Abstract: Intelligent bidirectional cement-soil mixing technology has been applied in the Baishan navigation lock of the Yangtze-Huaihe water diversion project. To investigate the strength variation of the cemented soil in the Baishan navigation lock and assess the effectiveness of the new technology, we prepared cemented soil specimens with varying shapes, cement ratios, and curing ages. These specimens underwent unconfined compressive strength tests and triaxial unconsolidated and undrained tests, allowing us to obtain the stress-strain relationship, compressive strength, and shear strength parameters. The results of the laboratory tests indicate that the stress-strain relationship of the cemented soil exhibits strain softening behavior. The unconfined compressive strength increases with the growth of cement ratio and curing age, showing an approximate linear correlation with the logarithm of curing age. Under the same conditions, 90-d age cylindrical specimens display a strength approximately 13% higher than cubic specimens. The ratio of deformation modulus to unconfined compressive strength ranges from 55.6 to 96.2 and is significantly influenced by the age of the specimens. Cohesion and unconfined compressive strength can be described as approximate linear growth relationship, and the internal friction angle ranges from 22° to 33°. The in-situ core samples exhibit a strength exceeding 70% of that of laboratory cemented soil, demonstrating that the strength ratio expression helps compensate for the strength discrepancy between laboratory and in-situ cemented soil. Scanning electron microscope (SEM) results also unveil the mechanism behind the strength growth of cemented soil from a micro perspective.

Key words: cemented soil, unconfined compressive strength, shear strength, triaxial test, micro-mechanism