Abstract
New, exciting opportunities for utilizing biological processes to modify the engineering properties of the soil (e.g. strength, stiffness, permeability) have recently emerged. Enabled by interdisciplinary research at the confluence of microbiology, geochemistry, and civil engineering, this new field has the potential to meet society's ever-expanding needs for innovative treatment processes that improve soil supporting new and existing infrastructure. Ureolytic bacteria are one of the most efficient organisms in producing amounts of carbonate that easily react with the free calcium ions available in the environment. Sporosarcina pasteurii, a robust microbial alkaline environment was used in this work for its high potential in the biocementation process that involves the biomediated calcite precipitation. This study presents the results of a model-scale laboratory investigation conducted on bio-cemented siliceous sand. Chemicals used in this study are commercially available in order investigate the viability of implementing this technique in the field at larger scales. To make it more practical, the microbial cells are directly used with neither sterilization nor utilization of a centrifuge process for the growth medium. Blocks of the bio-treated soil were excavated from the model and were tested to examine the strength and durability parameters of the improved soil. The results show that the unconfined compressive strength (UCS) and slake durability index significant increased upon biological treatment. However, due to the downwards permeation of the fluid due to gravity, samples obtained from the bottom and the center of the treated column gave larger UCS and slake durability indices than those obtained from the top and the sides of the column.
Highlights
Siliceous sands are widely available across the arid land of Egypt
An experimental program based on a model-scale laboratory investigation was conducted on bio-cemented siliceous sand through microbially induced carbonate precipitation
The improvement in the mechanical and durability properties of the tested sand was investigated through a series of unconfined compressive strength (UCS); slake durability and stability in water tests
Summary
Aeolian sand deposits cover significant area of the Egyptian deserts. Such deposits are characterized by very low densities and are found in a very loose state. Many applications, such as the construction of water canals and embankments, are introduced on weak siliceous sand formations. Construction of canals and embankments in such formations necessitates the need for soil improvement as one of the most economic engineering solutions to overcome stability, erosion and seepage problems [1,2,3]. Soil improvement or stabilization can take place using mechanical, biological or chemical methods
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