Study of Strength Parameter for Different Drain Material using PVD for Consolidation of Soft Clay by Radial Flow

Abstract

The rapid development and associated urbanization have compelled Engineers to construct earth structures, including major highways, over soft clay deposits of low bearing capacity coupled with excessive settlement characteristics. Consolidation due to radial drainage using PVD is one of the ground improvement techniques in which the consolidation is accelerated by reducing drainage path. Soil improvement is required to provide adequate bearing capacity and improve shear strength of the soft cohesive soils to satisfy the need for various type of construction on sites underlain by such soft soils. Amongst various ground improvement techniques the technique of preloading or pre-compression used in combination with vertical drains is one of the oldest and most widely used techniques to preconsolidate and strengthen weak compressible soils. Present research work focuses experimental model of various drain materials like Saw dust wrapped with Filter paper (SD), Saw dust wrapped with Geotextile (SDW), Sand drain and Jute wrapped with Polyamide Polyster Geosynthetics (JPPG) to expedite the in situ settlement due to excess pore water pressure dissipation under preloading by radial drainage taking advantage of having more horizontal permeability than vertical. The hydraulically pressurized Rowe-type oedometer was developed in the Applied Mechanics Department of M.S. University of Baroda, India. The present research work focuses on finding the most optimum drain in terms of materials (both natural and synthetic type), size (diameter of drain) and geometry to accelerate the consolidation of soft clays with a complete set-up of hydraulically pressurized modified oedometer with conventional bishop pore pressure measuring system and measuring settlement using a dial gauge. The effect of PVD of ‘n’ value (ratio of zone of influence to the diameter of drain) of 10, 12.09, and 14.76 on the consolidation characteristics of Kaolinitic clay was investigated to study the dissipation characteristics using isochrones & settlement characteristics. Time-pore pressure dissipation and timesettlement observations were recorded for different applied stresses under long duration testing. Average Degree of consolidation was computed using iso-chrones. The shear strength of the Kaolinitic clay was found out before and after the consolidation test by Vane shear test. The shear strength of different drain material is compared and also consolidation and compressibility of circular and cross shape drain is compared for good shear strength. Present work shows the Comparison of Experimental Results of shear strength for all the drain materials Keywords—Vane shear test, shear strength, cross and circulr shape , Effective shear strengt, n value