KAJIAN PENYEBARAN GROUTING DENGAN METODE GEOLISTRIK DI WATERPARK BUKIT WAHID REGENCY, KOTA SEMARANG, PROVINSI JAWA TENGAH

Abstract

Development in grouting technique and its material causes an increasingly demand of its using in geotechnical constructions. To evaluate the grouting effect, a laboratory or field test towards the physical and mechanical properties of grouted soil and rock is needed. One of methods for evaluate grouting distribution is geoelectric or resistivity sounding method. This study is purposed to identify the subsurface resistivity change of study area before and after grouting using resistivity data from resistivity sounding method. Evaluation towards grouting effect can be determined by comparing the resistivity value change before and after grouting. Grouting effect and its distribution in soil and rock is analysed using isoresistivity map before and after grouting. Methods used in this study are survey and descriptive method supported by literature references for determine geological and geotechnical characteristics of study area. Geoelectric measurement uses Schlumberger’s configuration array. Resistivity data before and after grouting is used to interpret subsurface section along the study area. Based on this data, the resistivity value change before and after grouting can be analysed. Isoresistivity map is needed to determine the grouting distribution at various definite depths. Type of soil is mould soil which is loose, not compacted, and has uneven density along this area. Otherwise, tuffaceous sand and tuff characterized with cracks and joints. Grouting is needed to fix these weaknesses. Data analysis shows there is a relatively decrease in resistivity value after grouting, which is mould soil has average value 27.43 ohm meter before grouting, decrease to 23.66 ohm meter after grouting; tuffaceous sandstone decrease from average value 22.15 ohm meter to 17.13 ohm meter; tuff decrease from average value 11.70 to 8.36 ohm meter. Depth of grouting distribution can reach 7 meter depth, which is minimum 1meter vertically from injection depth. Lateral distribution of grouting material can covers all of this grouted area with 3 meters spacing. Medium of grouting distribution is pore spaces in mould soil, otherwise cracks and pore spaces in tuffaceous sandstone and tuff.