PENGARUH MATRIC SUCTION TERHADAP PARAMETER GESER TANAH PADA TANAH LEMPUNG EKSPANSIF DUSUN KREBET, KULONPROGO YOGYAKARTA

NAFIATUSSAIDAH, Dr.Eng Iman Haryanto, S.T., M.T.

2015 | Tugas Akhir | D3 TEKNIK SIPIL SV

Tanah lempung Dusun Krebet, Kulonprogo, Yogyakarta termasuk jenis lempung ekspansif yang mempunyai sifat kembang susut sangat tinggi. Hal ini disebabkan karena tanah memiliki daya hisap terhadap air (suction). Pengukuran suction ini dilakukan menggunakan metode filter paper untuk mengetahui karakteristik air tanah yang dinyatakan dalam Soil Water Characteristic Curve (SWCC). Pengujian suction yang dilakukan pada tanah lempung asli meliputi pengujian sifat fisis tanah, terdiri dari uji kadar air awal yang dijadikan acuan penambahan air dan analisa butiran tanah untuk menentukan jenis tanah serta pengujian mekanis yang terdiri dari matric suction dengan metode kertas saring dan kuat geser menggunakan alat geser langsung dengan kombinasi beban 8kg, 12kg, 16kg, 24kg, 28kg, 32kg yang dilakukan pada kadar air 20%, 22%, 24%, 25%, 28%, 30%, 32%, 34%, 36%, 38%, 40%. Pengukuran fisis diperoleh nilai w=12,77% dan jenis tanah Clay Loam, sedangkan pengukuran matric sucion dihasilkan nilai suction (kPa) dan SWCC, serta kuat geser tanah diperoleh nilai sudut gesek dan kohesi (c). Semakin besar kadar air maka nilai suction semakin kecil dikarenakan keberadaan rongga kosong pada pori tanah. Semakin kecil nilai suction maka kuat geser tanah semakin besar dan sebaliknya, namun ketika telah mencapai kuat geser maksimum=63,4762 kPa pada suction sebesar 0,398107 kPa, kuat geser tersebut akan turun hingga mecapai konstan.

Clay soil from Krebet, Kulonprogo, Yogyakarta, including the type of expansive soil that have the nature and development of hight-shrinkage. This is because the soil has a suction power of water. Soil suction measurement is performed using filter paper method to determine the characteristic of the groundwater which is expressed in Soil Water Characterization Curve (SWCC). Suction power testing performed on the original clay soils include testing of soil physical properties, consisting of moisture content measurement which in turn referenced the addition of water, and grain size analysis to determine the type of soil. Mechanical test consist of measuring matric suction of filter paper method and shear strength using direct shear test with 8kg, 12kg, 16kg, 24kg, 28kg, 32kg load combination performed on 20%, 22%, 24%, 25%, 28%, 30%, 32%, 34%, 36%, 38%, 40% of water content. On the physical measurement obtained 12,77% value of water content and soil type is Clay Loam, while the resulting measurement value of matric suction and Soil Water characteristic Curve. The shear strength value obtained in the friction angle and cohesion. The greater of the water content, the smaller value of suction due to the presence of an empty cavity in the soil pores. The smaller value of suction then shear strength will be greater and vice versa. It is run until it reaches the maximum shear strength 63,4762 kPa at suction value 0,398107 kPa, then down and constant.

Kata Kunci : Soil suction, matric suction, parameter geser langsung, SWCC, kuat geser tanah