Explanation

It refers to the place used to approach the working face in the mine pit, which is usually used as the pillar between the bottom plate and the ceiling (only log is used directly). Short pit timbers are called slant support. pit wood is required to be strong, compressive and durable to ensure the safety of the tunnel. It is strictly prohibited to use brittle wood. Crisp core wood is the wood in the center of log. Its impact strength is very low, only half or less of the normal wood. When subjected to external force, it is easy to break suddenly, the section is neat without burrs, and there is no warning sound when ordinary wood breaks, so it is very unsafe.

Classification