What is the ruling on using a portable electric machine to dig graves, given the concern that the deceased might be harmed by the vibrations it causes?

The fundamental principle is the permissibility of using whatever aids in facilitating the digging of graves. There is no evidence that the deceased are harmed by vibrations and the sounds of machinery. If digging graves manually becomes impossible, there is no objection to using heavy machinery out of necessity, bearing in mind that clay soil is preferable for burial if it can be obtained.