Analisis Potensi Likuefaksi pada Tanah Pasir Akibat Gempa (Studi Kasus Mataram, Nusa Tenggara Barat)

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ABSTRAK

Pada hari Minggu, 5 Agustus 2018 pukul 19:46 WITA, gempa bumi mengguncang wilayah Labuan, Lombok, Nusa Tenggara Barat dengan skala magnitudo M7,0. Akibat guncangan tersebut, terjadi peristiwa likuefaksi di sebagian wilayah Provinsi Nusa Tenggara Barat dan menimbulkan kerusakan yang signifikan. Peristiwa likuefaksi dapat terjadi apabila mengalami peningkatan tekanan air pori yang dipicu oleh gempa bumi sehingga mengakibatkan tanah kehilangan kekakuan dan kuat geser tanah. Likuefaksi pada umumnya terjadi pada tanah pasir lepas dengan kondisi jenuh air. Dalam menganalisis potensi terjadinya likuefaksi di lokasi penelitian, digunakan nilai percepatan puncak di batuan dasar (PGA) sebesar 4,13 m/s2dan menggunakan data tanah hasil pengujian Standard Penetration Test (SPT). Hasil perbandingan antara ketahanan tanah atau Cyclic Resistance Ratio (CRR) dengan kemampuan tanah terlikuefaksi atau Cyclic Stress Ratio (CSR) menunjukkan bahwa likuefaksi terjadi pada rata-rata kedalaman 5,5 m – 19.5 m.

Kata kunci: likuefaksi, cyclic stress ratio (CSR), cyclic resistance ratio (CRR), faktor keamanan (FK)

 

ABSTRACT

On Sunday, August 5 2018 at 19:46 WITA, an earthquake has shook Labuan, Lombok, West Nusa Tenggara with magnitude 7.0 scale. As a result of the earthquake, liquefaction occurred in several regions of West Nusa Tenggara and caused severe damage. Liquefaction can occure when an increase in pore water pressure is triggered by an earthquake, which causes the soil losing its shear strength and stiffness. Liquefaction mostly occured in sand loose and saturated condition. Analysis of liquefaction based on Peak Ground Acceleration (PGA) at the research site 4.13 m/s2 were done according to the data of SPT (Standard Penetration Test). By comparing the value of soil resistance to liquefaction or Cyclic Resistance Ratio (CRR) and the ability of soil to be liquefied or Cyclic Stress Ratio (CSR), the analysis shows the soil in that area are liquefied at depth of 5.5 m – 19.5 m.

Keywords: liquefaction, cyclic stress ratio (CSR), cyclic resistance ratio (CRR), safety of factor (SF)