pburs

Pburs, short for Portal Borings, are a type of excavation method used in conjunction with tunnel boring machines to create portals for underground tunnel projects. They consist of a cylindrical section of bored rock that serves as an entry and exit point for the tunnel boring operation.

Pburs are typically constructed by drilling a shaft to a depth that allows access to the tunnel boring machine and to create a stable platform for the machine's operation. The diameter of the pbur will depend on the size of the tunnel boring machine being used and the geological conditions of the excavation site.

Pburs are commonly used in tunnelling projects where access for the tunnel boring machine is required at multiple points, or where complex geological conditions necessitate multiple entry points for the machine. They can also be used as a repair access point for maintenance and repair of the boring machine during operation.

If required, pburs can be constructed to allow for different types of tunnel boring operations such as conventional EPB (Earth Pressure Balance) boring, single or twin shield boring, or open face boring, depending on the geology and the method best suited for the project's requirements.

Pburs are designed to withstand the stresses of loading of the overlying rocks and also to limit the extent of settlement caused during the excavation of the tunnel.