HW#19 - Seismic Analysis

The following spreadsheet is designed to solve for a factor of safety for a seismic slope stability analysis using the Bishop's Simplified Procedure (BSP). The spreadsheet uses the simplified approach inolving an R-envelope. Pore pressures are calculated to ensure that effective stresses are used to compute the consolidation stress, resulting in a appropriately selected undrained strength value from the R-envelope. This approach would be appropriate for man-made slopes under long-term (post-consolidation) conditions.

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a) Assume that the slope is in St. George Utah. Find the peak accelaration assuming a 2% chance of exceedance in 50 years and enter the value in cell D4.

b) Enter the missing formulas in the yellow cells. The F (guess) value is the estimated F used in the numeractor of the factor of safety equation. You will need to iteratively solve for the final solution by entering new values for F (guess) until the residual is zero. You can use the Goal Seek command to do your iteration. To simplify the process, record a VB macro that solves for F using Goal Seek. Then associate the Solve button with your macro or copy the code from the macro to the code for the button.

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