Enhancement of PVD Performance by Thermal and Electro-Osmotic Techniques

Abstract

This paper examines the innovative techniques for enhancing the performance of the prefabricated vertical drain (PVD) consisting of thermal and electro-osmotic consolidation techniques. The electro-osmotic consolidation of soft Bangkok clay was first studied. Laboratory testing program were done on undisturbed and reconstituted sample in large consolidometer under voltage gradient of 60 and 120 V/m with 24 hours polarity reversal. The time to achieve 90% degree of consolidation induced by electro-osmosis ranged from 1.4 to 2.1 and 2.1 to 2.2 times faster than the normal consolidation with PVD only, for undisturbed and reconstituted samples, respectively. Faster rate of consolidation and higher magnitudes of settlement were achieved at higher voltage gradient. Subsequently, the performances of thermo-PVD which involves increasing simultaneously both the vertical effective stress and the surrounding clay temperature up to 90°C were investigated using the large consolidometer. The test results demonstrated that higher consolidation rates were observed for the clay specimen at elevated temperatures for both undisturbed and reconstituted specimens. This behavior can be attributed to the increase in the clay permeability with temperature. Therefore, raising the clay temperature can enhance the performance of PVD by reducing the drainage retardation at the smear zone around the PVD.