Abstract: Because of excellent physical and mechanical properties, cement-soil has been widely used in engineering construction. Compared with ordinary soil, the addition of cement makes cement-soil have lower permeability and better anti-seepage performance. The hydraulic conductivity of cement-soil is a principal indicator indicating the engineering properties of cement-soil, which can directly reflect the permeability of cement-soil. However, the current test methods for the hydraulic conductivity of cement-soil are unified, which may cause differences and deviations in actual work, so it needs to be studied. Based on the actual project, the onsite borehole water injection permeability test on the cut-off wall was conducted, and the indoor variable head permeability test and triaxial permeability test on the cement-soil sample made by core drilling were conducted at the same time.The results of the indoor test with the results of the field test were compared and the suitable indoor test method for detecting the cement-soil core sample were discussed.The influence of confining pressure on the hydraulic conductivity of cement-soil in the triaxial permeability test was analyzed. At the same time, the cement-soil samples were newly prepared indoors, the variable head permeability test, the triaxial permeability test and the cement-soil permeability test were carried out to study the difference of different methods to determine the cement-soil hydraulic conductivity. The study found that the original cement soil (core drilling) measured by the indoor triaxial permeability test is close to the result of the on site bore hole water injection permeability test. The hydraulic conductivity of original cement-soil (core drilling) measured by the indoor variable head test is too large. In the triaxial permeability test, the hydraulic conductivity of the undisturbed cement-soil sample will increase with the increase of pore water pressure when the confining pressure is 0, and the hydraulic conductivity will decrease with the increase of confining pressure when it changes. After the confining pressure is 20 kPa higher than the pore water pressure, the hydraulic conductivity becomes stable. The test results of indoor variable head permeability test, the triaxial permeability test and cement-soil permeability test are basically similar to each other. It can be concluded that the indoor triaxial permeability test is more suitable for measuring the hydraulic conductivity of undisturbed cement soil (core drilling) than the indoor variable head test. The Nan 55 type infiltration meter, the stress-strain controlled triaxial shear permeability test and cement soil permeability tester can be used to identify the hydraulic conductivity of cement soil (indoor preparation). The research results have important reference significance for the method of measuring the permeability coefficient of cement soil.

Key words: cement-soil, hydraulic conductivity, triaxial permeability test, core drilling, confining pressure