sentences:  It is desirable to keep the size and shape of rooms and pillars consistent, but some mines strayed from this formula due to lack of planning and deposit characteristics.Mine layout includes the size of rooms and pillars in the mines, but also includes factors like the number and type of entries, roof height, ventilation, and cut sequence.Room and pillar mines are developed on a grid basis except where geological features such as faults require the regular pattern to be modified.