| Recently, with the development of economy and construction in our country, more and more important projects are built on soft soil foundation, where soft soil engineering problem may occur because of the special characters of soft soil. The technique of cement-soil composite foundation has been widely used in the consolidation of soft soil foundation as a method of soft soil engineering technique. Since origin and composition of soft soil are various, the consolidation effect is different , even failure condition exited in some projects. In the engineering of Bin Jiang Road of Jiang Men, the cement mixing piles of some sections of the road can not shape up, and field personnel speculate that it might be relate of the contents of organic in soft soil. Therefore, it is necessary to study and evaluate the high organic cement-soil , Jiang Men.So the property of cement-soil of Jiang Men is study in this paper associated with the project of"Study on the influence of organic matter in the progress of marine soft soil foundation consolidation"sponsored by the national scientific fund. The progress of strength formation of cement soil is studied and microstructure fractal features of samples are discussed on the basis of indoors mechanical tests, chemical tests, quantitative analysis of microstructure parameters.Firstly, statistic and analyse the data of test indoors and in-field of soft soil in Jiang Men, and the results show that: (1) Soft soil in this area belongs to the sedimentary type of Quaternary system, the primary type is residual, drift bed, eluvial and alluvial. It distribute widely delta fluvial plains, hills and valleys between hills, and there into, thickness and distributing area of marine and marine soils of sea facies and continental facies sediment is large. The soft soil in this area is make up of the layer of○2 ,○3 ,○4 .and marine soil of the layer of○3 distributes in 2~20m under the earth's surface, its porosity ratio in average is 1.46 and natural water content ,50%,is larger than liquid limit; Natural water content of the layer of○2 ,○4 is 30%, and mostly deficiency. (2) Coefficients of compressibility of marine and marine soil are all larger than 0.5 MPa-1,and they are primary compression layer and belong to high compressibility soil. In the quick shear test, cq andΦq of this layer soil is lowand the more load , the slow it is increasing of speed of shear strength.Secondly, the strength of different ratio cement soil in the area of Jiang Men is studied that: cement soil samples of different cement ratio have different strength increasing characteristic, and it is very clear that form of strength of cement soil is effected by cement ratio. The mechanics of cement soil sample that is has 10% cement is similar to the sample that the cement ratio is 20%,and sometimes , the former is better than the latter. When the cement ratio is 5%, the mechanical property is worst. And perfect cement ratio is 15%.Thirdly, through the quantification analysis on microstructure picture of samples and the tests show that:(1) Silt content larger than 5μm increases obviously after it is consolidated by cement The more increasing of silt content is, the higher strength of sample is. Tegularity of abundance ratio value of structural unit is not obvious, and structural units of samples before and after hardened with cement are greatly oblate, but sample of after hardened is more round than before. Directional property of both before and after hardened with cement is obvious. The reason of inducing this phenomenon is that they are all effected by vertical force.(2) After hardened with cement , quantity of pores less than 2μm increase obviously. There is no regularity at bundance ratio value of pore and the sample after hardened with cement is similar to the before that they are oblate mostly. There is no directional in the sample of before hardened with cement, but there is obvious directing property in the sample after harden especially maintained for 28 days.Finally, through analyzing the character of different soil, before and after consolidating, we can get the mechanics of high organic cement-soil in Jiangmen. (1)Different soil has different strength character after consolidating. After consolidating, with the time goes, the product of the cement hydrating grow, the ionic exchange action intensify, granulation intensify, and the crystal of cement increase. These all cause the pore space reduce, and connect between the small grain intensify. So the strength of the cement soil enhance. (2) It is obvious that granularity component and organic quantity affecting the strength of cement soil. The more clay and organic content, the worse the cement soil strength is. Because the specific area of clay is very high, and the clay have some active material, these are all bad to harden the cement. There ismore organic means that there is more clay, and the fulvic acid can inhibit the cement hydrating and the humic acid can product complex compound with the calcium. These are all unfavorable factor, they are all bad to the strength of cement soil.(3) Because of cement hydrating, the soil change from acidity to alkalinity. After research we know that the strong acidity is bad to the strength. Through the analysis of mineral, we can find that illite, illire and smectite interbedded mineral, chlorite have obvious influence of the crystallization of cement. But the kaolininte is not.
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