Q. & Ans - What are the main cause of crushing of PRC sleeper in washable aprons and what are the remedial measures?

Q.  What are the main cause of crushing of PRC sleeper in washable aprons and what are the remedial measures?

Ans - The washable aprons are constructed on the concrete raft. The PRC sleepers placed on the raft and after palcing of sleeper the crib is casted one bitumen sheet also provided under the sleepers at both ends for facilitating the elastic medium between sleeper and raft. 

Now during casting of crib the concrete as well as cement sullary flows under the middle of sleeper which give the rigid support to the sleeper resulting to this the sleeper becomes centre rigid and ends on elastic support due to this uneven base the sleeper sheared while wheel load comes on the sleeper . 

A another cause of damage of sleeper in washable apron is regularly falling of water, and human waste from the coaches which eroded the sleeper surface and sleeper become to start damage. 

 As explained earlier that the ends of sleeper rests on the bitumen felt to provide elastic medium between raft and bottom of sleeper. But due to vibrations of moving trains if a small Qty. of water percolate from side of sleeper on the bitumen pad. The bitumen felt starts damage and lost its elastic property. This is the main cause of damage of concrete sleeper. 

During construction of washable apron it should be ensured that the placing of bitumen pad to done on quite smooth surface and water should not percolate. The side drain also to be made with proper slope so that water can not stagnate in drain. This stagnated water may become a source of percolation inside the bottom of sleeper. 

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