Evaluation of the settlement and pore water pressure attributes of soft clay soil under scoria vertical drains using FEM analysis.

Abstract

Construction of road embankments over soft soil such as expansive clay is so tiresome that the consolidation process may continue for a long time. This typical feature of the clay soil is associ ated with its poor potential to dissipate excess pore pressure when subjected to construction load.. The current study hence aimed at investigating the potential performance of vertically installed scoria drains in perpetuating consolidation process of the clay inhabited ground so that the com pressible ground. A finite element method was used to model the soft clay reinforced with a group of scoria drains. Three dimensional version of Plaxis software utilized to simulate both the pore water and deformation attributes of the problematic clay soil under embankment load. Likewise, both hardening soil and soft soil constitutive models were adopted to model the material proper ties. To systematically explore the critical effects of drain installation patterns, both square and triangular patterns were employed so that comparative analysis on effectiveness of the two meth ods in speeding up rate of consolidation could possibly be conducted. Besides, parametric study so as to assess influence of diameter, length and spacing of the drain was conducted. Finding of the study revealed that using scoria drain significantly improved consolidation rate of the clay soil. For any arbitrary time duration, considerably larger magnitude of vertical deformation was observed when using triangular installation pattern than that of square pattern. Besides, it was indicated that when using 8m, 12m and 15m long drains, the consolidation time was lessened by 35-79%, 44-86% and 54-89 % respectively. The rate of water dissipation increased with area replacement ratio which is directly related to drain diameter and spacing. The study apparently demonstrated that variation in magnitude of the dimension parameters significantly resulted in abrupt change in defamation performance of the clay soil