Experimental Study On Mechanical Properties Of Frozen And Cemented Weak Expansive Soil

Cemented soil reinforcement and artificial freezing method are two common methods in ground stabilization,which have certain contributions on obstructing water and bearing capacity,but each has its own advantages.In order to study the reinforcement effect and construction parameters of two methods for weak expansive soil,this paper carries out unconined compressive strength tests at different ages,temperatures,and cement contents to find the suitable cement content.The direct shear test and triaxial permeability test were carried out to study the shear strength index and permeability coefficient of soil,and the internal mechanism of cemented soil was further analyzed by SEM tests.(1)The unconfined compressive strength tests with cement content of 0%,5%,8%,10%,12%,15%,18%and 20%were carried out at 8 and-10 C.The strength,stress-strain curves and failure modes were analyzed and discussed.The suitable cement content for the soil is determined to be 10%～15%.The brittleness of soil increases with the addition of cement,but freezing can enhance the ductility of cemented soil and overcome the shortcomings of cemented soil.(2)The direct shear tests with 8 different cement contents were carried out at normal atmospheric temperature.The effects of cement content on cohesion and internal friction angle of cemented soil were studied.It is found that the cohesion can be improved obviously by adding cement,and the maximum value can be reached when the cement content is 12%,which is consistent with the result of unconfined compressive strength.The friction angle of soil can be increased significantly by adding cement,but the difference caused by different cement contents is not obvious.(3)The constant head permeability tests were carried out under different cement content and different effective confining pressure,and the permeability coefficient of the side wall under different osmotic pressure was studied,which has an effect on the results of cemented soil.The influence of cement content on cemented soil permeability coefficient decreases if the cement content is over 10%.(4)The properties of cemented soil are studied from the micro-perspective through SEM tests.Cement hydration products have a good filling effect on the fissure system of soil and improve the compactness of soil.With the increase of age,the hydration products develop into the interrelated rattan network,which is beneficial to the integrity and stability of soil.The brittleness of the hydration products results in the decrease of ductility of the cemented soil at normal atmospheric temperature.Figure 26 table 5 references 87...