Zahera, Nabilla (2021) PEDOMAN BAGI PEMECAHAN MASALAH STABILITAS ABUTMENT DAN OPRIT JEMBATAN DI ATAS TANAH LUNAK MENGGUNAKAN RELIEVING PLATFORM. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Permasalahan pada perencanaan jembatan yang sering terjadi adalah pergerakan yang berlebihan secara horizontal pada abutment. Kondisi ini timbul karena timbunan oprit jembatan tersebut dibangun di atas tanah lunak yang mungkin tidak kuat menahan beban diatasnya dan cenderung longsor ke arah sungai. Keadaan ini menyebabkan secara overall stability tanah dasar di bawah tanah timbunan oprit jembatan di belakang abutment tersebut tidak stabil.
Menyiasati kondisi tanah dasar yang lunak, banyak perencana mengganti konstruksi abutment jembatan menjadi konstruksi slab on piles. Hanya saja konstruksi slab on piles tersebut akan menaikkan biaya jembatan secara signifikan sehingga kurang efektif dalam mengatasi permasalahan yang terjadi. Berdasarkan alasan tersebut, maka diperlukan suatu alternatif yang dapat memberikan nilai yang lebih ekonomis yang dapat diterapkan di lapangan serta dapat menangani kestabilan pada abutment.
Metode alternatif yang paling efektif untuk mengatasi permasalahan tersebut adalah menggunakan relieving platform dan tiang-cerucuk yang dipasang di belakang abutment. Relieving platform berfungsi untuk menghilangkan sebagian dari beban timbunan tanah agar tidak membebani tanah asli yang merupakan tanah lunak. Tiang cerucuk berfungsi untuk memberikan tambahan tahanan geser pada tanah lunak sehingga meningkatkan overall stability; juga sebagai perantara agar beban timbunan oprit jembatan tersebut dapat terdistribusi ke lapisan tanah yang lebih dalam dan lebih kuat di dalamnya sehingga seolah-olah tanah asli tersebut tidak menahan beban timbunan.
Timbunan oprit jembatan tersebut dianalisis pada tanah dasar lunak dengan konsistensi very soft, soft, dan medium dengan asumsi ketebalan tanah dasar 30 meter. Tanah dasar lunak tersebut dimodelkan sebagai tanah lunak berlapis. Hasil penelitian pada berbagai ketinggian timbunan oprit jembatan (4m, 6m, 8m, 10m dan 12m) terhadap overall stability, tanah tersebut mengalami kemungkinan kelongsoran (SF ≤ 1). Hal ini menyebabkan perlunya perkuatan pada berbagai ketinggian timbunan oprit jembatan menggunakan relieving platform dan tiang-cerucuk. Pada perhitungan perencanaan relieving platform dan tiang-cerucuk diberi variasi diameter; 30 cm, 50cm, dan 60 cm; tipe kelas tiang-cerucuk; A2; A3, dan C; serta jarak antar tiang-cerucuk adalah 2,5D dan 3D untuk mengetahui sistem perencanaan yang paling efektif.
Kebutuhan jumlah tiang-cerucuk diasumsikan berdasarkan arah memanjang jalan (longitudinal). Hasil penelitian menunjukkan bahwa semakin tinggi timbunan oprit jembatan, kebutuhan tiang-cerucuk dan lebar relieving platform semakin besar. Kebutuhan tersebut juga dipengaruhi oleh diameter tiang-cerucuk, jarak tiang-cerucuk, dan tipe kelas tiang-cerucuk. Jika ukuran diameter tiang-cerucuk dan tipe kelas tiang semakin kecil, maka semakin banyak jumlah tiang-cerucuk yang diperlukan untuk menambah kekuatan geser tanah dalam asumsi menahan overall stability. Sedangkan pada asumsi menahan beban aksial, semakin kecil ukuran diameter tiang, maka Pijin 1 tiang juga semakin kecil yang menyebabkan kebutuhan tiang-cerucuk akan semakin banyak. Pada pengaruh jarak antar tiang-cerucuk, jarak 3D menghasilkan kebutuhan tiang-cerucuk dan lebar relieving platform lebih banyak daripada jarak 2,5D. Hal ini disebabkan saat menghitung kebutuhan tiang-cerucuk yang menahan overall stability, momen resistance harus dikali dengan jarak tiang-cerucuk. Jarak tiang tersebut menyesuaikan jarak pada kebutuhan tiang aksial. Hasil dari perhitungan antara jarak tiang 2,5D dan 3D, kebutuhan tiang pada jarak yang lebih besar menghasilkan lebar relieving platform dan tiang yang lebih banyak.
Pada analisis tambahan biaya perkuatan relieving platform dan tiang-cerucuk, semakin tinggi timbunan maka biaya yang akan dibutuhkan semakin besar. Hal ini berlaku untuk keseluruhan tipe diameter tiang dan variasi jarak antar tiang. Hasil penelitian menunjukkan bahwa konstruksi relieving platform dan tiang-cerucuk yang paling efektif pada berbagai ketinggian oprit jembatan (4 s/d 12m) adalah pada jarak antar tiang 2,5D dengan ukuran diameter 30 cm. Walaupun dari segi teknis ukuran diameter 60 cm merupakan variasi dengan jumlah tiang lebih sedikit, namun dari segi biaya ukuran diameter 60 cm memerlukan biaya yang jauh lebih besar. Selain harga tiang yang lebih mahal, variasi diameter 60 cm menghasilkan kebutuhan relieving platform yang lebih besar. Sedang pada ukuran diameter 30cm, meskipun menghasilkan jumlah tiang yang lebih banyak, kebutuhan lebar relieving platform akan jauh lebih sedikit. Biaya yang diperhitungkan hanya berdasarkan harga kelas C, namun hal ini sudah menunjukkan bahwa sistem relieving platform dan tiang cerucuk yang paling efektif berada pada diameter 30 cm dengan jarak 2,5D.
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The problem in bridge design that often occurs is excessive horizontal movement of the abutment. This condition arises because the bridge is built on soft soil which may not be strong enough to withstand the load on it and tends to slide towards the river. This situation causes the overall stability of the subgrade beneath the bridge oprit fill behind the abutment to be unstable.
To deal with soft subgrade conditions, many planners replace bridge abutment construction to slab on piles construction. It's just that the construction of the slab on piles will increase the cost of the bridge significantly so that it is less effective in overcoming the problems that occur. Based on these reasons, we need an alternative that can provide a more economical value that can be applied in the field and can handle the stability of the abutment.
The most effective alternative method to overcome this problem is to use a relieving platform and pillars mounted behind the abutment. The relieving platform serves to remove some of the load from the soil embankment so as not to burden the original soil, which is soft soil. The cone pile serves to provide additional shear resistance on soft soil so as to increase overall stability; also as an intermediary so that the load of the bridge oprit embankment can be distributed to a deeper and stronger layer of soil inside so that it is as if the original soil does not hold the embankment load
The bridge embankment was analyzed on soft subgrade with very soft, soft, and medium consistency with assume a subgrade thickness of 30 meters. The soil subgrade is modeled as layered soft soil. The results of the study at various heights of the bridge oprit (4m, 6m, 8m, 10m and 12m) on overall stability, the soil experienced the possibility of landslides (SF≤ 1). This causes the need for reinforcement at various heights of the bridge embankment using relieving platforms and piles. In the calculation of the planning of relieving platforms and piles, diameter variations are given; 30 cm, 50 cm and 60 cm; pile-cube class type; A2; A3, and C; and the distance between the pillars is 2.5D and 3D to determine the most effective planning system.
The need for the number of piles is assumed based on the longitudinal direction of the road. The results showed that the higher the oprit of the bridge, the greater the need for pillars and the width of the relieving platform. These requirements are also influenced by pile diameter, pile distance, and type of pile class. If the size of the pile diameter and the type of pile class is getting smaller, the more piles are needed to increase the shear strength of the soil in the assumption of maintaining overall stability. While on the assumption of holding axial load, the smaller the diameter of the pile, the smaller the Pallow 1 pile, which causes the need for more piles. On the effect of the distance between the piles, the 3D distance resulted in the need for recessed piles and the width of the relieving platform more than the 2.5D distance. This is because when calculating the need for piles that hold overall stability, the moment of resistance must be multiplied by the pile distance. The pile distance adjusts the distance to the axial pile requirement. The results of the calculation between 2.5D and 3D pile distances, the need for piles at a greater distance results in more width of the relieving platform and piles.
In the additional analysis of the cost of reinforcing the relieving platforms and piles, the higher the embankment, the higher the cost required. This applies to all types of pile diameters and variations in spacing between piles. The results showed that the most effective construction of relieving platforms and piers at various heights of bridge oprit (4m to 12m) was at a distance between 2.5D piles with a diameter of 30 cm. Although from a technical point of view the diameter of 60 cm is a variation with fewer poles, but from a cost point of view, a diameter of 60 cm requires a much higher cost. In addition to the more expensive pile price, the 60 cm diameter variation results in the need for a larger relieving platform. Medium in diameter 30cm, although it produces a larger number of piles, the width of the relieving platform will be much less. The cost calculated is only based on class C prices, but this has shown that the most effective system of relieving platforms and pile is 30 cm in diameter with a distance of 2.5D.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | guidelines, overall stability, pile, relieving platform, cerucuk, overall stability, pedoman, relieving platform. |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) |
| Divisions: | Faculty of Civil, Environmental, and Geo Engineering > Civil Engineering > 22101-(S2) Master Theses |
| Depositing User: | Nabilla Zahera |
| Date Deposited: | 28 Jul 2021 02:32 |
| Last Modified: | 28 Jul 2021 02:36 |
| URI: | http://repository.its.ac.id/id/eprint/84530 |
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