Abutment — In coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the solid coal along the sides, which act as abutments of the arch of strata spanning the roadway; and (2) the weight of the rocks over a longwall face is transferred to the front abutment, that is, the solid coal ahead of the face and the back abutment, that is, the settled packs behind the face.
Superior Industries' patent-pending Liberty® Jaw Crusher processes aggregates in stone, concrete, asphalt, and ore applications. Functioning as a primary crusher in mining and aggregate applications, the unit compresses material as it travels down the increasingly narrow angle between the crusher jaws.
So getting right to it then, what type of foundation are we going to build for our flagstone patio: sand, cement, or gravel?. Short answer: well it depends. Quarry screenings (if available in your area) are generally best for under the flagstones.