# Foundation Engineering Questions and Answers – Flexible Pavement – Equivalent Wheel and Axle Load

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This set of Foundation Engineering Interview Questions and Answers for Experienced people focuses on “Flexible Pavement – Equivalent Wheel and Axle Load”.

a) a single wheel
b) two wheels
c) three wheels
d) four wheels

Explanation: The maximum wheel load is the greatest load transmitted by a single wheel of the vehicle. The pavement is usually designed from the consideration of the greatest load transmitted by a single wheel.

2. The pressure transmitted to the surface of the pavement by the wheel is ________
a) differential pressure
b) absolute pressure
c) contact pressure
d) atmospheric pressure

Explanation: The contact pressure is the pressure transmitted to the surface of the pavement by the contact of the wheel on the pavement surface. This contact pressure depends upon:

• tyre pressure
• stiffness of the tyre walls.

3. The contact area of wheel is _______
a) triangular
b) square
c) rectangular
d) circular

Explanation: Since, Area=Load/Pressure, the contact area shape for the wheel and the pavement is nearly an elliptical region. It is assumed to be circular for making the problems simple to proceed.
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4. Based on the equal deflection criterion, the expression for the equivalent wheel load Pe is _________
a) $$F_e \sqrt{P_e}=(F_1+F_2)\sqrt{P}$$
b) $$F_e \sqrt{P_e}=(F_1-F_2) \sqrt{P}$$
c) $$F_e \sqrt{P_e}=(F_1*F_2) \sqrt{P}$$
d) $$F_e \sqrt{P_e}=(F_1/F_2) \sqrt{P}$$

Explanation: The equivalent wheel load Pe is given by,
$$F_e \sqrt{P_e}=(F_1+F_2)\sqrt{P},$$
P=wheel load of each of the dual tyres
Fe=settlement factor for equivalent wheel load
F1= settlement factor contributed by one tyre of the
F2= settlement factor contributed by other tyre.

5. _________is an empirical method based on soil classification and other factor like climate and moisture.
a) Group index method
b) Plate bearing test mathod
c) CBR
d) North Dakota cone method

Explanation: The group index method and the Federal aviation agency method are the empirical methods based on soil classification and other factor like climate and moisture.

6. The group index method of design of flexible pavement was suggested by __________
a) O.J. Porter
b) California state highway
c) Highway research board
d) North Dakota state highway

Explanation: The group index method of design of flexible pavement was suggested by Highway research board (1945). California state highway devised the California bearing ratio.

7. The California bearing ratio method was originally devised by ________
a) O.J. Porter
b) California state highway
c) Highway research board
d) North Dakota state highway

Explanation: The California bearing ratio method was originally devised by O.J. Porter and then by California state highway department. It has since been developed by other authorities in the U.S.A., notably by U.S Crops of Engineers.

8. In CBR test, the cylindrical plunger of ________ diameter is used.
a) 5 cm
b) 10 cm
c) 15 cm
d) 20 cm

Explanation: The California bearing ratio test carried out in small scale in which a cylindrical plunger is of 3 in2 or 5 cm in diameter is penetrated in to the soil mass or the sub-grade material.

9. In CBR test, the rate of penetration of plunger is _______ mm/min.
a) 0.25
b) 1.25
c) 2.35
d) 3.25

Explanation: The California bearing ratio test carried out in small scale in which a cylindrical plunger is of 3 in2 or 5 cm in diameter is penetrated in to the soil mass or the sub-grade material at the rate of 1.25 mm/min or 0.05 inch per minute.

10. In CBR test, the standard load is the penetration resistance of plunger into a _________
a) standard sample of crushed stones
b) clay
c) saturated silt
d) peat

Explanation: In California bearing ratio test, the standard load is the penetration resistance of plunger into a standard sample of aggregates. The test load is the penetration resistance of the sample that is tested.

11. The CBR is _______
a) $$\frac{Test \,load}{standard \,load}*100$$
b) $$\frac{standard \,load}{test \,load}*100$$
c) $$\frac{2*Test\, load}{standard \,load}*100$$

Explanation: The California bearing ratio (CBR) is defined as the ratio of the test load to the standard load, expressed as percentage of a given penetration of the plunger.
$$CBR=\frac{Test \,load}{standard \,load}*100.$$

12. The CBR mould has internal diameter of ______
a) 200mm
b) 50mm
c) 100mm
d) 150mm

Explanation: The CBR mould has an internal diameter of 150 mm and an effective height of 175 mm. The mould is provided with a detachable collar of 50 mm in height and a detachable perforated base plate.

13. The CBR values are generally calculated for penetrations of __________
a) 2.5mm and 5mm
b) 5mm and 7mm
c) 7mm and 9mm
d) 9mm and 10mm

Explanation: The CBR values are generally calculated for penetrations of 2.5 mm and 5 mm. This can be related from the graph of load and penetration which shows linear variation of penetration with the applied loads.

14. For CBR test, the specimens are submerged in water for 4 days before testing.
a) True
b) False

Explanation: For CBR test, the specimens are submerged in water for 4 days before testing. This is done so as to stimulate the worst moisture conditions in the field.

15. In general, the CBR values of 2.5mm penetration are smaller than 5mm penetration.
a) True
b) False

Explanation: The CBR values are generally calculated for penetrations of 2.5 mm and 5 mm. Generally, the CBR values of 2.5mm penetration are greater than 5mm penetration. If the CBR values of 2.5mm penetration are smaller than 5mm penetration, then the test is repeated.

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