Correlation of standard penetration test (SPT) and cone penetration test (CPT) data in tropical swampy soils: a case study of Akure, southwestern Nigeria.
OLOLADE S. OGUNJOBI*, ODUNYEMI A. ADEMESO, BAMITALE D. OLUYEMI-AYIBIOWU AND PAUL P. OGBORAFORAvailable online Apr 30, 2026.
[ Original ] Volume 32, Issue 2, 2026, Pages 285-297
Abstract
Subsurface characterisation in tropical swampy soils is critical for reliable foundation design. This study aimed to investigate the relationship between Standard Penetration Test (SPT) and Cone Penetration Test (CPT) results in lowland swampy soils in Akure, southwestern Nigeria, with the objective of developing locally calibrated empirical correlations for geotechnical design applications. It has been observed that conventional empirical correlations often fail to adequately represent the complex behaviour of waterlogged, organic-rich deposits, necessitating further empirical studies of relationships. Field investigations comprised sixteen SPTs and sixteen 2.5-ton CPTs, with an additional nine 10-ton CPTs conducted at selected locations. Corrected SPT blow counts (N₆₀) were correlated with cone resistance (qc) using linear and power regression models. For the 2.5-ton CPT, linear regression produced qc = 474.37N₆₀ + 303.53 (R² = 0.79), while the power model yielded qc = 636.57N₆₀⁰·⁸⁷³⁵ (R² = 0.80). For the 10-ton CPT, correlations were moderate (R² ≈ 0.53–0.54), reflecting increased scatter in the data at greater depths. Correlation strength improved with depth as organic influence diminished and soil stiffness increased in clayey sand and sandy clay strata. The results indicated that locally calibrated SPT–CPT relationships effectively capture soil strength trends in swampy tropical deposits. These findings provided a practical basis for geotechnical design in waterlogged lowlands and underscore the importance of site-specific empirical correlations to enhance reliability in foundation engineering within tropical environments. It is therefore recommended that site-specific SPT–CPT correlations be adopted for foundation design in tropical swampy terrains, rather than relying on generalised global correlations, to improve accuracy and reduce geotechnical uncertainty.
Keywords
SPT-CPT correlation, Tropical swampy soils, CPT, SPT, Geotechnical Characterisation,Download Article without Subscription
GLOBAL JOURNAL OF PURE AND APPLIED SCIENCES 2026
Volume 32 | Issue 2
Page Nos. 285-297
Online since Apr 30, 2026