Laboratory Experimental Study On The Dynamic Consolidation By Drainage Improving The Soft Clay And Analysis On The Soft Clay Microstructure

More and more theoretical study and successful engineering application examples indicatied that the method of dynamic consolidation by drainage (MDCD) for improving soft clay foundation can achieved the anticipative effect in proper treatment. Usually this method has the following advantages:construction period is short, the cost is save, the treatment effect is good. However, because of the soft clay's complexity and specificity, and this method is applied to application very fast, and it is at the experience accumulation stage now, it has been carried out without any guidance of mature theory or design calculational methods. Therefore, carrying on the experimental study on the MDCD, exploring its rational construction technology is of great importance.Meanwhile, the engineering characteristics of soil are influenced greatly by its microstruc- ture, any complex physical and mechanical properties of soil are the comprehensive reflection of its microstructure characteristics and their changes. Revealing the essential of the physical and mechanical behaviour of soil needs to master the change regulation of its microstructure before and after loading.The construction technology of soft clay foundation improvement by MDCD and the soft clay microstructure deformation characteristic are studied by laboratory experimental methods. The main work can be concluded as follows:1. Experimental method is determinated. The device project of laboratory equipment simu- lating the dynamic consolidation is expounded, its feasibility is affirmed. The pore water pressure and deformation characteristics of soft clay under impact loading in laboratory ex- periment are studied systematically, and the ascertain methods of construction technical para- meters such as the best impact energy, the impact times, the drop height and mass, the order of dynamic loading infliction and so on have been put forward.2. The parameters of the soil pores are found by studying on the microstructure images of the soft clay before and after impact, and the comparison of the parameters has been made. Based on the sample-made technology of the liquid nitrogen freeze-dry, samples of soft clay have been prepared. With the help of scan electron microscope (SEM) technology, the microstructure images of the soft clay before and after laboratory improvement with MDCD are taken. The changes of the soft clay microstructure parameters are studied by a program developed by the MATLAB language. The changes of the soil microstructure after the improvement have been studied preliminarily.3. By introducing the fractal geometry theory, the fractal properties of the soil pores are studied by using slit island method. The pores on the horizontal and vertical cross sections of the soil possess the fractal characteristic, their fractal dimensions range from 1 to 2 and both have been decreased after the impact.4. The achievements of this study are summarized, the later tasks are also prospected.