25 SEPTEMBER 2024 WorldWide Drilling Resource® History of the Tunnel Boring Machine Adapted from Information by the San Diego State University Before cars and trains, tunnels carried only water. Roman engineers created the most extensive network of tunnels in the ancient world. They built sloping structures, called aqueducts, to carry water from mountain springs to cities and villages. They carved underground chambers, and built elegant arch structures, not only to carry fresh water into the city, but to carry wastewater out. The bore construction method for tunnels involves digging a tubelike passage through the earth. With modern technology, a tunnel boring machine (TBM) consists of a shield and trailing support mechanisms. A rotating cutting wheel is located At the front end of the shield. Behind the cutting wheel there is a chamber where, depending on the type of the TBM, the excavated soil is either mixed with slurry or left as is. The choice for a certain type of TBM depends on the soil conditions. Systems for removal of the soil are also present. Behind the chamber, there is a set of hydraulic jacks supported by the finished part of the tunnel which is used to push the TBM forward. Once a certain distance has been excavated, a new tunnel ring is built using the erector. The erector is a rotating system which picks up precast concrete segments and places them in the desired position. Behind the shield, inside the finished part of the tunnel, several support mechanisms which are part of the TBM, can be found: dirt removal, slurry pipelines if applicable, control rooms, rails for transport of the precast segments, etc. The first successful tunneling shield was developed by Sir Marc Isambard Brunel to excavate the Thames Tunnel beginning in 1825, which would not be opened until 1843. Brunel is said to have been inspired in his design by the shell of the shipworms. He observed their efficiency at boring through submerged timber while working in a shipyard. Brunel's original design was substantially improved by Peter W. Barlow in the course of the construction of the Tower Subway, under the River Thames in central London in 1870. Probably the most crucial innovation of Barlow's design was the circular crosssection, which made it simpler in construction and better able to support the weight of the surrounding soil. The Barlow design was enlarged and further improved by James Henry Greathead for the construction of the City and South London Railway (today part of London Underground's Northern Line) in 1884. To this day, most tunneling shields are still loosely based on the Greathead shield. With the latest tunnel construction technology, engineers can bore through mountains, under rivers, and even beneath bustling cities. C&G
RkJQdWJsaXNoZXIy NDk4Mzk=