Harvard Developments.

Soldier Piles and Lagging

Project Description

Harvard Development’s The Hill Centre Tower III is located in downtown Regina. The shoring reaches depths of up to 9.1 meters, providing two levels of underground parking for the 20-storey building. RWH Engineering Inc. (RWH) worked with the shoring contractor, HCM, to create time and money saving innovations. RWH designed an efficient system which utilized one row of highly loaded tiebacks to minimize drilling time. High tieback loads require welding intensive connection and internal walers, costing both time and money. In lieu of conventional shoring methods, RWH designed a bypass shotcrete shoring system which consisted of mesh and rebar with concrete lagging; this design eliminated the costly connection and waler. Due to the cold temperatures in Regina, bypass shotcrete installation was deemed to be efficient only until the end of November, after which traditional timber lagging was continued to the bottom of excavation. One of the shoring requirements was that the shoring had to be cut down 1.8 meters below grade at the end of the job. For this reason, timber lagging was also used above the shotcrete. This resulted in the majority of the shoring being designed as timber lagging, with a 1.6 meter wide shotcrete strip at the tieback elevation. Caisson wall was implemented adjacent an existing neighbouring building on the north wall in order to effectively minimize shoring movements. RWH also incorporated the structural bell caissons into the caisson wall. This redesign allowed for an increase in the square footage of the building. Bell caissons reduce concrete while still achieving the necessary bearing area at the base.
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