Analisis Pengaruh Ketinggian Muka Air Terhadap Rembesan dan Kestabilan Lereng Tanggul 'SS' di Kawasan Industri Gresik

Safira, Amanda (2021) Analisis Pengaruh Ketinggian Muka Air Terhadap Rembesan dan Kestabilan Lereng Tanggul 'SS' di Kawasan Industri Gresik. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Tanggul 'SS' memiliki tanah asli berupa tanah lempung lunak serta timbunan inti clay dan limestone (bongkahan dan tanah pedel padat). Potensi longsor dapat disebabkan oleh rentannya tanah asli karena memiliki konsistensi lunak, serta kemampuan air untuk memasuki pori tanah hingga mengurangi ketahanan gesernya. Penelitian ini bertujuan untuk mengetahui pengaruh ketinggian muka air terhadap rembesan dan kestabilan lereng Tanggul ‘SS’. Nilai parameter tiap lapisan tanah pada tanggul didapatkan melalui analisis data tanah, analisis rembesan dilakukan dengan menentukan fungsi volumetric water content (VWC) dan permeabilitas (k), serta analisis kestabilan lereng dilakukan berdasarkan metode finite element (FEM). Variasi muka air yang digunakan pada penelitian ini berada pada elevasi +0, +1.5, +3, dan +4.5 meter. Analisis rembesan menghasilkan bentuk-bentuk pola rembesan dan debit rembesan. Semakin tinggi elevasi muka air, garis ekipotensial yang terbentuk semakin banyak dan rapat, garis freatik semakin curam, dan debit rembesan yang semakin cepat. Aliran air terdapat baik pada timbunan maupun tanah asli, namun debit rembesannya jauh lebih besar pada timbunan yang disebabkan oleh sifat limestone dan tanah pedel yang dapat lebih mudah meloloskan air dibandingkan lempung yang lebih kedap air. Permeabilitas lempung jauh lebih kecil sehingga rembesan yang terjadi pada tanah asli tidak terlalu signifikan. Pengaruh air terhadap kestabilan lereng bergantung pada ketinggian muka airnya: jika relatif rendah (+0, +1.5 m), bidang keruntuhan paling kritis berada di lereng kiri karena beban air tidak cukup besar untuk melawan gaya longsor, ditunjukkan dengan meningkatnya nilai FK dan menurunnya besar perpindahan total seiring bertambahnya muka air. Sebaliknya, jika relatif tinggi (+2.7, +3, +4.5 m), bidang keruntuhan paling kritis berada di lereng kanan karena beban air membuat tanah menjadi terlalu jenuh dan berat sehingga gaya angkat air semakin mengurangi kuat geser tanah. Nilai FK hasil perhitungan metode FEM dan LEM menghasilkan klasifikasi keamanan yang sebagian besar sama. ===================================================================================================== ‘SS’ Embankment has soft clay as its primary soil layer, along with clay and limestone (boulders and compacted ‘tanah pedel’) as its pile on top. The embankment has the potential to collapse due to critical conditions such as soft soil layers or the ability of water to seep into soil pores and reduces its soil strength, brings this research goal to do seepage and slope stability analysis on different water levels. The soil parameters for each layer results from the soil parameter analysis, the seepage analysis is done by defining the volumetric water content (VWC) and hydraulic permeability (k) functions, and the slope stability analysis is done based on the finite element method (FEM). Four variations of water levels are used, which are on the elevation of +0, +1.5, +3, and +4.5 meter. The results of seepage analysis are seepage patterns and flux values. As the water level rises, there are more equipotential lines and the spaces get tighter, the phreatic line gets steeper, and flux values increase. Water flows are present on both the primary soil layer and embankment pile, but the flux value shown on the embankment pile is much higher because limestone and 'tanah pedel' are more capable to drain water out if compared to clay – which is less permeable. That also explains how seepage on clay is not that significant. Water affects slope's stability in different ways, depending on the water level elevations: if it is relatively low (+0, +1.5 m), the critical slip surface is located on the left slope, because the water weight is not heavy enough to create a resistance towards the sliding force, which is shown by the increasing FS value and shorter total displacement as the water level gets higher. In contrary to that, if the water level is relatively high (+2.7, +3, +4.5 m), the critical slip surface is located on the right slope, because the water weight makes the soil becomes more saturated and heavy, so that the water's lifting force tends to reduce the soil's strength until the slope becomes unstable. FS values resulting from FEM and LEM methods are quite different, but are mostly classified as 'Safe Slope'.

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: Faktor Keamanan, Ketinggian Muka Air, Perpindahan Total, Rembesan, Stabilitas Lereng, Safety Factor, Seepage, Stability, Total Displacement, Water Level
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA169.5 Failure analysis
T Technology > TA Engineering (General). Civil engineering (General) > TA347 Finite Element Method
T Technology > TA Engineering (General). Civil engineering (General) > TA749 Soil stabilization
T Technology > TC Hydraulic engineering. Ocean engineering > TC424 Water levels
Divisions: Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis
Depositing User: Amanda Safira
Date Deposited: 23 Aug 2021 08:01
Last Modified: 23 Aug 2021 08:01
URI: https://repository.its.ac.id/id/eprint/89471

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