In the heart of China, a groundbreaking method is being employed to tackle a pressing environmental challenge: the containment of organic compound contamination. Researchers from the Institute of Geotechnical Engineering at Southeast University, led by MA Tongxiao, have successfully constructed vertical barriers using a small-scale TRD (Trench Cutting and Backfilling with Soil Mixing) method, marking a significant stride in environmental remediation technologies.
The team, in collaboration with the Jiangsu Provincial Academy of Environmental Science and Beijing Zhong Yan Dadi Technology Co Ltd., constructed vertical barriers with lengths of 70 meters and depths of 7.0 and 5 meters. The barriers were built using a small-scale TRD method and a cutting-backfilling-mixing approach. The workability of bentonite materials was thoroughly studied through a combination of field and laboratory tests.
The results, published in the Chinese journal ‘Yantu gongcheng xuebao’ (translated to English as ‘Rock and Soil Mechanics’), revealed that the organo clay-enhanced bentonite material could not be effectively hydrated. Additionally, the viscosity and slurry fluidity of the activated carbon-enhanced bentonite did not meet the construction requirements of the small-scale TRD method with a liquid-solid ratio of 4:1. However, the sodium hexametaphosphate-enhanced bentonite slurry prepared well met the construction requirements.
“Our findings indicate that the sodium hexametaphosphate-enhanced bentonite slurry is a viable solution for constructing vertical barriers using the small-scale TRD method,” said MA Tongxiao, the lead author of the study. The barriers were sampled and subjected to a series of tests, including grain-size distribution, water content, liquid limit, pH, characteristic element (sodium) content, and flexible-wall hydraulic conductivity tests after construction of 14 days.
The test results were used to assess the uniformity of geotechnical parameters along the barrier depths. The hydraulic conductivity test results revealed that the vertical barriers constructed by the small-scale TRD method exhibited lower hydraulic conductivity (1.3×10-10~2.4×10-10 m/s) compared to that constructed by the conventional construction method (7.5×10-10~9.3×10-10 m/s). This indicates that the SHMP-SB possesses superior hydraulic conductivity.
The barrier materials constructed by the small-scale TRD method also demonstrated superior uniformity in terms of lower coefficient of variation values of water content, liquid limit, sodium content, and pH along the depths. This research has significant implications for the energy sector, particularly in the containment and remediation of contaminated sites, ensuring safer and more efficient operations.
As the world grapples with increasing environmental challenges, innovations like the small-scale TRD method offer hope for more effective and sustainable solutions. The research conducted by MA Tongxiao and his team not only advances our understanding of vertical barrier construction but also paves the way for future developments in environmental remediation technologies.