Trenchless technology is the technique used for repairing, installing, and renewing ducts and pipes without any need for excavating long trenches. The digging of trenches can often cause a disruption in traffic and other activities. Trenches can also become unsafe and can cause accidents.
Tunneling has always been a part of construction methods to cut horizontally through natural obstructions and was earlier carried out manually. It was only later that types of machinery that functioned like augers were used to replace manual labor. Trenchless technology is an adaption of horizontal boring technologies used to install pipes underground without disturbing the soil above. Underground piping for sewers or other utilities has manholes and other inspection chambers at regular intervals. The location of these manholes is used to install small boring machines that cut through the soil while simultaneously installing the required pipes or casings. The boring machine is directed towards the next manhole or drive-pit location that can be hundreds of meters away, or at distances specified. Pipes are rammed or jacked into place as the excavation proceeds.
The excavated material that the boring machine creates, is sent back to the original drive-pit through screw conveyors or other devices. The material requires to be separately disposed of. The boring machine is small enough to fit into the diameter of the pipe being installed and is remotely controlled. As the boring machine drives into the soil, it pulls behind it the pipe that is required to be installed, and this prevents the tunnel of soil from collapsing, and any subsidence in such operations is minimal. Each length of pipe is pushed into place and new lengths of pipe are added for the drilling to continue. This sequence is continued until the required length of the pipeline is installed.
Impact moling is another form of trenchless installation that uses a piercing tool that is pneumatically operated and displaces the soil instead of removing it. It is a method that is used for small diameter pipes, cables or ducts where the volume of earth removal required is small, and the impact tool merely compacts the soil around the opening created to create space for the installation. It is the least expensive method of trenchless installation and is used for service connections for gas, sewer and water mains.
Pipe jacking and pipe bursting are other methods that are used in trenchless installation, and many other technologies are being constantly developed for underground construction and installation.
