foundation engineering belong to take cover engineering, underground engineering quality in addition to the geotechnical engineering condition, foundation and structure design,the pile soil interaction,construction technology and the professional level and the associated factors such as experience, but also has high concealment, are more likely to have the features of quality hidden trouble, it is difficult to find quality problems, after the completion of the construction, if appear the accident treatment more difficult, so the structural integrity of pile testing is very important and necessary.In this paper, we mainly study the application of low strain reflected wave method in pile integrity test. Through the field data acquisition, and then use the low strain instrument inherent software to deal with different low pass filter, wavelet contrast analysis of effects of post processing method to explain and highlight the wavelet analysis in low strain reflected wave method for data processing explained the superiority of, is conducive to more accurate judgment of pile body completeness.Low strain reflected wave method as a fast, simple detection method, widely used in pile foundation detection. It reveal the stress wave in the pile body propagation rules and characteristics to judge pile integrity status and local defect location, data collected on the site before the pile top need for grinding processing, the distance from the pile 2R/3 symmetrical grinding four diameter 3 ~ 5cm plane, and detector are arranged on the plane using butter or toothpaste etc. it and pile top bond. After debugging the parameters of equipment at the top of the pile center of percussion,collecting signal curve in different positions.In the actual acquisition process due to the pile top of the transient impact(such as hammer head materials, drop hammer height different) will produce different frequency stress wave. When the pile defect type or location is not the same, the different frequency signal will be shaped to judge the position of interference, so as to affect the judgement, so in the process of testing data and need to signal tointerference noise reduction processing, the wavelet analysis method is used to extract the useful signal curve, as far as possible, the defect signal becomes clear. Pile dynamic measuring instrument with Fourier transform function, can through speed amplitude frequency curve analysis to judge pile integrity, namely transient frequency domain analysis method.Interference signals are generally concentrated in the high-frequency, and signal spectrum distribution on a finite interval, using the Fourier transform the interference signal is transformed to the frequency domain, then the low strain instrument inherent software using low pass filter, this is a practical application in conventional data processing method, we hope that in the conventional methods based on the wavelet transform method further analysis and in the interpretation of the results by contrast, reflects the introduction of wavelet analysis method of noise reduction of data, the extraction and processing of has more accurate method.Interference signal is relatively speaking, in the judgment of the pile body shallow defects, the high frequency signal is more applicable, but the signal is complex, easy to mistake. This paper introduces the characteristics of shallow defects,and also makes use of the wavelet analysis method of signal processing, found the method can better extraction characteristics of defect signal or eliminate interference signal, to effectively save the useful signal spikes and mutation, then determine the degree of pile defects and its position.Combined with the practical engineering case, using low strain reflection wave method in pile integrity application, makes conventional methods: low strain inherent in software for processing and analysis of the data collected on the spot, and then combine the wavelet analysis method to further data processing and interpretation.The results showed that after the introduction of wavelet analysis we of pile integrity determine more clearly and accurately.