Mayurbhanj School Of Engineering

Baripada

757107

CIVIL ENGGINEERING DEPARTMENT

SEME : 4th

SUBJECT : SURVEY-I

TOPIC:CHAINING

BY

Er. Saroj Kumar Nayak

(Lect. In Civil Engineering Department)

AY:2021-2022

INSTRUMENTS REQUIRED :

1. Chain
2. Tape
3. Ranging rods
4. Clinometer

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• 1. Direct Method (Stepping Method):
• The method consists in measuring the line in short horizontal lengths called steps. Suppose it is required to measure the horizontal distance between the points A and B (Fig. 2.19). For convenience and to obtain better results, chaining is done from top of hill to the toe i.e. downhill.

The follower holds the zero end of the chain at A on the ground and the leader with the other handle of the chain and a ranging rod moves in the forward direction at a convenient distance apart.

The leader then stops and the follower directs him to be in line with B. The leader then stretches the chain in the horizontal position and transfers the end point of the chain on the ground with the help of a plumb-bob or ordinarily with a ranging rod or by dropping a piece of stone.

• The follower then moves and reaches the station occupied by the leader and then the leader moves in the forward direction. The process is repeated for several times until the whole line is chained. The lengths of all the steps are added up so as to obtain the total horizontal distance. In this case, the horizontal distance between AB = Ap + Pq + Qr + Rb.

• The vertical distance between the end of the chain and the point vertically below it on the ground such as pP, qQ etc. should not exceed 1.8 m (man’s height) as otherwise the chain cannot be stretched to the horizontal position i.e. a sag would occur in the chain and the measured length will be more than the actual length of the step. Therefore when the slope of the ground is steep, the chain of smaller length is used. For this purpose, the chain may be broken into different portions say 10, 20, 30 or 50 links.

Clinometer method

Procedure:

1. At first fixed the ranging rod top and bottom of the slope A and B.
2. Two point A1 and B1 are marked on the ranging rod AA1=BB1.
3. The Clinometer are placed at A1 and the point B1 is straight by tilting the Clinometer.
4. The angle of slope is measured and the horizontal distance is calculated.