Stone Columns with Vibroflot
197 Stone Columns
The City of Richmond was planning to replace the Horseshoe Slough Drainage Pump Station due to seismic upgrade requirements in BC. The pump station is on Dyke Road between Shell Road and No. 5 Road. Vibro Replacement stone column densification was required beneath the new pumping station in order to prevent settlement caused by soil liquefaction in the event of an earthquake.
The site’s subsurface stratigraphy consisted of the following:
• Approx. 1m of compact to medium dense sand fill with some silt and gravel;
• Underlain by 8m of soft to firm clay to silty clay;
• Underlain by 19m of loose to compact silty sand to sand susceptible to liquefaction;
• Over firm to stiff silt.
Groundwater was encountered at approximately 1.5m from the ground surface.
Menard utilized wet-top-feed stone column installation techniques. Stone columns were installed up to 30m depth on a regular grid pattern to meet the specified CPT tip resistance performance-based requirements.
Densification work began with an initial trial area consisting of 20 stone columns to assess the effectiveness of the proposed methods and stone column spacing. Production work applied similar methodologies to those proven successful in the trial area.