Microtunneling becomes more and more popular as a method of building trenchless collectors in big cities. For several decades microtunneling method is main method used in construction of collectors in Europe, USA and Japan. Important feature of this method is high accuracy of drilling and constant course control. Microtunneling enables laying communications under the most difficult conditions, where all other methods without special measures such as water depression or freezing, are helpless. This method allows laying high-diameter collectors with accuracy of several centimeters.
Basic scheme of microtunneling technology
Starting and receiving shafts are built on the surface, the distance between them varies between 50 and 1500 m, depth – 8-12 m. Shafts can be round or square with sides up to 6 m depending on microshield type.
Actuating cutting device of microtunnel complex AVN (microshield) effects drilling from the starting shaft in conditions of excessive water pressure in the bottom. Water transmission to the actuating device and pumping of appeared pulp is done by pumps installed on the surface near the starting shaft or near the driving frame inside the shaft. Separate sections of reinforced concrete oк steel lining are also delivered into starting shaft, they are pushed into the ground with jacks, which allows horizontal collector laying. Accuracy of driving of the ground station is corrected by a laser ray. All technological and control functions of microtunneling are computerized. Pulp is delivered by pumps in the mucrotunnel complex separator, where appeared water is re-used and scale, as long as it accumulates, is removed to dump.
Microtunneling by AVN complex is fully automated and is effected under control of operators, who sit in command block of a microtunnel.