Discussion

MR M. F. BOARDMAN, Fairclough Civil Engineering Ltd, Adlington

An even simpler 'instrument' than that suggested by Mr Dunnicliff in Session 1 consists of a 15 mm dia. plastic tube grouted in the ground to below the level of the inspected slip plane. A 12 mm dia. steel rod suspended on a fishing line and lowered down the tube will be impeded by the kink in the tube if ground movement occurs. This is sufficient to show that movement has occurred and determine the level of the slip plane.

MR L. THREADGOLD, Geotechnics Limited, Coventry Mr Dunnicliff has raised the question of the requirements for grouts used to seal and hold instruments in to the ground which they are required to monitor. I wish to comment on the strength of grouts required for inclinometer installations, and on the characteristics of grouts for piezometer installations.