Pengaruh Nilai Lugeon (Lv) pada Test Grouting Proyek Pembangunan Waduk Gongseng di Kabupaten Bojonegoro

Abstract

ABSTRACT
Cement injection pressured procedure/cementation (grouting) is one process of some fluid material were injected in appropriate water pressure test in cavity, fracture, and cracks of rocks/soils, which its fluid will become physical or chemical.
Aim of this evaluation was to gain comparison mixture design of cement, water, and injection fluid volume (grout) which were needed in grouting working based on lugeon value (Lv) and to get effective interval distance between grouting point according to grouting effectiveness counting which was presented in percentage (%) (Cendergren, 1967).
Based on the highest counting result in each stages on the hole of first grouting stage was PH1 Lv = 48,12 lt/minutes/m’(lugeon), on CD1second stage was Lv = 20,61 lt/minutes/m’, on PH1third stage was Lv = 61,01 lt/minutest/m’, on PH1fouth stage was Lv = 22.86 lt/minutes/m’, on PH1 fifth stage were Lv = 21,46 lt/minutes/m’. According to the result, the mean lugeon value for all stages weere > 15 lt/minutes/m’(lugeon), so it can be concluded that the comparison of mixture design of cement and water for grouting was 1 : 2. From the lugeon results > 30, it was used for comparison the mixture of cement and water 1 : 2, so mixture densities of 1 : 2 were amount of 7,30 t/m3 with the use of the mixture in mixer volume was 200 l so the semen weight was 86,30 kg. Injection fluid volume (grout) needed with composition of cement volume was 27,40 l and water volume was 172,60 liter, while according to test of grouting effectiveness, it was gained Efs dominant value > 80 %, so that for 3m interval distance was effective enough.
Keywords: water pressure test, stage, lugeon value, mixture design, grouting.

ABSTRAK
Injeksi semen bertekanan/sementasi (grouting) adalah suatu proses, di mana suatu cairan diinjeksikan/disuntikan dengan tekanan sesuai uji tekanan air (waterpressure test) ke dalam rongga, rekah dan retakan batuan/tanah, yang mana cairan tersebut dalam waktu tertentu akan menjadi padat secara fisika maupun kimiawi.
Tujuan dari test grouting ini, adalah untuk mendapatkan desain perbandingan berbagai variasi campuran semen dan air serta volume cairan injeksi (grout) yang diperlukan dalam pekerjaan grouting berdasarkan besarnya angka lugeon (Lv) dan mendapatkan interval jarak efektif antar titik grouting berdasarkan perhitungan efektifitas grouting yang dinyatakan dalam % (Cendergren 1967).
Berdasarkan hasil perhitungan terbesar disetiap stage pada lubang grouting stage pertamaPH1 didapat Lv = 48,12 lt/menit/m’(lugeon) , pada CD1 stage kedua didapat Lv = 20,61 lt/menit/m’, pada PH1 stage ketiga didapat Lv = 61,01 lt/menit/m’, pada PH1 stage keempat didapat Lv = 22.86 lt/menit/m’, pada PH1 stage kelima didapat Lv = 21,46 lt/menit/m’. Berdasarkan hasil perhitungan didapat besarnya angka lugeon (Lv) rata-rata untuk semua stage >30 lt/menit/m’(lugeon), maka dapat disimpulkan bahwa desain perbandingan campuran semen dan air untuk grouting adalah 1 : 2. Dari angka lugeon >30 lugeon dipakai perbandingan campuran semen dan air 1 : 2, maka berat jenis campuran 1 : 2 didapat sebesar 7,30 t/m3 dengan memakai campuran dalam volume mixer sebesar 200 liter, maka didapat berat semen sebesar 86,30 kg. Jadi volume cairan injeksi (grout) yang diperlukan dengan komposisi volume semen sebesar 27,40 liter dan volume air sebesar 172,60 liter, sedangkan berdasar perhitungan efektifitas test grouting didapatkan harga Efs dominan > 80 %, sehingga untuk jarak interval 3 m cukup efektif.
Kata kunci: water pressure test, stage, lugeon value, desain campuran, grouting