Improvement for a Soft Subgrade in a Railway Track

This is a brief description on how to improve a soft subgrade in a railway track.

This portion of the track is a cut through a small mountain with sharp soil embankments in both sides of the track .Existing soil is of a sandy clay type and there was no proper drainage system to drain out the water which gets accumulated owing to the soil embankments.The track has suffered rapid settlements and constant ballast creep.

                                   

The first step in improving this soft subgrade was to cut two deep drains on either side of the mountain embankments to drain out the accumulated water ,making the surface dry  for machine movements.

Step two was to provide a geo -grid to arrest the ballast creep along with a 200mm layer of Aggregate Base Course (ABC).

Ultrasonic pulse velocity (USPV) Test - Compressive strength of Concrete

 
Ultrasonic test for concrete is a field test for quality control and inspection of concrete structures. It uses measurement of the speed of ultrasonic pulses through the concrete to correlate concrete strength to standard strength. Using this test we can identify non-homogeneous conditions in the structure such as honeycombs, voids, cracks and frozen concrete.

First the instrument is calibrated using a standard calibration bar and the receiving and the transmitting ends are coated with a thin uniform grease layer. The concrete surface is cleaned well to make it dust free and uniformly distributed grease layer is applied on the concrete surface as well. The transmitting and receiving ends of the apparatus is then placed on marked locations of the structure and the machine is turned on to get the reading. The test is repeated after switching the positions of the transmitting and receiving ends. Then obtained readings are compared with the standard values to arrive at a conclusion about the concrete quality.

The use of the teat is covered by BS 4408: part 5