The design of choice by the Vancouver Port Authority for anchoring marine piling to resist seismic tension forces is the drilling of centralized anchors beneath the base of the pipe pile. First Canada Place Pier Extension used 9″ casing to 150′ deep and one central DCP anchor.
This extension required 250 ton tension loads; design included 2-#18 OCP anchors. This required the use of 10″0 casing and reverse circulation drilling to take the holes to a maximum 250′ below the deck level. The drilling later had to be quickly modified once it was found that the tills directly beneath the pipe piles had large pockets of hydraulic sands under 150′ of hydraulic head pressure.
A new drilling system from Sweden directed the high pressure air to the center of the hole rather than hydro fracturing the sands and allowed the drilling to proceed with an external water head to counteract the incoming sands.