2701 ROCKEFELLER AVE NIMBUS Geotech Report 2023-12-29

Opportunity Zone Development uc June 8, M19 JN 19152 Page 9 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 transferad 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 8 they will affect the configuration and length of the tiebacks. Based on the results of our analyses and our experience at other construction shes, we suggest using an adhesion value of 2,500 psf in the very dense native soils 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 she. 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 thesetiebacks should not be grouted until the performance tests are completed. Unfavorable results from these performance tests could require increasing the lengths of the tiebacks. The remaining anchors should be proof -tested to at least 135 percent of their design value before being 'locked off.' After testing, each anchor should be locked off at a prestress load of 80 to 100 percent of its design load. If caving or water -bearing soil is encountered, the Installation of tieback anchors will be hampered by caving and soil flowing into the holes. It will be necessary to was the holes, if such conditions are encountered. Alternatively, the use of a hollow - stem auger with grout pumped through the stem as the auger is withdrawn would be satisfactory, provided that the injection pressure and grout volumes pumped are carefully monitored. All drilled Installations should be grouted and backfilled immediately after drilling. No drilled holes should be left open overnight. Soil Nallina Soil nailing is a shoring system where closely spaced, tieback anchors (nails) are grouted into drilled holes in the cut face as the excavation proceeds, thereby reinforcing the cut face. More anchors are required for this system than for conventional systems, but steel soldier piles and timber lagging are eliminated. The anchored or nailed system essentially operates as a reinforced soil wall or a gravity wall, with the nails tying the soil mass OEOTECH CONSULTANTS, INC.