ANALYTICAL SOLUTION FOR VERTICAL DRAINS CONSIDERING THRESHOLD GRADIENT AND SMEAR EFFECT

For some saturation clay with low-permeability, an initial hydraulic gradient i₀ (i.e., threshold gradient) exists, and seepage occurs only when the hydraulic gradient of a specific point in the soil exceeds i₀. Based on the traditional shaft foundation consolidation theory, a new consolidation computational model considering the effect of the threshold gradient was established, and the relationship between the seepage moving boundary and time in the shaft foundation was obtained under the influences of a threshold gradient and a smear effect. Through comparative calculations, the effects of a threshold gradient, the load and permeability coefficient on shaft foundation seepage moving boundary and consolidation were analyzed. Considering the effect of a threshold gradient, the excess pore-water pressure in a shaft foundation cannot completely dissipate and the residual pore pressure still exists. The final degree of consolidation of the shaft foundation under the definition of pore pressure cannot reach 100%. The degree is related to the load q and initial gradient i₀ but unrelated to s or k_h/k_s.