Studies on the use of DCIS piles for mitigating Liquefaction of Soils-Paper

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The study evaluates driven cast-in-situ (DCIS) displacement piles as a ground-improvement method for mitigating liquefaction at a site in northeastern India. Liquefaction assessments identified susceptible layers at approximately 8–14 m depth at Building A and 10–14 m at Building B. The site’s profile includes silty sand and silty clay, with groundwater depths of 4.3–9.2 m.<br /><br />DCIS pile groups were installed at two locations, using pile spacings of 4D and about 5D, where D is pile diameter. Cone penetration tests (CPTs) conducted before and after installation measured changes in cone resistance and supported reassessment of liquefaction triggering.<br /><br />Post-installation CPT results showed substantial increases in cone resistance, especially in cohesionless silty sand. In the susceptible depth range, reported increases in cone resistance were 7–22 MPa at Building A and 11–22 MPa at Building B. Geometric-average cone resistance increased by 172% for 4D spacing and 145% for approximately 5D spacing. Improvement extended below pile bases, indicating that pile driving densified soil at depth.<br /><br />Post-treatment liquefaction analyses showed factors of safety of approximately 1.5–7 in silty sand, suggesting that liquefaction triggering was mitigated there. Improvements in silty clay were more limited, attributed to remoulding during installation.<br /><br />The findings indicate that DCIS piles can improve liquefaction resistance in deeper silty-sand layers and may offer an alternative ground-improvement technique. Further study is recommended to assess their performance more broadly.

Keywords

driven cast-in-situ piles

DCIS displacement piles

liquefaction mitigation

ground improvement

cone penetration test

cone resistance

silty sand

silty clay

pile spacing

liquefaction resistance