Foundations Settlement Estimation by Non-Linear Stress-Strain Approach Using CPT Records-Paper

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The paper presents a CPT-based method for estimating shallow-foundation and pile-group settlement using Janbu’s nonlinear stress–strain framework. Conventional Janbu calculations use broad, fixed ranges for the stress exponent, <em>j</em>, and modulus number, <em>m</em>, which can introduce uncertainty. The proposed method instead derives continuously varying values from corrected cone resistance and friction ratio, and relates <em>m</em> to cone resistance with a factor that accounts for foundation width and scale effects. Settlement is calculated by dividing the soil profile into layers and summing their strains within the stress-influenced zone.

The method was calibrated and assessed using 22 published foundation case histories, including footings on sands, silts, and mixed soils. Its predictions were compared with measured settlements and estimates from Janbu and Schmertmann methods. The authors report that the proposed method generally predicted settlements closer to measured values, while the comparison methods tended to underestimate them. In an example case, the estimate differed from the measured settlement by about 10%.

The approach is also proposed for pile groups: represent the group as an equivalent shallow foundation at the neutral plane, then apply the same CPT-based procedure. The authors conclude that the method offers an alternative way to use continuous CPT data for settlement estimation, although its calibration and evaluation rely on a relatively limited set of case histories.

Keywords

CPT-based settlement prediction

Janbu nonlinear stress-strain framework

cone resistance

friction ratio

shallow foundation settlement

pile group settlement

soil layer strain summation

foundation case histories

equivalent shallow foundation

geotechnical calibration