Shear Strength of Unsaturated Soils with Different Plasticity

A series of shear box tests were conducted on four different types of soils in this study. The first set , (clay1) is the host clay, Middle Delta Nile clay “MDNC” which was obtained from Mid Delta Nile zone, Qalyubiyya Governorate, Egypt. The second set, (clay2) consists of the host clay MDNC but mixed with 40% sand. The third set of tests (clay3) was carried out on natural low plastic clay samples brought from El-Tal El-Kbeer area in Ismailia Governorate. The fourth set (clayey sand -SC) consists of 25% of the host clay MDNC mixed with 75% sand. The purpose is to predict the unsaturated shear strength for various soil types. The results illustrate that for clay1, clay2, and clay3, the relationships between the unsaturated shear strength and matric suction are approximated to two linear failure envelopes intersected at matric suction equals to plastic limit. Each segment has an angle of internal friction due to matric suction  b ranging from 1.80 o to 2.90o for the first zone and  b ranging from 0.28 o to 0.20o for the second zone. Meanwhile, for SC soil it appears to have one linear failure envelope for all saturation levels with angle of internal friction due to matric suction;  b=1.19 o.. Design- Expert® software applied the least square method (LSM) to fit a mathematical model for the experimental data. The Response Surface Methodology (RSM) of the program is used to predict the required model. The paper proposed two general equations to calculate the shear strength of unsaturated clays and one equation for granular soils, which are presented at the end of the paper with their coefficients.

Influence of Spent Bleaching Earth and Misspend Cement on Shear Strength Behaviour of Unsaturated Clays

Expansive clay is a major source of undulations induced in any type of structures. Swelling of expansive soils causes serious problems and produces harm to many structures. Many research organizations are doing extensive work on waste materials concerning the viability and environmental suitability. Spent bleaching earth and misspend cement are waste derivatives from oil industry and cement warehouse. To avoid dumping problem and storage problems, it is the best method technique applied in expansive soils. Attempts are made to investigate the stabilization process identified in unconfined compressive strength and tri-axial compressive strength.Stability of any structure depends on strength properties of underground soil on which it is constructed. Structures basically transfer all the loads come on itself directly to the ground. If the underlying soil is not stable enough to support transferred loads then various types of failure occur such as settlement of the structure, cracks and so on. To solve this issue, soil improvement is necessary because it not only lowers the construction cost but also cuts the risk of any damage of structure later on. Numerous improvement methods can be adopted to make ordinary soil stable enough to support the structural loads. In this research work a number of tests may conduct using both ordinary soil and stabilised soil. This thesis explains the strength behavior of SBE treated black cotton soil reinforced with MC. The various percentage of SBE as 5%, 10%, 15%, 20% and 25% was used to find out the optimum value of RBI Grade. MC has been randomly included into the SBE treated soil at four different percentages of MC content, i.e. 2%, 4%, 6%, 8% and 10%.