Spatial and temporal progression of internal erosion in cohesionless soil

Abstract

Artículo de publicación ISIPermeameter tests were performed on four widely graded cohesionless soils, to study their susceptibility to internal erosion. Test specimens were reconstituted as a saturated slurry, consolidated, and then subjected to multi-stage seepage flow under increasing hydraulic gradient. The occurrence of internal instability is described qualitatively, from visual observations through the wall of the permeameter during a test and from post-test observations; it is also described quantitatively, from change of hydraulic gradient within the specimen and from axial displacement during a test. The results provide a novel insight into the spatial and temporal progression of seepage-induced internal instability. This insight yields an improved characterization of suffusion and suffosion in cohesionless soils, the progression of which appears governed by a critical combination of hydraulic gradient and effective stress.British Columbia Hydroelectric Power Authorit

Applying Empirical Methods to Assess the Internal Stability of Embankment Dam Cores of Glacial Till

“…Furthermore, Moffat et al [10] found that suffusion occurred as the "episodic migration of the finer fraction" with no change in volume but a "relatively small and slow change in local hydraulic conductivity".…”

“…These were the investigations by Lafleur and Nguyen [8], Wan [9], Moffat et al [10], Hunter et al [11], and Lilja et al [12], which all incorporated glacial till samples that were either related to, or directly sourced from, dam core zones or transitions.…”

“…However, few laboratory studies have been performed, and little data are available. Nonetheless, the internal stability of glacial tills has been investigated by Lafleur and Nguyen [8], Wan [9], Moffat et al [10], Hunter et al [11] and Lilja et al [12], who report that instability may indeed occur in glacial tills.…”

Experimental Investigation of Suffusion in Dam Core Soils of Glacial Till

“…Lafleur and Nguyen (2007) found that glacial tills with less than 12 % fines when scalped to D max ¼ 37.5 mm (fines, F #200 , is the amount of material <0.075 mm) were susceptible to suffusion, whereas higher content of fines were not; this agrees with the stable glacial till with 20 % fines (D max ¼ 9.5 mm) found by Wan (2006). However, tests performed by Moffat et al (2011) contradict this result: they observed internal instability in glacial soils with fines up to 30 % (D max ¼ 19 mm). In addition, Lilja et al (1998) reported internal instability in glacial tills with fines between 20 and 38 % (D max ¼ 63 mm).…”

“…A gradation that is internally unstable may be susceptible to suffusion (ICOLD 2013). Laboratory studies of suffusion on glacial till gradations are that by Wan (2006), Lafleur and Nguyen (2007), Moffat et al (2011), and Lilja et al (1998). Lafleur and Nguyen (2007) found that glacial tills with less than 12 % fines when scalped to D max ¼ 37.5 mm (fines, F #200 , is the amount of material <0.075 mm) were susceptible to suffusion, whereas higher content of fines were not; this agrees with the stable glacial till with 20 % fines (D max ¼ 9.5 mm) found by Wan (2006).…”