Laboratory Facilities for the Field Testing of Excavation Support Fluids

Excavation support fluids are widely used for the construction of diaphragm walls and bored piles. They are also used in slurry tunnelling, horizontal directional drilling and borehole and well drilling. These fluids must support the excavation during digging and through to the placement of a permanent element such as concrete, a liner, tunnel ring, etc. They are commonly based on bentonite clay or water soluble polymers. The creation of sound foundation elements requires that the properties of the support fluid are kept within appropriate project specification and this, in turn, requires regular, reliable and accurate testing of the fluids. Much has been written on the test equipment employed including the Marsh funnel, sand content thimble, mud balance, filter press and direct indicating viscometers. However, there is almost no published advice on the facilities and services required to house and operate the test equipment in the field so as to enable accurate and reliable results to be obtained.