Temporary and Permanent Earth Anchors: Three Monitored Installations

Abstract

This paper presents the results of measurements of earth anchor performance for three separate installations in Metropolitan Toronto. The first case records the results of instrumentation on the high grout pressure Bauer anchor used to support an approximately 30 ft (9.1 m) deep excavation in dense fine sand. The second presents the load measurements made on low grout pressure earth anchors installed in very stiff clay of a 29 ft (8.8 m) excavation. The third installation involved measurements on permanent vertical anchors set in extremely dense silt till.In the first instance the average measured load was somewhat lower than the installed load and the design assumption. In the second case, in the stiff clay, the load was somewhat higher than the design value but this was attributed to the probability of load transfer because of inadequate support at lower levels. In this case, considerable variation and possible overstressing of anchor wires was noted.A very high uplift resistance was recorded for the permanent anchors in dense till. Control of groundwater during installation of these anchors was the principal lesson learned from this work.