The international definition of microtunneling includes pipe with diameter up to 1,000mm only. However, in the United States, it allows for larger pipe size when defining microtunneling in which pipe with diameters up to 144 inches are also counted within the ambit of microtunneling.
The basic concept of microtunneling has changed gradually owing to recent technological developments and past experience. For instance, the use of alignment control system with advanced surveying techniques allows for longer drives with good control and curved microtunneling. The use of automatic lubrication system enhances lower jacking forces. The employment of gripper in microtunneling machines helps develop adequate loads on cutter discs for cutting rock.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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