Design Guidelines for Increasing the Lateral Resistance of Highway-Bridge Pile Foundations by Improving Weak Soils (2011) / Chapter Skim
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From page 61... ...
6.2 Mass Mix Depth Effect (Below the Cap) on Lateral Resistance The second parametric study investigated the effect of the depth of a mass mix layer below the pile cap on the lateral pile group resistance.
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Parametric study of mass mix depth adjacent to the cap on the computed load-displacement curve.
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Improvement ratio as a function of mass mix depth adjacent to cap. Figure 6-4.
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underneath the cap, the lateral resistance will increase by approximately 40% to 86% for similar soil and pile profiles. The increased resistance from the soil treatment is partially due to the increased passive area and partially due to constraint of piles by the mass mix (so that the mass mix and the piles can be considered as an integrated block)
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From page 65... ...
In this case, the mass mix block also was assumed to be beside the pile cap but not in contact with the piles. The depth of the block was fixed at 12.5 ft and the width was taken as 9.0 ft perpendicular to the lateral load direction (4.5 ft in the FEM model due to symmetry)
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From page 66... ...
6.4 Jet Grout Depth Effect (Beside the Cap) on Lateral Resistance This parametric study is very similar to that conducted for the mass mix treatment except that the improved soil is now soilcrete produced by jet grouting, which has a higher strength than that from the soil mixing.
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From page 67... ...
Parametric study of jet grout depth adjacent to the cap on the computed load-displacement curve.
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From page 68... ...
Again, the improved soil below the cap will resist external load in any direction. It also is important to note that the increase in lateral resistance for the soilcrete produced by jet grouting was very similar to that obtained for the soilcrete produced by mass mixing despite the lower compressive strength.
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Jet grout depth intervals below cap for parametric study. Figure 6-14.
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Improvement ratio as a function of jet grout treatment depth below the cap.
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, provided the improved soil is much stiffer than the virgin clay. The typical mass mix and jet grouting soilcrete are much stiffer than the soft clay.
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From page 72... ...
Note 21 261 63 452 126 640 Typical mass mix 252 905 300 987 600 1400 Typical jet grout 900 1710 1200 1980 4000 3600 7700 5000 Typical concrete The final set of parametric studies involved varying the compressive strength of the soilcrete zone directly below the pile cap as shown in Figure 6-22. As shown, the soilcrete zone was 9 ft square in plan view and extended 12.5 ft below the ground surface.
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From page 73... ...
Based on the parametric analyses some important conclusions have been developed, as follows: 1. The lateral resistance of the pile group is not sensitive to the material strength of the improved soil (including mass mix and jet grouted soilcrete)
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From page 74... ...
Treatment zone relative to pile group for parametric study involving the effect of compressive strength of the improved soil below the cap.
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From page 75... ...
4. Improving the soil directly below the pile cap increased lateral resistance by 40% to 85% relative to untreated clay for the improved soil depths of 5.0 to 12.5 ft (4.7D to 11.8D)
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