Road embankment using vacuum consolidation method

Abstract

This paper presents the soft ground improvement using Prefabricated Vertical Drains (PVD) in combination with vacuum pump and surcharge preloading on a road project in Ho Chi Minh City (HCMC). Several techniques are described including: construction of vacuum consolidation method (VCM), post construction primary settlement and stability criteria according to Vietnamese standards, observational methods and back analyses with 1D settlement analysis. The vacuum pressure in the soil and in the PVD, as monitored by electric piezometers, showed that the average vacuum pressure reached 60-80 kPa. In some sections the vacuum pressure at the bottom of the PVD gradually lost pressure during the surcharge loading stage possibly due to the leaking effect of the bottom sandy layer. The lateral displacements recorded by the inclinometers showed that displacement occur inward towards the center of the embankments. Therefore, the traditional control stability method was not applicable. The coefficient of horizontal consolidation (ch) is back-calculated to 1.683 m²/year for kh/ks = 2. This value of ch=1.683m²/year is lowest among the back analysis values that as calculated by Long et al (2013) (North South Expressway Project ch = 2.48 m²/year and Cai Mep International Terminal ch = 3.58 m²/year).