Question

The method of setting out curve in underground road ways is

• A. Chord and off set method
• B. Chord and angle method
• C. Tangent and off set method
• D. Two theodolite method

Hint:

In underground surveying, methods that rely on precise angular measurements from a single station are generally preferred over methods that require extensive linear measurements or multiple setups.
The chord and angle method fits this requirement perfectly.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks for the most suitable method for setting out a curve in the confined environment of an underground mine roadway.

Step 2: Detailed Explanation:
Setting out curves underground presents unique challenges compared to the surface: limited space, poor visibility, dust, and potential obstructions.
Methods are chosen based on their practicality and accuracy in these conditions.
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Offset Methods (A and C): These methods involve measuring linear distances (offsets) perpendicular to a tangent line or a chord.
Accurately setting out a 90-degree angle for the offset is difficult and prone to error in a cramped, dark roadway.
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Two Theodolite Method (D): This highly accurate surface method requires two instruments set up at each end of the tangent, with clear lines of sight between them and to the curve points.
This is generally not feasible in a narrow mine roadway.
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Chord and Angle Method (B): This method, also known as the

deflection angle method, is the most widely used and practical method for underground curves.
It requires only one theodolite set up at the beginning of the curve (the tangent point).
Points on the curve are located by turning a series of calculated small angles (deflection angles) relative to the tangent line and measuring a fixed chord length along that new line of sight.
This method relies primarily on accurate angular measurement, which a theodolite excels at, and is well-suited to the linear nature of a roadway.

Step 3: Final Answer:
The preferred method of setting out a curve in underground roadways is the Chord and angle method.
This corresponds to option (B).