But it was found that Some log Segments were not truncated/deleted after log backup was successful.
And what exactly makes you think that log Segments should be truncated/deleted after log backup was successful?
That's not the way how it works.
Good news is:You may manually trigger a deletion.
There's a useful command, also mentioned in SAP notes 1679938 and 2083715.
http://help.sap.com/hana_one/html/sql_alter_system_reclaim_log.html
I suppose you haven't tried yet?
hope this helps