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Numerical Studies on the Effectiveness of Dynamic Compaction in Loose Granular Deposits Using Shear Wave Velocity Profiling

By: Kundu, Saptarshi.
Contributor(s): Viswanadham, B. V. S.
Publisher: New York Springer 2018Edition: Vol,48 (2), June.Description: 305-315p.Subject(s): Civil EngineeringOnline resources: Click Here In: Indian geotechnical journalSummary: Over the past few decades, Dynamic compaction (DC) has gained popularity as an effective improvement technique for geomaterials in view of its simplicity, low-environmental impact and cost effectiveness. The low carbon footprint associated with this ground remediation method addresses the adverse ecological threats imposed on the environment and society due to unsustainable geotechnical engineering practices encountered in the face of rapid urbanization. In the literature, studies related to numerical modelling of DC are limited, and the existing databases are founded on field trials, past experience and empirical equations. Further, till date, numerical evaluation of improvement in soil strength post DC is restricted primarily to change in relative density of soil samples before and after impact, whereas, in the field, shear wave velocity (Vs) profiling is frequently adopted as a monitoring technique for measuring the degree and depth of improvement. This necessitates a quantitative correlation between the DC design parameters (tamper radius, energy and momentum) and the available shear wave profile data measured in the field for effective design and execution of DC methodology. In order to overcome the above mentioned research gaps, an elasto-plastic soil model with Drucker–Prager failure criteria is incorporated in the present study using FE software ABAQUS. The response of the soil model to large strains developed during multiple tamper drops on dry sand is investigated numerically, and validated with the results of a centrifuge model test, and numerical analyses published in literature. Further, the shear wave velocity of soil samples is assessed numerically based on the value of shear modulus, and subsequent improvement in model soil due to impact (66% in the present case) is studied to arrive at a better practical application. The results are compared with physically observed field data, and are found to corroborate well. Subsequent parametric studies are carried out by varying the design parameters related to DC, which indicates that the degree and depth of improvement of soil in terms of Vs increases substantially (about 40%) with an increase in momentum and decreasing tamper radius (about 60%), whereas, energy imparted has comparatively lesser impact on improvement. A method is eventually proposed with design equations to calculate the improvement after DC in field based on Vs profiling, depending on momentum and radius of tamper. Further, structural requirements coupled with Vs profile data computed in the ground remediated by DC can help in avoiding construction of expensive deep foundations in sites exhibiting poor subsoil profiles, thereby economizing the project. In addition, the above concept ensures sustainability in engineering practices by enabling land-reclamation and utilization of sites exhibiting locally available compressible soils for infrastructure construction and foundation support.
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Over the past few decades, Dynamic compaction (DC) has gained popularity as an effective improvement technique for geomaterials in view of its simplicity, low-environmental impact and cost effectiveness. The low carbon footprint associated with this ground remediation method addresses the adverse ecological threats imposed on the environment and society due to unsustainable geotechnical engineering practices encountered in the face of rapid urbanization. In the literature, studies related to numerical modelling of DC are limited, and the existing databases are founded on field trials, past experience and empirical equations. Further, till date, numerical evaluation of improvement in soil strength post DC is restricted primarily to change in relative density of soil samples before and after impact, whereas, in the field, shear wave velocity (Vs) profiling is frequently adopted as a monitoring technique for measuring the degree and depth of improvement. This necessitates a quantitative correlation between the DC design parameters (tamper radius, energy and momentum) and the available shear wave profile data measured in the field for effective design and execution of DC methodology. In order to overcome the above mentioned research gaps, an elasto-plastic soil model with Drucker–Prager failure criteria is incorporated in the present study using FE software ABAQUS. The response of the soil model to large strains developed during multiple tamper drops on dry sand is investigated numerically, and validated with the results of a centrifuge model test, and numerical analyses published in literature. Further, the shear wave velocity of soil samples is assessed numerically based on the value of shear modulus, and subsequent improvement in model soil due to impact (66% in the present case) is studied to arrive at a better practical application. The results are compared with physically observed field data, and are found to corroborate well. Subsequent parametric studies are carried out by varying the design parameters related to DC, which indicates that the degree and depth of improvement of soil in terms of Vs increases substantially (about 40%) with an increase in momentum and decreasing tamper radius (about 60%), whereas, energy imparted has comparatively lesser impact on improvement. A method is eventually proposed with design equations to calculate the improvement after DC in field based on Vs profiling, depending on momentum and radius of tamper. Further, structural requirements coupled with Vs profile data computed in the ground remediated by DC can help in avoiding construction of expensive deep foundations in sites exhibiting poor subsoil profiles, thereby economizing the project. In addition, the above concept ensures sustainability in engineering practices by enabling land-reclamation and utilization of sites exhibiting locally available compressible soils for infrastructure construction and foundation support.

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