关键词: 紫色土, 木质素磺酸钙固化, 三轴压缩试验, 凝聚力, 内摩擦角

Abstract: Purple soil is widely distributed in Chongqing City, which is easy to cause soil erosion under the effect of rainwater infiltration. In this paper, purple soil was solidified by adding calcium lignosulfonate to improve its engineering properties. Firstly, calcium lignosulfonate was mixed with purple soil at the mass fractions of 0.5%, 2%, 5%, 8%, 12% and cured for 7 days. Then the stress-strain curve and shear strength of solidified soil were studied by Triaxial unconsolidated undrained(UU) shear test. The results showed that the shear strength increased best when the content was 5%, cohesion and the internal friction angle increased 62.73% and 11.84% respectively compared with the plain soil, and the cohesion increase dominates. Secondly, triaxial compression tests were carried out after curing for 7 days, 14 days and 28 days under the condition of 5% optimal dosage to study the relationship between shear strength index of solidified soil and curing time. The results showed that the shear strength of calcium lignosulfonate solidified soil with 5.0% content will not increase after 14 days of constant temperature and humidity curing, reaching the ultimate strength, and cohesion and the internal friction angle will increase by 76.03% and 18.88% respectively compared with that of plain soil. Finally, SEM and XRD tests were conducted to analyze the microstructure and mineral composition of the samples cured for 7 days with 5% content. The results showed that no new minerals generated in the solidified soil, but the filling and compaction of pores were the main reasons for the strength improvement. The research results can provide reference for chemically solidified soil in purple soil area.

Key words: purple soil, calcium lignosulfonate solidified soil, triaxial compression test, cohesion force, internal friction angle;