A Study On Density Measuring Of Soft Subsoil By Instant Hammering Method

The dynamic method for testing the density of soft subsoil by instant hammering is fully a new research subject. In this dissertation, experiments of instant hammering and measurements of dry density and water content have been carried out in laboratory for Hangzhou clayey silt. By analyzing and comparing existed signal processing methods, a new method suitable to the instant hammering is obtained, which has a better frequency resolution. Meanwhile a pre-processing method is also established. Based on the results of spectrum analysis, a signal spectrum characteristic parameter is picked out. Further more, the relationships among dry density, water content, the characteristic parameter are studied systematically and deeply for Hangzhou clayey silt.The spectrum analysis of instant hammering signal is based on the data which have been pre-processed. The pre-processing method established is realized by cutting out a integral instant pulse from the original signal and regarding its initial point as start point of time, then making its average value be zero.A method for wavelet multi-resolution analysis associated with self-regression spectrum analysis is proposed, which can realize the direct decomposition of signal frequency band, eliminate the high frequency noises, and extract the characteristic frequency band of the testing signals as well as estimate the frequency content of the band by using the self-regression spectrum analysis method. By comparing and analyzing the various results of multiple signal processing method for the testing signals, it is found that this method is not only the most suitable one for the testing signal spectrum analysis but also has a good frequency resolution.It has been shown by all the results of the classic spectrum analysis, the modern spectrum analysis and multi-resolution analysis of wavelet for the instant hammering signals: 1. As a characteristic parameter of spectrum, the main peak frequency can be used to analyze the relationship between soil density and the corresponding testing signals; 2. With the same water content, the greater the density of soil is ,the higher the main peak frequency; 3. With the same density, the higher the water content of soil is, the lower the main peak frequency.