McAllister Bros.Ltd. is a leading tunnelling, shaft sinking, micro-tunnelling & pipejacking contractor also with extensive experience in traditional hand excavated tunnelling, pipejacking and timbered headings. Our specialist tunnelling division IRISH TUNNELLING LTD carries out these specialist works. Please see below for a brief overview of the technologies and methods we employ. Pipejacking is a specialist tunnelling method for installing undergroung pipelines with the minimum of surface disruption. Primarily used for new sewer construction it is also used for sewer replacement and re-lining, gas and water mains, oil pipelines, electricity and telecommunication installations, culverts and subways. Segmental Tunnels can be installed varying in diameter from 1.2 metres upwards and lengths in excess of 300 metres have been installed There are various methods and techniques that we employ depending on ground conditions, size, cost, local circumstances, environmental factors etc. Irish Tunnelling Ltd. scope of activities and plant incorporate all of the below methods. For rock conditions the open faced hand-dig method utilising a shield can be limited. When rock strengths go up to 40 Mpa progress is very slow with this method and other methods such as utilising a roadheader or the drill & blast technique need to be considered. Roadheaders offer a unique capability and flexibility for the excavation of soft to medium strength rock formations and are widely used in tunnelling operations.They were first developed for mechanical excavation of coal in the early 50ís. Today, their application areas have expanded beyond coal mining as a result ofcontinual performance increases brought about by improvements such as increased machine weight, size and cutterhead power, improved design of boom, muckpick up and loading system, more efficient cutter head design, metallurgical developments in cutting bits, advances in hydraulic and electrical systems and automation. Drill and blast tunnelling consists of drilling a controlled number of holes into a tunnel face to a designated depth and then loading the drilled holes with an appropriateblasting agent. The loaded holes are detonated and the broken rock is removed from the tunnel. The most important aspect of the D&B method is allowing the energycreated by the explosive to be directed in the correct alignment. The geological conditions of the rock, the angle of the drill holes, the size and spacing of the drill holes,and the energy factor (kcal/cy) accomplish this. Irish Tunnelling Ltd. has an extensive range of equipment and experienced personnel to utilise all tunnelling techniques. Traditional Methods With the advent of modern technology traditional methods of tunneling are utilized less and less. However we find that sometimes the old way is still sometimes the best way. A timber heading is one such method. This type of tunneling utilizes a man-made timber frame to secure the tunnel structure after the material has been excavated. Its distinct advantage is the saving of working space required compared to other tunneling methods. This advantage pays huge rewards in areas of restricted space such as narrow streets. Once the Timber Heading has been piped, the resultant annulus is usually stowed with concrete and finally topped up with PFA/OPC grout.Timber Headings can be installed in varying ground conditions, from dewatered sands and gravels or clay onto soft/hard rock.