Maple GO Transit

Printable PDF version › RisiStone_CS-MapleGo

Maple-Go-CaseStudy

Fully Monitored Wall Meets & Exceeds Expectations for MTO Demonstration Project

 

GO Transit, the public transit service for the Greater Toronto and Hamilton areas, planned an ambitious parking expansion project at the existing Maple GO Station in Vaughan, Ontario. A large 6m high, 300m long retaining wall was specified in order to maximize the
usable parking area.

Based on several, past successful projects with GO Transit, Risi Stone Systems provided a full wall design utilizing the SienaStone System. The wall contract was awarded to Regent Landscape, one of the GTA’s premiere Wall Builders with over 30 years of experience.

This SienaStone wall was constructed in two phases, with the first being a 100m section that required additional foundation replacement and improvement due to poor site conditions. Use of geotextiles and high quality imported fill was mandatory to achieve the bearing capacities stated in the Design. To ensure the minimum 150 kPa allowable Bearing Capacity below the wall, the Site Geotechnical Engineer recommended OPSS Granular B fill material be compacted to 98% SPD in the designated areas. Because the “Wall” is not limited to just the SienaStone facing units, but is in fact the entire Geogrid Reinforced structure, it was necessary to redevelop the foundation for the entire width of the reinforced zone, plus an additional 60cm in front and behind. This is an effective method of reaching the “competent” founding elevations without increasing the height of the Wall. 

Prior to the construction of the remaining 200m of wall, it was decided that this wall would be utilized as demonstration project by Risi Stone Systems and Unilock to advance the SienaStone product on the Ministry of Transportation Designed Source for Materials (DSM) List from the existing status as a “Non-Reinforced” wall to a Geogrid Reinforced System. 

The MTO specifications required that the SienaStone product meet a minimum compressive strength requirement of 40 MPa. Research done by the NCMA (National Concrete Masonry Association) has shown that the compressive strength of a block is directly related to its long term durability and freeze-thaw resistance, particularly in cold climates. 

As part of the approval process, the MTO also requires the demonstration project to be regularly monitored (every 2 months) following construction for a period of 1 year to observe any settlement or movements that may occur. The size and scale of the GO Transit project was ideal for the type of structure the MTO would consider, so detailed monitoring began shortly after construction. After a year round survey & monitoring program, the SienaStone wall performed beyond expectations, with little to no movement observed. The maximum movement on the 6m height was in the range of 3mm-4mm, which is considered to be within measuring tolerance by the Surveyor. 

This level of performance is a testament to the Contractor’s thorough quality control and construction practices, which are as important as any aspect of the design or engineering, as well as the stability and dependability of the SienaStone wall system.

 

West London Dyke

Printable PDF version › RisiStone_CS-London_Dyke

 

This project is part of a large-scale reconstruction of the existing dyke system along the Thames River in London, Ontario. In this phase,approximately 300m (1000ft ) of the dyke was replaced with a new 8m (26ft ) high DuraHold wall.

Extreme 2 year and 75 year flood events in the Thames River have the potential to completely submerge the entire new wall. Due to the rapid fl owing hydraulic conditions, the DuraHold product was used because its smooth surface reduces drag eff ect from fl owing water. This, combined with DuraHold’s structural stability, high rate-of-installation and the capacity to create curves with its Tapered Half units, made it the ideal choice for this project.

With the river limiting site access, and the necessity to prevent contamination of the Thames River, all construction had to be completed from the high side of the wall. Proper coordination of the excavation, block placement, and infi ll material was crucial because of the limited space. Due to the height of the wall, a fall arrest system was utilized, with anchor wires secured to large blocks. Workers could then harness themselves to the wire allowing the range of movement required to construct the wall.

The complex space constraints and additional factors of the site made excavation and fi lling operations diff icult and consequently reduced the installation rate to approximately 45m2 (484ft 2) per day. Under ideal conditions, machine-placed wall systems can be installed at much higher rates (100–150m2 per day [1076–1614ft 2]). However, because machine-placed walls do not rely on the physical capacity of the workers to place the block, the rate of installation was maintained at the same level throughout the day.

A reinforced toe wall that was constructed to stabilize the original dyke in the 1980’s, was used as erosion protection. It was cut to fit the new wall layout and riprap was placed between it and the DuraHold wall. To allow for the water to exit the infi ll zone as quickly as possible following a fl ood event, the wall was backfilled with a 60cm gap-graded drainage layer. Drainage tiles were installed at grade, and fl ood event elevations, with the drainage tiles outlet through the wall face at 15m intervals.

 

London-Dyke-CaseStudy2

On the North end, a 90 degree “hidden wall” was incorporated into the layout with a curved section abutting it. This new curved section reduces fl ow turbulence and allows the wall to taper back into the existing dyke structure. The “hidden wall” permits for a future planned expansion and will eliminate the need to dismantle a large portion of the new wall. Simply by removing the curved section and abutting to the “hidden wall”, the wall can quickly and easily be extended.

A pathway running alongside the Thames River was incorporated into the layout atop the new DuraHold wall. The South end of the wall was terraced, allowing the pathway to extend down under the Queens Ave. and Kensington Bridges, and connect to Riverside Park.