Temporal scour evolution at bridge piers: effect of wood debris roughness and porosity

Figures & data

Figure 1 Debris accumulation at bridge piers of Arno River in Pisa, Italy

Table 1 Sediment characteristics of the tested material

Material	d 16 (mm)	d 50 (mm)	d 84 (mm)	σ	ϕ (°)	ϕ′ (°)	Δ
S1	0.9	1.0	1.3	1.2	31	36	1.44

Figure 2 Tested debris accumulation of different roughness (a) type a: impervious parallel disposition, (b) type b: impervious quasi-parallel disposition, (c) type c: pervious accumulation with metal cage, (d) type d: pervious random disposition, (e) type e: smooth impervious accumulation, (f) type f: pervious quasi-parallel disposition

Table 2 Geometric characteristics of tested debris accumulation

Type	n d	d f (cm)	d d (cm)	l d (cm)	ϵ (cm)
a	0	1.06	17	7.5	1.31
b	0	0.63	17	7.5	0.80
c	0.7	0.80^a	17	7.5	1.04
d	0.6	0.63	17	7.5	0.89
e	0	0	17	7.5	0
f	0.7	0.63	17	7.5	0.82
^aActual log diameter inside metal cage d f  = 0.63 cm.

Figure 3 Sketch with rough debris accumulation (a) top view, (b) frontal view, (c) side view and (d) roughness definitions

Figure 4 Test with rough debris accumulation (d _f /D = 0.21, h/D = 5.67, U/U _c  = 1): (a) downstream view, (b) side view with scour formation

Figure 5 Non-dimensional scour evolution for various roughness conditions for (•) tests without accumulation, (□) d _f /D = 0, n _d  = 0; (○) d _f /D = 0.21 n _d  = 0; (▵) d _f /D = 0.35 and n _d  = 0; (*) d _f /D = 0.21 and n _d  = 0.6; (+) d _f /D = 0.21 and n _d  = 0.7

Figure 6 Temporal scour evolution for U/U _c  = 0.83, ΔA = 12.1 and (a) h/D = 2.67, (b) h/D = 5.67

Figure 7 Effect of accumulation roughness d _f /D on ξ for various test conditions

Figure 8 Effect of accumulation porosity on scour evolution for h/D = 2.67 and d _f /D = 0.21 for (a) U/U _c  = 0.67, (b) U/U _c  = 0.84

Figure 9 Effect of accumulation porosity on ξ for various accumulation porosities and d _f /D = 0.21

Figure 10 Curve ξ(U/U _c ) for 2.67 < h/D < 5.67 and 5.4 < ΔA < 5.7, (▪) data, (―) regression line, and 2.67 < h/D < 5.67 and ΔA = 12.1, (▵) data, (––) regression line

Figure 11 Dependence of ξ from the flow intensity and blockage ratio (R ² = 0.73) for (♦) h/D = 2.67 and ΔA = 5.7, (⋄) h/D = 2.67 and ΔA  =  12.1, (•) h/D = 5.67 and ΔA = 5.4, (○) h/D = 5.67 and ΔA = 12.1

Figure 12 Dependence of ξ(U/U _c ΔÃ ^0.4) for (♦) h/D = 2.67 and ΔA = 5.7, (⋄) h/D = 2.67 and ΔA = 12.1, (•) h/D = 5.67 and ΔA = 5.4, (○) h/D = 5.67 and ΔA = 12.1

Figure 13 Comparison between measured ξ data and data calculated from Eq. (4). Symbols as in Fig. 12 for (–) type c data with 0.67 < U/U _c  < 1, 2.67 < h/D < 5.67, 5.4 < ΔA < 12.1, d _f /D = 0.26. (―) Perfect agreement, (––) ±25% deviation

Figure 14 Comparison between measured and calculated non-dimensional scour depths (Eq. 4) for various roughness and (□) d _f /D = 0, n _d  = 0; (○) d _f /D = 0.21, n _d  = 0; (▵) d _f /D = 0.35, n _d  = 0; (*) d _f /D = 0.21, n _d  = 0.6; (+) d _f /D = 0.21, n _d  = 0.7. (―) Perfect agreement and (––) ±25% deviation

Figure 15 Non-dimensional end scour z/D contour lines for U/U _c  = 1, h/D = 5.67, and (···) ΔA = 0 and U/U _c  = 1, h/D = 5.67, (―) ΔA = 12.1, (––) symmetry axis

Figure 16 Non-dimensional scour hole profile z/ž _max (x/x _max ) for 0.83 < U/U _c  < 0.84 and ΔA = 12.1

Figure 17 Non-dimensional scour profiles z/ž _max (x/x _max ) for h/D = 2.67, d _f /D = 0.21 and (a) U/U _c  = 0.67 and (b) U/U _c  = 0.84

Figure 18 Non-dimensional scour profiles z/ž _max (x/x _max ) for h/D = 5.67, d _f /D = 0, ΔA = 12.1 and 0.67 < U/U _c  < 1