Rail ballast is a rockfill construction that serves to bind sleepers and rail which distributes trainload to ground. The function of rail ballast is vital to the quality and strength of the rail track, but are prone to overtopping. The relationship between overtopping high and scouring has been investigated, as well as the effect of the high external prevention structure against the length of scouring. This study focuses on the effectiveness of external prevention structure at downstream in its ability to dampen and reduce the length of scouring due to overtopping by the mean the physical model. This research simulates the scouring prevention structure at downstream of ballast with several variations of type (T) and structures distance (L) so that the most effective structure is obtained, i.e. the structure which can maximum reduce the length of scouring. From the research, the most effective structure is the Type T1 at L1 distance. The modeling was carried out at the Hydraulic Laboratory of Civil Engineering Diponegoro University, with the prototype of the Mangkang-Semarang Railway KM.12 Indonesia, with the scale of 1: 5. The structure types which are simulated consist of T, T1 and T2 with the variation of structure distance L1 = 40 cm and L2 = 60 cm from downstream of toe ballast. The results of this study can be utilized by railway operator as a safety measure and especially against the danger of scouring due to flooding.
Concrete-faced rockfill dam (CFRD) has a similar weakness to other types of dams, namely deformation. Surface movement monuments can be used to monitor the deformation that occurs on the surface of the dam. Analysis of the monument's measurement data can show settlement and displacement trends that are closely related to the deformation of the dam itself. In this research, the monuments measurement data are compared to acceptance criteria from ICOLD, Sowers, Clements, Fell, and the Ministry of Public Works and Housing as outlined in the Guidelines for The Design and Construction of Concrete Membrane Stone Backfill Dams. This study aims to analyze data from surface movement monuments to determine the settlement and displacement of the dam based on the criteria of deformation. According to the obtained result, the first segment of surface monuments settlement values ranged from 0.028 to 0.165%, which meet the majority of the criteria. In addition, displacement values at the first segment of surface movement monuments were within 0.022 – 0.071%, which meets the ICOLD and Clements criteria. Meanwhile, for the second to fourth segments of surface movement monuments, settlement values of 0.007 – 0.102% were obtained, which still conform to the ICOLD and Fell criteria.
Kabupaten Garut khususnya Kawasan Kota Garut merupakan daerah dengan potensi bencana banjir yang tinggi. Kawasan Garut masih dinyatakan sebagai daerah rawan bencana. Hal tersebut berdasarkan hasil laporan dari Badan Penanggulangan Bencana Daerah (BPBD) Kabupaten Garut. Kawasan Kota Garut dilalui oleh Sungai Cimanuk yang berhulu di Pegunungan Mandalagiri di Kabupaten Garut mengalir ke dan bermuara di Laut Jawa di Kabupaten Indramayu. Pada tanggal 21 September 2016, Garut mengalami banjir bandang yang banyak menyebabkan korban jiwa. Banjir yang menimpa Kota Garut disebabkan oleh buruknya kondisi DAS Cimanuk, dikarenakan alih fungsi tata guna lahan. Selain upaya struktural, kerusakan dan kerugian dapat diminimalisir dengan upaya nonstruktural yaitu peringatan dini banjir. Peringatan dini banjir pada penelitian ini melakukan analisis banjir menggunakan pemodelan hidrologi dan hidrolika, dimana analisis hidrologi dilakukan di DAS Cimanuk Hulu mulai dari Kecamatan Cikajang Kabupaten Garut, hingga batas daerah genangan Waduk Jatigede di Kecamatan Wado Kabupaten Sumedang. Analisis hidrolika dilakukan mulai Bendung Cimanuk di Kecamatan Bayongbong hingga Bendung Copong di Kecamatan Garut Kota. Hasil analisis berdasarkan kala ulang 2, 5, 10, 25, 50 dan 100 tahun menunjukan bahwa debit banjir Q5, Q10, Q25, Q50 dan Q100 berpotensi menimbulkan bencana banjir di 9 desa atau 6 kecamatan yaitu Kecamatan Bayongbong, Cisurupan, Cilawu, Garut Kota, Tarogong dan Banyuresmi. Waktu tempuh desa yang berada di luar Kawasan Kota Garut adalah Desa Bayongbong dan Desa Cilea di Kecamatan Bayongbong yaitu 0.1 jam (6 menit) jika banjir terjadi dengan Q ≥ Q50 tahun. Untuk desa yang berada di dalam Kawasan Kota Garut adalah Desa Sukakarya dan Desa Cisurupan di Kecamatan Bayongbong, yaitu 1.5 jam (90 menit) jika banjir terjadi dengan Q ≥ Q50 dan Q100 tahun. Warga mulai evakuasi saat status level peringatan dini menunjukkan peralihan dari level Siaga ke level Awas.
AbstrakDalam penelitian pemodelan, perumusan korelasi antara satu variabel dengan kelompok variabel lain dapat diselesaikan dengan analisis dimensi atau statistik. Analisis dimensi dalam hal tertentu akan lebih mudah dan relatif cepat untuk mengetahui hasilnya. Ada beberapa metode analisis dimensi yang sering digunakan, antara lain Metode Buckingham, Indicial, dan matrix. Tulisan berikut akan menggunakan analisis dimensi metoda Buckingham's untuk menentukan korelasi konsentrasi sedimen yang tergerus (C) dan kelompok variabel lain (H w , g, ρ w, Q w, H s , d s , ρ s , v) pada model penggelontoran sedimen. Berikutnya akan dapat diketahui korelasi konsentrasi sedimen maksimum hasil penggelontoran terhadap tinggi muka air hulu pada setiap tebal sedimen (d) yang telah mengendap. Pemodelan dengan skala 1:66,67, menggunakan sedimen tiruan serbuk batubara. Tebal sedimen yang mengendap diasumsikan 1,5; 2,25; 3,00; 3,75; 4,50 cm. Pengukuran konsentrasi yang tergelontor pada saat setiap muka air turun 1,50 cm dari tinggi muka air awal 13,90 cm. Hasil analisis didapat korelasi: C /ρ s = ƒ( Q w .v / H 3 w . ɡ), dan konsentrasi sedimen maksimum hasil penggelontoran setiap tebal endapan didapat pada ketinggian muka air : H w = 10,58 H s -0,12 H w Kata-kata Kunci: Analisis dimensi, Buckingham, Korelasi antara variabel, Konsentrasi sedimen. Abstract In the modeling research, the correlation formulation between one variable to a group of other variables can be solved by dimensional analysis or statistics. Dimensional analysis would be easy and relatively quick to obtain results in the certain cases. There are several methods of analysis dimensions that are often used, among other methods are Buckingham's, Indicial, and matrix. The following article will use the dimensional analysis Buckingham's method to determine the correlation of flushed sediment concentration (C) and a group of other variables (H W , g , ρ w , Q W , H s , d s , ρ s , v) in the flushed sediment modeling. The next step its will be known correlation maximum concentration of sediment flushed results against upstream water level at each sediment thickness (d) which has been deposited. Modeling scale of 1 : 66.67, use sediment artificial with coal dust. The thickness of sediment that settles at the assumed 1.5 ; 2.25 ; 3.00 ; 3.75 ; 4.50 cm. The flushed sediment concentration measurements were conducted during the upstream water level every drop of 1.50 cm, from the initial water level 13.90 cm. The results of the analysis correlation can be obtained : C /ρ s = ƒ( Q w .v / H 3 w . ɡ), and the maximum concentration of flushed every sediment thickness can be obtained at water level : H w = 10,58 H s -0,12 H w
Abstrak Tataguna lahan di Sub Daerah Aliran Sungai (DAS)Banjaran
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