3.1 What is the main function of a manhole? 3.1.2 Identify A - NSC Civil Technology Civil Services - Question 3 - 2018 - Paper 1

A represents the component known as 'Benching', which is designed to support workers and facilitate flow within the manhole.

B refers to the 'Pipe channel', which is the passageway that allows the sewage to flow through the manhole.

Greased double seals are installed primarily to:

1. Make the manhole airtight, preventing any sewage gases from escaping.
2. Ensure that liquids cannot escape, thus maintaining the integrity of the sewage system.

The sectional front view A-B should depict a T-junction with five courses of stretch bonds. Ensure the drawing correctly represents the brick layout with alternated half bricks on the left side.

1. The excavation must be adequately protected by a fence to prevent unauthorized access.
2. Workers must wear personal protective equipment (PPE) at all times.
3. Red warning lights and signs should be placed at regular intervals and should be clearly visible.

Type A shoring will be more suitable for use in loose or water-logged soil due to its design that provides better support.

Type A shoring employs vertical members that are closer together, preventing loose or waterlogged soil from filtering through its openings.

manhole

lifeline

The formula for the volume of a rectangular prism is: $Volume = l imes b imes h$ Given dimensions:

• Length (l) = 1.150 m
• Breadth (b) = 1.0 m
• Height (h) = 0.125 m Substituting these values gives: $Volume = 1.150 imes 1.0 imes 0.125 = 0.14375 ext{ m}^3$ Rounded to TWO decimals: 0.14 m³

Given that the wall is one-brick wide:

• The centre line for the manhole is 4.96 m.
• Using the standard of 100 bricks per square meter, we first calculate the area of the wall. The height will be considered to a standard height of approximately 1 m for simpler calculations: $ext{Number of bricks} = 4.96 ext{ m} imes 1 ext{ m} imes 100 ext{ bricks/m}^2 = 496 ext{ bricks}$