Study On Signal Analysis Method Of Instant Vibration Testing For Soil Compactness

Based on a great amount of laboratory test, the instant vibration signal from soil compactness (include dry density and water content) testing is analyzed systemically and the corresponding quantitative analysis method is put forward for the determination of soil compactness. The main work is as follows.1. By using the soil samples prepared with different dry density and water content, a great amount of instant vibration test is performed and the signals of acceleration and force are acquired.2. The applicability of several commonly used de-noising methods is examined in signal analysis of instant vibration testing for soil compactness. The analysis result indicates that the method based on wavelet thresholds is the best. The method for determination the threshold of wavelet de-noising is also proposed to satisfy soil compactness test signal.3. The signal of instant vibration testing for soil compactness is analyzed both in time domain and frequency domain. Some feature parameters reflecting the characteristics of the signal are extracted. The relationship between soil compactness and feature parameters is then investigated and the corresponding experiential formulas are established.4. The experiential formulas are verified by experimental results and then-correctness and reliability is discussed. Furthermore, the capability in determining soil compactness of these formulas is compared and analyzed.5. Based on the fundamental of ANN, the model of BP neural networks is built for soil compactness quantitative analysis, and the corresponding computer program is developed. The correctness and reliability of the model and the program are then validated and discussed.6. To overcome the disadvantages of standard BP networks, two unproved algorithm are put forward. One is information entropy based, and the other is genetic algorithm based. By comparing with standard BP model, it shows that both the two improved methods can improve the precision of ANN efficiently.7. Comparisons are made among the all quantitative analysis methods for the determination of soil compactness proposed herein, and the result shows that the models based on information optimization and on genetic algorithm (GA) are the best.The dissertation established a set of analysis method for the determination of soil compactness by instant vibration testing, and the feasibility of the method was verified by laboratory test. This provides a new non- destructive, reliable and fast testing method for determining soil compactness in engineering practice.