粘性土壤剪切强度与容重和含水量之间关系的研究

RESEARCH ON THE RELATION OF SHEAR STRENGTH,DRY DENSITY AND WATER CONTENT FOR CLAYEY SOILS

本文在Mitchell等人关于土壤剪切强度唯一性研究的基础上,利用热力学第二定律作指导,由试验和分析建立了剪切强度与热扩散系数之间关系。据此关系,综合De Vries和佐滕用三相比表达热扩散系数的方程式,得到一个四参数剪切强度-干容重-含水量模型。对于一种粘土在各种容重和含水量下进行了三轴剪切试验,本模型拟合实测数据的精度(用相关系数表示)皆在0.9以上。

Works by many persons indicated that it was extremely difficult to find the shear strangth-dry density-water content relation directly,so a wise approach is to find an equivalent for shear strenth with a prerequisite that it’s easier to determine the correlation among this equivalent,dry density and water content.By means of rate process theory, Mitcbell etc. found that there is an unique linear relationship between shear strength and number of interparticle bonds,and this relationship doesn’t change with soil type,consolidation condition,density and water content.As a result,number of interparticle bonds is an equivalent of shear strength.However,it is a pity that correlation among number of bonds,dry density and water content is still not known,so lo oking for anotber equivalent is necessary.Take a block of soil as an example,the second law of thermodynamics can be written byU_2-U_1=W十Q (1)where U is internal energy of soil mass,W the work done by external environment to soil mass,and the thermal quanutity absorbed by soil mass from external anyironment.The petiod of the interaction between soil and plow is short in general,hence it’s acceptable that the process of soil deformation is considered as an adiabatic process. In an adiabatic process,variation of internal energy in a certain system is fulfilled by chanying W;in a heat transfer process,vatiation of Q is the only way to chang internal energy in a giveln system,so in the system of thermodynamics,it might be assumed that there is certain similarity between an adiabatic process of soil deformation and a heat transfer process,because both process can change the internal energy of system and W has an equal position in Eq. (1) in comparison with Q. As a result,it’s admittable for us to try to substitute soil parameter of thermal property for number of bonds or shear strength.Thermal diffusivity is a parameter which denotes the ability of temperature conductance and has within a certain extent a clear relationship with dry density and water content.The experimantal relation between shear strength and thermal diffusivity for clayey soil is set up.Synthesis of this relation and the representation of thermal diffusivity of soil proposed by de Veries and Sato,yields a shear strength-dry density-water content model with four toefficients. A seties of triaxial tests of one kind of clay have been done,and the correlation coefficients for evaluating the fitness of the model to measured valties are above 0.9.