Yeraltı suyu akımı etkisinde 45 derecelik şevde oluşan kumlu tın toprak erozyonunun deneysel incelenmesi

Yeraltı suyu akımları doğal şevlerde toprak kaymasına; toprak dolgu şevlerde ve barajlarda da sığ ve derin kayma yüzeyli göçmelere yol açan erozyonun başlıca etkeni olabilmektedir. Bu çalışmada, yeraltı suyu akımı kaynaklı erozyon mekanizmaları kumlu tın toprak kullanılarak inşa edilmiş üç-boyutlu fiziksel şev modeli ile incelenmiştir. Bu amaçla, laboratuvarda 100 cm uzunluğunda, 50 cm genişliğinde ve 60 cm yüksekliğinde bir erozyon kanalı inşa edilmiştir. Homojen bir kumlu tın fiziksel modeli elde edebilmek için 45 derecelik yüzey açısında sahip olan şev 2.5 cm yüksekliğinde basamaklar halinde kontrollü olarak sıkıştırılmıştır. Yeraltı suyu erozyon kanalının bir tarafında bulunan su haznesinde uygulanan 50 cm-su piyezometrik yük altında oluşturulmuştur. Su haznesinden (memba) akışa geçen yeraltı suyu erozyon kanalının diğer tarafındaki şev yüzeyinden (mansap) sızma suyu olarak çıkış yapmıştır. Toprak partikülleri doygun durumdaki şev yüzeyinden çıkış yapan sızma suyu tarafından sürüklenmiştir. Sızma suyu erozyonunun oluşturduğu oyuk deney süresince memba kesimine doğru toprak kaymaları ile ilerlemiş ve yüksekliği deney sonunda şev kretine kadar ulaşmıştır. Şev erozyonunun kararlı akım durumundaki boşluk-suyu basınçlarına bir etkisi olmamıştır.

Anahtar Kelimeler:

Yeraltı suyu akımı, Sızma erozyonu, Erozyon kanalı, Sediment taşınımı

Experimental investigation of sandy loam soil erosion on a 45-degree slope under the effect of groundwater flow

Groundwater flow is considered as a major contributor for erosion that may result in landslides of natural hill slopes and shallow and deep-seated failures of engineered embankments. In this study, erosion mechanisms of a sandy loam slope due to groundwater flow were investigated using a three-dimensional physical model. For this purpose, an erosion flume with dimensions of 100 cm long, 50 cm wide and 60 cm high was constructed in the laboratory. The physical slope model with a 45 degree slope angle was compacted in 2.5 cm lifts to obtain a homogenous sandy loam slope. The groundwater flow was generated under a piezometric head of 50 cm-water that was applied at the water reservoir located at one end of the erosion flume. The groundwater flow directed from the water reservoir (upstream) seeped out of the slope surface at the other end of the flume (downstream). Soil particles became entrained in the seepage flow that exfiltrated the slope surface at the saturated zone. The extent of the cavity due to seepage erosion progressed upstream via sapping during the experiment and the height of the cavity reached the crest of the slope at the end of the experiment. Seepage erosion did not affect the steady-state pore-water pressures.

Keywords:

Groundwater flow, Seepage erosion, Erosion flume, Sediment transport,

PDF

___

C. Orman ve Su İşleri Bakanlığı. “Erozyonla Mücadele Eylem Planı 2013-2017”. http://www.cem.gov.tr/ erozyon/Files/yayinlarimiz/EROZYON%20EYLEM.pdf (20.12.2017).
Aksoy H, Kavvas ML. “A review of hillslope and watershed scale erosion and sediment transport models”. Catena, 64(2-3), 247-271, 2005.
Tóth J. “Groundwater discharge: A common generator of diverse geologic and morphologic phenomena”. International Association of Scientific Hydrology. Bulletin (Hydrological Sciences Journal), 16(1), 7-24, 1971.
Liu L, Liu QJ, Yu XX. “The influences of row grade, ridge height and field slope on the seepage hydraulics of row sideslopes in contour ridge systems”. Catena, 147, 686-694, 2016.
Bryan RB. “Soil erodibility and processes of water erosion on hillslope”. Geomorphology, 32, 385-415, 2000.
Regmi RK, Jung K, Nakagawa H, Kang J. “Study on mechanism of retrogressive slope failure using artificial rainfall”. Catena, 122, 27-41, 2014.
Aksoy H, Unal NE, Cokgor S, Gedikli A, Yoon J, Koca K, Inci SB, Eris E. “A rainfall simulator for laboratory-scale assessment of rainfall-runoff-sediment transport processes over a two-dimensional flume”. Catena, 98, 63-72, 2012.
Aksoy H, Unal NE, Cokgor S, Gedikli A, Yoon J, Koca K, Inci SB, Eris E, Pak G. “Laboratory experiments of sediment transport from bare soil with a rill”. Hydrological Sciences Journal, 58(7), 1505-1518, 2013.
Römkens MJM, Helming K, Prasad SN. “Soil erosion under different rainfall intensities, surface roughness, and soil water regimes”. Catena, 46, 103-123, 2001.
Rockwell DL. “The influence of groundwater on surface flow erosion processes during a rainstorm”. Earth Surface Processes and Landforms, 27, 495-514, 2002.
Rockwell DL. “Headcut erosive regimes influenced by groundwater on disturbed agricultural soils”. Journal of Environmental Management, 92, 290-299, 2011.
Fox GA, Wilson GV, Periketi RK, Cullum RF. “Sediment transport model for seepage erosion of streambank sediment”. Journal of Hydrologic Engineering, 11(6), 603-611, 2006.
Fox GA, Wilson GV, Simon A, Langendoen E, Akay O, Fuchs JW. “Measuring streambank erosion due to ground water seepage: correlation to bank pore water pressure, precipitation and stream stage”. Earth Surface Processes and Landforms, 32, 1558-1573, 2007.
Wilson GV, Periketi RK, Fox GA, Dabney SM, Shields FD, Cullum RF. “Soil properties controlling seepage erosion contributions to streambank failure”. Earth Surface Processes and Landforms, 32, 447-459, 2007.
Wilson CG, Kuhnle RA, Bosch DD, Steiner JL, Starks PJ, Tomer MD, Wilson GV. “Quantifying relative contributions from sediment sources in conservation effects assessment project watersheds”. Journal of Soil and Water Conservation, 63(6), 523-532, 2008.
Akay O, Özer AT, Yüzer YL, Bilen M, Bozkır Ş. “Sızma erozyonunun laboratuvar ölçeğinde değerlendirilmesinde üç-boyutlu lazer tarama”. 9. Ulusal Hidroloji Kongresi, Diyarbakır, Türkiye, 4-6 Ekim, 2017.
Rinaldi M, Mengoni B, Luppi L, Darby SE, Mosselman E. “Numerical simulation of hydrodynamics and bank erosion in a river bend”. Water Resources Research, 44, 1-17, 2008.
Chen CH, Hsieh TY, Yang JC. “Investigating effect of water level variation and surface tension crack on riverbank stability”. Journal of Hydro-environment Research, 15, 41-53, 2017.
Fox GA, Wilson GV. “The role of subsurface flow in hillslope and stream bank erosion: A review”. Soil Science Society of America, 74(3), 717-733, 2010.
Lourenço SDN, Sassa K, Fukuoka H. “Failure process and hydrologic response of a two layer physical model: Implications for rainfall-induced landslides”. Geomorphology, 73, 115-130, 2006.
Fox GA, Chu-Agor ML, Wilson GV. “Erosion of noncohesive sediment by ground water seepage: lysimeter experiments and stability modeling”. Soil Science Society of America Journal, 71, 1822-1830, 2007.
Chu-Agor ML, Fox GA, Cancienne R, Wilson GV. “Seepage caused tension failures and erosion undercutting of hillslopes”. Journal of Hydrology, 359, 247-259, 2008.
Chu-Agor ML, Fox GA, Wilson GV. “Empirical sediment transport function predicting seepage erosion undercutting for cohesive bank failure prediction”. Journal of Hydrology, 377, 155-164, 2009.
Lu Y, Lu Y, Chiew Y. “Incipient motion of cohesionless sediments on riverbanks with ground water injection”. International Journal of Sediment Research, 27, 111-119, 2012.
Akay O, Özer AT, Fox GA. “Experimental investigation of failure mechanism of expanded polystyrene block geofoam slope system under seepage”. 5th European Geosynthetics Congress (EuroGeo5), Valencia, Spain, 13-17 September 2012.
Akay O, Özer AT, Fox GA, Bartlett SF, Arellano D. “Behavior of sandy slopes remediated by EPS-block geofoam under seepage flow”. Geotextiles and Geomembranes, 37, 81-98, 2013.
Akay O, Özer AT, Fox GA. “Use of EPS block geofoam with internal drainage for sandy slopes subjected to seepage flow”. 10th International Conference on Geosynthetics, Berlin, Germany, 21-25 September 2014.
Akay O, Özer AT, Fox GA. “Assessment of EPS block geofoam with internal drainage for sandy slopes subjected to seepage flow”. Geosynthetics International, 21(6), 364-376, 2014.
Akay O, Özer AT, Fox GA, Wilson GV. “Behavior of fiber-reinforced sandy slopes under seepage”. ASCE EWRI World Environmental and Water Resources Congress, West Palm Beach, Florida, USA, 22-26 May 2016.
Akay O. “Slope stabilisation using EPS block geofoam with internal drainage system”. Geosynthetics International, 23(1), 9-22, 2016.
Özer AT, Akay O, Fox GA, Bartlett SF, Arellano D. “A new method for remediation of sandy slopes susceptible to seepage flow using EPS-block geofoam”. Geotextiles and Geomembranes, 42(2), 166-180, 2014.
Özer AT, Akay O. “Use of interlocked EPS block geofoam for sandy slopes subjected to seepage flow”. 10th International Conference on Geosynthetics, Berlin, Germany, 21-25 September 2014.
Özer AT. “Laboratory study on the use of EPS-block geofoam for embankment widening”. Geosynthetics International, 23(2), 71-85, 2016.