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DIFFERENTIAL LANDFILL SETTLEMENT - 5% FINAL CLOSURE SLOPE <br />DIFFERENTIAL LANDFILL SETTLEMENT SC I <br />;This is a spreadsheet model to estimate landfill differential settlement assuming secondary type settlement j <br />after closure due primarily to decomposition of refuse. The following generally describes the structure of ' <br />.the model: <br />1. The model consists of 10 horizontal " lifts" of waste laid out as a series of cells. <br />12. A base settlement percentage and a differential reduction percentage is applied to each cell to produce <br />(a post -settlement depth for the cell. The differential reduction percentage in each cell is calculated by j <br />,multiplying the differential settlement percentage by a random number between 0 to 1. For example, if the I <br />base setdement is 10% and the differential,setttement is 5%, then the range of settlement for the cell will be <br />�a random number between 10% to 15%. <br />�3. It is assumed that "bridging" of the refuse will tend to decrease in influence of differential settlement. <br />,Also the vertical summation of cells may overestimate the effect of differential settlement by not accounting <br />for the horizontally random distribution of the refuse. To compensate, the differential settlement of the cell <br />;is a weighted average of the main cell and the four adjacent cells as follows: <br />[( STARTING LIFT HEIGHT x (BASE SETTLEMENT % - (RANDOM # x DIFF SETTLEMENT %)) <br />+ AVERAGE OF ADJACENT CELL HEIGHTS] / 2 <br />4. The vertical column of cells is then summed to estimate a post settlement surface elevation.fromAhese <br />elevations and grid spacing, the final slope between cells is calculated. For demonstration purposes a <br />single cross section is graphed. <br />qW <br />• <br />