For this project both the wall foundation and the wall face utilized precast double tee segments that were post tensioned together in the field. In addition, to eliminate shoring that would have been required for conventional wall options, the double tee footing extended in front of the wall. To increase sliding resistance a cip grade beam was linked to the double tee foundation segment following wall erection. Due to the post tensioning the wall tee stems are always in compression thereby eliminating the possibility of tension cracks forming on the fill side of the wall which can occur with typical cip walls.
The Mid-Coast Transit Corridor Transit Project is currently utilizing All the Walls’ Stresswall precast post-tensioned/prestressed counterfort wall system for the Midcoast Corridor Transit Project. The MCTC project extends the light rail from Old Town north to UCSD and La Jolla. It also adds a second heavy rail track through the entire Midcoast corridor.
The rail corridor runs through Rose Creek Canyon with 4 tracks: 2 light and 2 heavy E 80 rail. Due to the additional live tracks, there is a need for many different retaining walls along the alignment. There are both cut and fill wall applications since the track grade is also being raised in places to be above the 100-year flood elevation.
All the Walls originally approached Mid Coast Transit Constructors, the general contractor for the project, starting in 2015 proposing the Stresswall design as an alternative, cost effective option that met or exceeded all of the E 80 and LRT load criteria. MCTC realized the cost effectiveness and time savings available with the system so they successfully value engineered Stresswall for many of the walls.
Walls 508 and 563 were originally designed as CIDH soldier pile walls with two-stage tiebacks. Conventional walls of this type would be very expensive and time consuming to construct, as well as the associated inherent risks involved with drilling in difficult areas.
After months of extensive design review meetings with SANDAG, NCTD, WSP, HDR, TY Linn and other design firms, the Stresswall option was approved for construction. The acceptance of the Stresswall system on this project saved millions of dollars in construction costs that were credited back to SANDAG and MCTC and also saved months on the critical path construction schedule. Construction of these walls has gone very well and all parties are pleased with the design and final product.
Wall 482 ( 4,500 sq. ft.) was built over a weekend with two crews working around the clock while the track was shutdown. This site was excavated and the precast components installed and backfilled in 47 straight hours. The original approved plan design was an MSE wall backfilled with Cell Crete, which would not have been cost effective.
Walls 600 and 624 were both originally designed as MSE walls, however North County Transit District (NCTD) no longer allows MSE walls to be built to support their track embankments, so Stresswall was selected as the most viable alternative. The change to Stresswall eliminated the shoring that would have otherwise been required for MSE walls, resulting in substantial excavation savings while providing with a total precast/prestressed product.
This project used All the Walls’ patented proprietary retaining wall system. It was also awarded PCI’s 2019 Best Non Highway Bridge Project.
This project exemplifies many unique features of the Stresswall Product. The project developer for the South Coast Medical Center Hospital expansion project, Sheldon Pollock in Santa Monica, requested that we provide a wall that would eliminate shoring that would have been required for any other wall option to support the existing Hospital embankment.
We proposed the “Terrace Wall” counterfort wall option which could be installed w/o shoring. A new building was to be constructed in front of and at a lower elevation than the existing five story structure. To do this a portion of the sloping embankment in front of the existing center would have to be removed w/o disturbing the existing building (maximum allowed settlement would have to be less than 0.5 inch!
To accomplish this the contractor cut deep slots into the existing slope between the existing deep caisson foundation for the existing structure. Since the site was is a stones throw from the ocean there is always a risk of morning rains etc. so the contractor was required to provide a site cover to eliminate any potential erosion should storms occur during wall construction. The slope face was covered every night and over weekends.
Following the slot cutting the contractor placed the open face counterforts in the slots and backfilled the portion of the counterforts w/in the slot cuts with slurry. Subsequently the .5 meter wide wall panels were placed in the Terrace Wall reverse batter voids.
Due the the spacing and orientation of the wall panels there is approximately half of the wall face area that could be planted. By selecting maintenance free, continuously blooming plants with an emitter irrigation system the concrete members quickly disappeared as the planting matured. As can be seen from the shots the result is a constantly changing pallet of color instead of a stark industrial look as would be the case for a conventional wall. In addition, the wall reduces the effect highway and other noise sources which is an advantage for patients in the new structure.
At the request of the ASCE we presented the Project for their annual meeting due to the unique features and advantages of the counterfort wall system.
The result of a VECP submittal by Faltiron Construction the Stresswall option was selected due to speed of erection and cost savings due to elimination of shoring that would have been required for any other wall option at that location. Typical shots show the “slot cut” excavation method wherein the existing emabankment was substantially left in place instead of removal which would have been required for other wall types. By cutting 4″ wide slots into the embankment at 15′ centers the precast counterforts could be placed w/o total wall excavation or any site shoring.
The precast wall was an alternate in the Woodward-Clyde bid package and was selected by Granite Construction over the MSE wall alternate. An integral wave deflector was monolithically cast with the top wall panels instead of the field cast cap that would shown for the MSE wall.
Prior to the wall installation a trench was cut into the slope and a cip cut off wall was constructed behind rip rap. The precast wall components were then installed. Since sand was used for wall fill filter fabric/geotextiles were placed over the fill side of the precast elements.
The wall has been subjected to many extreme load conditions compared to a typical seawall/erosion control structure. Locals claim that the tallest wave ever recorded in North America occurred at Pacifica. There are shots of these giant waves at local establishments. Some smaller waves are shown crashing into the wall in the shots.
Also the wall was impacted by the San Francisco earthquake which hit shortly after the wall was completed. The existing MSE wall north of the fishing pier has not fared so well. We understand that due to the corrosion of the metal soil reinforcement and movement fill has been lost from behind the wall. To address this issue the city has apparently refilled voids with concrete fill. There have been no issues with the Stresswall Structure.
The wall was installed into an existing embankment at the east end of the Hilton site along the Colorado River in 1989. The structure was built concurrently with the building construction. Depending on electrical power generation demands river flow rates vary on a daily basis. The wall was designed for water surface elevation variations of up to 12′ per day. To prevent fines migration filter fabrics/geotextiles were placed on the fill side of the wall structure.
To lengthen the radius of a curve as well as to smooth out the road alignment a cut was required for Wiley Canyon. To accomplish this without shoring the Stresswall system was selected. Although the wall face is at a 1:12 batter (essentially vertical) random planting areas within the wall face for internal landscaping options were made possible with the large random planting “pockets” in the wall face. Plants included both large flowering bushes as well as vines and ivy.
The counterforts were placed in slots cut into the existing embankment so that no shoring was required as would have been the case for other wall options. Wall cut was utilized for wall fill.
Noveco Inc. Client
Installation of Stresswall into Existing Slope Scope Of Work
Single tier seawall structure placed along WashDOT SR31 at the Canadian Border.
The counterforts were placed in slots cut into the existing roadway embankment. Due to the constant border traffic it was necessary to construct the wall as one lane was kept open. Other wall options would have required shoring.
By utilizing the “slot cut” installation method temporary shoring was eliminated that would have been requires for other wall types. Therefore the overall wall cost and construction time was greatly reduced compared to other wall options.