Kapasitas tampung check dam tipe tertutup dan tipe slit

SETIYAWATI, Endang, Prof. Ir. Djoko Legono, Ph.D

2008 | Tesis | S2 Teknik Sipil

Bencana alam akibat aliran sedimen sering terjadi pada daerah vulkanik maupun pada daerah non vulkanik. Bencana aliran sedimen mempunyai daya rusak yang besar dan merupakan salah satu bencana alam yang paling berbahaya. Salah satu alternatif pengendalian aliran debris yaitu dengan bangunan check dam. Check dam dikelompokkan menjadi dua, yaitu tipe terbuka dan tipe tertutup. Untuk mengkaji kapasitas tampung check dam tipe tertutup dan check dam tipe terbuka dalam hal tampungan mati (Vs), volume kontrol (Vc) dan tinggi endapan kontrol sedimen di hulu dam celah (Zs), maka dilakukan uji model. Uji model check dam dilakukan di Laboratorium Hidraulika Teknik Sipil dan Lingkungan UGM. Lebar model check dam 70 cm dimana lebar pelimpahnya 42 cm. Check dam tipe terbuka terdiri dari 4, 3, dan 2 slit, dengan lebar celah tetap 8 cm. Debit aliran yang dipakai adalah Q1 = 0.78ℓ/s, Q2 = 0.65ℓ/s dan Q3 = 0.52ℓ/s disesuaikan dengan kapasitas pompa yang ada. Kedalaman slit dimodifikasi dari 3 cm menjadi 5 cm. Tampungan mati uji model pada check dam tipe terbuka lebih kecil dari tipe tertutup. Hal ini sesuai dengan pendekatan teoritik. Perbedaan tampungan mati antara uji model dan pendekatan teoritik check dam tipe 4, 3 dan 2 slit berturut-turut adalah 0.50%, 12.87%, 20.77%, sedangkan untuk tipe tertutup adalah 0.17%. Volume kontrol uji model check dam tipe terbuka lebih besar dari tipe tertutup, hal ini berkebalikan dengan pendekatan teoritik. Perbedaan volume kontrol antara uji model dan pendekatan teoritik check dam tipe 4 slit adalah ΔVcQ1 = 94.09%, ΔVcQ2 = 95.34%, ΔVcQ3 = 96.63%; tipe 3 slit adalah ΔVcQ1= 94.33%, ΔVcQ2 = 95.56%, ΔVcQ3 = 96.58%; tipe 2 slit adalah ΔVcQ1= 93.76%, ΔVcQ2 = 95.20%, ΔVcQ3 = 96.47% dan tipe tertutup adalah ΔVcQ1= 57.95%, ΔVcQ2 = 59.01%, ΔVcQ3 = 57.88%. Dalam uji model maupun pendekatan teoritik, jumlah slit tidak mempengaruhi kapasitas tampung sedimennya.. Volume kontrol berdasarkan pendekatan teoritik dipengaruhi oleh Zs, jika ΔZs = 10.59% maka ΔVc = 22.3% dan jika ΔZs = 12.64% maka ΔVc = 26.85%, sedangkan dalam uji model, volume kontrol tidak dipengaruhi oleh Zs.

Natural disaster due to sediment/debris flow often occurs in volcanic area or non-volcanic area. Sediment/debris flow has a big destruction endangering human lifes and infrastructures along the river and for surroundings. One of many alternatives in controlling the debris flow is by constructing check dams. Check dams can be classified into two types, i.e. the open and closed types. To observe storage capacity of closed and open dam in the case of dead storage (Vs), control storage (Vc), and height of sediment control in the upstream of slit dams (Zs), the model testing was conducted. The model testing was conducted in the Hydraulic Laboratory, The department of Civil and Environmental Engineering, Gadjah Mada University. The check dam model is 70 long whose overflow section is 42 cm long. The open type check dam consists of 4, 3, and 2 slits, whose open width is kept constant at 8 cm. Flow rate was introduced into Q1 = 0.78ℓ/s, Q2 = 0.65ℓ/s and Q3 = 0.52ℓ/s in compliance with the pump capacity. The depth of the slits was modified from 3 into 5 cm. The dead storage in the model testing of open type dam was smaller than closed type dam. This condition was similar to the theorytical analysis. The difference volume of dead storage from model testing and theorytical analysis for 4, 3 and 2 slit types i.e. 0.50%, 12.87%, 20.77% whereas for closed type that was 0.17%. In open type dam, the control storage from theorytical analysis was bigger than model testing. This condition was different with the theorytical analysis. The difference volume of control storage from model testing and theorytical analysis for 4 slits i.e. ΔVcQ1 = 94.09%, ΔVcQ2 = 95.34%, ΔVcQ3 = 96.63%; for 3 slits i.e. ΔVcQ1= 94.33%, ΔVcQ2 = 95.56%, ΔVcQ3 = 96.58%; for 2 slits i.e. ΔVcQ1= 93.76%, ΔVcQ2 = 95.20%, ΔVcQ3 = 96.47% and for closed type i.e. ΔVcQ1= 57.95%, ΔVcQ2 = 59.01%, ΔVcQ3 = 57.88%. In the model testing and theorytical analysis, the number of slit was not influenced the sediment storage. Height of sediment control in the upstream of slit dams (Zs) in theorytical analysis has influence to control storage, if ΔZs 10.59% so ΔVc = 22.3%, and if ΔZs = 12.64%, so ΔVc = 26.85%. In the model testing, Zs was not influence to the control storage.

Kata Kunci : Check dam,Tampungan sedimen,Uji model fisik, check dam, sediment storage, physical model testing.