3322 BROADWAY COMPASS HEALTH 2025-10-03

Compass Health June 26, 2019 JN 19178 Page 10 The vertical capacity of soldier piles to carry the downward component of the tieback forces will be developed by a combination of frictional shaft resistance along the embedded length and pile end -bearing. Pile Shaft Friction 2,500 psf Pile End -Bearing 20,000 psf Where: psf is Pounds per Square Foot. The above values assume that the excavation is level in front of the soldier pile and that the bottom of the pile is embedded a minimum of 10 feet below the floor of the excavation. For the pile end -bearing to be appropriate, the bottom of the drilled holes must be cleaned of loosened soil. The shoring contractor should be made aware of this, as it may affect their installation procedures. The concrete surrounding the embedded portion of the pile must have sufficient bond and strength to transfer the vertical load from the steel section through the concrete into the soil. Tieback Anchors General considerations for the design of tied -back or braced soldier -pile walls are presented on Plate 8. We recommend installing tieback anchors at inclinations between 20 and 30 degrees below horizontal. The tieback will derive its capacity from the soil -grout strength developed in the soil behind the no-load zone. The minimum grouted anchor length should be 10 feet. The no-load zone is the area behind which the entire length of each tieback anchor should be located. To prevent excessive loss -of -ground in a drilled hole, the no-load section of the drilled tieback hole should be backfilled with a sand and fly ash slurry, after protecting the anchor with a bond breaker, such as plastic casing, to prevent loads from being transferred to the soil in the no-load zone. The no-load section could be filled with grout after anchor testing is completed. During the design process, the possible presence of foundations or utilities close to the shoring wall must be evaluated to determine if they will affect the configuration and length of the tiebacks. Based on the results of our analyses and our experience at other construction sites, we suggest using an adhesion value of 2,500 psf in the very dense glacial till to design temporary anchors, if the mid -point of the grouted portion of the anchor is more than 10 feet below the overlying ground surface. This value applies to non -pressure -grouted anchors. Pressure -grouted or post -grouted anchors can often develop adhesion values that are two to three times higher than that for non -pressure -grouted anchors. These higher adhesion values must be verified by load testing. Soil conditions, soil -grout adhesion strengths, and installation techniques typically vary over any site. This sometimes results in adhesion values that are lower than anticipated. Therefore, we recommend substantiating the anchor design values by load -testing all tieback anchors. At least two anchors in each soil type encountered should be performance - tested to 200 percent of the design anchor load to evaluate possible anchor creep. Wherever possible, the no-load section of these tiebacks should not be grouted until the GEOTECH CONSULTANTS, INC.