CASE STUDY OF REINFORCED UNSTABLE SLOPE IN SOFT CLAY USING MICROPILE

摘要

ABSTRACT: This paper presents a case study of unstable slope at a retention dam on the thick clay deposit. Dam was situated on a hill with purpose of capturing stormwater from houses area before releasing it to lower ground area. The problems faced due to the embankment has been constructed on thick soft clay deposit with higher groundwater table changing followed by crack and displacement at slope crest and needed to overcome immediately. Therefore, a series site investigations were conducted to be consists of soil profiles, slope geometric, and groundwater level. Soft clay was deposited below the embankment at the dam bench ranging from 7 - 13 meters thick at the northern side, so that the slope reinforcement was recommended by end bearing driven micropiles type with inclined configuration and head of micropiles to be fixed with slab concrete. At eastern side of the dam, infiltration of water from the dam to the embankment was prevented by using geomembrane / geosynthetic clay liners then woven geobag / geocontainer filling with gravels-sands and to be placed in front the ground slope. Due to bedrock is located at a deeper level of 25 m, water table below embankment is lowered in order to improve stability by floating sheet pile of span deck type with 10 meters length. Those cases are being to be constructed under these slope geometrics grand design. Furthermore, finite element analysis were performed to examine the effect of those method for improving slope stability of embankments. The results reveal that the ground reinforcement by micropile are able to increase the safety factor (SF) of the slope from 1.13 to 2.03 based on a traffic load of 20 kN/m2.