Analysis On The Consolidation For Vertical Drains Considering Hansbo’s Flow

The existing consolidation theories with vertical drains have a large deviation interms of some saturated cohesive soils. One important reason is the pore water flowin these soils does not conform Darcy’s law, which is assumed in consolidationtheories by vertical drains. Therefore, the Hansbo’s equation which is moreappropriate to describe the water seepage in saturated cohesive soils is applied toconsolidation theories for vertical drains, then the new consolidation equation isestablished and the numerical analysis is performed using the finite difference method.Using the computer language of Fortran90, the related calculation program which isverified the validity is complied. According to the obtained numerical solution, theeffects of the parameters of Hansbo’s flow, the vertical flow of pore water in the soil,well resistance and smear zone on the consolidation process of ground with verticaldrains are investigated. Some conclusions can be arrived as flow:（1）Analyzing consolidation process with vertical ideal sand drains in saturatedcohesive soils which including only radial flow, the behavior of non-Darcian flowcontrols the dissipation of pore water pressure in clay ground，and reduces theconsolidation rate of soil. The pore water pressure dissipation rate, consolidation rateand ground settlement rate will decrease with the increasing of the Hansbo’s flowparameters m and i1or the radius ratio, or the decreasing of the surface load p. But forradius ratio, it has some influence on the consolidation rate when change withinsmaller value, while little influence when change within bigger value.（2）If the vertical flow of pore water in the soil is considered, the zone whereexisting larger vertical component of seepage in the ground will reduce with theincreasing of the parameters m and i1, namely the more the flow in the soil deviatefrom Darcy’s law, the smaller impact of vertical flow on the seepage andconsolidation of ground. In addition, the thicker the ground，the less its consolidationrate and the more close to radial consolidation.（3）In the analysis of consolidation process with vertical non-ideal sand drains,there exist larger vertical component of hydraulic gradient in the whole soil depth when considering the well resistance, so the effect of vertical seepage should not beignored. To the vertical drains only considering the effect of smear, the zone ofexisting larger vertical component of seepage is small, so it can only consider theinfluence of radial seepage under certain conditions. Well resistance have moreinfluence on the pore water pressure around the vertical well in the early stage ofconsolidation, and radial hydraulic gradient will break at the border of smear zoneand undisturbed zone if considering the effect of smear. Considering well resistancewill have more influence on consolidation rate in the early stage, while smear in themedium stage.