Abstract

Coarse-grained soils are preferably used in geotechnical infrastructure projects such as retaining walls and highway embankments due to their superior drainage and frictional properties. However, such materials are not always available on or near the construction site. Given the limited availability, high cost, and transportation issues associated with coarsegrained fill, using the locally available marginal soil for the various infrastructure projects becomes essential. Marginal soils are soils with a high percentage of fines that can be cohesive or non-cohesive. The primary concern with marginal soil is its low permeability, which causes excess positive-pore water pressure evolution during load application. As a consequence, the soil loses shear strength over time. Previous researchers have provided some information on the dynamic behaviour of marginal soils in terms of cyclic strength and pore pressure development. However, more research is needed to understand the dynamic response of compacted marginal soils in terms of cyclic resistance ratio (CRR) using field and lab data. Therefore, an attempt has been made in this study to evaluate the cyclic resistance of compacted marginal soil (clayey sand) by performing stress-controlled cyclic simple shear (CSS) tests in the laboratory and Standard Penetration Test (SPT) and Dynamic Cone Penetration Test (DCPT) in the field. The cyclic strength of marginal soil has been determined as Cyclic Resistance Ratio (CRR) by using laboratory (CSS) and field (SPT, DCPT) test data.

Abstract

In the simplified methods for estimating the cyclic resistance ratio (CRR) based on the flat dilatometer test (DMT), the liquefaction triggering curve is defined as a function of the horizontal stress index. A DMT-based calibration of a simplified pore water pressure model for effective stress analyses has been also recently proposed by Chiaradonna et al. (2023), even though limited to an ideal clean sand. This paper aims to explore the effects of the fines content on the seismic response of a liquefiable site where the cyclic strength of the soils is estimated by dilatometer tests. This evaluation is firstly performed on an ideal one-dimensional soil column, where the percentage of fines content is parametrically changed. Then, the study is verified on a real case, by considering a well-investigated site located in the Emilia-Romagna plain (Italy), where widespread liquefaction occurred in the 2012 seismic sequence. Indeed, a comprehensive site characterization from previous in-situ and laboratory tests carried out by various research groups is available for sand, silty sand, and sandy silt deposits encountered in that area. The nonlinear dynamic analyses accounting for the fines content effect are compared with that obtained by adopting the calibration procedure based on laboratory tests. Guidelines and limitations of the proposed approach obtained from this study are useful in providing awareness to practitioners about the calibration strategies for dynamic analysis based on DMT-tests.