Civil Engineering All Engineering Career

A transition curve, when inserted between the tangent and the circular curve, should fulfill all of the following conditions:

1. The rate of increase of curvature along the transition curve should be the same as that of the increase of super-elevation: This helps in providing a smooth transition from the tangent to the circular curve, ensuring that the lateral friction and super-elevation adjustments are gradual.

2. Should meet the original straight tangentially: This ensures a smooth connection between the tangent and the transition curve, avoiding sudden changes in alignment.

3. Should meet the circular curve tangentially: This ensures a smooth transition from the transition curve to the circular curve, avoiding sudden changes in curvature.

So, the correct answer is:

All of the above

Let's analyze each statement:

1. "The uniformly spaced contour lines indicate a plane surface": This statement is correct. Uniformly spaced contour lines indicate that the surface is flat or a plane, as the elevation changes at a constant rate.

2. "A series of closed contour lines on the map indicates a depression if the higher values are inside out": This statement is correct. When contour lines form a closed loop with higher values on the outside and lower values inside, it indicates a depression or a sinkhole.

3. "A series of closed contour lines on a plane indicates a hill if the higher values": This statement is incomplete but generally correct. Closed contour lines with higher values towards the center of the loop indicate a hill or peak.

Given these points, the correct answer is:

All of the above are not correct, because the second and third statements are correct, and the first one is also correct.

The two theodolite method of setting out a curve involves:

Both linear and angular measurements

This method uses two theodolites to measure both angles and distances to accurately set out a curve. One theodolite is typically used to measure angles from a known point, while the other helps in verifying and establishing the alignment of the curve.

In a direct vernier, the smallest division of the vernier scale is:

Shorter than

The direct vernier scale is designed so that the smallest division on the vernier scale is shorter than the smallest division on the main (primary) scale. This allows for more precise measurements by enabling the user to read fractions of the smallest division on the primary scale.

The line joining the points having the same elevation above the datum surface is called a:

Contour line

A back sight indicates the:

Setting up

The back sight is used to establish the instrument’s line of sight relative to a known point or benchmark, ensuring that the instrument is correctly set up and aligned for subsequent measurements.

A scale which has a common representative fraction but is read in different measures is called a:

Comparative scale

Comparative scales allow for the representation of different measurements using the same representative fraction, making it easier to compare different units or scales on the same drawing or map.

When the curve is to be set out over rough ground, the method used is:

Either (b) or (c)

• Tacheometric method is useful for rapid and accurate measurements over rough or uneven terrain.
• Two theodolite method can also be used effectively over rough ground to set out curves by measuring angles and distances.

Both methods are suitable for dealing with the challenges posed by uneven surfaces.

To find the back bearing when given the fore bearing, you use the relationship:

Back bearing=Fore bearing+180∘\text{Back bearing} = \text{Fore bearing} + 180^\circBack bearing=Fore bearing+180∘

If the fore bearing is θ\thetaθ, then:

Back bearing=θ+180∘\text{Back bearing} = \theta + 180^\circBack bearing=θ+180∘

However, if the result exceeds 360∘360^\circ360∘, subtract 360∘360^\circ360∘ from it.

In this case, if the back bearing is 36∘15′36^\circ 15'36∘15′, you can find the fore bearing by subtracting 180∘180^\circ180∘:

Fore bearing=36∘15′−180∘\text{Fore bearing} = 36^\circ 15' - 180^\circFore bearing=36∘15′−180∘

Fore bearing=36∘15′+180∘=216∘15′\text{Fore bearing} = 36^\circ 15' + 180^\circ = 216^\circ 15'Fore bearing=36∘15′+180∘=216∘15′

Thus, if the fore bearing is 216∘15′216^\circ 15'216∘15′, its back bearing will be 36∘15′36^\circ 15'36∘15′.

The correct answer is:

216° 15'

Let's analyze each statement:

1. "The effect of refraction in levelling is to increase the staff reading": This statement is correct. Refraction bends the line of sight downward, which makes the staff reading appear slightly higher than it would be in the absence of refraction.

2. "The combined effect of curvature and refraction in levelling is to increase the staff reading": This statement is not entirely accurate. While refraction increases the staff reading, the curvature of the Earth actually decreases the staff reading. The combined effect is a slight decrease in the staff reading, but refraction partially counteracts this effect.

3. "In levelling, the effect of curvature is to decrease the staff reading": This statement is correct. The curvature of the Earth causes a decrease in the staff reading due to the Earth's surface curving away from the line of sight.

Given this, the correct answer is:

The effect of refraction in levelling is to increase the staff reading and In levelling, the effect of curvature is to decrease the staff reading. However, because the second statement about the combined effect is misleading, "all of the above" is not correct.