Abstract

The increasing emphasis on seismic performance and the prevalence of shallow foundations on gypsum-rich soils in Iraq necessitate an in-depth investigation of earthquake effects. To address this, a mechanical approach was developed and refined to simulate the impact of seismic events. In this study, laboratory soil specimens with varying gypsum contents (10%, 30%, and 75%) and three relative density levels (50%, 70%, and 80%) were prepared and tested under simulated seismic loading conditions. Three real earthquake scenarios were considered—Turkey–Çınarcık–Yalova (1999), Bolu’nun Kuzeydoğusu (1999), and Kaynaşlı–Bolu (2000)—and their key characteristics were used to replicate realistic loading conditions during the experiments. The parameters analysed included stress distribution beneath the foundation, settlement, lateral displacement, acceleration response, and their relationships with soil density and foundation slope. Additionally, two static load tests were conducted to evaluate the static bearing capacity of the soils. The results revealed that higher local magnitudes and peak accelerations produced greater settlement and lateral displacement ratios. Multidirectional shaking resulted in significantly higher settlement compared to single-direction loading. Furthermore, increasing the soil’s relative density led to reduced settlement ratios and smaller foundation tilts. Overall, the findings highlight that earthquake-induced dynamic loads significantly affect the behaviour of shallow foundations on gypsum soils. The results demonstrate that improving soil relative density is an effective method for mitigating foundation settlement and tilting under seismic loading.

Keywords

Gypsum soils, Shallow foundations, Seismic loading, Relative density, Settlement and lateral displacement, Dynamic soil–structure interaction.

Cite this article

Tawfeeq RS, Salih BM. Seismic bearing capacity of shallow foundations on gypsum soils. International Journal of Advanced Technology and Engineering Exploration. 2025; 12(130):1347-1359

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