Advanced Support Structure
The aim is to create a full support structure prior to doing any of the major excavation. This can be done by using jacking, microtunnelling or pipe ramming methods to form an advance support structure. The illustrations shows a series of interlinking tubes installed by microtunnelling to form the support structures for an arch and rectangular structure.. Frequently an arch structure is created but virtually any shape is possible. The interlinking steel tubes which form the support canopy are filled with reinforced concrete. Once the main excavation starts additional internal framing is installed as work proceeds to support and complete the structure. This technique has been used for the construction of large underground structures such as metro stations.