Experimental Study On Artificial Frozen Soil Of Typical Strata In Tianjin Binhai New Area

The artificial soil freezing method has become the main technology in the construction of subway and other underground engineering.When artificial freezing method is applied in the subway construction of Tianjin Binhai New Area where typical silty clay and silt soil layers is widely disturbed.Therefore,it is significant to study the basic mechanical and thermal characteristics of artificial frozen silty clay and silt soils.Based on a large number of sampling within the planning area of Tianjin Binhai New Area subway,this research is focused on artificial frozen silty clay and silt soil in the underground from 20 to 40 meters.The specific research results are as follows:(1)In the uniaxial compressive test of artificial frozen soil,the stress-strain characteristics of frozen silty clay and silt soil of Tianjin Binhai New Area at three different temperatures are analyzed and studied,and the stress-strain curves of artificial frozen soil are summarized with mathematical expressions.At the same time,the results show that the relationship between uniaxial compressive strength and the freezing temperatures can been described as follows: artificial frozen silty clay with linear relationship and artificial frozen silt soil with quadratic function.(2)The bending strength test is carried out in the improved uniaxial compression test apparatus.The physical formula proves the brittle characteristics of frozen soil and testify the rationality of the improved device.In the paper,the relationship between the bending strength and the freezing temperature is analyzed and summarized,and the quadratic function relationship between the above two issues is proposed.(3)In the triaxial test of artificial frozen soil,the deviatoric stress-strain characteristics of frozen silty clay and silt soil of Tianjin Binhai New Area at three different temperatures are analyzed and studied,and the stress-strain curves of artificial frozen soil are summarized with unified constitutive relation.The triaxial shear strength indexes of artificial frozen soil is obtained according to the Mohr-Coulomb criterion,and the result shows that the relationship between the triaxial strength indexes and the freezing temperatures can been described as linear relationship.(4)The variation law of the thermal physical parameters is summarized after the artificial frozen soil thermal physical test.At the same time,combined with the general situation of the soil of Tianjin Binhai New Area,numerical simulation of freezing temperature field is carried out.The analyzed and compared results of the freezing time between the numerical analysis and the theoretical calculation show that simulation analysis has certain rationality.