Filling tunnels on the London Underground
As Propump prepare to pump more specialist foamed concrete into a network of passageways in London’s Underground during engineering hours in this iconic part of London in front of the Royal exchange., is a statue of James Henry Greathead (1844 – 1896), Inventor of the “traveling shield” (1869). The Greathead shield made significant technological improvements over Brunel’s square shield design which allowed the current style of subterranean tunnelling to develop, still based to this day on its basic design and fundamentals.
It comprises a circular ring which used hydraulics (1879) and water jets (as well as hand digging) to remove material from the face of a tunnel. It used cast iron rings to make the new tunnel safe whilst the digging face was propelled forward to continue the cutting and material removal.
James Henry Greathead also successfully patented and used various other ground breaking innovations such as using pressure differentials to reduce the likely hood of collapse (subaqueous tunnelling) , as well as the first form of pressure grouting, used to stabilise overhead soil, as wells as the precursor to shock- crete.
Foamed concrete has a great number of potential uses. The fluid nature of this Foamed cement / grout combination allows it to be pumped much easier and at considerably less pressure than conventional concrete mixes. This allows a sufficiently fluid foamed concrete with no large aggregate to fully encapsulate utilities. It is also a key component to minimising any voids or gaps without the use of vibration or tamping.