FIELD WORK #2: LAYING OUT COMPOUND CURVE

I. OBJECTIVE: The student should be able to lay out a reverse curve through location of points on

the curve by chord distance-deflection angle method.

II. ILOS:1. To be able to compute for the other elements of the curve using the given

elements. 2. To be able to lay-out the curve.

III. INSTRUMENTS: 1 - Total Station2 – prism - Chalk

IV. PROCEDURE:1. Set/level total station on the field convenient enough to lay out a reverse curve.

Set as station PRC. (0 + 50)

2. Before laying out the curve, make sure that all the necessary elements of the curve is calculated using the given data.

3. Start laying out the first simple curve. Using the calculated length of curve, interpolate stations with distance of 5m on the curve between sta PRC to the other

point of the curve (sta PT).

4. Repeat until all stations between PRC and PT is obtained.

5. Lay-out the second curve on the other side of station PRC. Start by sighting a point on the tangent line of the first curve adjacent to sta PRC. Then rotate the total station 180° to locate the PI of the second curve using the calculated tangent distance. Mark the point.

6. Using the total station, sight station PT, again rotate the total station 180° to lay out the length of long chord of the second curve. Mark the point and set as sta PC.

7. Calculate the deflection angle from the second tangent line to the interpolated stations to lay-out the second curve.

8. Tabulate the data.

V. TABLE:

For first curve:

Stations Points Central Angles

Deflection Angles

Chord Length

0+45 A1 13°3’ 6°31’30’’ 4.98m0+40 A2 26°6’ 13°3’ 9.913m0+35 A3 39°9’ 19°34’30’’ 14.708m0+30 A4 52°12’36” 26°6’18’’ 19.317m0+25 A5 65°15’36” 32°37’48’’ 23.671m0+20 A6 78°18’36” 39°9’18’’ 27.719m

0+16.69 PC 86°47’24” 43°23’42’’ 30.205m

For second curve:

Stations Points Central Angles

Deflection Angles

Chord Length

0+55 B1 19°40’32.69” 9°50’16.35’’ 4.975m0+60 B2 39°21’5.39” 19°40’32.7’’ 9.804m0+65 B3 59°1’38.08” 29°30’49.04’’ 14.344m0+70 B4 78°42’10.78” 39°21’5.39’’ 18.460m

0+72.055 PT 86°47’24” 43°23’42’’ 20.03m

VI. COMPUTATION:

VII. SKETCH

R1 R1

R2

R2

t1

t2

t2

t1PT

PC

PRC

I1

P

I2

A

B

D

VIII. DOCUMENTATION

Setting up the total station at PRC

Levelling the total station

Laying out the length of long chord of the first curve

Locating the Middle Ordinate of the first curve

Laying-out the first curve

Locating the PT of the second curve

Locating the middle ordinate of the second curve

Laying out the second curve