| The marine soft soil is distributed widely in coast areas in China. This kind of soft soil has specially characteristics such as high water content, large void ratio, low strength and bearing capacity, which is decided by its specially deposit environment. With the rapid development of littoral economic construction, more and more people pay more attention to the relevant engineering problems. In view of that mentioned above, combining with the national natural science foundation "The study on structural property and structural mechanical model of marine soft soil in China"(No.40172092), and using the method which combined macroscopic mechanical tests with microscopic tests, we investigated structural property and mechanical model of different marine soft soils in the present thesis such as Tianji, Shanghai, Hangzhou and Shenzhen. The purpose of this investigation lies in exploring the relationship of structural strength and pre-consolidation and the cause of structural strength is analyzed primarily. Firstly, the experimental study on the structural property of marine soft soil in different areas has been performed, the results show that: â‘ the marine soft soil has strong structural property, which displays high sensitivity; the curves of compressibility and consolidation are distinctively different between undistrubed sample and remolded sample in simple compression test. â‘¡marine soft soil has structural strength obviously. According to conventional method of pre-consolidation pressure solve, the solved pressure is not true pre-consolidation pressure of structure soil, and it is structural yield pressure, which is the sum of pre-consolidation pressure and structural strength.Secondly, investigation on the stress history problem of structural soft soil has been conducted. The thesis has studied on qualitative description and quantitative calculation of pre-consolidation pressure of marine soft soil in different areas. the results are as follows: â‘ If using conventional method, the solved pre-consolidation pressure is more than weight of upper soils, then the soil is over-consolidation soil. However, according to site investigation, there is no more natural or artificial loading which is more than upper pressure of the soil. So the pressure should be called structural yield pressure, which differs from pre-consolidation pressure. â‘¡In aspect of pre-consolidation pressure solve and structural strength solve of structural soil, the thesis use characteristic that unloading-reloading curve slope of remolded soil is same generally in definite range and establish a mathematical model, which can work out the pre-consolidation pressure of structural soil. It got a good result through verification. â‘¢ Based on the analysis and calculation, the concept of pre-consolidation pressure and structural strength was clarified. In order to reflect the structural strength of marine soft clay quantitatively, the structural stability coefficient is led into for the first time, which can better reflect the steady degree of the characteristics of marine soft clay, and it can provide for engineering properties.â‘£ On the ground of simple compression test, a damage equation which reflect structuralstrength change with pressure is carried out. And it discriminated from the strain types of common soft soil and structural soft soil. Thirdly, through SEM technique and relative computer program, micro texture is studied. From the SEM pictures we know that the micro-texture of soft soil is mostly regiment grain texture, regiment-honey texture, and honey-comb texture. On the whole, the structure of marine soft soil is commonly consisted of bigger power particles which made up the skeleton of the soft soil and other smaller clay particles which lies in or around of bigger power particles. In undisturbed sample, the effect of components on marine soft clay mainly manifested on the effect of the microstructure and characteristics. While in remolded sample, the marine soft soil's engineering properties were mai...
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