Improved methods to prevent railway embankment failure and subgrade degradation: a review by Roshan, Mohammad Jawed, A. Rashid, Ahmad Safuan, Abdul Wahab, Norshakila, Tamassoki, Sakina, Jusoh, Siti Norafida, Hezmi, Muhammad Azril, Nik Daud, Nik Norsyahariati, Mohd Apandi, Nazirah, Azmi, Mastura