Rolling Dynamic CompactionSHUZHUANG CHEN, ZHONGYAN YUDAVID, AIERYSchool of Civil EngineeringFACULTY OF ENGINEERING & INFORMATION TECHNOLOGIES

IntroductionBackground Rolling Dynamic CompactionRolling Dynamic Compaction (RDC) is a widely used ground improvement technique which has been particularly cost-efficient in large construction areas. Despite its popularity, there is a general lack of understanding on its working mechanism.

Objective of ResearchA 1:15 physical impact roller model was employed to examine the effectiveness RDC as well as the feasibility of testing this technique in a laboratory environment.MethodologyBasic Configuration River sand and River sand mixed with 20% fines were tested at three different RDC running speed. In total 9 sets of tests were conducted for this project in a 1.4x0.5x0.28m tank.

Measuring DeviceThe settlement of subgrade soil due to RDC was measured by buried displacement plates connected to LVDT at the tank base. Additionally, CPT was performed as an alternative method to evaluate soil densification.

Results and DiscussionQualitative Observation The videos and photos taken by high speed camera during the test shows the roller was compacting the soil downward as well as pushing the soil out of its way at the same time.

THIS RESEARCH IS SP

THIS RESEARCH IS SPONSORED BY

CPT Results The comparison of CPT results before and after RDC in some group of tests shows a significant improvement of cone tip resistance.

Calibration of sand with different densities was performed to investigate the correlation between normalized and relative densities for a more in-depth dimensionless analysis.

The correlation was found to be. River Sand : Mixture Sand:The relative density vs depths profile produced by dimensionless analysis does not show a clear densification caused by RDC.

Nevertheless, student-T test results suggested that some CPT results may be subjected to severe disturbance from soil surface and should be not relied upon as the lone source of evidence, because of the exceptionally low probabilities values for pre-RDC data.

Settlement Results Subgrade soil settlement provides a solid evidence of soil densification up to 80 mm underneath the surface.

Applying 1-D elastic theory on the settlement results, relative densities before and after RDC can be estimated by the following calculation.

Id(%) = For this research project, the density was shown to experience a 20%-30% increase.

Scale-up of Results The empirical formula for influence depth estimate produced by Maneard and Borise (1975) suggests the following relationship

The laboratory results returns n values ranging from 0.24 to 0.69 It is consistent with the research result conducted by Rollins and Rogers (1994) which approximated the n value to be 0.4-0.6. Conclusion 1. Loosening and densification were both

observed near soil surface at RDC.2. Soil densification (up to 20-30%increase)

occurred under the surface 3. The influence depth of RDC model has a

minimum value of 80 mm. 4. CPT result can be used as a more reliable

evaluating tool at tests with larger scale. 5. The use of empirical methods for influence

depth estimate has worked reasonably successfully.

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Loose sand relative density vs Depth

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Calibration Results with Different Densities

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Relative Density(%) vs Normalised qc (MPa)

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Student T-Test Results 1m/s

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