Siena Stone: Strength, Beauty and Speed of Installation


Project:Kennedy Road Culvert,Brampton,ON

Civil Engineer: David Schaeffer Engineering Limited

Geotechnical Engineer: Coffey Geotechnical

Wall Design Engineer: Risi Stone Systems

Wall Contractor: Regent Landscape

Wall System and Manufacturer:Siena Stone by Unilock

Geogrid Reinforcement and Manufacturer: Stratagrid 500 by Stratasystems

Culvert Structural Engineer: GD Jewel Engineering

Big projects require big solutions.  When Civil Engineering firm David Schaeffer Engineering reviewed options to support the 10m (33 ft) high earth embankments surrounding a new culvert installation under the realigned Kennedy Road in Brampton, Ontario, they chose the Siena Stone retaining wall system.  Designed by Risi Stone Systems and manufactured by UnilockOntario, the Siena Stone system is a large, machine placed, segmental retaining wall that has a proven track record of over twenty years in large scale and critical applications.

With a unit weight of over 200 kg (450 lbs) per block, and an integral tongue and groove shear connection system, the Siena Stone unit is able to develop a maximum shear capacity that exceeds 147 kN/m (10,000 lb/ft), making this block ideal for significant structural uses.

The Siena Stone system was paired with a proven, reliable partner for the geogrid reinforcement design.  The Stratagrid 500 geogrid reinforcement by StrataSystems was chosen based on it’s successful past use with Siena Stone, reliability, and overall robustness in the field.   This combination has been successfully used in hundreds of applications to date.  The proven track record of the geogrid was of particular importance to the City ofBrampton, providing a measure of confidence that the 75 year design life specified in the contract documents would be met.

The wall/culvert design was expertly coordinated by the Civil Engineer and involved all relevant design parties throughout the entire process.  The Site Geotechnical Engineer, Culvert Structural Engineer, Wall Design Engineer, and Fluvial Engineer worked together to address the numerous issues relating to the site, interaction between structures, and presence of water.

As the Siena Wall was constructed around the new culvert, issues related to the interfacing of the two different structures were dealt with in the early design stages.  For each end of the culvert, the Siena Stone head wall was designed essentially as three separate structures.  The middle wall bears directly on top of the culvert, while the sidewalls bear on native subgrade.   As these wall sections were founded differently, slip joints were designed between them to allow vertical movement that may occur due to differential settlement.  This measure controls the effects of differential settlement such as diagonal or vertical cracking in the units.

Due to the height of the walls, and presence of high groundwater, a full geotechnical investigation and global stability analysis was conducted by Coffey Geotechnical.  The GS analysis ultimately determined the final geogrid lengths used in the design.  Through ongoing coordination between the Site Geotechnical Engineer and Wall Design Engineer, the global stability requirements were included in the final wall design.

High quality, well graded, free draining gravels were used as backfill materials on all walls.  Regular inspection, compaction testing, and supervision of wall construction was conducted by the Site Geotechnical Engineer.  Immediately behind the face of the wall, a 0.6m layer of rapid draining, gap graded aggregate known as High Performance Pipe Bedding (Dufferin Aggregates) was used to provide instant drainage in this area as well as preventing down drag on the geogrid reinforcements due to normal backfill settlement.  For additional drainage, a chimney drain of the same material was placed at the rear of the reinforced zone.

In addition to a significant amount of wall embedment specified in the wall design, the Fluvial Engineer designed the erosion protection in front of the walls to guard against potential scouring at the base.

The Wall Contractor, Regent Landscape, one of the most experienced and knowledgeable Wall Builders inCanada, had many years previous experience with the Siena Stone product.  With the large face area of each Siena Stone unit (2.4 sq.ft), Regent was able to construct the walls quickly to meet the demanding construction schedule.  It is not uncommon for a Contractor to be able to machine place 80-100 sq.m (800-1000 sq.ft) of wall in a day using the specialized mechanical clamps.  Even greater installation rates have been achieved using the new Triple Clamp designed by Risi Stone Systems.  This innovative mechanical clamp is allows the Contractor to lift three Siena Stone units at a time, placing 7.2 sq.ft of wall with every cycle.

With a maximum height exceeding 11.0m, including embedment, the Kennedy Culvert walls were some of the highest Regent had ever tackled.  However, given his long, successful history with the Siena Stone product, Regent had all the confidence needed to take this project on.

2 Responses to “Siena Stone: Strength, Beauty and Speed of Installation”

  1. Great study Tyler!

    • markrisi
  2. Very detailed & informative

    • jag
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