2701 ROCKEFELLER AVE NIMBUS Geotech Report 2023-12-29

OpporWnhy Zone Development LLC June 6, 2019 JN 19152 Page 10 together. We recommend that an allowable adhesion value of 2,000 pounds per square foot (psf) be used for the design of the soll nails. The process begins by making a 4- to 6400t vertical cut In the shoring area followed Immediately by the placement of anchors. The cut face is then covered with a wire mesh, and shotcrete is placed over the mesh and soil face. Generally, no temporary, unsupported excavations for will walls should be allowed to stand longer than 12 hours without the acceptance of the gectechnical engineer. Furthermore, vertical cuts may be difficult in the underlying clean, outwash sand without minor sloughing. It may be necessary to use sloped cut faces or fill berms within the sand to install the soil nails; a shoring contractor should be consuited about this situation. Once the shotcrete has hardened, the excavation again proceeds and the nails are placed. A geotexiile drainage composite must be placed over the face of the cut prior to shotcreting to prevent buildup of hydrostatic pressures behind the shotcrete facing. As the excavation progresses downward, the drainage composite strips are extended, until reaching the base of the excavation, where weep holes are placed through the shotcrete to be tied into an underslab footing drain. Because soll nails are passive elements (they are not pre -stressed as tiebacks are), soil -nail walls will typically deflect more than a soldier -pile wall. This involves more risk of causing damage to adjoining utilities, streets, and other on -grade elements. The shoring designer should provide an estimate of the lateral deflection that is anticipated for the soil nail wall. Caving of loose or granular soils, or in zones of seepage, can require that the shoring contractor modify their installation techniques. This can increase the cost and time necessary to Install the nailed wall. This may specifically be an Issue In the clean, underlying, outwash sand encountered beneath the site. Again, we recommend that the shoring oontracor be consulted regarding potential difficulties and modifications that can occur during the construction of a soil -palled well. This adhesion value should be substantiated by load -testing at least two anchors In each soil type to at least 200 percent of their design capacity, prior to installing production anchors. During shoring construction, at least 5 percent of the production anchors should be proof -tested to 130 percent of the design anchor capacity. The shoving designer will likely utilize one of several commercially available computer programs to design the nailed walls. We recommend that the following soil strength parameters be used in the nail wall design: Sog Type Moist Uolt BReMlvelnhrnal Frletion W t c Angle (dea re Effective Cohesion(pA) FIIVI7S , native 125 30 50 Glacial Till 140 40 Wit Advance Outwash Sand 135 42 50 Surcharges from adjacent existing structures and roads must be included in the design. EXCAVATION AND As with any shoring system, there Is a potential risk of greater -than -anticipated movement of the shoring and the ground outside of the excavation. This can translate into noticeable damage of OEOTECfl CONSULTANTS, INO.