Outflow Lab

TITLE

Outflow Meter Test

OBJECTIVES

To evaluate the surface drainage of a surface course of a pavement and its relationshi  p with skid resistance value

APPARATUS

1) Outflow meter 2) Stopwatch 3) Stabilizer board

MATERIALS

1) Tap water

PROCEDURE

1.

The outflow meter is placed on a pre-determined surface and the stabilizer board is fitted to the outflow meter.

2.

Two persons of approximately the same weight is asked to stand on the stabilizer    board to stabilize the outflow meter.

3.

Tap water is filled into the outflow meter until the 2500ml gradation.

4.

The stopper in the outflow meter is opened and the time for the water to reach 500ml from 2500ml is recorded.

5.

Steps 1-5 are repeated three times for the smooth, intermediate and rough surface.

6.

The data collected are tabulated.

RESULTS

The water flow is calculated using the following formula : Q (Flow) = Volume of water / Time taken

Volume of water = 2000 ml = 0.002

m

3

Surface

Time Taken (s)

Q ( m /s)

Smooth

572

3.5 x 10-6

Intermediate

131

1.5 x 10-5

Rough

5

4.0 x 10-4

3

DISCUSSION

From the table above, it can be seen that the rougher the surface, the higher the flow of water. Since the outflow meter simulates the pavement in a wet condition, the most suit able type of skid resistance test to be correlated with is the skid resistance test in a wet condition. Based on our skid resistance test in a wet condition for the same types of surfac e,the skid resistance for a rough surface is higher than the skid resistance for the sm ooth surface. This means that the rougher the surface, the better is the pavement for the users.

  However, a surface that is too rough can also make the users not comfortable to us e the road, thus the most suitable type of surface that will ensure a comfortable ride for the users while at the same taking taking in account the skid resistance and outfl ow of water is the intermediate type of surface. Some precautions to be taken in this experiment are : i.

Make sure that the apparatus (outflow meter) has no leakage at the part that con nects the cylinder and the base.

ii.

The base must be stabilized to ensure a uniform flow.

iii. The persons that steps on the board must maintain the same position because if t hey move about the flow will not be uniform and the data will be faulty.

CONCLUSION

The outflow meter test and skid resistance test come hand in hand when determin ing the texture of the pavement surface and from our experiment, it can be conclude that the higher the discharge of the water, the better is the pavement texture. Howeve r,it is not the only governing effect and other effects such as comfortability of users must also be taken into consideration when determining the surface texture.

REFERENCES

1)

California Department of Transportation, Surface Characteristics. Retrieved from ht tp: //www.dot.ca.gov/hq/maint/RPMTAGChapter2-SurfaceCharacteristics.pdf accessed   on 15th April 2017.

2)

Garber, J. N., Hoel, L. A., (2015). Highway and Traffic Engineering. USA: Ceng age Learning.