Can we build multi-level graves to bury our dead due to limited space?

It is legally established that each body must be laid down separately in a separate lahd [grave with a lateral hollow] or shaqq [a simple trench dug down in the middle of the floor of the grave], except when graves become full. The Prophet (peace and blessings be upon him) buried two or three of the martyrs of the Battle of ‘Uhud in a single grave. There must also be separate graves for men and women.
Based on the above and in reference to the question, when necessity calls for burying more than a one individual in a single grave, it is permissible to construct multiple levels inside the grave to accommodate the increasing number of dead.
And God Almighty knows best.