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Room and pillar or pillar and stall is a variant of breast stoping. It is a mining system in which the mined material is extracted across a horizontal plane, creating horizontal arrays of rooms and pillars.
General layout of a room-and-pillar mine. Retreat mining is the removal of pillars in the underground mining technique known as room and pillar mining.. In the first phase of room and pillar mining, tunnels are advanced into the coal or ore body in a rectangular pattern resembling city streets.
Once room and pillar mines have been developed to a stopping point limited by geology, ventilation, or economics, a supplementary version of room and pillar mining, termed second mining or retreat mining, is commonly started. Miners remove the coal in the pillars, thereby recovering as much coal from the coal seam as possible.
Advanced Placement (AP) examinations are exams offered in United States by the College Board and are taken each May by students. The tests are the culmination of year-long Advanced Placement (AP) courses, which are typically offered at the high school level. AP exams (with few exceptions [1]) have a multiple-choice section and a free-response ...
In architecture, a post-and-lintel or trabeated system refers to the use of horizontal stone beams or lintels which are borne by columns or posts. The name is from the Latin trabs, beam; influenced by trabeatus, clothed in the trabea, a ritual garment.
A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member .
The Dreieckiger Pfahl is a granite pillar that once marked the border between the Kingdom of Hanover and the Duchy of Brunswick. The Wolfsangel in its horizontal form was used as a boundary marker in forests, and has been recorded as early as 1616 in a boundary treaty concluded between Hesse and the Duchy of Brunswick-Lüneburg
AP 3-D Art and Design is a three-dimensional (3-D) art course that holds many similarities to the 2-D course. The course deals with 3-D artistic applications such as metalworking, sculpture, computer models, and ceramics. Like AP Studio Art 2D, the focus is on the design of the artwork itself as opposed to its composition.