Many cemeteries now have bylaws that require caskets to be enclosed within a burial vault or grave liner.   These containers are engineered to support the weight of the earth above the grave as well as the heavy equipment that passes over it.  The weight of the earth and heavy equipment used to dig graves far exceeds what an unprotected casket can withstand.  Burial vaults are made of specifically formulated and reinforced concrete, designed to support these elements and more.

Concrete becomes stronger as it continues to cure after being placed in the ground.  So a vault properly buried many years ago, could actually be stronger today.

Sealed, lined burial vaults are made to place protection from impact and the elements between the earth and the casketed remains of a loved one.  Most concrete vaults are made to exceed cemetery requirements for strength and rigidity.