GEOTECHNICAL ENGINEERING AND HYDRAULICS) PDF

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CE BOARD EXAM MAY 2016 (GEOTECHNICAL ENGINEERING AND HYDRAULICS) 1. A cohesive soil deposit is considered soft if the unconfined compression strength, in kPa is between A. 0 to 25 C. 96 to 192 B. 50 to 100 D. 25 to 50 Solution:

2. In a triaxial shear test of a cohesionless soil, the soil cylinder was subjected to a liquid pressure of 16 kPa inside the chamber. It was observed that failure of the sample in shear occurred when the axial compressive stress reached 40 kPa. The angle of internal friction in degrees is nearest to A. 27.40 C. 26.80 0 B. 29.1 D. 25.40 Solution:

3. A layer of soft clay having an initial void ratio of 2.0 is 10 m thick. Under a compressive load applied above it, the void ratio decreased by one-half. Evaluate the reduction in the thickness of the clay layer, in meters. A. 3.5 C. 3.33 B. 3.74 D. 3.15 Solution:

4. Evaluate the resisting capacity against axial load due to skin friction. Size of pile= 0.30 m square Depth of penetration into the soil =20 m Unconfined compression strength = 110 kPa  = 1.0 A. 1010 C. 780 B. 1320 D. 660 Solution:

5. The permeameter in a falling head permeability test setup involves a cylindrical soil sample 50 mm in diameter and a height 200 mm. The hydraulic head in the 10-mm diameter standpipe through which test water passed dropped from 900 to 600 mm in one-minute of observation. In that duration the water collected in the graduate was recorded at 1.5 liters. Evaluate the coefficient of permeability of the soil sample, in cm/sec. A. 0.00924 C. 0.00715 B. 0.00541 D. 0.00689 Solution:

6. A soil sample has a water content of 20 percent and moist unit weight of 18 kN/m3. The specific gravity of the solids is 2.65. Obtain the void ratio of the soil. C. 0.733 A. 0.407 B. 0.635 D. 0.368 Solution:

7. An unconfined compression test was conducted on a sample of clay having a diameter of 50 mm. The failure load was recorded at 240 N. The cohesion strength of the clay, in kPa, is nearest to a value of C. 61.1 A. 64.0 B. 45.0 D. 101.0 Solution:

8. A layer of soft clay having an initial void ratio of 1.50 is 10 m thick. Under a compressive load applied above it, the void ratio decreased by one-half. Evaluate the reduction in the thickness of the clay layer. C. 3.00 A. 4.25 B. 3.75 D. 5.50

Solution:

Situation – The coefficient of permeability below a dam is 4 m/day. The water on the upstream side is 20 meter higher than on the downstream side. To estimate the seepage below the dam, a flow net was graphically drawn such that the number of potential drops, Nd=10 and the number of flow channels Nf=4. The base of the dam is founded 1 m below the ground. Between the heel and the toe of the dam, a distance of 30 meters, there are 8 potential drops. 9. Evaluate the seepage flow per meter width of dam, in liters/min. A. 18.6 C. 32.5 D. 22.2 B. 20.6 10. Determine the uplift pressure at the heel of the dam, in kPa. A. 198 C. 177 B. 186 D. 114 11. Determine the uplift pressure at the toe of the dam, in kPa. C. 29.4 A. 21.4 B. 24.7 D. 27.6 Solution:

Situation - According to the elastic theory, the vertical stress induced by flexible line load of infinite length that has an intensity of q units/length on the surface of a semi-infinite soil mass can be estimated by the expression p = 0.637 q/N where: N = z[1+(r/z)2]2 r = horizontal distance from the line of the load z = depth of interest at which stress is induced A concrete hollow block wall weighing 6 kN per linear meter is carried by a wall footing 0.60 m wide. 12. Evaluate the bearing pressure, in kPa, exerted by the footing onto the supporting soil. A. 14 C. 10 B. 12 D. 16 13. Evaluate the stress in the soil caused by the load if the depth equal to twice its width. A. 7.25 C. 3.19 B. 6.47 D. 5.31 14. Evaluate the stress at a depth of 2 m and a horizontal distance of 3 m from the line of the load. A. 0.180 C. 0.668 B. 0.531 D. 0.302 Solution:

Situation – A square footing 4 m on a side is founded 1.2 m below the ground surface for which the bulk unit weight of the soil is 20 kN/m3, the cohesion strength is 10 kPa, and the angle of internal friction is 20 degrees. Under the condition of general shear failure, evaluate the contribution of the following to the ultimate soil bearing capacity, in kPa. The ground water table is at a level that does not affect the unit weight of the soil. Use Terzaghi’s bearing capacity factors. TABLE can be useful.

15. cohesion strength A. 259 C. 230 B. 235 D. 287 16. soil overburden A. 247 C. 179 B. 260 D. 185 17. footing dimension A. 98 C. 128 B. 116 D. 102 Solution:

Situation – A soil sample has a dry unit weight of 17 kN/m3 and a void ratio of 0.60. 18. Evaluate the specific gravity of the soil solids. A. 2.44 C. 2.77 B. 2.65 D. 2.56 19. Obtain the unit weight of the sample in kN/m3 when fully saturated. C. 20.7 A. 21.3 B. 18.6 D. 19.6 20. What is the hydraulic gradient at hydraulic condition? A. 1.43 C. 1.35 B. 1.11 D. 1.28

Solution:

21.

A fireman has to put out a fire but is blocked by a fire wall. To reach over the wall, he directed the water jet from the nozzle at an angle of 30 degrees to the horizontal. Evaluate the velocity of the water, in meters/sec, leaving the nozzle of his hose to reach over the wall if he stands 30 meters away from the wall and the wall is standing 2 m higher than the nozzle of the hose. Neglect friction in the jet. A. 16.8 B. 20.6

C. 18.2 D. 19.6

Solution:

22.

A line joining the points of highest elevation of water in a series of vertical open pipes rising from a pipeline in which water flows under pressure is referred to as: A. hydraulic loss B. hydraulic gradient

23.

C. hydraulic jump D. hydraulic head

A barge, weighing 350 kN when empty, is 6 m wide, 15 m long, and 3 m high. Floating upright, evaluate the draft of the barge, in meters, when transporting 3000 bags of cement along a river, each bag having a mass of 40 kg. Assume the specific gravity of the water in the river to be 1.02. A. 1.38 B. 2.57

Solution: Wbarge = 350 kN = 35,677.88 kg Wcement = 40(3000) = 120,000 kg Wtotal = 155,677.88 kg W = BF 155677.88 = 1.02(1000)(6)(Draft)(15) Draft = 1.70 m

C. 2.01 D. 1.70

24.

A spherical balloon 6 m in diameter is filled with gas weighing 5 N/m3. In standard air weighing 12 N/m3, evaluate the maximum load, in N, excluding its own weight, that the balloon can lift. A. 812 B. 792

C. 672 D. 916

Solution:

25.

Determine the pressure in a vessel of mercury at a point 200 mm below the liquid surface, expressing the answer in kPa absolute. A. 132 B. 130

C. 134 D. 128

Solution: Pabs = Patm + Pgage = 101.3 + 13.6(9.81)(0.2) Pabs = 128 kPa

26.

Water flows through a rectangular irrigation canal, 500 mm deep by 1 m wide, with a mean velocity of 2 meters per second. Determine the rate of flow in m3 per minute. A. 50 B. 70

C. 80 D. 60

Solution: Q = Av = 0.5(1)(2) Q 1

m3 60 s  s 1 min

Q  60

27.

m3 min

A ship having a displacement of 20,000 metric tons enters a harbor of fresh water. The ship captain recorded a draft of 8.4 m while the ship was still in seawater (specific gravity = 1.03). Obtain the draft, in meters, of the ship in fresh water if the horizontal section of the ship below the waterline is 3000 m2 in both instances. A. 8.75 B. 7.78

C. 9.54 D. 8.59

Solution:

28.

A pressure surge or wave caused when a fluid in motion is forced to stop or change direction suddenly (momentum change) is referred to in hydraulics as: A. potential head B. hydraulic jump

29.

C. water hammer D. hydrodynamics

For the tank shown in FIGURE HHP-1, obtain the depth d, in meters, of the oil if its specific gravity is 0.84. A. 1.44 B. 1.19

C. 1.37 D. 1.28

Solution:

ΣPressures] 0 + 0.84(9.81)(d) – 9.81(1) = 0 d = 1.19 m

30.

When the path lines of the individual particles of a flowing liquid are irregular curves and continually cross each other, and form a complicated network, the flow is called: A. uniform B. laminar

31.

C. continuous D. turbulent

A trapezoidal canal has a bottom width of 4 m and side slopes of 2 horizontal to 1 vertical. When the depth of the flow is 1.2 m, the flow is 30 m3/sec. The roughness coefficient n = 0.015. Evaluate the slope of the channel using Manning’s formula. A. 0.00195 B. 0.00316

C. 0.00412 D. 0.00447

Solution:

32.

If the velocity head at one point of a pipeline is 5 m, what would be the velocity head, in meters, at the point of the pipeline if the velocity is increased three times? A. 20 B. 45

C. 15 D. 30

Solution:

In FIGURE HTRS-2, reservoir A is the source of water supply and is at Elev. 150 m, B is the junction at Elev. 91.46 m, C is a town at Elev. 30.49 m with 25,000 inhabitants, D is another town at Elev. 15.24 m with a population of 30,000. Length AB is 15,240 m, BC is 9150 m, BD is 6100 m. Determine the size of the pipes if the consumption is 150 liters per capita per day. For the pipes, frictional factor f = 0.02. Determine the required diameter, in meters, of: 33.

Pipe AB A. 0.450 B. 0.330

34.

Pipe BC A. 0.366 B. 0.500

35.

C. 0.390 D. 0.420

C. 0.216 D. 0.196

Pipe BD A. 0.450 B. 0.205

C. 0.300 D. 0.150

Solution:

A rectangular gate 1.5 m wide and 3 m high is vertically submerged in water with its top edge horizontal and 2 m below the water surface. 36.

Evaluate the total force acting on one side of gate, in kN. A. 177 B. 143

37.

Obtain the location of the force from the center of gravity of the plate, in meter(s). A. 0.316 B. 0.225

38.

C. 154 D. 165 C. 0.214 D. 0.355

Obtain the location of the force from the liquid surface, in meters. A. 3.71 B. 3.96

C. 3.82 D. 3.61

A solid block having a specific gravity of 3.5 is placed in a container containing liquid having specific gravity of 13.6. 39.

If the volume of the block is 0.020 cubic meter, obtain the weight of the block, in kN. A. 0.824 B. 0.687

40.

Evaluate the percentage volume of the block that floats in the liquid. A. 82.5 B. 74.3

41.

C. 0.566 D. 0.751

C. 67.3 D. 53.3

Obtain the downward force in kN required to make it completely submerged in the liquid. A. 1.05 B. 3.22

C. 1.98 D. 2.05

Solution:

An irrigation canal with trapezoidal cross sections has the following dimensions: Bottom width = 2.00 m, depth of water = 0.90 m, side slope = 1.5 horizontal to 1 vertical, slope of the canal bed = 0.001, coefficient of roughness = 0.025. The canal will serve clay-loam Riceland for which the duty of water per hectare is 3.0 liters/sec. Using Manning’s formula: 42.

Determine the hydraulic radius of the canal, in meter(s). A. 0.432 B. 0.242

43.

Velocity of the water in m/sec. A. 0.308 B. 0.479

44.

C. 0.501 D. 0.575

C. 0.652 D. 0.874

Number of hectares served by the irrigation canal. A. 897 B. 879

C. 978 D. 789

Solution:

A rectangular irrigation canal 6 m wide contains water 1.0 m deep. It has a hydraulic slope of 0.001 and a roughness coefficient of 0.013. 45.

Evaluate the mean velocity of the water in the canal, in m/sec. A. 1.52 B. 1.06

46.

Evaluate the discharge in the canal, in m3/sec. A. 10.8 B. 13.8

47.

C. 2.01 D. 1.38

C. 11.5 D. 12.0

What would have been the depth of the canal, in meters, using the more economical proportions but adhering to the same discharge and slope? A. 2.38 B. 2.06

Solution:

C. 1.67 D. 2.52

An open cylindrical vessel 1.3 m in diameter and 2.1 m high is 2/3 full of water. If rotated about the vertical axis at a constant angular speed of 90 rpm, 48.

Determine how high is the paraboloid formed of the water surface, in meter(s). A. 1.26 B. 1.91

49.

Determine the amount of water in liters that will be spilled out. A. 140 B. 152

50.

C. 2.46 D. 1.35

C. 340 D. 146

What should have been the least height of the vessel, in meters, so that no water is spilled out? A. 2.87 B. 2.55

Solution:

C. 3.15 D. 2...