Study On The Consolidation Theory For Vertical Drains Considing The Variety Of Permeability Within The Smear Zone

Till now these consolidation theories for vertical drains (including sand wicks and plastic band etc.) have been based on the assumptions that initial excess pore water pressure was uniform distribution and the permeability of soil within the smear zone constant. However, the permeability within the smear zone couldn't be constant in the practice. Due to the effect of disturbance during the installations of vertical drains, the permeability within the smear zone becomes variable. Meanwhile, the distribution of initial excess pore water pressure is usually in-uniform. In order to make the theory be closer to the actual cases, new consolidation theory for vertical drains was studied. The original work was as follows:1. The consolidation problem for vertical drains under the non-uniform distribution of initial excess pore water pressure was studied and a general analytical solution was obtained under equal strain condition. The exact analytical solutions corresponding to trapezoidal distribution, triangular distribution, and inverse triangular distribution of initial pore water pressure were then derived. Based on these solutions, the computer program was developed and parameter study made, and the results show that the distribution form of initial pore water pressure has great influence on the consolidation behavior, and the influence was more significant on excess pore water pressure in the soil than on the consolidation degree. For the condition of single-drainage, the rate of consolidation was fastest when the distribution of initial pore water pressure was in a inverse triangular pattern, while it was the slowest when the distribution was in a triangular one. For the condition of double-drainage, the rate of consolidation was independent of the distribution form of initial pore water pressure.2. Analytical solution was given to the consolidation problem for vertical drains considering the variety of permeability within the smear zone with the five change modes for the disturbance proposed. It shows that the variety of permeability within the smear zone has significant influence on the consolidation behavior. In general, the rate of consolidation was fastest when the change mode was in the second. case while it was the slowest when the change mode was in the third.3. Study was made on the consolidation for vertical drains considering not only the non-uniform distribution of initial excess pore water pressure but also the variety of permeability within the smear zone. Meanwhile the corresponding general solutions and the exact solutions in the particular cases were obtained. It shows that the rate of consolidation was fastest when the distribution of initial pore water pressure was in a inverse triangular pattern and the change mode of soil permeability in smear zone was in the Second case, while it was the slowest when the distribution was in a triangular one and the change mode was in the third. It also shows that the consolidation theory for vertical drains under equal strain condition so far available was just a special case of the analytical theories developed herein.