Shallow Foundation Design over Diagenetic Limestone along the Arab Gulf Coast: An Overview

Abstract

The near surface, highly weathered limestones of the southern shores of the Arab Gulf region have complex lithologies attributable to post depositional changes that have altered hard rocks into soils and some carbonate soils into a rock matrix. The matrix, often clayey, sometimes cemented (with gypsum, anhydrite, and /or calcite grains) is not a rock nor could be considered as a soil per se. These deposits are: difficult to sample in the undisturbed state, extremely variable in composition and properties, and are susceptible to degradation, particularly when wet. The paper presents typical geotechnical information from selected sites where these deposits (diagenetic limestone) have been encountered. Plate load test data, carried out to predict settlements, are shown. Arrival at appropriate foundation geometries and allowable bearing capacity values, consistent with field conditions, are noted. For the present, design of shallow foundations along Region’s coasts and in nearby areas, has remained empirical and dependent upon site-specific information aided by: judgment, local experience, and plate load test results. Moving forward, and thus reducing ambiguity and uncertainty in design of shallow foundations, would invariably require a long-term commitment to: i) proper analysis and scrutiny of appropriate field data, ii) modeling of soil/rock behavior under changes in stress, and iii) the arrival at “well thought out” design guidelines to help practitioners overcome the difficulties usually faced, when designing shallow foundations in these deposits.