Modeling and Laboratory Testing of Port Said Marine Clay and Applications on Geotechnical Design of Ports

Abstract

The current study aimed at providing a complete geotechnical characterization for Port-Said Clay encountered in North-eastern Egypt. Port-Said Clay is considered one of the most problematic soils in Egypt. This is attributed to its very weak strength, high compressibility and time-dependency of deformations. The geographical area underlain by Port-Said Clay has a strategic location due to its proximity to Port-Said East Port and the international trade movement in Suez Canal. Hence, major development is currently undergoing in the area. Although some geotechnical investigations were carried out for this region, there is still no clear characterization for Port-Said Clay in terms of its physical and mechanical properties, and geotechnical design parameters. This is attributed to the fact that the previous investigations were carried out for design projects. Hence, routine in-situ and laboratory tests with rather limited amount and area coverage have been carried out. The deduced parameters cannot be considered applicable to the full geographical extent of Port-Said Clay. The geological survey of Port-Said Clay indicated that it is part of El-Tina plain in which very soft to firm clays extend down to more than fifty meters. Port-Said Clay was deposited during the Holocene and the Pleistocene ages, when one of the Nile tributaries was crossing El-Tina plain. The area was exposed to invasion from the sea in old geologic ages, which accounts for the marine nature of Port-Said Clay. In order to achieve the main objective of this research study, comprehensive laboratory and in-situ testing programs were carried out. The field drilling program and in-situ tests were carried out for the industrial zone located at the south of East Port-Said Port. The investigated area is about 42 square kilometers. Six onshore boreholes were drilled to depths ranging from 42 to 63 meters, with an average depth of 55 m. Field Vane Shear Tests (FVST) and Standard Penetration Tests (SPT) were carried out in the drilled boreholes. Thin-walled tube samplers were utilized to collect undisturbed samples from different depths. The laboratory program included different types of tests ranging from simple index tests to more advanced tests measuring the mechanical properties such as one-dimensional consolidation tests, isotropically consolidated undrianed triaxial tests (CIU) and isotropically consolidated drained triaxial tests (CID). The results of the in-situ and laboratory tests carried out as part of this research study were compiled with the results of other available tests from well-documented reports in order to interpret and define general patterns for the physical and mechanical properties of Port-Said Clay. The outcome of the results indicated that a characteristic value of (0.2) could be adopted for the normalized undrained shear strength ( ). Port-Said Clay is moderately sensitive to sensitive clay, its moisture content increases with depth from 20 to 80 % until a depth of 35 m, then remains constant. A typical value of 2.6 can be attributed to its specific gravity, its unit weight decreases with depth from 17 to 15 kN/m3 with an average of 16 kN/m3 and the void ratio oscillates around 2.0. The plasticity index of Port-Said Clay could be correlated to depth. It can be classified as normal to active clay. The liquidity indices values indicated that the consi