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.

Yeraltý suyu akýmý etkisinde 45 derecelik þevde oluþan kumlu týn toprak erozyonunun deneysel incelenmesi

Yeraltý suyu akýmlarý doðal þevlerde toprak kaymasýna; toprak dolgu þevlerde ve barajlarda da sýð ve derin kayma yüzeyli göçmelere yol açan erozyonun baþlýca etkeni olabilmektedir. Bu çalýþmada, yeraltý suyu akýmý kaynaklý erozyon mekanizmalarý kumlu týn toprak kullanýlarak inþa edilmiþ üç-boyutlu fiziksel þev modeli ile incelenmiþtir. Bu amaçla, laboratuvarda 100 cm uzunluðunda, 50 cm geniþliðinde ve 60 cm yüksekliðinde bir erozyon kanalý inþa edilmiþtir. Homojen bir kumlu týn fiziksel modeli elde edebilmek için 45 derecelik yüzey açýsýnda sahip olan þev 2.5 cm yüksekliðinde basamaklar halinde kontrollü olarak sýkýþtýrýlmýþtýr. Yeraltý suyu erozyon kanalýnýn bir tarafýnda bulunan su haznesinde uygulanan 50 cm-su piyezometrik yük altýnda oluþturulmuþtur. Su haznesinden (memba) akýþa geçen yeraltý suyu erozyon kanalýnýn diðer tarafýndaki þev yüzeyinden (mansap) sýzma suyu olarak çýkýþ yapmýþtýr. Toprak partikülleri doygun durumdaki þev yüzeyinden çýkýþ yapan sýzma suyu tarafýndan sürüklenmiþtir. Sýzma suyu erozyonunun oluþturduðu oyuk deney süresince memba kesimine doðru toprak kaymalarý ile ilerlemiþ ve yüksekliði deney sonunda þev kretine kadar ulaþmýþtýr. Þev erozyonunun kararlý akým durumundaki boþluk-suyu basýnçlarýna bir etkisi olmamýþtýr.