Estimation of Modular Ratio and Modulus of Deformation of Granular Piles from In Situ Compression Tests-PPT Presentation

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The presentation proposes a method for estimating the deformation modulus of granular piles (Egp) and the surrounding soil (Es) from in-situ load-test results. Based on the elastic settlement framework of Mattes and Poulos (1969), the method uses measured load and settlement, pile geometry, and an influence factor linked to the assumed modular ratio, K (the ratio between pile and soil stiffness).<br /><br />The procedure estimates Es for a range of assumed K values, plots these estimates against typical soil-modulus ranges for the site, and uses the overlap to identify plausible values of K and Es. The granular-pile modulus is then calculated as Egp = K × Es.<br /><br />The method is illustrated using three published case studies from India: a 10 m-long pile in coastal Andhra Pradesh, a 12 m-long pile in Delhi, and a 4.9 m-long pile on India’s eastern coast. For a 25% load proportion, the estimated soil-modulus ranges were approximately 3.6–5.3 MPa, 7.6–15.3 MPa, and 1.4–2.3 MPa, respectively. Corresponding estimated granular-pile moduli ranged from 26.5–115.2 MPa, 91.8–760 MPa, and 11.5–140 MPa.<br /><br />The authors argue that estimating deformation parameters from field behavior can improve settlement prediction and the design of granular-pile ground improvement. The approach depends on selecting an appropriate soil-modulus range and interpreting the load-test data in relation to site conditions.

Keywords

granular pile

deformation modulus

in-situ load test

settlement prediction

soil modulus

modular ratio

Mattes and Poulos

ground improvement

elastic settlement

pile-soil interaction