Question from Cumbian writer - Familial interment in chest or table tombs

I would like help or information with the nature of familial interment in chest or table tombs, with particular reference to the the Dacre tombs at Lanercost Abbey. I wish to know whether further subsequent burials were carried out, (of unmarried children for exmaple, in the vault beneath tombs of this type, and if so, how the vault beneath (supposing that the coffins were buried beneath and not inside the chest) was accessed.