| Dynamic Compaction (Dynamic Consolidation), shortening DC, a kind of the technique used to treat foundation treatment in the field of civil engineering, refers to lifting the tamping hammer with 100~400kN weight to some height (about 6~40m) then dropping freely and impacting the foundation.It often happens that in such projects as civil engineering, traffic services, water conservancy and etc, a lot of natural foundation sites can not meet the requirement of the buildings in the respect of strength, deformation and stability and so on. Therefore, the artificial treatment and reinforcement of the natural foundation are needed to deal with it. Of many approaches to the foundation treatment, DC has been a widely adopted technique just because of its wide adaptation to the soils, sound effects, economical building material even no material, lower cost, and shorter construction period etc. It has great advantages over other approaches if DC is applied in the large scale projects of foundation treatment, such as: airport, wharf, large industrial factory district and so on. That's why DC can be used extensively in the field of civil engineering throughout the world.The current situation in the field of civil engineering is that the theory of DC falls behind its practical applications. To some extent, there have been some problems in the reinforcement mechanism and design theory due to the shortage of the design standard and theoretical basis of DC, and the design of its construction parameters has been experiential and confused. In the case, it has to be determined by means of small scale tests, as a result, the architects act blindly and do as they please, whichresulted in a waste of time and money. All these factors interfered with the rapid development of DC technique and its practical applications.To sum up, in order to supply theoretical basis for the design and construction of DC, it is necessary to make a systematic research in the vibration characteristics of soil, the problems of site of dynamic stress in soil, effective reinforcement wave, the model of dynamic consolidation of soil, reinforcement mechanism and effective reinforced depth of DCThe following are the researches in the featured of dynamic compaction of soil and its engineering applications.1. The vibration characteristics of soil of DCIn the prof. Qian Jiahuan's theory, the elastic model of the stress-strain of foundation soil has been used as the theoretical basis of the analysis of the vibration characteristics of soil of DC. In fact, in the projects of practical engineering are mostly unelastic body. Therefore, in my dissertation, one new calculation model, the quasi-elastoplastic model, is adopted to analyze the vibration characteristics of soil of DC, and the analytical approach is used to calculate two practical engineering projects and compare with prof. Qian's elastic and ideal elastoplastic model14?analytical results. The comparisons show that my new theory has great advantage in the analysis of the vibration characteristics of soil of DC. Specifically speaking, the former (the result of the quasi-elastoplastic model) approximates the practical figures, and the latter (the that of ideal elastoplastic model) comes second, while the that of prof. Qian's elastic model is far from them. So the conventional theory of the vibration characteristics of soil of DC can be improved.2. The reinforcement effects of Rayleigh wave (R-wave) in DC There are two different opinions about the effects of Rayleigh wave inDC. Some hold the view that R-wave has some positive effects, it can make foundation volume compacted or reinforced. The other think that R-wave has negative effects, that is to say, it can make foundation volume swelled or loose. In my dissertation, the research of reinforcement action of R-wave for foundation is be made in DC., where the transmitting characteristics, the influenced depth, the law of the deformation and volume variation of R-wave are discussed by means of the vibration characteristics of soil. It turns out...
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