Liquefaction Mitigation â€“ Indian practice and recent studies-Paper

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The paper reviews liquefaction mitigation practice in India and recent research on ground-improvement methods. Liquefaction occurs when earthquake shaking raises pore-water pressure in saturated soil, reducing its strength and stiffness and potentially causing settlement, foundation damage, or slope failure.<br /><br />Assessment typically compares the soil’s cyclic resistance ratio with earthquake-induced cyclic stress ratio, using SPT, CPT, or shear-wave-velocity data. The authors emphasize reliable site investigation, accurate measurement of SPT hammer energy, and careful determination of fines content. For important projects, estimated liquefaction-induced settlement should also be checked against structural tolerances.<br /><br />Mitigation methods include soil replacement, densification, solidification, reinforcement, and drainage. In India, vibro compaction and vibro stone columns are the predominant approaches, with dynamic compaction and compaction grouting used at some sites. Vibro compaction works best in sands and gravels with low fines; trials help establish suitable spacing and verify improvement. Stone columns can mitigate liquefaction through densification, increased lateral stress, reinforcement, and drainage.<br /><br />A key research finding concerns the reinforcement effect of stone columns. Traditional shear-strain-compatibility assumptions may overestimate their ability to reduce seismic shear stresses. Numerical studies suggest that reinforcement alone may reduce stresses by roughly 10–30%; the densification achieved during installation should be evaluated separately through field testing. Research also indicates that lattice-shaped reinforcement, such as deep soil mixing or jet-grouted grids, may be more effective than isolated columns, particularly where soils cannot be densified.<br /><br />The authors recommend selecting techniques according to site conditions, verifying performance through appropriate testing, and updating Indian practice to reflect advances in liquefaction assessment and mitigation design.

Keywords

liquefaction mitigation

ground improvement

earthquake shaking

cyclic resistance ratio

cyclic stress ratio

SPT

CPT

vibro compaction

stone columns

deep soil mixing