Fundamentals of Geotechnical Engineering (MindTap Course List)
5th Edition
ISBN: 9781305635180
Author: Braja M. Das, Nagaratnam Sivakugan
Publisher: Cengage Learning
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Question
Chapter 7, Problem 7.2P
(a)
To determine
Find the flow rate beneath the dam (q).
(b)
To determine
Find the rise of water level.
(c)
To determine
Find the pore water pressure at the tip of the sheet pile.
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EXAMPLE 8.2
A flow net for flow around a single row of sheet piles in a permeable soil layer is
shown in Figure 8.7. Given that k, = k = k = 5 x 10-³ cm/s, determine
a. How high (above the ground surface) the water will rise if piezometers are
placed at points a and b
b. The total rate of seepage through the permeable layer per unit length
c. The approximate average hydraulic gradient at c
Water level
Ground surface
Scale
5 m
5.6 m
2.2 m
Water table
Flow channel 1
Flow channel 2
Flow channel 3
Impervious layer
FIGURE 8.7 Flow net for seepage around a single row of sheet piles
b
1/
b
= 1
= 1
1 1
T
0.38
Nf : 5
Nd=16
25 m
Question 4
Seepage take place beneath a concrete dam as shown in Figure 2. The soil beneath the dam is a
fine silty sand with hydraulic conductivity of 4.2 x 10“cm/s and saturated unit weight of 19.5
kN/m³.
6 m
1.75 m:
1) Find the rate of seepage beneath the dam in m³/day/m
2) If a standpipe piezometer is installed at the tip of the sheet pile, how high will the water
rise?
Impervious stratum
For the figure shown below, if the area of the tank is 0.5 m² and hydraulic
conductivity of sand is 0.1 cm/sec.
a. What is the magnitude and direction of the rate of seepage?
b. If the value of h=1.2m, will boiling occur? Why?
c. What should be the value of "h" to cause boiling?
Outflow
Inflow
1m
2m
A
B
h = 1.2m
e = 0.55
G=2.68
Valve (open)
Chapter 7 Solutions
Fundamentals of Geotechnical Engineering (MindTap Course List)
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- Water flows at the rate of 4 x 10-2 cm³/s through a cylindrical sand sample with a diameter of 10 cm and a coefficient of permeability of 8 x 10-4 cm/s. In Case I, the flow is in upward direction, as shown in Figure 3a. In Case II, the flow is in downward direction, as shown in Figure 3b. For each case: a). The total head loss through the sand. b). The total stress, the effective stress and the PWP at points A, B and C if the soil has a saturated unit weight of 19 kN/m³. a). Case I 9 cm 12 cm 12 cm ▼ C B A D = 10 cm 9 cm 12 cm 12 cm b). Case II Figure 3. Seepage through soil ▼ с B A ? D = 10 cmarrow_forwardb) For h 150 mm, 175 ml of water was collected in 15 minutes. Find the 15% followings. 4) i) Soil permeability. ii) Effective vertical stress at A which is a point exists 220 mm below the top of the sample. See the flow net shown in Fig. Q4 for analysing the seepage beneath the concrete dam. 5 m H=3m 08m 12 m R 3 m 교 Datum TH=0 m Fig. Q 4 a) Compute the flow rate through the soil beneath the concrete dam. Consider 10% the soil permeability as 3.2 * 104cm/s. b) Compute the pore water pressures at points A, B, and C. 15% End of Question Paper 3arrow_forwardRefer to Figure 7.24. The following data were collected during the field permeability measurement of a confined aquifer using a pumping test. Determine the hydraulic conductivity of the permeable layer. Use Eq. (7.49). Thickness of the aquifer, H = 4.5 m Piezometric level and radial distance of the first observation well: h1 = 2.9 m; r1 = 17.8 m Piezometric level and radial distance of the second observation well: h2 = 1.8 m; r2 = 8.1 m Rate of discharge from pumping, q = 0.5 m3/minarrow_forward
- (b) Seepage takes place beneath a concrete dam as shown in Figure Q3. The soil beneath the dam is fine silty sand with hydraulic conductivity (permeability) of 4.2 x 10- cm/sec and saturated unit weight of 19.5 kN/m³. i. Calculate the rate of seepage beneath the dam in m/day/m. ii. If a standpipe (piezometer) is installed at point A, how high will the water rise? i. Calculate the pore water pressure at point A. R1.75m Impervious stratum Figure Q3arrow_forwardQ.1. The figure below shows the flow net for seepage under a concrete dam. The is silty sand with coefficient of permeability of 4X104 cm/sec, a void ratio of 0.6 and specific gravity of 2.7. The height of water upstream is H=( 6+) (a) Determine the flow rate under the dam in m/day per m length of the dam. (b) Determine the water pressure distribution at the base of the dam. (Select 3 points under the base. Comment on your results. m (where X is your group number). (c) From (b), calculate the resultant uplift force and its location from the upstream face of the dam. Also, calculate the weight of the dam to prevent uplift using a factor of safety of 5. (d) What is the factor of safety against piping? Is the dam safe? (e) Calculate the total vertical overburden stress, pore water pressure and the effective vertical overburden stress at Points A and B. Comment on your results. H 17.5 m 1.25 m x B 4 m Impervious clayarrow_forwardj: A dam shown in Figure 1 retains 10 m of water. A sheet pile wall (cutoff curtain) on the upstream side, which is used to reduce seepage under the dam, penetrates 7 m into a 20.3 m-thick silty sand stratum. Below the silty sand, there is a thick deposit of practically impervious clay. The average hydraulic conductivity of the silty sand is 2x10 cm/s. Assume that the silty sand is homogeneous and isotropic. a) Draw the flow net under the dam. b) Calculate the flow rate, q. c) Determine the hydraulic gradient at exit path ED. 10 m A 20.3 m B 2.4 mt C 30.6 m -Sheet pile wall E k = 2 x 10 cm/s Clay (impervious) Harrow_forward
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- A dam section is shown in Figure 8.11a. The hydraulic conductivity of the permeable layer in the vertical and horizontal directions are 2.9×10^-2 mm/sand 4.6 ×10^−2 mm/s, respectively. Calculate the seepage loss of the dam in ft^3/day/ftarrow_forwardplease explain every steparrow_forward3 Seepage is occurring through the sandy layer underneath the concrete dam as shown in Figure 7.30. Concrete dam H₁ Seepage H₂ H₂ Sandy layer Impervious rock PXSXX2X L Figure 7.30 Given: upstream water level, H₁ = 16 m; downstream water level, H₂ = 2.3 m; thickness of the sandy layer, H, = 0.75 m; hydraulic conductivity of the sandy layer, k = 0.009 cm/sec; void ratio of sand, e = 0.8; and L = 45 m. Determine: a. Rate of seepage per unit length of the dam (in m³/hr/m) b. Seepage velocity c. Quantity of seepage per day if the dam is 350 m longarrow_forward
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