Support of 25m deep excavation using ground anchors in Russia
Dr Devon Mothersille, BEng (Hons) PhD CEng FICE
Managing Director, Single Bore Multiple Anchor Ltd, Harrogate, UK
Dr Rasin Duzceer, PhD CE
Vice Manager, Kasktas A.S., Istanbul, Turkey
Mr Alp Gokalp, BSc MSc
Technical Manager, Kasktas A.S., Istanbul, Turkey
Mr Bora Okumusoglu, BSc MSc
Geotechnical Engineer, Kasktas A.S., Moscow, Russia
The paper describes the design, construction and testing of some 3600 temporary single bore multiple anchors (SBMAs) used to support the deep basement which 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 45m deep diaphragm wall constructed for supporting a 25m deep excavation in the geotechnically challenging Moscow mixed soils, comprising combinations of low strength clays, sands and silts. Previous attempts to sustain the required work loads 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. In addition, the introduction of fixed anchor enhancement techniques such as end-of-casing grouting in granular soils and post-grouting in cohesive soils resulted in the achievement of anchor capacities more than double those previously achieved in the prevailing ground conditions.
Also described are the extensive programme of investigation tests, carried out to establish important parameters on the behavior of the ground and the performance data on the ground anchors that effectively limited wall displacements, and this was a crucial requirement due to the sensitivity of adjacent underground services.
Details of full paper can be found on the ICE publishing website: Proceedings of the Institution of Civil Engineers. http://dx.doi.org/10.1680/geng.14.00043. Paper 1400043. Keywords: anchors & anchorages/diaphragm walls/grouting.