Strength Design of Cement-Treated Piles Subjected to Lateral Flow of Liquefied Ground-Paper

Paper

Pdf Summary

The study evaluated a pile-type ground improvement method for reducing liquefaction-induced lateral flow behind quay walls and examined how to design the strength of cement-treated piles. The method uses deep-mixing piles arranged in a staggered pattern, with their tops connected by a stabilised shallow layer. It permits the surrounding ground to liquefy while restricting its movement and helping preserve a usable ground surface.<br /><br />Centrifuge model tests at 50g compared unimproved ground with improved models using either acrylic piles or cement-treated soil. The models were shaken until the sandy ground liquefied. In the improved area, horizontal displacement was substantially reduced: at the downstream edge it was 23% of the displacement in the unimproved case. Ground-surface settlement in the improvement area fell from 0.4 m to zero.<br /><br />Bending moments measured in the acrylic piles were considerably lower than those calculated by the proposed design method, which assumes lateral force equal to 30% of the overburden pressure and hinged pile support conditions. The method therefore appears conservative in estimating pile moments, although it does not account for the inertia of the piles and shallow stabilised layer, which could increase demand.<br /><br />Cement-treated piles and shallow ground remained intact in the model tests, even though their strengths were below the design values. This supports the effectiveness of the strength-design approach, but the authors note that its strength requirements may be high for practical construction. Further work is needed to develop a more economical and realistic design method.

Keywords

ground improvement

liquefaction

lateral flow

quay wall

pile-type method

cement-treated piles

centrifuge model test

staggered piles

bending moment

cemented soil