Harijan, Harijan (2022) Analisis Stabilitas Lereng Ditinjau Dari Pengaruh Infiltrasi Air Hujan Dan Perkuatan Geometri Lereng Studi Kasus : Kelongsoran Lereng Di Dusun Kondoruba (Km. 25+575 - 26+100) Preservasi Jalan Kalukku-Salubatu-Mambi-Malabo, Sulawesi Barat. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Kelongsoran lereng bawah yang terjadi di dusun Kondoruba, Sulawesi Barat telah menyebabkan amblasnya badan jalan sehingga perlu dilakukan penanganan secara permanen dengan menggunakan perkuatan struktur penahan longsor seperti secant pile. Dengan material penyusun lereng berupa pasir kelanauan maka secant pile didesain menggunakan encapsulated stone column dan bored pile yang dipasang berselang-seling. Tujuannya adalah agar air bisa keluar dari dalam lereng tetapi material tanah tetap tertahan.
Untuk memenuhi desain yang diperlukan tersebut, penelitian ini bertujuan mengalisis stabilitas lereng dipengaruhi oleh faktor internal (kemiringan lereng, adanya gempa, dan muka air tanah) serta faktor eksternal (infiltrasi air hujan, dimensi pile). Analisis dengan variasi dari faktor internal dan eksternal tersebut dilakukan dengan menggunakan program bantu Seep/W dan Plaxis 2D. Output dari Seep/W berupa posisi perubahan muka air tanah akibat infiltrasi, yang selanjutnya akan diinput ke dalam Plaxis beserta parameter tanah yang lain untuk menentukan stabilitas lereng yang ditinjau.
Hasil analisis infiltrasi menunjukan safety factor semakin menurun seiring dengan bertambahnya durasi hujan yang terjadi. Pada kondisi tanpa hujan safety factor lereng adalah 0,999 sedangkan pada kondisi hujan selama 5 jam safety factornya menjadi 0,994, terjadi penurunan nilai safety factor sebesar 0,05% akibat adanya hujan selama 5 jam. Hasil analisis stabilitas dengan variasi penelitian ini menyimpulkan semakin besar kemiringan lereng (>45°) maka bidang keruntuhan mencapai tiang secant pile sehingga keberadaan secant pile berperan meningkatkan safety factor, didapat rata-rata safety factor pada lereng yang curam adalah 2,1036. Sebaliknya semakin kecil kemiringan lereng (≤45°) bidang keruntuhan berada di atas secant pile sehingga keberadaan secant pile kurang berperan, didapat rata-rata safety factor pada lereng yang landai adalah 2,0193. Terdapat selisih safety factor untuk kemiringan lereng yang curam dan kemiringan lereng yang landai sebesar 4,17%.
Untuk perbandingan hasil analisis stabilitas desain eksisting (gabion+geogrid) dan desain usulan (secant pile) didapatkan safety factor dengan perkuatan secant pile lebih tinggi nilainya dari pada menggunakan perkuatan gabion dan geogrid pada konfigurasi lereng yang sama. Dengan perkuatan secant pile didapat safety factor sebesar 2,1705 sedangkan perkuatan gabion dan geogrid didapat safety factor sebesar 1,182. Terdapat selisih safety factor untuk perkuatan menggunakan secant pile terhadap perkuatan gabion dan geogrid sebesar 83,63%.
Kata Kunci : Stabilitas lereng, kemiringan lereng, infiltrasi, gempa dinamis, secant pile, Seep/W, Plaxis 2D, safety factor.
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The downslope landslide that occurred in the hamlet of Kondoruba, West Sulawesi has caused the subsidence of the road, so it is necessary to treat it permanently by using the reinforcement of landslide-retaining structures such as secant piles. With the slope building material in the form of silty sand, the secant pile is designed using encapsulated stone columns and bored piles which are installed alternately. The goal is to allow water to escape from the slope but retain soil material.
To fulfill the required design, this study aims to analyze slope stability influenced by internal factors (slope slope, earthquake, and groundwater level) as well as external factors (rainwater infiltration, pile dimensions). The analysis with variations of internal and external factors was carried out using the Seep/W and Plaxis 2D programs. The output of Seep/W is the position of the change in ground water level due to infiltration, which will then be inputted into Plaxis along with other soil parameters to determine the stability of the slope under review.
The results of the infiltration analysis show that the safety factor decreases as the duration of the rain increases. In conditions without rain the slope safety factor is 0.999 while in rainy conditions for 5 hours the safety factor becomes 0.994, there is a decrease in the safety factor value of 0.05% due to rain for 5 hours. The results of the stability analysis with variations in this study concluded that the greater the slope (>45 °), the failure plane reached the secant pile pile so that the presence of the secant pile played a role in increasing the safety factor, the average safety factor on steep slopes was 2.1036. On the other hand, the smaller the slope (≤45°) the failure plane is above the secant pile so that the presence of the secant pile is less important, the average safety factor on gentle slopes is 2.0193. There is a difference in safety factor for steep slopes and gentle slopes of 4.17%.
To compare the results of the stability analysis of the existing design (gabion + geogrid) and the proposed design (secant pile), it is found that the safety factor with secant pile reinforcement is higher than using gabion and geogrid reinforcement on the same slope configuration. With secant pile reinforcement, a safety factor of 2.1705 was obtained, while gabion and geogrid reinforcement obtained a safety factor of 1.182. There is a difference in safety factor for reinforcement using secant pile against gabion and geogrid reinforcement of 83.63%.
Keywords: Slope stability, slope, infiltration, dynamic earthquake, secant pile, Seep/W, Plaxis 2D, safety factor.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Stabilitas lereng, kemiringan lereng, infiltrasi, gempa dinamis, secant pile, Seep/W, Plaxis 2D, safety factor. Slope stability, slope, infiltration, dynamic earthquake, secant pile |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA347 Finite Element Method |
| Divisions: | Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22101-(S2) Master Thesis |
| Depositing User: | Harijan Harijan |
| Date Deposited: | 10 Feb 2022 02:46 |
| Last Modified: | 17 Oct 2024 06:58 |
| URI: | http://repository.its.ac.id/id/eprint/93431 |
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