The Effect of Shear Stress on Armor Layer Thickness Under Steady Uniform Flow

Cahyono Ikhsan

Abstract


The armor layer is essential for maintaining stability on riverbed surfaces. This layer forms when bedload sediment moves until the bed's surface erodes, resulting in a stable layer that reaches an equilibrium state where no further sediment transport occurs. Therefore, the objective of this study is to investigate the effect of grain size and shear stress on armor layer thickness using evenly mixed sand and gravel with five different grain size variations. The research methodology consists of laboratory experiments and optimization analysis. The main instrument used is a sediment-recirculating flume constructed from plexiglass, measuring 10, 0.60, and 0.45 m in length, width, and height, respectively. Bed slope varies across gradients of 1%, 1.4%, 1.8%, 2.2%, and 2.6%. The constant flow rate is set at capacities of 25 l/s, 30 l/s, 40 l/s, and 45 l/s. The results show the consistent behavior of the channel bed surface under different flow rate variations. Meanwhile, the variables affecting armor layer thickness are the uniformity coefficient (Cu), the difference in shear stress on the bed surface (τo-τc)/τc), beds shear stress, and the critical shear stress of the sediment grain. The primary novelty of this research is a formula to determine armor layer thickness. It showed that both shear stress and the proportion of sand-to-gravel materials play significant roles in the armoring process and subsequent changes in the riverbed.

 

Doi: 10.28991/CEJ-2023-09-11-012

Full Text: PDF


Keywords


Armor Layer Thickness; Bed Materials Grain Size; Flow Shear Stress; Flume.

References


Hunziker, R. P., & Jaeggi, M. N. R. (2002). Grain Sorting Processes. Journal of Hydraulic Engineering, 128(12), 1060–1068. doi:10.1061/(asce)0733-9429(2002)128:12(1060).

Vázquez-Tarrío, D., Piégay, H., & Menéndez-Duarte, R. (2020). Textural signatures of sediment supply in gravel-bed rivers: Revisiting the armour ratio. Earth-Science Reviews, 207. doi:10.1016/j.earscirev.2020.103211.

Cooper, J. R., & Tait, S. J. (2009). Water-worked gravel beds in laboratory flumes - A natural analogue? Earth Surface Processes and Landforms, 34(3), 384–397. doi:10.1002/esp.1743.

Yager, E. M., Kenworthy, M., & Monsalve, A. (2015). Taking the river inside: Fundamental advances from laboratory experiments in measuring and understanding bedload transport processes. Geomorphology, 244, 21–32. doi:10.1016/j.geomorph.2015.04.002.

Recking, A. (2013). Simple Method for Calculating Reach-Averaged Bed-Load Transport. Journal of Hydraulic Engineering, 139(1), 70–75. doi:10.1061/(asce)hy.1943-7900.0000653.

Heays, K. G., Friedrich, H., & Melville, B. W. (2014). Laboratory study of gravel-bed cluster formation and disintegration. Water Resources Research, 50(3), 2227–2241. doi:10.1002/2013WR014208.

Ancey, C. (2020). Bedload transport: a walk between randomness and determinism. Part 1. The state of the art. Journal of Hydraulic Research, 58(1), 1–17. doi:10.1080/00221686.2019.1702594.

Wang, L., Wang, D., Cuthbertson, A., Zhong, D., & Pender, G. (2021). Hysteretic Implications for Graded Bed Load Sediment Transport in Symmetrical Hydrograph Flows. Frontiers in Environmental Science, 9. doi:10.3389/fenvs.2021.800832.

Mrokowska, M. M., & Rowinski, P. M. (2019). Impact of unsteady flow events on bedload transport: A review of laboratory experiments. Water (Switzerland), 11(5). doi:10.3390/w11050907.

Negara, A. S., Ikhsan, C., Hadiani, Rr. R., & Purwana, Y. M. (2023). Effect of bed shear stress on the mobile armor layer at the riverbed. IOP Conference Series: Earth and Environmental Science, 1195(1), 012057. doi:10.1088/1755-1315/1195/1/012057.

Chin, C. O., Melville, B. W., & Raudkivi, A. J. (1994). Streambed Armoring. Journal of Hydraulic Engineering, 120(8), 899–918. doi:10.1061/(asce)0733-9429(1994)120:8(899).

Wilcock, P. R., & DeTemple, B. T. (2005). Persistence of armor layers in gravel-bed streams. Geophysical Research Letters, 32(8), 1–4. doi:10.1029/2004GL021772.

Aberle, J., & Nikora, V. (2006). Statistical properties of armored gravel bed surfaces. Water Resources Research, 42(11), 1-11. doi:10.1029/2005WR004674.

Zhang, S., Zhu, Z., Peng, J., He, L., & Chen, D. (2021). Laboratory study on the evolution of gravel-bed surfaces in bed armoring processes. Journal of Hydrology, 597. doi:10.1016/j.jhydrol.2020.125751.

Marion, A., & Fraccarollo, L. (1997). Experimental investigation of mobile armoring development. Water Resources Research, 33(6), 1447–1453. doi:10.1029/97WR00705.

Elgueta-Astaburuaga, M. A., & Hassan, M. A. (2019). Sediment storage, partial transport, and the evolution of an experimental gravel bed under changing sediment supply regimes. Geomorphology, 330, 1–12. doi:10.1016/j.geomorph.2018.12.018.

Church, M., Hassan, M. A., & Wolcott, J. F. (1998). Stabilizing self-organized structures in gravel-bed stream channels: Field and experimental observations. Water Resources Research, 34(11), 3169–3179. doi:10.1029/98WR00484.

Ikhsan, C., Rahajo, A., & Legono, D. (2014). The formation of static armour layer. International Journal of Civil & Environmental Engineering, 14, 19-23.

Mao, L., Cooper, J. R., & Frostick, L. E. (2011). Grain size and topographical differences between static and mobile armour layers. Earth Surface Processes and Landforms, 36(10), 1321–1334. doi:10.1002/esp.2156.

Spiller, S. M., Rüther, N., & Friedrich, H. (2015). Dynamic lift on an artificial static armor layer during highly unsteady open channel flow. Water (Switzerland), 7(9), 4951–4970. doi:10.3390/w7094951.

Curran, J. C., & Waters, K. A. (2014). The importance of bed sediment sand content for the structure of a static armor layer in a gravel bed river. Journal of Geophysical Research: Earth Surface, 119(7), 1484–1497. doi:10.1002/2014JF003143.

Ikhsan, C., Raharjo, A. P., Legono, D., & Kironoto, B. A. (2020). Effek Tegangan Geser dan Keseragaman Butiran terhadap Tebal Armour Layer pada Kondisi Statis di Dasar Saluran. Jurnal Teknik Sipil, 27(3), 247. doi:10.5614/jts.2020.27.3.6. (In Indonesian).

Almedeij, J. H. (2002). Bedload transport in gravel-bed streams under a wide range of Shields stresses. Ph.D. Thesis, Virginia Tech, Blacksburg, United States.

Powell, D. M., Ockelford, A., Rice, S. P., Hillier, J. K., Nguyen, T., Reid, I., Tate, N. J., & Ackerley, D. (2016). Structural properties of mobile armors formed at different flow strengths in gravel-bed rivers. Journal of Geophysical Research: Earth Surface, 121(8), 1494–1515. doi:10.1002/2015JF003794.

Marion, A., Tait, S. J., & McEwan, I. K. (2003). Analysis of small-scale gravel bed topography during armoring. Water Resources Research, 39(12). doi:10.1029/2003WR002367.

Wang, Q., Pan, Y., Yang, K., & Nie, R. (2020). Structural properties of the static armor during formation and reestablishment in gravel-bed rivers. Water (Switzerland), 12(7). doi:10.3390/w12071845.

Graf, W. H., & Altinakar, M. S. (1998). Fluvial hydraulics: Flow and transport processes in channels of simple geometry. Wiley, New York, United States.

26-Lisle, T. E., & Madej, M. A. (1992). Spatial variation in armouring in a channel with high sediment supply. Dynamics of gravel-bed rivers, 277-293. John Wiley & Sons, Hoboken, United States.

Wilcock, P. R., Kenworthy, S. T., & Crowe, J. C. (2001). Experimental study of the transport of mixed sand and gravel. Water Resources Research, 37(12), 3349–3358. doi:10.1029/2001WR000683.

Vericat, D., Batalla, R. J., & Garcia, C. (2006). Breakup and reestablishment of the armour layer in a large gravel-bed river below dams: The lower Ebro. Geomorphology, 76(1–2), 122–136. doi:10.1016/j.geomorph.2005.10.005.

Viparelli, E., Gaeuman, D., Wilcock, P., & Parker, G. (2011). A model to predict the evolution of a gravel bed river under an imposed cyclic hydrograph and its application to the Trinity River. Water Resources Research, 47(2), 1-22. doi:10.1029/2010WR009164.

Bertin, S., & Friedrich, H. (2018). Effect of surface texture and structure on the development of stable fluvial armors. Geomorphology, 306, 64–79. doi:10.1016/j.geomorph.2018.01.013.

Berni, C., Perret, E., & Camenen, B. (2018). Characteristic time of sediment transport decrease in static armour formation. Geomorphology, 317, 1–9. doi:10.1016/j.geomorph.2018.04.004.

Ardiclioglu, M., Selenica, A., Ozdin, S., Kuriqi, A., & Genç, O. (2013, July). Investigation of average shear stress in natural stream. International Balkans Conference on Challenges of Civil Engineering (BCCCE), 19-21 May, 2011, Tirana, ALBANIA.

Te Chow, V., (1964). Applied Hydrology, International. McGraw-Hill, New York, United States.


Full Text: PDF

DOI: 10.28991/CEJ-2023-09-11-012

Refbacks

  • There are currently no refbacks.




Copyright (c) 2023 Cahyono Ikhsan

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
x
Message