2.3.1. Unconfined Compression Experiment

This experiment refers to the standard of the “geotechnical test standard (GB/T 50123-2019)” and uses a microcomputer-controlled electronic universal testing machine of Naier Co., Ltd, Jinan, China. for testing. In the experiment, the axial strain rate was set to 1% per minute. Through pre-testing, the curing ages were set to 1, 3, 5, 7 and 14 days, which were more appropriate. The samples with curing ages of 1, 3, 5, 7 and 14 days were used to study the effect of the curing age on their strength. Additionally, the PU dosages of 2, 4 and 6% (the ratio of PU weight to dry clay weight) and chromium ion amount of 1000, 2000 and 3000 mg/kg were considered. In addition, the samples with the PU dosages of 0, 2, 4, 6 and 8% were used to study the effect of the PU dosage on the strength, while the chromium ion content was 2000 mg/kg and the curing ages were 1, 3, 5 and 7 days (see second part of Table 3). Furthermore, the samples with the chromium ion content of 1000, 2000 and 3000 mg/kg were prepared to study the influence of the clay with different chromium ion contents, while the PU dosages were 2, 4 and 6% and the curing age was seven days (see third part of Table 3).

Samples in unconfined compression experiment.

d = day.