2701 ROCKEFELLER AVE NIMBUS 2024-01-03

Opportrmnyzone Deveropmonr LLC June 6, 2079 JN 19152 Page 10 together. We recommend that an allowable adhesion value of 2,000 pounds per square toot (psf) be used for the design of the soll nails. - The process begins by making a 4- to 6400t vertical out 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 soil -nail walls should be allowed to stand longer than 12 hours without the acceptance of the geotechnical engineer. Furthermore, vertical cuts may be difficult in the underlying clean, outwash sand without minor sloughing. It may be necessary to use eloped cut faces or fill berms within the sand to install the soil nails; a shoring contractor should be consulted about this situation. Once the shotcrete has hardened, the excavation again proceeds and the nails are placed. A geotextile 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 underelab footing drain. Because soil 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, outman sand encountered beneath the she. Again, we recommend that the shoring contractor be consulted regarding potential difficulties and modifications that can occur during the construction of a soil -nailed wall. 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 shoring 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: Soil Type Moist Unit Effective internal Friction Wd t c Angle l reea 1 Effective Cohesion(psf) FIIVlooae native 125 30 50 Glacial Till 140 1 40 300 Advance Outwaeh 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 GEOTECH COnULTANTs, INC.