In the heart of China, researchers from Nanjing Tech University and Jiangsu Geological Engineering Co., Ltd have been delving into a groundbreaking approach to tackle a longstanding challenge in geotechnical engineering: the problematic expansion and contraction of expansive soils. Their work, published in the journal *Yantu gongcheng xuebao* (translated to *Rock and Soil Mechanics*), focuses on a green reinforcement technology known as microbial-induced calcium carbonate precipitation (MICP). This method, which uses microorganisms to improve soil properties, could have significant implications for the energy sector, particularly in areas where expansive soils pose risks to infrastructure stability.
Dr. Deng Chengye, the lead author of the study, explains, “Expansive soils are a major headache for engineers. They swell when wet and shrink when dry, causing significant damage to buildings, roads, and pipelines.” The research team, including Dr. Xiao Jianxun, Dr. Zhu Rui, and Dr. Wang Xudong, sought to understand how MICP could mitigate these issues, especially under freeze-thaw conditions, which are common in many regions.
The team used Bacillus pasteurii, a bacterium known for its ability to precipitate calcium carbonate, to reinforce expansive soils. They conducted a series of tests to analyze the effects of different concentrations of the cementing agent on the soil’s expansion characteristics. The results were promising. “We found that MICP can significantly improve the expansion characteristics of expansive soils,” says Dr. Deng. “The best results were achieved with a cementing agent concentration of 1.25 mol/L, which reduced the free expansion rate by about 17.9%, the no-load expansion rate by 6.6%, and the load expansion rate by 0.7%.”
However, the researchers also discovered that higher concentrations of the cementing agent did not necessarily lead to better outcomes. At a concentration of 2.0 mol/L, the no-load expansion rate and load expansion rate actually increased by about 1.6% and 0.24%, respectively. This finding underscores the importance of optimizing the concentration of the cementing agent to achieve the best results.
The study also explored the impact of freeze-thaw cycles on the reinforced soils. The researchers found that repeated freeze-thaw action weakened the expansion characteristics of the microbial-reinforced expansive soils. After three freeze-thaw cycles, the no-load expansion rate and load expansion rate of the specimen with a cementing concentration of 1.25 mol/L reached their lowest values, which were 3.4% and 0.87%, respectively.
So, what does this mean for the energy sector? Expansive soils are a common challenge in the construction and maintenance of energy infrastructure, such as pipelines and power plants. The use of MICP to reinforce these soils could lead to more stable and durable structures, reducing maintenance costs and improving safety. Moreover, as Dr. Deng points out, “This technology is not only effective but also environmentally friendly. It uses natural processes to improve soil properties, making it a sustainable solution for the future.”
The research published in *Yantu gongcheng xuebao* opens up new avenues for the application of MICP in geotechnical engineering. As the energy sector continues to expand into areas with challenging soil conditions, this green technology could play a crucial role in ensuring the stability and longevity of infrastructure. The findings of this study not only advance our understanding of MICP but also pave the way for future developments in the field, offering a glimpse into a more sustainable and resilient future for construction and energy projects.