Construction of Commercial Office SpaceContractor:
Retaining Awll Company,Alpharetta,Georgia,USAConsultant :
M/s REDI Engineering,Alpharetta,Georgia,USAProject Location:
Northeast Georgia,USASRV Block Unit:
Keystone Compac IIProduct:
TechGrid Geogrid TGU40&TGU80
Availability of poor quality soil at site and other constraints on a new commercial development dictated that retaining walls to be consructed to develop usable development space.Due to the severity of the soil,the site required to be constructed reinforced soils walls over 20,000sq.ft.to achieve the developers targeted land are.
These walls were required to facilitate the construction of a two-story office building and linked parking areas.Some of the walls face areas were visible, while some were buried providing support. As a result, both SRW concrete block wall facia and wire form-facing options were utilized.The maximum wall height approached 40 ft.(12.192 meters)
In this complicated site, on many occasions the global stability was critical to the design.During constriction on area of the sub grade was considered unstable.Significant remedial work was required, including over-excavation and reconstruction with a combination of wire form facing internally reinforced with geogrids.
The plan view for this site is included as
Photo 1 wall locations surround the property,running along the Western and Southwestern property line.
Photo 2 show the redesign of the Southwetern corner of the site,a change made after the initial wall location plan was developed to accommodate soft soils uncovered during initial construction.Wall 2,2A and wall 2B are the replacements for the original wall 5.Note that wall 2B is a wire formed reinforced retaining wall.The site was mostly underlain by silty, sandy clay soils.Soil testing was done to obtain information on soil strength properties for use in design.
Part of the site had previously been used as a waste disposal area and an unsuitable fill was encountered during excavation for the wall. These condition were kept in mind while designing wall 2B, the wire formed wall describe the design section below.
The significant grade change on the southwest portion of the site (from elev. 1330 at the toe of slope to elev. 1375, or more than 45 feet) required extensive global stability analyses to be performed. This was combined with the existing wall above the sewer plant to provide the critical section.
Two design concepts were used in this site:
A wire form faced Geogrid reinforced steep slope(wall 2B Section A-A)
A Geogrid reinforced segmental block retaining wall(Wall 2,section B-B )
There were more walls on site,but these two are representative of critical sonditions faced for this project.
Photo 3 shows the cross section and elevation view near the begining of wall 2B where more than 40 ft of elevation difference and an existing retaining wall needed to be accommodated.
GSLOPE 4.0(MITRE Corporation, Canada) a limit equilibrium slope stability analysis program was used for the global stability analysis.This program allows different soil layers, as well as geogrid strengths to be used.
Photo 4 presents the results of the wall 2B Section A-A analysis.Minimum Factor of safety(FOS) of 1.3 was required.
Geogrid reinforced Segment Reatining wall (SRW) designs SRW geogrid walls comprised the majority of the wall face area for this site,all reinforced with TechGrid geogrids. Design procedures followed the National Concrete Masonry Association (NCMA) Segmental Retaining Wall design manual, 2nd edition (1977) and the accompanying software.
Connection strength testing was performed with the Keystone Compac II to allow the wall design to be completed.These results were input to the SRWall design software for the TechGrid geogrids TGU40 & TGU80.The result was an efficent design, using the combination of TechGrid geogrids TGU40 & TGU80.
Removal of the waste soils from the site was required before construction could commerce.Intial exposures of the wire formed sections of the wall were designed and subsequently it was buried upon completion and final depending on location.
Photos 5 & 6 shows majority project has been completed as per above mentioned information.Later the market conditions for commercial construction were such that the project has been put on hold indefinitely.
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