Temporary VENIS© Shoring Wall
LEGACY TOWERS PROJECT
When Legacy Partners and the Fria Company requested bids
for a 25,000 square foot Owner-Design conventional shoring
wall, as well as a proposal for a Design-Build alternate,
Ground Support PLLC and Malcolm Drilling Company Inc.
proposed the VENIS© system, with roughly a 25% cost
savings compared to the Owner-Designed shoring system.
View from the Northwest of the East and South Walls After
- Subsurface conditions consisted of 10- to 15-ft of fill
underlain by glacial soils. The glacial soils consisted of
an erratic sequence of recessional outwash, transitional
materials, and hard silts and clays.
- The groundwater table was encountered near the base of
the fill. Dewatering wellpoints were installed to
depressurize the face of the excavation.
- Three-sided excavation along Broad Street, Western
Avenue, and Clay Street, North of downtown Seattle.
- Excavation was up to 42-ft deep, with over 25,000
square feet of shoring wall face, and was surrounded by a
variety of deep electrical and telephone duct banks and
- Because of the nature of the fills and recessional
outwash, and the presence of groundwater, it was generally
agreed that standard soil nailing was not practical due to
inadequate face stability. Therefore, the Owner-Design
consisted of a conventional anchored soldier pile and
View from the Southwest of the East and North Walls After
SHORING DESIGN SUMMARY
- Ground Support and Malcolm Drilling proposed a
Design-Build alternate to the Owner-Design shoring system.
The Owner-Design conventional shoring wall was bid at
roughly $40 per square foot (SF) of wall face. The
Design-Build alternate VENIS© system was bid at just
under $30 per SF, for a $10 per SF savings to the Owner.
- VENIS© stands for Vertical Element and Nail
Integrated Support system. The shoring system combines a
modified facing system with standard soil nails in order to
deal with adverse face stability conditions that would
normally require a timber-lagged shoring wall.
- In most situations, the VENIS© system will be more
economical than conventional shoring. The most beneficial
situations will occur when the VENIS© system is used
to get through upper less competent soils, below which
standard soil nailing may be used in underlying more
- The presence of deep utility duct banks and vaults
required that the first row of soil nails be installed from
5- to 13-ft below existing grade. This was accomplished to
some extent through the use of sloped cuts, but mainly
through the use of high cantilevers in the vertical
elements above the first row of soil nails.
View of Soil Nail Installation.
View of Wall Face Excavation.
SHORING CONSTRUCTION SUMMARY
- The soil nail support system on this project generally
consisted of a 6-ft horizontal by 7- to 8-ft vertical
staggered soil nail pattern. The increased vertical nail
spacing is possible with the presence of the vertical
elements, allowing the elimination of 1 or 2 rows of soil
- The facing system was comprised of vertical elements on
3-ft spacings around the site perimeter. The soil nails
were attached to the vertical elements with walers and
shotcrete lagging was connected to the vertical elements
with headed studs.
- Face stability problems were essentially non-existent
in all of the soils. Prior to application of shotcrete
lagging, vertical cuts of 6- to 8-ft in height stood well
for days with essentially no fallout or sloughing.
- Wall face excavation was simplified because the
excavator would run the hoe bucket down the face of the
piles, prohibiting inadvertent over-excavation.
- Because of the simplified facing design and the large
vertical nail spacing, installation of shotcrete lagging
was very efficient and productive. It was not uncommon to
exceed 2000 SF of shotcrete facing installation per day.
- Optical survey monitoring was performed along the edge
of the adjacent streets and at the top of the vertical
elements. The measured lateral and vertical movements were
typically less than 1/4-inch on average and never exceeded