بسم الله الرحمن الرحيم
There is no need to look after the graves regularly. If the grave is new or only a short time has passed and the grave is swamped then it may be repaired with soil etc. there is no harm in it according to Shariah.
وإذا خربت القبور فلا بأس بتطيينها وهو الأصح وعليه الفتوى (هنديه)
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.