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Ground Improvement Dr. Talat Bader

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CE353Dr.TALATBADERCE353Dr.TALATBADER Ground Improvement Dr. Talat Bader Slide 2 CE353Dr.TALATBADERCE353Dr.TALATBADER Dynamic Compaction Slide 3 CE353Dr.TALATBADERCE353Dr.TALATBADER Dynamic Deep Compaction Dynamic compaction was first used in Germany in the mid- 1930s. Menard technique France Dynamic Deep Compaction is simply the dropping of heavy weights on ground surface to densify soils at depth Slide 4 CE353Dr.TALATBADERCE353Dr.TALATBADER Why Dynamic Deep Compaction Reduce foundation settlements Reduce seismic subsidence Permit construction on fills Densify garbage dumps Improve mine spoils Induce settlements in collapsible soils Slide 5 CE353Dr.TALATBADERCE353Dr.TALATBADER Dynamic Deep Compaction Design Steps 1. Perform site investigation 2. Develop settlement influence diagrams 3. Develop initial DDC program 4. Develop numerical performance prediction 5. Develop QA/QC plans Slide 6 CE353Dr.TALATBADERCE353Dr.TALATBADER Important Construction Conditions The Drop Weights ranges from 8 to 200 tons Drop Heights ranges from 50 to 100 ft. Impact grids of 7 x 7 ft to 20 x 20 ft Minimum 100-150 ft clearance from any structure Review site for vibration sensitivity Primarily for silts and sands but also clays w h } Slide 7 CE353Dr.TALATBADERCE353Dr.TALATBADERLimitations Problems near groundwater Problems near groundwater Multiple passes to compact at depth Multiple passes to compact at depth Slide 8 CE353Dr.TALATBADERCE353Dr.TALATBADER Effect of Drop on the Ground Slide 9 CE353Dr.TALATBADERCE353Dr.TALATBADER Important Terms Effective Depth -- Maximum depth of ground improvement Zone of Major Densification -- About upper 2/3 of effective depth Energy Level -- Energy per blow (weight times drop height) Energy Intensity Factor -- Involves energy level, spacing, and number of blows Slide 10 CE353Dr.TALATBADERCE353Dr.TALATBADER Depth of Influence From Holtz and Kovacs, 1981 w = Weight of drop (Tons) h = Height of drop (m) D = Depth of influence (m) C = Factor=.3-.7 Depends on soil type Slide 11 CE353Dr.TALATBADERCE353Dr.TALATBADER Dynamic compaction Slide 12 CE353Dr.TALATBADERCE353Dr.TALATBADER Dynamic Compaction Slide 13 CE353Dr.TALATBADERCE353Dr.TALATBADER Important Geotechnical Parameters Soil conditions Groundwater level Relative density Degree of saturation Permeability Slide 14 CE353Dr.TALATBADERCE353Dr.TALATBADER Quality Control Crater depths (map) Surface elevation monitoring Decrease in depth of weight penetration with successive drops Pore pressures Geophysical monitoring Slide 15 CE353Dr.TALATBADERCE353Dr.TALATBADER Thank you Question Time Dr. Talat Bader