Principles of Geotechnical Engineering (MindTap Course List)
9th Edition
ISBN: 9781305970939
Author: Braja M. Das, Khaled Sobhan
Publisher: Cengage Learning
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Chapter 8, Problem 8.4P
To determine
Draw the flow net for flow through the permeable layer and calculate the seepage loss in
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Consider the hydraulic structure shown in the figure below. In the flow net for flow through the permeable layer, the number of flow channels is Nf
= 5 and the number of potential drops is Ng = 12 Calculate the seepage loss.
25 m
10 m
1.67 m
3.34 m
20 m
k = 0.002 cm/sec
1.67 m
1.67 m
Permeable layer
| Impermeable layer
Select the correct response:
7.21 m3/day/m
O 2.17 m/day/m
6.28 m3/day/m
O 6.82 m/day/m
11
for the hydraulic structure shown in figure 8.19 draw a flow net through the permeable layer and calculate the seepage loss in m3/day/m
Q.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 clay
Chapter 8 Solutions
Principles of Geotechnical Engineering (MindTap Course List)
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- Problem 1: An unconfined aquifer underlies a confined aquifer as shown in the figure: 44 m K1 - 40 m/day 55 m 47 m 36 m K2 = 35 m/day 2,000 m 1. What is the equivalent coefficient of permeability for flow in the horizontal direction in meter per day? 2. What is the hydraulic gradient? 3. What is the rate of flow from one stream to another per meter width?arrow_forwardWater 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_forwardFor 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)arrow_forward
- in figure below , a flow net is showing underneath a reinforced concrete dam .the permeability (k ) of the soil underneath the dam is 5*10 " m/s. Find the flowing: |a-the rate of seepage in m’/s if the dam is 350 m in length. b-the volume in (m3) of water loss underneath the dam in one year . the pore water pressure (u) at location A ,B ,C, D. -7 15 m A 30 m 18 m 12 m 10marrow_forwardNf : 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 stratumarrow_forwardRefer to the cross section of the earth dam shown below. Calculate the rate of seepage through the dam (q in m/min/m) using Schaffernak's and Casagrande's solutions. +7 m→| 3 m G.W.T. 1 32 m 2.0 2.0 Impermeable layerarrow_forward
- 5.4 The figure shows the cross-section of a levee that is 500 m long and is underlain by a 2-m-thick permeable sand layer. It was observed that the quantity of water flowing through the sand layer into the collection ditch is 250 m³/day. What is the hydraulic conductivity of the sand layer. Ans. k = 3.125 m/day Elv. 160 m Levee Elv. 150 m 2 m Ditch 125 m Impervious Sandarrow_forwardSeepage around a retaining wall is shown in the figure below. The hydraulic conductivity of the sand is 1.8 x 10-5 cm/s. The retaining wall is 20 m long. Determine the quantity of seepage across the entire wall per dayarrow_forwardA pump well is dug through a confined aquifer having a thickness of 32 meters. The piezometric surface of the aquifer is 18 meters measured from the top impermeable layer. The first observation well is 75 feet directly west of the pump well and the second observation well is 75 feet directly north of the first observation well. Determine the hydraulic conductivity of the aquifer if it supplies a discharge of 10 liters per second and the drawdown of the observation wells are 13 feet and 23 feet.arrow_forward
- Situation 2: 4. 5. For the given figure, r₁ = 30 m r₂ = 10 m H = 20 m t = 15 m Q = 13 L/s h = 13.6 m h₁ = 17.6 m h₂ = 16.3 m d = 0.6 mø draw down H t d ₂1 C Find the permeability of the aquifer in m/s. Compute for the transmissivity of the impermeable layer in m²/s. h₂ 5 h₁ -observation wells -impermeable Confined layer Aquiferarrow_forwardA drainage pipe beneath a dam has clogged with sand whose coefficient of permeability is found to be 8.0 meters per day. The average difference in headwater and tailwater elevation is 21.6 meters and it has been observed that there is a flow of 162 liters per day through the pipe. The pipe is 96.3 meters long and has a cross-section area of 180 sq. cm. What length of the pipe is filled with sand?arrow_forwardFigure 1. Figure 2. Figure 3. Explain the differences in the patterns in terms of the hydraulic conductivity within the circular region and the surrounding region.arrow_forward
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