Amalia, Dewi (2020) Pengembangan Program Bantu Analisa Stabilitas Lereng berdasarkan “The Concept of Cracked Soil”. Doctoral thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Penelitian ini merupakan bagian dari upaya riset untuk mengembangkan dan menetapkan konsep tanah retak (the concept of cracked soil) yang telah dilakukan oleh para peneliti sebelumnya. Dalam penelitian ini, the concept of cracked soil dikaji dalam lingkup mengenai stabilitas lereng setelah keretakan terjadi di dalam tanah dan ketika lereng terguyur hujan. Dalam hal kekuatan geser tanah, telah ditetapkan pada penelitian sebelumnya bahwa kondisi drained selalu terjadi pada keretakan yang mengalami geser, sehingga kekuatan geser tanah sepanjang retakan tampak berperilaku seperti kondisi pasir (behaving like sands). Retakan timbul secara random pada lereng dan meyebar secara betahap disebabkan alasan yang belum dipahami sepenuhnya.
Semua program bantu yang tersedia untuk menghitung stabilitas lereng belum mencakup adanya retakan di dalam lereng sehingga lereng dianggap satu kesatuan yang utuh tanpa retakan. Asumsi ini telah menyebabkan kesalahan signifikan dalam banyak perhitungan stabilitas lereng. Banyak lereng yang telah diperbaiki mengalami longsor kembali setelah hujan lebat, dan kegagalan lereng menunjukkan kekuatan geser yang lebih kecil daripada yang telah diperkirakan sebelumnya. Lereng yang telah jelas stabil selama bertahun-tahun, tiba-tiba gagal saat kondisi hujan lebat. Untuk itu, perlu dikembangkan program bantu yang dapat digunakan untuk mendapatkan kondisi stabilitas lereng yang sesungguhnya di lapangan sehingga tidak akan lagi terulang tebing tanah yang sudah diperkuat mengalami kelongsoran pada saat hujan sangat lebat terjadi.
Pengembangan program bantu ini diselesaikan melalui tiga tahapan, yaitu tahap persiapan, tahap pemodelan, dan tahap terakhir yang meliputi validasi terhadap program yang telah ada, simulasi, serta analisis model. Teknologi gambar digital diterapkan melalui program bantu yang didasarkan pada antarmuka pengguna grafis (GUI) yang ada di dalam MATLAB dan memanfaatkan opsi format warna RGB (Merah, Hijau, Biru). Dengan teknik ini, retakan tanah yang telah didapat dari data geolistrik dapat diambil secara otomatis sehingga dapat digunakan sebagai input untuk program analisis stabilitas lereng guna menentukan nilai faktor keamanan lereng. Teknik pemrosesan gambar dalam penelitian ini didasarkan pada penggunaan persamaan garis lurus untuk mendeteksi geometri lereng, stratigrafi tanah, dan posisi retakan pada lereng berdasarkan data geolistrik.
Penelitian ini menghasilkan pemodelan numerik untuk stabilitas lereng, yang berbentuk program bantu bernama NSSAP 1.0 (New Slope Stability Analysis Program Versi 1.0). Program bantu yang dikembangkan ini sudah dicoba untuk menganalisis ulang stabilitas lereng yang sebelumnya dianalisa sebagai lereng yang aman (SF > 1.0) Namun, setelah dianalisis dengan NSSAP 1.0 dengan menggunakan konsep tanah retak (cracked soil concept), hasilnya menunjukkan bahwa lereng tersebut tenyata dalam kondisi yang tidak stabil; hasil ini sesuai dengan kondisi lapangan dimana tebing longsor setelah hujan lebat. Jadi, hujan deras hingga sangat deras dan pola retak adalah faktor penentu stabilitas lereng. Apabila program bantu NSSAP 1.0 yang mengadopsi konsep tanah retak ini digunakan untuk menganalisis stabilitas lereng maka fenomena kontradiksi antara analisis geoteknis dan kondisi lapangan tidak akan terjadi. Dalam program NSSAP 1.0 ini, teknik pemrosesan gambar dari data geolistrik untuk mendeteksi geometri lereng, stratigrafi tanah, dan posisi retakan pada lereng, memberikan nilai yang akurat yaitu mencapai 5,78 cm / piksel.
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This study is part of research attempts to develop and establish the concept of cracked soil that had been conducted by other previous researchers. In this study, the concept of cracked soil is explored in area concerning the stability of earth slope after cracks occur in the soil and when the slope is subjected to rainfall. In term of the soil shear strength, it has been established by previous studies that the drained condition always prevails in any crack that is subjected to shear, so that the soil shear strength along the shearing crack seems to behave like those of sands. Cracks seems to appear on any slope randomly and gradually propagating, for some reasons that have not been understood entirely.
All existing programs available to calculate slope stability have not taken the existence of cracks and influence of rain into consideration, so that slope is considered as single unit of soil without cracks. This assumption had led to significant error in many calculations of slope stabilities. Many repaired slopes had slided again after heavy rain, and the failed slopes showed apparent shear strengths much lower than those initially assumed. Slopes that had been obviously stable for many years, suddenly failed under heavy rain condition. For this reason, it is necessary to develop a program which can be used to obtain the actual slope stability in the field so that landslide in reinforced slopes will not happen again when heavy rains occur.
The development of this program was completed in three stages, namely: preparation, modeling, and the final stage which includes validation of existing program, simulations, and model analysis. This digital image technology (image processing) is applied through program based on graphical user interfaces (GUI) in MATLAB and utilizes the RGB (Red, Green, Blue) color format option. With this technique, soil cracks that have been obtained from the geoelectric data can be retrieved automatically so that it can be used as input for the slope stability analysis program to determine the safety factor of the slope. Image processing technique in this research is based on the use of linear equation to detect slope geometry, soil stratigraphy, and crack positions on slopes based on geoelectric data.
This research produced numerical modeling for slope stability in the form of a program named NSSAP 1.0 (New Slope Stability Analysis Program 1.0). This program has been tested to re-analyze the stability of certain slopes that had been analyzed previously as stable slopes (SF > 1.0) using existing program. However, after being analyzed with NSSAP 1.0 by using cracked soil concept, the results show that the slopes are not in stable condition (SF < 1); which matches the field condition where the landslide did occur after subjected to heavy rains. It is also found that heavy to very heavy rains and crack patterns are the determining factors for slope stability. If the NSSAP 1.0 that adopts the concept of cracked soil is used to analyze slope stability, the contradiction between geotechnical analysis and field conditions will no longer occur. In this NSSAP 1.0 program, the image processing technique that are based on geoelectric data to detect slope geometry, soil stratigraphy, and crack positions on slopes, has provided rather highly accurate value of 5.78 cm/pixel.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Additional Information: | RDS 624.151 363 Ama p-1 |
| Uncontrolled Keywords: | Kekuatan geser “drained”, New Slope Stability Analysis Program (NSSAP), pengolahan citra digital, the concept of cracked soil, pengaruh hujan terhadap stabilitas lereng Drained shear strength, new slope stability analysis program, image processing, the concept of cracked soil, effect of rain on slope. |
| Subjects: | 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 > 22001-(S3) PhD Thesis |
| Depositing User: | Dewi Amalia |
| Date Deposited: | 04 Aug 2020 08:05 |
| Last Modified: | 22 May 2023 01:14 |
| URI: | http://repository.its.ac.id/id/eprint/76146 |
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