Combined conditioning of dispersant and foam agent for the soil with different clay minerals: an experimental study

• Published in: Bulletin of engineering geology and the environment 2023-07, Vol.82 (7), Article 248
• Main Authors: Zhuo, Bin, Fang, Yong, Zhu, Muyuan, Yubo, Wang, Yuxiang, Yao, Gongyun, Xu
• Format: Article
• Language: English
• Subjects: Earth and Environmental Science; Earth Sciences; Foundations; Geoecology/Natural Processes; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Nature Conservation; Original Paper
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-023-03275-4

Clogging in the cutter head, bulk chamber, or screw conveyor is a very common problem when EPB shield tunneling in ground with high clay mineral content. Conditioning methods that involve foam agents only may not guarantee a safe and efficient excavation process. A dispersing can effectively improve the adhesion and flow characteristics of clayey soils. Hence, two different types of dispersants (sodium hexametaphosphate and sodium silicate) in different concentrations were selected, and their influence on the liquid limits of different clayey soils was studied. Then, clayey soil samples with various clay mineral content and types were conditioned using a mixture of 3% foam agent and 2% sodium hexametaphosphate, and the flow behavior of the conditioned soils was investigated with slump tests. The relationships of the slumps and the water content and the foam injection ratio (FIR) of the dispersive foam agent were established, respectively. Finally, a rotational torque test was conducted and the influence of FIR on the flow characteristics of the conditioned soil under various pressures was analyzed. For soil conditioning in the high clay content ground, a combined use of sodium hexametaphosphate and foam agents is suggested with sodium hexametaphosphate less than 4% in concentration. The slump height for the conditioned clayey soils is also suggested: it should not be lower than 10 cm or higher than 17 cm.