Study On Rheological Characteristics Of Lacustrine Soil In Dongting Lake Area

Dongting Lake District is located in the south of the middle Yangtze River,with well-developed river and soft soil,which seriously affects the stability of the road and restricts the road construction in the Dongting Lake District.For a long time,influenced by the developing policy in China,scholars have paid more attention to soil type of coastal areas,so the research of the Xiang soil of the inland lake is backward.Although there is common in properties of both,there is also huge difference.Xiang soil of lake is dispersed,denser and in mixed arrangement,with anisotropic feature.Xiang soil of sea is flocculent,with big holes,sensitive to the disturbance and the property is uniform,of which the isotropy is good.Although there is the relatively perfect theory of Xiang soil of sea,the theory can't be used in the Xiang soil of lake.In conclusion,there is important significance in the study of Xiang soil of lake in Dongting Lake District.The paper uses the undisturbed soil as the object of the national highway from Nanxian country to Mao Cao street of part of the road to make the following research.(1)The object of the study is the undisturbed soil,with many geotechnical tests.Through the analysis of index statistics,the study provides the referable physical and mechanical indexes for the project;uses regression equation to analyze the water content,void ratio and the relation between the physical index and the mechanical index.The test results show that the soil sample has a high water content and void ratio,which is typical soft soil.Due to its low shear strength,small compression modulus and poor mechanical properties,which is easy to cause accidents and should be paid attention to in engineering.(2)As the object of the undisturbed soil,with the method of multi-stage loading,the author uses GDS advanced hydraulic pressure to make unidimensional consolidation tests and creep tests;under pre-loading condition,makes the unidimensional consolidation tests and creep tests in order to get curves in all kinds of conditions and analyze its features.The results show that the soil sample has creep characteristics,and preloading has influence on the consolidation creep characteristics of the soil sample.(3)Compared with four ways of primary and secondary concretion demarcation,the author chooses the most applicable strain rate-strain curve demarcation to distinguishprimary and secondary concretion.According to the changing rule of creep curve,the author introduces the three-element K-N model and on the basis of plotting method of Casagrande,and put forwards logarithmic empirical model for creep features,both of which can well describe the creep characteristics of the soil sample.