Resisting Pressures/Loads Sample Clauses

Resisting Pressures/Loads. Passive earth pressure • The passive earth pressure, Pp, below the excavation line may be computed by Rankine or Log-Spiral theories, but not the Coulomb theory. • For Log-Spiral theory, the interface friction angle shall not be greater than one-half of the effective friction angle of the soil, or that consistent with published values for specific types of soil in contact with either steel or concrete. • The passive earth pressure for cohesionless soils (sands, gravels and some silts), uncontrolled fill, and mixed layers of cohesive and cohesionless soil shall be calculated based on the effective friction angle of the soil. • The passive earth pressure for cohesive (clay and some silts) soils and controlled backfill shall be calculated for the effective stress condition (see Section 3.5d.i for definition), unless the resulting earth pressure for the total stress condition (i.e., Su) is less. • For conditions where the slope in front of the shoring slopes down and away from the wall, the slope in front of the wall shall be considered when calculating passive pressure. If the ground in front of the shoring slopes upwards away from the wall, the ground level shall be assumed to be level for analysis. • For reference, Rankine equations are provided below: KP – Passive Earth Pressure Coefficient σPH – Horizontal Passive Earth Pressure (lbf/ft2) ϕ’ – Effective Friction Angle (deg) c’ – Effective cohesion (lbf/ft2) Su – Undrained Shear Strength (lbf/ft2) γ – Moist Unit Weight of Soil (lbf/ft3) z – Depth Below Ground Surface (ft) β – Front Slope Angle (deg) 𝜎𝑃𝐻 = 𝐾𝑃 𝛾 𝑧 , 𝑤ℎ𝑒𝑟𝑒 𝐾𝑃 = 𝑡𝑎𝑛2 (45 + 𝜙′) 2 ▪ Use only if ground is sloping down and away from shoring (i.e., β is negative) 𝑐𝑜𝑠𝛽 + √𝑐𝑜𝑠2𝛽 − 𝑐𝑜𝑠2𝜙′ 𝜎𝑃𝐻 = 𝐾𝑃 𝛾 𝑧 cos 𝛽 , 𝑤ℎ𝑒𝑟𝑒 𝐾𝑃 = cosβ ( ) 𝑐𝑜𝑠𝛽 − √𝑐𝑜𝑠2𝛽 − 𝑐𝑜𝑠2𝜙′ 𝜎𝑃𝐻 = 𝐾𝑃 𝛾𝑧 + 2𝑐′√𝐾𝑃 𝐾𝑃 = 𝑡𝑎𝑛2 (45 + 𝜙′) , 𝐹𝑜𝑟 𝐿𝑒𝑣𝑒𝑙 𝐹𝑟𝑜𝑛𝑡𝑠𝑙𝑜𝑝𝑒 𝑐𝑜𝑠𝛽 + √𝑐𝑜𝑠2𝛽 − 𝑐𝑜𝑠2𝜙′ 𝐾𝑃 = cosβ ( ) , 𝐹𝑜𝑟 𝑆𝑙𝑜𝑝𝑖𝑛𝑔 𝐹𝑟𝑜𝑛𝑡𝑠𝑙𝑜𝑝𝑒 𝑐𝑜𝑠𝛽 − √𝑐𝑜𝑠2𝛽 − 𝑐𝑜𝑠2𝜙′ ▪ Effective cohesion shall be assumed to be zero unless local experience by a Licensed Geotechnical Engineer indicates the fully softened strength of the clay will have an effective cohesion greater than zero. ▪ The passive resistance for fractured rock and intermediate geomaterials (e.g., weak shales, sandstone, etc.) shall be based on either the rock mass effective cohesion and friction angle, or mass shear strength. The mass strength parameters shall be determine using a methodology that accounts for rock type, intact strength, spacing and conditions of j...