Purnamayoga, Wahyu (2024) Analisis Kestabilan Lereng Galian yang Bervariasi dan Perancangan Sistem Drainase Permukaan pada Kondisi Curah Hujan Maksimum Studi Kasus Pembangunan Jalan Tol Serang – Panimbang STA 54+550 – 55+150. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Pembangunan jalan tol Serang – Panimbang seksi III (Cileles – Panimbang) STA 54+550 – 55+150 merupakan area pekerjaan galian untuk desain finishing grade jalan. Permasalahan yang umumnya timbul pada lereng galian adalah kestabilan lereng galian. Kelongsoran lereng galian tersebut dapat dipengaruhi oleh berbagai macam faktor, diantaranya adalah infiltasi air hujan. Infiltrasi akan meningkatkan tekanan pori yang dapat mengurangi tegangan efektif tanah yang berpengaruh pada pengurangan kekuatan tanah. Infiltrasi akan terjadi semakin cepat saat ditemukannya retakan pada tanah (cracked soil). Celah retakan memudahkan infiltrasi ke lapisan-lapisan tanah dan menggerus material tanah sehingga ikatan antar partikel tanah semakin lemah. Oleh sebab itu, masalah yang perlu dicari jawabannya dalam penelitian ini adalah apakah kemiringan dan kedalaman galian serta intensitas curah hujan dan keretakan tanah berpengaruh terhadap stabilitas lereng galian.
Pada penelitian ini, pemodelan lereng galian dilakukan dengan metode finite element menggunakan program PLAXIS 2D dengan variasi ketinggian lereng pada kondisi curah hujan maksimum. Pendekatan teori cracked soil dimodelkan dengan lapisan tanah yang lebih lemah pada bidang gelincir (thin-weak layer) untuk mengetahui pengaruh retakan terhadap stabilitas lereng. Pengaruh perilaku model thin weak layer divariasikan tehadap perbedaan tebal weak layer dan rasio pengurangn nilai kohesi pada lapisan tipis secara bertahap.
Hasil analisis pengaruh pemodelan thin weak layer menunjukan bahwa rasio penurunan kohesi memiliki pengaruh lebih besar dibandingkan dengan variasi ketebalan weak layer. Setiap penambahan 0,5 m tebal weak layer akan menurunkan faktor keamanan rata-rata 1,3% sedangkan penurunan nilai kohesi sampai bernilai nol (cohesionless) dapat menurunkan nilai faktor keamanan sampai 29,14%. Di sisi lain, thin weak layer tidak memiliki pengaruh terhadap besaran deformasi yang terjadi pada tiap variasi pemodelan karena besaran deformasi yang terjadi cenderung tidak berubah.
Selain itu, pengaruh hujan tidak terlalu signifikan terhadap faktor keamanan lereng. Rata-rata penurunan nilai faktor keamanan akibat adanya hujan untuk STA 54+625, 54+600 dan 55+125 secara berurutan sebesar 1,54%; 7,05%; dan 1,81% serta masih diatas batas keamanan lereng. Ketiga model lereng galian ini memiliki lapisan material tanah berupa berbutir halus (lempung dan lanau) yang memiliki permeabilitas rendah, sehingga air hujan sulit untuk menginfiltrasi ke dalam tanah.
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The construction of Serang - Panimbang toll road section III (Cileles - Panimbang) STA 54+550 - 55+150 is an excavation work area for road finishing grade design. The problem that generally arises on the excavation slope is the stability of the excavation slope. Slope failure can be influenced by various factors, including rainfall infiltration. Infiltration will increase the pore pressure which can reduce the effective stress of the soil, leading to a reduction in soil strength. Infiltration will accelerate when cracked soil is found. Cracks facilitate infiltration into the soil layers and erode the soil material so that the bond between soil particles is weakened. Therefore, the problem that needs to be answered in this research is whether the slope and depth of excavation as well as the intensity of rainfall and soil cracks affect the stability of excavation slopes.
In this study, slope modeling was conducted using the finite element method using the PLAXIS 2D program with variations in slope height under maximum rainfall conditions. The cracked soil theory approach is modeled with a weaker soil layer on the slide plane (thin-weak layer) to determine the effect of cracks on slope stability. The effect of the thin weak layer model behavior was varied with the different thicknesses of the weak layer and the ratio of cohesion value reduction in the thin layer gradually.
The results of the analysis of the influence of thin weak layer modeling show that the cohesion reduction ratio has a greater influence than the variation in weak layer thickness. Each additional 0.5 m of weak layer thickness will reduce the factor of safety by an average of 1.3%, while a decrease in the cohesion value to zero (cohesionless state) can reduce the factor of safety value to 29.14%. On the other hand, the thin weak layer does not influence the rate of deformation that occurs in each modeling variation because the rate of deformation that occurs tends not to change.
Other analysis results show that the effect of rain is not very significant on the slope safety factor. The average decrease in safety factor value due to rain for STA 54+625, 54+600 and 55+125 is 1.54%; 7.05%; and 1.81% respectively and is still above the slope safety limit. These three excavation slope models have a layer of fine-grained soil material (clay and silt) which has low permeability, making it difficult for rainfall to infiltrate into the soil.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | slope stability, maximum rainfall condition, cracked soil approach, stabilitas lereng galian, curah hujan maksimum |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA455.S6 Soil (Materials of engineering and construction) T Technology > TA Engineering (General). Civil engineering (General) > TA749 Soil stabilization |
| Divisions: | Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22101-(S2) Master Thesis |
| Depositing User: | Wahyu Purnamayoga |
| Date Deposited: | 05 Feb 2024 07:20 |
| Last Modified: | 05 Feb 2024 07:20 |
| URI: | http://repository.its.ac.id/id/eprint/106111 |
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