Support of 25 m deep excavation using ground anchors in Russia

Abstract

The paper describes the design, construction and testing of some 3600 temporary single-bore multiple anchors used to support the deep basement that formed part of the foundation support system for the Kuntsevo Plaza, a pedestrian-oriented, mixed-use development in the Kuntsevo district of south-western Moscow, Russia. Single-bore multiple-anchor technology was used effectively to provide support for a 45 m deep diaphragm wall constructed to support a 25 m deep excavation in the geotechnically challenging Moscow mixed soils, comprising combinations of low-strength clays, sands and silts. Previous attempts to sustain the required workloads of up 600 kN in the anchors had failed due to unacceptable creep. However, an understanding of the concept of progressive debonding, and the use of this knowledge in the design of efficient fixed anchor lengths, proved highly effective. Also, the introduction of fixed anchor enhancement techniques such as end-of-casing grouting in granular soils and post-grouting in cohesive soils enabled anchor capacities more than double those previously achieved in the prevailing ground conditions. Also described is the extensive programme of investigation tests conducted to establish important parameters regarding the behaviour of the ground and the performance data relating to the ground anchors that effectively limited wall displacements; this was a crucial requirement due to the sensitivity of adjacent underground services.