Study On Triaxial CD Test Of Wide Grading Gravelly Soil

The Earth-rock dam was one of the most important choices on the construction of dam. The gravelly clays, which mixed with clay and gravel (it is called wide grading gravelly soil in this paper), owns the merits of high compactness, high shear strength, and low compressibility, meanwhile it is multi-supplied and cheap and still meets the design requirements of anti-seepage performance, so the wide grading gravelly soil is widely used as the anti-seepage material of the Earth-rock dam, which has become a new trend worldwide. And the study of its engineering properties has become an important content in the research of Earth-Rock dam project.Based on the projects supported by the National Natural Science Foundation (No. 41102167) and Fuzhou university science and technology fund development(No. 2011-XQ-12), the study on the triaxial CD tests on wide grading gravelly soil was carried out, then the influencing factors of consolidation duration and shear rate were analyzed, and the shear rate of triaxial tests was discussed.Firstly, the duration of consolidation of triaxial tests on wide grading gravelly soul was studied, according to the four important factors, gravel content, ambient pressure,compactness,and drainage condtion.The study show that the effect of gravel content on the duration of consolidation is related with its structure, the duration of consolidation would decreased while the gravel content increased,but it would sudden decreased when its gravel content in more than 60%.the ambient pressure affected in the duration of consolidation was that the greater the ambient pressure they were,the more the displacement and the duration of consolidation accordingly. The effect of compactness in this experiment was quite small,the consolidation coefficient was approximately. the effect of drainage conditions on the duration of consolidation was while in the two-way drainage under the same gravel content,the time was greatly reduced.Secondly,based on the Gibson formula,it is analysis the rule of the non-dissipation pore water pressure in different shear rate which designed the experiment according to the characteristics of wide grading gravelly soil, and then changed the gravel content and the degree of compactness to contrast with the research that the relationship has been find between the shear rate and the non-dissipation of pore water pressure,so it draw a conclusion that:the greater the shear rate in the sample,so the peak value of the pore water pressure increased in the end, but the volumn change was smaller,and so as to the affect of shear strength in different shear rate; the gravel content in the sample was decreased, the peak value of the pore water pressure was greater to the contrary,and its would be more as the shear rate rise; as in the same shear rate,when the gravel content decreased,the greater peak value of pore pressure would be,while the gravel content would has greater influence in the peak value of pore pressure as the shear rate rise,but as in a sufficient slow rate,this effect was smaller.Finally,it was summarized the result of triaxial CD experiment for wide grading gravelly soil, and discussed the applicability of the Gibson formula in wide grading gravelly soil,based on it,the Gibson formula had been improved,which that factor A,related to the gravel content,had been added in the formula,so it can be suitable for wide grading gravelly soil.