Perpustakaan Digital ITB

Abstract : The vertical drain method combined with preloading has been commonly used in many countries for a long time, to accelerate the consolidation process in soil stabilization. Many types of vertical drains made of either natural or synthetic materials, have been selected to support the successful application of the vertical drains. A Trial Embankment for the Surabaya Eastern Ring Road was used to test the performance of several vertical drain materials, i.e. Colbonddrain, Fibredrain and Mebradrain. Prediction of the total settlement (primary settlement) of ground surface at the centreline of the embankment, analyzed by the finite element method of Sigma/W program with an elastic-perfectly plastic soil model and the given embankment loading, gave 101.4 cm. The three types of vertical drains at the trial embankment had a similar performance at 180 days from the beginning of the embankments construction. This was indicated by surface settlement data at the centreline of the embankment: 87.5cm for Colbonddrains, 90.6cm for Fibredrains, and 91.6cm for Mebradrains. If these values are compared with the predicted settlement, a degree of consolidation of 86% to 90% is obtained. The prediction of degree of consolidation around the vertical drains with ideal conditions gave 94% at 180 days, and this result was close to the required 95% consolidation at 180 days. The calculation of the actual compression index (CC act) gave 0.873 (3m depth), 0.558 (10m depth), and 0.612 (17m depth). These values were below the CC in laboratorium for soil samples at similar depths, with a difference of 19% to 28%. The calculation of actual radial consolidation coefficient (cr) gave 8.156x10-4 cm2/sec for Colbond drains, 7.961x10-4 cm2/sec for Fibredrains, and 8.225x10-4 cm2/sec for Mebradrains. When these values were compared with the average design c, obtained from laboratory data, an average ratio of 0.967 was obtained. This is below the predicted cr/c, of 1.20 used for the prediction of settlements. This means that other assumptions, i.e. smear effect, or well resistance, may need to be considered in analysis of consolidation, beside the ideal condition.