TECHNICAL | GROUND CONDITIONING
GROUND CONDITIONING OVER THE DECADES
Lars Langmaack, Technical Director (TBM) of MC-Bauchemie Müller GmbH’s tunnelling business unit, gives a personal review of EPB tunnelling development, including the development of soil conditioning additives in recent decades, and ways ahead
IMAGES COURTESY OF LARS LANGMAACK, UNLESS OTHERWISE INDICATED
INTRODUCTION This article is a personal review concerning the development of earth pressure balance (EPB) tunnelling and especially concerning the research and development of soil conditioning additives over the last two decades. It does not claim to be complete and all-embracing, and only highlights some important steps and encourages innovation to drive forward. Innovation is necessary to bring new solutions to
the market – making tunnelling overall cheaper, more efficient, more secure and also more environmentally friendly. This cannot be driven forward only by the chemical suppliers – it needs the joint effort of clients, construction companies, tunnel boring machine (TBM) manufacturers, universities and the chemical suppliers.
Below, figure 1: Homogeneous paste after soil conditioning
TBM TUNNELLING – A HISTORY The first steps of a shield tunnelling method were made by Sir Marc Brunel in 1825-1842 with the world’s first underwater tunnel (River Thames, London) using a rectangular shield in soft ground. A more modern-like,
update was designed by Barlow-Greathead, in 1869, for a Thames crossing again, this time near the Tower of London with circular-shaped shield, a separate air pressure chamber, hydraulic jacking system for metal segments and segment erector. The first drilling machines were operational in 1846,
designed by Henri Joseph Maus, in France, for the Mount Cenis Tunnel and in the US by Charles Wilson, starting in the early 1850s, for the Hoosac Tunnel. The 1880s saw a drilling machine for an exploratory bore at the English Channel. What we call today a ‘Tunnel Boring Machine’ (TBM)
was for the first time assembled in 1931 by Schmidt- Kranz for the German coal mines, followed by the first Robbins hard rock TBM, developed by James S. Robbins, in 1952, to use drag bits and disc cutters for tunnels at Oahe dam in South Dakota. The precursor of all modern pressurised and shielded soft ground TBMs was developed again by Robbins and successfully used in 1964-65 for the Paris RER transport tunnels, in France. (See Figure 2). The compressed air supported TBM was equipped with a cutterhead and soft ground excavation tools, with a cutterhead bearing and bull gear, a protected conveyor to transport the muck out of the excavation chamber, a segment erector for concrete segments and universal seals, and also a proper TBM driver cabin. As described by Maidl et al (2012), the design of the
first Earth Pressure Balance (EPB) TBMs was started in 1963 by Sato Kogyo Co. with a working chamber and screw conveyor system (see Figure 3). The first site use took place in Tokyo, in 1974. These first EPBMs were used in rather cohesive soils with high plasticity, using mineral oil-based foam to reduce the cutterhead torque and achieve better control of the ground support pressure by turning the muck into a compressible medium – which is normally not the case.
FROM JAPAN TO EUROPE – THE BOOST OF GROUND CONDITIONING ADDITIVES Unlike the very homogeneous silty soils in Japan, tunnelling in Europe takes place in rather non- homogeneous ground, resulting nearly always in mixed face conditions at the cutterhead level as well as along the longitudinal profile of a tunnel. The mixed face conditions can range from highly cohesive clogging clay
10 | November 2023
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49
