Pengaruh Hujan Pada Stabilitas Lereng Di Jalan Tol Gempol – Pandaan

Dewi Atikah, Pitojo Tri Juwono, Andre Primantyo Hendrawan

Abstract


Jalan tol Gempol - Pandaan sta 6+275 – 6+375 hasil pengeprasan bukit mengalami kelongsoran pada  tanggal 3 Februari 2015 dengan didahului oleh hujan. Studi ini bertujuan mengetahui pengaruh hujan pada stabilitas lereng di jalan tol Gempol – Pandaan. Intensitas hujan sebagai input Geostudio Seep/W, hasil analisisnya menjadi input Slope/W. Hasilnya angka keamanan saat terjadi longsor adalah 1.10595 (Bishop), 1.060512 (Fellenius), dan 1.100788 (Morgenstern-Price). Berdasarkan data hujan selama 10 tahun, intensitas 0.0077 m/jam, merupakan nilai maksimal karena setelah nilai ini tercapai, angka keamanannya tidak bisa berkurang lagi.  Alternatif perkuatan soil nailing mempunyai angka keamanan 1.555921, lebih tinggi dari bored pile dan anggaran biaya lebih kecil sebesar Rp. 1.938.804.000,00 lebih kecil dari bored pile. Ambang batas hujan yang dapat memicu longsor adalah kombinasi hujan 60 mm dan hujan 100 mm selama 30 hari yang menghasilkan total hujan sebesar 960 mm.

Kata kunci: stabilitas lereng, intensitas hujan, Seep/W, Slope/W, ambang batas hujan

ABSTRACT: Gempol - Pandaan toll road at sta 6 + 275 - 6 + 375 is formed by cutting hill. On February 3th, 2015 this location suffered landslide that was preceded by rainfall. This study aims to determine the effect of rainfall on slope stability in Gempol - Pandaan toll road. Rainfall intensity was apllied as input in Geostudio Seep / W and the results of Seep/W analysis became input in Slope / W. As a result, factor of safety when landslide occured was 1.10595 (Bishop), 1.060512 (Fellenius), and 1.100788 (Morgenstern-Price). Based on rainfall data for 10 years, rainfall intensity 0.0077 m / h was the maximum value. After this value was reached, the factor of safety cannot be reduced again. Factor of safety from soil nailing reinforcement increases up to 1.555921, higher than bored pile application and the cost budget of soil nailing (Rp. 1,938,804,000.00) is cheaper than bored pile. The rainfall threshold value to initiate landslide is a combination of 60 mm rainfall and 100 mm rainfall for 30 days that produce total amount of 960 mm of rain.

 

Keywords: slope stability, rainfall intensity, Seep/W, Slope/W, rain threshold


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