PENENTUAN HYDRAULIC CONDUCTIVITY TANAH PASIR BERLANAU KONDISI JENUH DAN JENUH SEBAGIAN BERDASARKAN PENGEMBANGAN ALAT

HERDY SETIAWAN, Dr. Ir. Ahmad Rifa’i, M.T.

2014 | Skripsi | TEKNIK SIPIL

Permasalahan menggenangnya air setelah hujan di Halaman 1 Candi Prambanan terjadi akibat perubahan karakterisitik tanah yang disebabkan oleh kegiatan pemugaran pasca gempa tahun 2006. Dengan hal itu dibutuhkan sebuah alat dan prosedur lapangan yang mampu menghitung perubahan karakteristik tanah, khususnya hydraulic conductivity dari kondisi jenuh sebagian hingga jenuh. Ada dua macam prosedur pengujian permeabilitas lapangan yang dikembangkan yaitu immediate flow dan constant flow. Pengujian immediate flow menggunakan tabung uji yang digenangkan air dan dihitung waktu penurunannya pada tinggi tertentu. Pengujian constant flow menggunakan tabung uji yang dialirkan debit konstan hingga mencapai ketinggian tetap. Kedua pengujian dilakukan dari kondisi tanah jenuh sebagian hingga jenuh. Selama pengujian perubahan volumetric water content diukur menggunakan alat Decagon Device. Dari hasil pengujian diperoleh hubungan k dengan  menggunakan pendekatan numerik VG model. Terdapat parameter r dalam perhitungan VG model yang dapat ditentukan melalui pengujian ataupun pemodelan. Hasil menunjukkan nilai r optimum diperoleh pada kondisi tanah kering oven. Nilai koefisien permeabilitas tanah dengan kepadatan 2,04 gr/cm3 dari kondisi jenuh sebagian adalah 4 x 10-6 cm/detik (Sr=83%) sampai kondisi jenuh adalah 1 x 10-5 cm/detik (Sr=95%). Alat yang dikembangkan cukup efisien untuk mengetahui hydraulic conductivity tanah pasir berlanau kondisi jenuh sebagian hingga jenuh tanpa menggunakan Soil Water Characteristic Curve yang cukup mahal. Kata kunci: genangan, hydraulic conductivity, pengembangan alat pengujian, tanah pasir berlanau.

post-rain puddles problem that occurs in The First Yard of Prambanan Temple is caused by soil characteristics changes when the post-quake restoration was being done in 2006. Thus an instrument and method which capable to effectively measure field soil characteristics, especially hydraulic conductivity from unsaturated to saturated condition is highly needed. In this research, there are two developed instrument and procedure to measure field hydraulic conductivity, the immediate flow and constant flow method. Immediate flow method used a test tube filled with water until certain height. Afterwards, the time period of water level changes were being counted. Constant flow method used a test tube filled with constant water flow until the height remains at a particular position. Both methods were carried out from unsaturated to saturated condition. Decagon Devices were used to measure volumetric water content variance during testing. Based on the results, hydraulic conductivity relation to volumetric water content variance was obtained by using numerical approach. r parameter used in VG model calculation can be determined by testing or modeling. The results showed that r obtained from very dry soil conditions had the optimum value. Hydraulic conductivity range value with a density of 2.04 gr/cm3 for unsaturated condition is 4 x 10-6 cm/sec (Sr= 83%) to 1 x 10-5 cm/sec (Sr = 95%). The developed equipment that was being used for this test was sufficiently effective to measure in situ hydraulic conductivity in silty sand soil without using Soil Water Characteristic Curve which is quite expensive. Keywords: puddles, developed in situ measurement, hydraulic conductivity, silty sand soil.

Kata Kunci : genangan, hydraulic conductivity, pengembangan alat pengujian, tanah pasir berlanau.