ANTILIQUEFACTION MEASURE FOR SAND SOIL

Abstract

One of the major cause of catastrophic damage to structures during the earthquakes have been liquefaction of loose, saturated cohesionless soil deposits. Structures resting on such deposits may experience large scale tilt and movements due to liquefaction of foundation soil. One of the measures to alleviate the chance o.f liquefaction of sands is to provide drains filled with materials of greater permiability than that of surrounding soil. A number of studies have been conducted to study the performance of gravel drains, but the information available to provide guidance for design of drains is limited. Therefore, there is-a need of collecting laboratory test data under different conditions. The present investigation aims to study the performance of vertical gravel drains and horizontal filter under surcharge load for the control of liquefaction. For present investigation, samples have been prepared using Unr..h river sand. Samples were prepard in a test tank (1.05 m x IA.6Hm x f1f.40 in high) by pouring the sand with the help of a funnel and the relative density so achieved was of the order of 257.. Samples were then subjected to sinusoidal horizontal vibrations after putting the dead weight surcharge of 735.8 kg. The pore pressure was recorded with the help of piezometer fitted at the center and 7.5 cm above the bottom of tank. Based on this study it is concluded that, horizontal filter below surcharge is more effective than vertical drains and combination of the two is most effective. The most effective spacing of drain from pore pressure pick up in laboratory is about 24 cm for 75 mm dia drains.