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North Oaks Company LLC <br />Project B2402335 <br />August 22, 2024 <br />Page 16 <br />As shown in Figure 3, we recommend Zone 2 consist of retained engineered fill, and this material will <br />control lateral pressures on the wall. <br />C.4.11b. Configuring and Resisting Lateral Loads <br />Below -grade wall design can use active earth pressure conditions, if the walls can rotate slightly. If the <br />wall design cannot tolerate rotation, then design should use at -rest earth pressure conditions. <br />Rotation up to 0.002 times the wall height is generally required for walls supporting sand. Rotation <br />up to 0.02 times the wall height is required when wall supports clay. <br />Table 11 presents our recommended lateral coefficients and equivalent fluid pressures for wall design of <br />active, at -rest and passive earth pressure conditions. The table also provides recommended wet unit <br />weights and internal friction angles. Designs should also consider the slope of any engineered fill and <br />dead or live loads placed behind the walls within a horizontal distance that is equal to the height of the <br />walls. Our recommended values assume the wall design provides drainage so water cannot accumulate <br />behind the walls. The construction documents should clearly identify what soils the contractor should <br />use for engineered fill of walls. <br />Table 11. Recommended Below -Grade Wall Design Parameters — Drained Conditions <br />Active <br />At -Rest <br />Passive <br />Wet Unit <br />Equivalent Fluid <br />Equivalent Fluid <br />Equivalent Fluid <br />Weight <br />Friction Angle <br />Pressure <br />Pressure <br />Pressure* <br />Retained Soil <br />(Pcf) <br />(degrees) <br />(Pcf) <br />(Pcf) <br />(Pcf) <br />Clayey soil <br />(CL, SC) <br />125 <br />26 <br />50 <br />70 <br />320 <br />Silty Sand <br />(SM) <br />130 <br />30 <br />42 <br />62 <br />390 <br />Sand <br />120 <br />34 <br />35 <br />55 <br />N/A <br />(SP, SP-SM) <br />*Based on Rankine model for soils in a region behind the wall extending at least 2 horizontal feet beyond the bottom outer <br />edges of the wall footings and then rising up and away from the wall at an angle no steeper than 60 degrees from horizontal. <br />Sliding resistance between the bottom of the footing and the soil can also resist lateral pressures. We <br />recommend assuming a sliding coefficient equal to 0.3 between the concrete and on site soil. <br />The values presented in this section are un-factored. <br />BRAUN <br />INTERTEC <br />