portal
Quick Summary
Portals are the entrances to underground mines, providing access for workers, materials, ventilation, and drainage. These openings are crucial for mine development and are typically the first to be completed and the last to be sealed.1
There are three main types of portals:
* Drifts: Horizontal entries driven into a coal seam that outcrops to the surface.1
* Slopes: Sloping tunnels driven through intervening ground to access seams not far below the surface. They are used for transporting coal via belt and for ventilation and material transport.1
* Shafts: Vertical openings used when coal seams are deeper than 250-300 meters or when ground conditions favor shafts over slopes. Shafts can be divided into compartments for various functions, including air circulation, transport, and haulage.1
The choice of portal type depends on factors like the depth of the resource, cost of construction and operation, and the specific needs of the mine.1
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tunnels and underground excavations…tunnel entrance is called a portal; tunnels may also be started from the bottom of a vertical shaft or from the end of a horizontal tunnel driven principally for construction access and called an adit. So-called cut-and-cover tunnels (more correctly called conduits) are built by excavating from the surface, constructing…
Read More…tunnel entrance is called a portal; tunnels may also be started from the bottom of a vertical shaft or from the end of a horizontal tunnel driven principally for construction access and called an adit. So-called cut-and-cover tunnels (more correctly called conduits) are built by excavating from the surface, constructing…
Read More- tunnels and underground excavationsGeologic investigation
Portals of rock tunnels are often in soil or in rock weakened by weathering. Being shallow, they are readily investigated by borings, but, unfortunately, portal problems have frequently been treated lightly. Often they are only marginally explored or the design is left to the contractor,…
Read MorePortals of rock tunnels are often in soil or in rock weakened by weathering. Being shallow, they are readily investigated by borings, but, unfortunately, portal problems have frequently been treated lightly. Often they are only marginally explored or the design is left to the contractor,…
Read More