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Geotechnical Investigation Report 03/11/2025 <br />2234 S Lowell St., Santa Ana, CA 92707 Page | 8 <br /> <br />Active earth pressure coefficient π‘˜=π‘‘π‘Žπ‘›45 βˆ’βˆ…= 0.30 <br />Passive earth pressure coefficient π‘˜=π‘‘π‘Žπ‘›45 +βˆ…= 3.40 <br />At-rest earth pressure coefficient π‘˜°= 1 βˆ’ sin (βˆ…) = 0.45 <br /> <br />Equivalent fluid active pressure p = 0.30 × 120 = 36 pcf <br />Equivalent fluid passive pressure p = 3.40 × 120 = 408 pcf <br />Equivalent fluid at-rest pressure p = 0.45 × 120 = 54 pcf <br />The friction coefficient between the bottom of foundation concrete and the soil is 0.25. <br />SEISMIC ACTIVE EARTH PRESSURE COEFFICIENT <br />Mononobe-Okabe method can be used to estimate the seismic lateral earth pressure on the <br />retaining walls. For a horizontal backfill behind a vertical retaining wall, considering the backfill <br />strength parameters (βˆ… = 33 π·π‘’π‘”π‘Ÿπ‘’π‘’,𝛾= 120 𝑝𝑐𝑓), seismic peak ground acceleration (𝑃𝐺𝐴= <br />0.656𝑔), horizontal seismic acceleration coefficient π‘˜ and seismic lateral earth pressure <br />coefficient can be as in the following table: <br />Table 3– Horizontal acceleration coefficient and seismic lateral pressure coefficient <br />Wall Movement (inches) π’Œπ’‰ (g) 𝑲𝒂𝒆 <br />More than: 2 0.22 0.43g <br />Note: <br />For 𝐾 calculation, the horizontal seismic acceleration coefficient π‘˜=𝑃𝐺𝐴 if the wall can <br />rotate and move laterally more than 2 inches. If the wall is not capable /allowed to move laterally <br />use π‘˜=𝑃𝐺𝐴. For 1 to 2 inches lateral movement use π‘˜= 0.5 𝑃𝐺𝐴 <br /> <br /> <br /> <br /> <br />