Pisa2 - Byrd Park

Wall System : Pisa2
Owner: City of Richmond, VA
Landscape Architect : Higgins Associates, Inc.,Richmond, VA
Structural Engineer : Mr. Mike Matthews, P.E.,The Structures Group, Inc.
Contractor: Mid Atlantic Retaining Wall Systems,Inc.
Materials Supplier: Custom Concrete, Inc., Williamsburg, VA
Geogrid Manufacturer : Conwed Strata Systems

In 1992, the City of Richmond, VA selected a Pisa2 / Risigrid reinforced retaining wall system to protect the lakefront surrounding a large municipal retention pond. The size of the wall was approximately 6 ft high and 2,350 ft long. The pond was pumped dry for cleaning and general rehabilitation. A stable footer/leveling pad was constructed to provide a firm foundation for the base course of blocks. Due to the soft foundation in the lake bed, all materials were “handed down” from the top of the excavation using a pair of Skytrack 6036’s. Number 10 manufactured crushed stone was specified as infill material for its high internal angle of friction and compactability properties.

The geogrid specified was Risigrid with a long-term allowable design strength of 541 lbs/ft (ultimate strength = 1,979 lbs/ft). Two six-foot-long layers were required to satisfy minimum factors of safety against failure by sliding,overturning, overstressing, and pullout. There were 22 pipes which penetrated this wall, ranging from 8 to 36 inch drainage outfalls. The Pisa2 blocks were field-cut to fit snugly around the pipes and the annulus was grouted.

The construction of the wall began on April 11th, 1992 and was completed on May 22nd. Not including rain days, an average of 470 square ft per day was realized. All granular backfill was placed with a Case 621 wheelloader and compacted to 95% Standard Proctor with two Case 900 plate compactors. This retaining wall adds outstanding aesthetic appeal to this neighbourhood lake. Most importantly, it has stabilized the shoreline against erosion for its 75-100 year design life. The project was completed on time and under budget.

“This wall looks great and is performing better than expected. We are very pleased.”
Mr. Saeed Rabie, City Engineer, City of Richmond

“The experience we had on the Byrd Park Project with Risigrid gives us a lot of confidence in its future use for soil reinforcement.”
Mr. Bill Spell, ASLA, RLA, Higgins Associates, Inc.

"From the manufacturing and installation aspect, Pisa2 with geogrids are a joy to work with. The solid Pisa2 wall units provide superior strength and durability in comparison to other hollow units available. Their performance will secure much more work for us in this field."
Mr. Bob Swope, Custom Concrete

Pisa2 - A Residential Delight

Retaining Wall System: Pisa2 with Stratagrid 200 Geogrid Reinforcement
Owner: Private Residence
Contractor: Bob Morawczynski,Regent Landscape Ltd.,Newmarket, ON
Wall Design/Certification: Moraw Consultants, Newmarket, ON
Retaining Wall Manufacturer: Unilock, Ltd., Louis Tolfo, Territory Manager

The land on this residence was very uneven and was causing grading problems with the landscaping design. The goal of this project was to aesthetically maintain the grade difference between the existing topography and the proposed driveway elevations, while keeping costs low. With this in mind, Bob Morawczynski along with Moraw Consultants used the Risiwall software to design a project that utilized the Pisa2 system.

The proposed wall was to be located in close proximity to the house, and the homeowner required a balcony that extended from the house and ended directly behind the wall. This meant that a concrete footing would have to be poured within the fill material behind the wall. In order to minimize the effects of the balcony on the wall, it was required that the balcony’s foundations be extended to the base of the wall, transmitting most of the external forces to the wall’s foundation soil.

To meet the design requirements set forth by the Ontario Building Design Code, the wall required stabilization using the Stratagrid 200 extending into Granular B backfill. To accommodate the balcony footings, the sonotube was placed in the Granular B as the wall was constructed, and the geogrid was cut perpendicularly to the wall so that it could be wrapped around the sonotube. These procedures ensured the integrity of the wall.

In total the design included two walls with a combined face area of 400 m2 and a maximum height of 7.9 m. At the beginning of the summer in 1999 with a crew of three, the wall was placed at around 24 m2 a day, and the job was completed in approximately two weeks. Moraw Consultants verified that the wall was constructed to meet the design specifications and provided certification of the wall.

The owner of this residence was provided with a stable and attractive wall that generates the required grade difference for his driveway. He is very pleased with the results of the construction. The results show that a properly constructed Pisa2 wall can be an economical and aesthetically pleasing way to create large walls in high profile areas.