Mulifandi, Alfian Wildan (2024) Pengaruh Kecepatan Pentahapan Penimbunan Terhadap Stabilitas Timbunan dengan Tinggi Bervariasi di Atas Tanah Lunak Organik Pada Proyek Jalan Tol Ruas Sicincin-Padang Sta 10+250-10+400. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Jalan tol trans Sumatera merupakan program Pemerintah Indonesia dalam rangka percepatan pengembangan kawasan di pulau Sumatera. Salah satu jalan tol trans Sumatera yang sedang dalam tahap pembangunan adalah jalan tol ruas Pekanbaru – Padang seksi Sicincin – Lubuk Alung – Padang. Pada ruas jalan tol tersebut terdapat beberapa permasalahan geoteknik, salah satunya pada pelaksanaan pekerjaan timbunan di lokasi Sta 10+275-10+375, dimana pada pelaksanaan timbunan setinggi 4,0 meter terdapat permasalahan yang berupa terjadinya retakan pada kaki timbunan sisi kiri. Berdasarkan hasil evaluasi monitoring instrument geoteknik dilapangan, retakan yang terjadi dapat diakibatkan oleh bearing capacity failure atau akibat pola pelaksanaan pekerjaan timbunan yang terlalu cepat. Untuk itu perlu dilakukan analisis guna mengetahui penyebab terjadinya retakan tersebut dan dilakukan penelitian untuk mengetahui kestabilan lereng timbunan dengan variasi tahapan pelaksanaan pekerjaan. Metode yang digunakan dalam penelitian ini adalah menggunakan simulasi numerik elemen hingga menggunakan bantuan program PLAXIS 2D untuk mengetahui stabilitas lereng timbunan sesuai tahapan pelaksanaan dilapangan dan simulasi atau modeling dengan memodelkan penimbunan bertahap pada variasi ketebalan setiap lapis/lift timbunan 15 cm, 20 cm, dan 25 cm dan variasi waktu konsolidasi 1 hari, 3 hari, 5 hari, 7 hari dan 14 hari disetiap penambahan tinggi timbunan 1 meter. Pemodelan dilakukan pada 3 titik lokasi yaitu Sta 10+250, Sta 10+350 dan Sta 10+400 dengan tinggi akhir timbunan bervariasi 4,5-6,5 meter. Studi ini bertujuan untuk mengetahui tahapan pelaksanaan yang aman dan sesuai terhadap persyaratan kriteria desain.
Dari hasil back analysis berdasarkan pemodelan Plaxis 2D dengan tahapan yang dilaksanakan dilapangan pada tinggi timbunan 4,0 didapatkan bahwa nilai angka keamanan stabilitas timbunan masih dalam kondisi stabil sebesar 1,919 dan menjadi tidak stabil (SF<1,35) pada saat tinggi timbunan mencapai tinggi 12,9 m dengan besar nilai angka keamana sebesar 1,156. Nilai daya dukung tanah pada tinggi timbunan 4,0 m mencapai kondisi tidak stabil yaitu sebesar 1,135 dengan pendeketan φ = 0 pada kondisi tanah jenuh (undrained). Sehingga keretakan dilapangan diindikasikan akibat vertical drain dan horizontal drain belum bekerja secara penuh saat awal pelaksanaan pekerjaan timbunan sehingga tanah masihdalam kondisi jenuh air yang menyebabkan daya dukung tanah tersebut tidak stabil saat menerima beban timbunan.
Dari hasil pemodelan yang telah dilakukan pada Sta 10+250-10+400 didapatkan dengan penambahan waktu konsolidasi yang ditinjau menghasilkan peningkatan stabilitas timbunan dengan kenaikan nilai angka keamanan rata-rata sebesar 2,18%, kenaikan besar penurunan rata-rata sebesar 1,29%, penurunan besar pergerakan lateral tanah 3,93% dan penurunan tekanan air pori ekses sebesar 16,22%. Dengan pengurangan tebal lapis/lift timbunan menghasilkan peningkatan stabilitas timbunan rata-rata sebesar 0,96%, kenaikan besar penurunan rata-rata sebesar 0,58%, penurunan besar pergerakan lateral tanah 1,51% dan penurunan tekanan air pori ekses sebesar 6,25%.
Tahapan pelaksanaan ditentukan dengan pemenuhan persyaratan kriteria desain pada SNI 8460:2017, untuk angka keamanan tahap pelaksanaan sebesar 1,35 dan persyaratan konsolidasi tercapai minimum 90%. Didapatkan tahapan pelaksanaan pada Sta 10+250 adalah dengan tebal lapis/lift timbunan 25 cm dan waktu konsolidasi 14 hari, Sta 10+350 dengan tebal lapis/lift timbunan 15 cm dan waktu konsolidasi 7 hari, Sta 10+400 dengan tebal lapis/lift timbunan 25 cm dan waktu konsolidasi 5 hari. Terdapat perbedaan waktu efektif pada masing-masing lokasi yang ditinjau, hal ini disebabkan akibat perbedaan geometrik kondisi timbunan tanah yang berbeda-beda di setiap lokasi.
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The trans-Sumatra toll road is a program of the Government of Indonesia in order to accelerate regional development on the island of Sumatra. One of the trans Sumatra toll roads under construction is the Pekanbaru - Padang section of the Sicincin - Lubuk Alung - Padang toll road. On the toll road section there are several geotechnical problems, one of which is the implementation of embankment work at the Sta 10+250-10+400 location, where in the implementation of a 4.0 meter high embankment there are problems in the form of cracks on the left side of the embankment. Based on the evaluation of geotechnical instrument monitoring in the field, the cracks that occur can be caused by bearing capacity failure or due to the pattern of embankment work implementation that is too fast. For this reason, it is necessary to analyze to determine the cause of the cracks and conduct research to determine the stability of the embankment slope with variations in the stages of work implementation. The method used in this research is to use finite element numerical simulation using the help of the PLAXIS 2D program to determine the stability of the embankment slope according to the stages of implementation in the field and simulation research or modeling by modeling gradual backfilling at variations in the thickness of each layer of embankment 15 cm, 20 cm, and 25 cm and variations in consolidation time of 1 day, 3 days, 5 days, 7 days and 14 days for each additional 1 meter of embankment height. Modeling was carried out at 3 locations at Sta 10+250, Sta 10+350 and Sta 10+400 with the final height of the embankment varying from 4.5-6.5 meters. This study aims to determine the stages of implementation that are safe and in accordance with the requirements of the design criteria.
From the results of back analysis based on Plaxis 2D modeling with stages carried out in the field at a height of 4.0 embankment, it is found that the safety number value of embankment stability is still in a stable condition of 1.919 and becomes unstable (SF < 1.35) when the height of the embankment reaches a height of 12.9 m with a large safety number value of 1.156. The soil bearing capacity value at 4.0 m embankment height reaches an unstable condition of 1.135 with φ = 0 approach in undrained(saturated) soil conditions. So that the cracks in the field are indicated due to the vertical drain and horizontal drain not working fully at the beginning of the embankment work so that the soil is still in a water-saturated condition which causes the bearing capacity of the soil to be unstable when receiving the embankment load.
From the modeling results that have been carried out at Sta 10+250-10+400, it is obtained that the addition of the consolidation time under review results in an increase in the average embankment stability of 2.18%, an increase in the average settlement size of 1.29%, a decrease in the size of soil lateral movement of 3.93% and a decrease in excess pore water pressure by 16.22%. Reducing the layer thickness of the embankment resulted in an increase in average embankment stability by 0.96%, an increase in average settlement by 0.58%, a decrease in lateral movement by 1.51% and a decrease in excess pore water pressure by 6.25%.
The implementation stage is determined by meeting the requirements of the design criteria in SNI 8460: 2017, for an implementation stage safety number of 1.35 and a minimum consolidation requirement of 90%. The implementation duration at Sta 10+250 is obtained with a layer embankment thickness of 25 cm and a consolidation time of 14 days, Sta 10+350 with a layer embankment thickness of 15 cm and a consolidation time of 7 days, Sta 10+400 with a layer embankment thickness of 25 cm and a consolidation time of 5 days. There is a difference in effective time at each location reviewed, this is due to differences in geometric conditions of different soil embankments at each location.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Stabilitas timbunan, kecepatan tahapan penimbunan, Penurunan, Tanah Organik, Plaxis 2D. Slope stability, stage construction, settlement, organic soil, Plaxis 2D |
| Subjects: | H Social Sciences > HE Transportation and Communications > HE355.4 Toll roads T Technology > TA Engineering (General). Civil engineering (General) > TA347 Finite Element Method T Technology > TA Engineering (General). Civil engineering (General) > TA455.S6 Soil (Materials of engineering and construction) |
| Divisions: | Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22101-(S2) Master Thesis |
| Depositing User: | Alfian Wildan Mulifandi |
| Date Deposited: | 06 Feb 2024 01:56 |
| Last Modified: | 06 Feb 2024 01:56 |
| URI: | http://repository.its.ac.id/id/eprint/106165 |
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