الفهرس 
Biocementation of calcite precipitation for stabilization of sandy and calcareous soils in Egypt and Tunisia
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Abstract
The use of soils with poor mechanical properties frequently requires the improvement of their characteristics, mainly the strength and stiffness. For construction purposes, it is very essential to provide a strong foundation for the structure. If required, the suitability of soil has to be improved; this process of improving properties of soil is called soil stabilization. Egypt has more than 50,000 km irrigation and drainage channels. The main type of soil constituting a soil layer of most of the canal embankment in the Nile delta is the loosely soil. It is exposed to slope stability problems. This work focused on studying stabilization of the siliceous sand, silty sand and calcareous sand soils via biocementation process and it was applied on sands to improve their mechanical properties by different treatment methods using bacteria named Sporosarcina pasteurii. These methods are injection with and without fixations and mixing. The effectiveness of biocementation is studied in terms of unconfined compressive strength (UCS), stability biocemented samples in water, direct shear (cohesion, C and angle of internal friction Z) and slake durability index test. The X-ray diffraction (XRD) was used to identify the formation of CaCO3 along with using a scanning electron microscope (SEM) to identify the microstructure of the deposited CaCO3. The main results showed that, in ii general, the injection method of the bacteria with fixation solution in the treated soil was more effective than the injection without fixation solution at the same conditions