Estimation of Reconstructed Strength of Disturbed Biologically Cemented Sand Under Unconfined Compression Tests

Abstract

One of the most important characteristics of soils is their resistance to structural loads. Improvement of mechanical properties of soils can help to control soil stresses and deformations. There are different methods for this purpose. One of the latest methods for stabilization of soils, which is a combination of chemistry and biological sciences, is the use of calcium carbonate microbiological sediment as a suitable injection material. In this study, the effects of using a bacterium spore called Bacillus pasteurii and production of biological deposition of calcium carbonate on improvement of the mechanical properties of sandy soils through the production of sandstone have been investigated. According to the results, when the calcium chloride in Bacillus pasteurii matrix is injected into the sandy soils, the strength of these soils increases. After this kind of cementation, an increase of considerable amount of water content, which is a kind of disturbance in the samples, can reduce the bio-cemented strength. This time, if we let the samples go for a period of time (about 24 h), the soil will revert to some part of its former strength and it can modify itself. This kind of strength is called reconstructed strength in this study. This research is designed to investigate the reconstructed strength of bio-cemented sands under unconfined compression tests. Results of the study show the strength of disturbed bio-cemented samples is sensitive to the void ratio.