High-Modulus Columns for Liquefaction Mitigation

Abstract

This paper presents the performance of a shopping complex in Turkey where the soils were improved with jet-grout columns and preload fills and subjected to the 1999 Kocaeli Earthquake (Mϭ7.4). Under construction at the time of the earthquake, the Carrefour Shopping Center covers an area of 55,000 m 2 and is founded on shallow footings, mats, and slabs-on-grade that rest on soft, saturated alluvial sediments consisting of clays, silts, and sands. High-modulus columns constructed by jet grouting were installed at close-tomoderate spacings to reduce anticipated static settlements in the clays and mitigate liquefaction in the sands. The site was subjected to a peak acceleration of approximately 0.2g during the earthquake. Grouting had been completed for about two-thirds of the site when the earthquake struck. Following the event, a field reconnaissance found stark contrast between the performance of the improved and unimproved sections. The jet-grout-treated areas suffered no apparent damage, whereas the unimproved sections of the complex, along with nearby untreated building sites, commonly suffered liquefaction-related settlements of up to 10 cm. This is the only case history known to the authors that documents the field performance of high-modulus columns used in this manner for liquefaction mitigation and direct instrumented measurement of liquefaction-induced settlements.

Numerical assessment of high‐modulus columns on liquefaction triggering potential

“…Martin et al . compared the improved and non‐improved areas at a shopping center in Kocaeli, which was under construction during 1999 Kocaeli, Turkey, earthquake. The authors mentioned that no damage (settlement) was seen in treated areas, whereas the liquefaction‐induced settlements in non‐treated areas reached up to 10 cm.…”

Liquefaction Mitigation Using Jet-Grout Columns — 1999 Kocaeli Earthquake Case History

“…Of concern to the designers was the potential liquefaction of the loose-to-medium SP/SM stratum found at an average depth of 6 m. This stratum varies from 2 to 4 m in thickness across the site and contains and average of 30% non-plastic fines. And although not understood at the time, the ML/CL and CH strata were also vulnerable to significant earthquake-induced deformations beneath loaded areas, as measured by site engineers; see Martin et al (2004). The ML/CL has a PI = 10 and LL = 34, whereas the CH has a PI = 37 and LL = 66.…”

Simulation of cyclic strength degradation of natural clays via bounding surface model with hybrid flow rule

“…A notable example are the landslides that took place in Anchorage as a result of the Alaskan earthquake of 1964 in which the strength loss of natural clays (in this case, Facie III of Bootlegger Cover Formation [BCF]) due to seismic shaking has been recognized as a critical factor for failure initiation . Similarly, the cyclic strength degradation of natural clays has been identified as the cause of bearing capacity failures of structure foundations during several earthquakes . To prevent and mitigate these hazards, numerical simulations (eg, finite element or finite difference analyses) have been used to assess the performance of existing and/or planned geotechnical facilities subjected to earthquake shaking.…”

“…1,[6][7][8] Similarly, the cyclic strength degradation of natural clays has been identified as the cause of bearing capacity failures of structure foundations during several earthquakes. [9][10][11] To prevent and mitigate these hazards, numerical simulations (eg, finite element or finite difference analyses) 12,13 have been used to assess the performance of existing and/or planned geotechnical facilities subjected to earthquake shaking. A principal requirement for achieving reasonably accurate results is that the selected constitutive law represents reliably the mechanical behavior of the soils present within the affected deposits.…”