MAPPING AND ANALYSIS OF ENGINEERING GEOLOGICAL CONDITION FOR GROUTING PROCESS AT THE FOUNDATION OF GONDANG DAM BODY IN KERJO DISTRICT, KARANGANYAR REGENCY, CENTRAL JAVA

• Main Author: Purnama Gumilar, Hanif
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/32799
• Institution: Institut Teknologi Bandung

Pembangunan Bendungan Gondang di Kabupaten Karanganyar memiliki fungsi sebagai sumber air bagi sawah di daerah sekitarnya, sumber air baku, perlindungan sumber daya air, dan objek wisata baru. Daerah penelitian terletak pada koordinat 7?56’40” LS - 7?57’21” LS dan 111?07’24” BT - 111?08’33” BT yang secara administratif berada di Kecamatan Kerjo, Kabupaten Karanganyar, Provinsi Jawa Tengah dengan luas 0,81 km2. Penelitian ini bertujuan untuk memetakan kondisi geologi di area pembangunan Bendungan Gondang melalui pemetaan geologi teknik dengan skala 1:5000 dan menganalisis kondisi geologi teknik dalam kaitannya dengan proses injeksi pada pondasi tubuh Bendungan Gondang. Metode yang digunakan mencakup studi literatur, pemetaan lapangan, pengujian batuan dan tanah di laboratorium, serta analisis data uji tekanan air untuk mengetahui nilai lugeon. Data yang digunakan berasal dari 9 titik pemboran dengan spesifikasi data uji tekanan air, data inti bor, dan data Rock Quality Designation (RQD). Daerah penelitian memiliki ketinggian antara 450 m - 540 m di atas permukaan laut dengan kemiringan lereng 0% - 70%. Proses geomorfik yang teramati berupa erosi, longsor, dan sedimentasi. Geologi teknik daerah penelitian terdiri atas empat satuan dari tua ke muda, yaitu Satuan Breksi Tuf, Satuan Tanah Pasir Berfragmen, Satuan Lahar, dan Satuan Tanah Timbunan. Struktur geologi yang teramati berupa kekar dengan orientasi baratlaut - tenggara. Daerah penelitian berada pada zona kerentanan gerakan tanah menengah dan kawasan rawan gempa bumi rendah. Penelitian pada pondasi tubuh bendungan menunjukkan pola turbulent merupakan pola lugeon yang umum terbentuk. Hasil analisis uji tekanan air menunjukkan bahwa permeabilitas pada pondasi tubuh Bendungan Gondang memiliki nilai lugeon antara 1,28 Lu - 20,52 Lu dengan dominasi 5 Lu - 15 Lu. Perbedaan nilai lugeon dipengaruhi oleh sifat heterogen pada batuan. Berdasarkan analisis nilai lugeon yang menjelaskan kondisi permeabilitas, sepanjang pondasi tubuh bendungan perlu dilakukan proses injeksi kecuali pada beberapa interval kedalaman di PH 03, PH 18, PH 23, PH 29, PH 32, dan PH 33. Kata kunci: Pondasi tubuh Bendungan Gondang, geologi teknik, pola lugeon, nilai lugeon, proses injeksi. v ABSTRACT MAPPING AND ANALYSIS OF ENGINEERING GEOLOGICAL CONDITION FOR GROUTING PROCESS AT THE FOUNDATION OF GONDANG DAM BODY IN KERJO DISTRICT, KARANGANYAR REGENCY, CENTRAL JAVA by: Hanif Purnama Gumilar NIM: 12014054 (Department of Geological Engineering) Construction of Gondang Dam in Karanganyar Regency has a function as a source of water for fields in the surrounding area, raw water resources, water resources protection, and new tourist attraction. The research area is located at coordinates 7?56’40” S - 7?57’21” S and 111?07’24” E - 111?08’33” E that administratively located in Kerjo District, Karanganyar Regency, Central Java with 0.81 km2 wide area. The purposes of this research are mapping about engineering geological condition in Gondang Dam area by 1:5000 scale and analyzing engineering geological condition that related with grouting process at the foundation of Gondang Dam body. The methods used in this research are literature study, field mapping, testing rocks and soil in the laboratory, and analyze water pressure test data to determine lugeon values. The data used in this research comes from 9 drilling points with water pressure test data, drill core data, and Rock Quality Designation (RQD) data. The research area’s elevation is 450 m - 540 m above sea level with slope ranging from 0% - 70%. The geomorphic process that observed in this area are erosion, landslide, and sedimentation. The engineering geological condition of the area can be divided into Tuff Breccia Unit, Sand with Gravel Soil Unit, Lahar Unit, and Embankments Soil Unit. Geological structures that observed in the area are joints with northwest - southeast orientation. The research area is located at medium mass movement susceptibility zone and low earthquake prone zone. The research on the foundation of dam body suggests that turbulent pattern is a common pattern formed. The results of analyzing water pressure test data show that permeability in the foundation of Gondang Dam body has value range 1.28 Lu – 20.52 Lu and dominated by value range 5 Lu - 15 Lu. The difference in lugeon values is influenced by heterogeneous properties in rocks. Based on lugeon values analyze that illustrate permeability condition, as long as the foundation of dam body is required grouting process except at some depth interval at PH 03, PH 18, PH 23, PH 29, PH 32, and PH 33.