Abstract
Taking cement-improved frozen soil as the research object, this paper, based on uniaxial unconfined compressive tests of improved-frozen soil under the conditions of different cement contents (6%, 12%, 18%) and curing ages (7 d, 14 d, 28 d), analyzed the results and probed the relationship between the strength and elastic modulus of cement-improved frozen soil and cement content and curing age. In combination with laboratory test results, numerical simulations were set with the PFC3D group, building on the samples with 6% and 18% cement content at 14 days of curing, respectively, and the mesoscopic parameter values of the two different amounts were calibrated, which proved the simulation of cement with PFC3D reliable to improve frozen soil, and from the microscopic view, the crack development, stress field, and the particle displacement field of the two samples were analyzed. The result shows that the force is not evenly distributed in the samples; with the main force chain on the cement particles, an increase in particles can lessen the cracks, and the failure of the 6% sample is a tensile plastic failure and that of the 18% sample is a tensile shear failure.
Highlights
In underground engineering, using the freezing method to reinforce water-bearing and soft stratum is an effective method, but there are security risks in the freezing method, such as the weak stability of stratum and the excessive deformation of soil body, so it is effective to freeze soil after improvement of its body
Liang et al [9] believed that soil–cement exhibits the characteristics of brittle failure when the cement incorporation ratio is greater than 7%, but when the cement content is lower than 15%, the compressive strength has little to do with the cement incorporation ratio
To compare the strength of cement-improved frozen soil with the strength curves and the failure modes, a comparative test of uniaxial compression was conducted between the remolded soil specimens under the condition of 40% water content at a freezing temperature of −10 ◦ C and the soil specimens with 18% cement content and curing ages of 7 d, 14 d, and 28 d
Summary
In underground engineering, using the freezing method to reinforce water-bearing and soft stratum is an effective method, but there are security risks in the freezing method, such as the weak stability of stratum and the excessive deformation of soil body, so it is effective to freeze soil after improvement of its body. After a soil body is mixed with cement, the cement’s strength is significantly improved [1] and the compressive and shear resistances are enhanced [2] This method has been applied more and more in underground construction. A series of achievements in the field of geotechnical research has been made using the discrete element particle flow method, there are few literature reports on the study of frozen soil and improved frozen soil. Based on the macrocosmic parameter of the uniaxial unconfined compressive tests on cement-improved frozen soil, with PFC3D 5.0 particle flow software, the stress–strain characteristic curves of cement-improved frozen soil was simulated, and the crack, displacement field, stress field, and destruction form of the samples were analyzed and studied
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