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Unconfined compressive strength, point load index, and slake durability values of treated sand samples
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Egyptian irrigation and drainage system consists of the River Nile, its branches, canals and drains. It is very important to keep them working in good condition to assure efficient water management and distribution process. Water channel embankments made of silicate sandy soils, carbonate sandy soils, and sandy silt soils are exposed to slope stabi...
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The potential of microbially induced carbonate precipitation (MICP) for soil bio-improvement has been widely studied as an alternative to traditional cementation by Portland cement. While multiple-phase injection techniques are commonly used for MICP treatment, they impose complexities and require a high number of injections. One of the latest deve...
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Citations
... These problems are considered some of the common canal embankment problems in Egypt. Soil stabilization is one of the economic engineering solutions to overcome soil problems [1]. ...
Loose sands (siliceous, silty, and calcareous classes) are extensively found near arid areas in Egypt. Furthermore, many geotechnical structures, like water channels and roads, may be constructed on weak or loose sand soils. The geotechnical behavior of loose sands is usually connected with different interdependent problems, such as high permeability, low shear strength, low bearing capacity, high seepage, and low stability. This work characterized the effect of stabilization of the siliceous, silty, and calcareous sandy soils via biocementation process using Sporosarcina pasteurii bacteria as a potential eco, commercial, and engineering solution. This was carried out using bacteria, fixation, and cementation solutions (BFC) at different times number additions. The results indicated that the addition times of solution have a remarkable effect on the physical and mechanical properties of sandy soils. The results also proved that the precipitation of calcite by the bacterial activity led to cohesion of soil grains, and this increased the resistance of soils to deterioration. In addition, the high content of the precipitated calcium carbonate enhanced the shear strength and the unconfined compressive strength and decreased the soil permeability. S. pasteurii bacteria can be used successfully and commercially in the biocementation process for siliceous sand, silty sand, and calcareous sandy soils in Egypt using the recommended conditions and mixes.
... Interestingly, the high starting biomass (OD 600 : 2Á04 AE 0Á015) used in this study was appropriate to induce desirable levels of strength (Table 4 and Fig. 5) without the need for repeated bacterial injections. The bacterial culture and the cementation solution ratio (1 : 5) were reduced about 50% instead of 1 : 10 in a similar study (Elmashad and Hafez 2017). This reduction favours lower cost expenditure. ...
Aims:
Calcium carbonate is a biomineral whose precipitation could be mediated by ureolytic bacteria and contributes in strengthening of sandy soils. The type of bacteria and grade of reagents have significant influence on microbially induced calcite precipitation (MICP). In the present study, factorial experiments based on these two factors were designed to determine their potential on MICP process, taking into consideration the economic advantages while giving quality results as well.
Methods and results:
For the first time, Alkalibacterium iburiense strain EE1 (GenBank accession no. MF355369.1) is reported for its biogrouting activity. Optimum growth conditions for MICP treatments were pH (9·56 ± 0·021), EC (44·7 ± 0·057 mS cm-1 ), OD600 (2·04 ± 0·015), NH4 + concentration (487·06 ± 1·021 mmol l-1 ), and urease activity (20·0 ± 0·75 mmol l-1 urea hydrolysed min-1 ) after 72-h incubation. Statistical analysis comparing the growth in technical-grade medium prepared in tap water and analytical-grade medium prepared in deionized water showed no significant differences (P = 1·0) in biomass and urease activity. In contrast to previous studies, the current approach could reduce the bacterial culture and cementation solution ratio by about 50%, using a simple surface percolation method with staged injection instead of parallel injection to treat different sand columns. Using fixation solution could immobilize the bacteria over the full length of columns for better strength improvement. The unconfined compressive strength ranged between 0·64 to 2·11 kg cm-2 , and the corresponding CaCO3 contents 5·7-38·5%. The scanning electron microscope images indicated that the precipitated CaCO3 by bacteria was stable calcite.
Conclusions:
Alkalibacterium iburiense and technical-grade reagents under nonsterile conditions are satisfactory consolidating agents for sandy soils.
Significance and impact of the study:
This approach is considered eco-friendly and cost-effective for future scale-up applications in various geotechnical engineering.
... The cost of replacing loose deposits is significantly high, thus it led various researches to investigate other methods in order to solve this problem [4]. Over the past decades, bio-cementation has emerged an advanced and sustainable technique for soil improvement [5,6]. ...
... One of main concern in the biocementation of soil is the effect of water on the strength of the bio-cemented soil. Therefore, stability in water tested was investigated by submerging the samples in tap water at room temperature for 24 hours [6,7]. Samples from similar locations to those described in Table 1 were submerged then visually checked for loss of integrity. ...
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.
... The result of an application of a technique may be; increased strength, reduced compressibility, reduced permeability, or improved ground water condition (Mohie and Nehad, 2017). The transformation and improvement of soil properties accordingly involves the application of chemicals such as Portland cement, lime, fly ash, sawdust ash, Rice husk ash etc or combination of them (Amadi, 2010). ...
The importance of soil stabilization in road construction cannot be overemphasized as it improves the geotechnical properties of the lateritic soil. It is not in all cases that soil has the desired geotechnical properties in its natural state; hence there is need for modification. The study was carried out in two phases. The first phase was to determine the geotechnical properties of the soil without adding any additives (control experiment) and the second phase was to add varying percentage of additives (test experiment).Woodash was added to the soil sample in varying amount of (0, 2,4,6,8 and 10 of weight of sample) to stabilize the soil while the following tests; Atterberg's limit, Compaction and California Bearing Ratio) were carried out on the stabilized soil. The results showed that the addition of woodash can significantly increase the strength of the soil. It was found that there was an increase in Optimum Moisture Content from 7.7% at 0% woodash to 17.23% at 10% woodash and with a corresponding decrease in Maximum Dry Density from 1970 kg/m 3 at 0% woodash to 1840 kg/m 3 at 10% wood ash. The CBR value increases from 31.44% at 0% woodash to 46.13% at 10% woodash; hence percentage increase of 46.72%.
