Increase of CPT Cone Resistance in Sand Due to Installation of Press-In Piles-Article

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The study examined whether installing press-in piles alters nearby soil conditions measured by cone penetration testing. At a reclaimed site in Tuas, Singapore, three closed-toe, 600-mm-diameter, approximately 30-m-long spun piles were jacked through loose hydraulic sand fill, marine clay, and deeper natural soils. CPTU soundings were conducted before and after installation at several distances from each pile.<br /><br />Post-installation soundings showed a substantial increase in cone resistance in the sand fill, indicating densification. The increase was greatest close to the piles and remained evident as far as 1.5 m away—about 2.5 pile diameters from the pile center. At the nearest sounding locations, average post-installation cone resistance was approximately 1.8 times the pre-installation value. In contrast, the CPT records showed no clear installation-related change in cone resistance in the natural soils below the fill.<br /><br />The authors caution that the dataset was too small for robust statistical conclusions: only ten soundings were taken before and ten after installation, and pre-installation measurements already varied. Some observed differences may therefore reflect natural variability or measurement scatter. The results nevertheless suggest that even static press-in installation can densify loose sand beyond the immediate pile vicinity. Pile-driving methods might produce an even stronger effect.<br /><br />This finding matters when estimating pile performance from CPT data. Because many CPT-based methods relate pile response to cone resistance, measurements taken after installation may not represent the original soil conditions, while pre-installation values may not capture the soil state around the installed pile. The authors recommend further studies of installation effects across pile types and soil conditions.

Keywords

press-in piles

cone penetration testing

CPTU

soil densification

cone resistance

reclaimed site

pile installation effects

loose sand fill

spun piles

pile performance estimation