Study On Physical And Mechanical Characteristicsof Frozen Soil With Large Porosity Soft Soil

The artificial freezing method has the advantages of safety and wide use,it is used in more and more underground engineering construction,however,there are many engineering problems in the development of underground engineering,it includes shallow biogas geological hazards,such as the existence of this special geological condition in some shallow layers in the Hangzhou area.Therefore,when the artificial freezing method is applied in the area,special consideration should be given to the effect of the formation of methane on the freezing effect caused by the formation of large porosity soft soil,the research topic in this paper is put forward in this context,two research methods combined with indoor test and numerical simulation,Study on physical and mechanical properties of frozen soil with large porosity soft soil in Hangzhou area.First,the preparation method of frozen soil with large porosity soft soil samples is studied,proposing preparation of frozen soil with large porosity soft soil samples by adding foam particles,and the related thermal physical test and unconfined uniaxial compression comparison test are carried out,verifying the feasibility of this paper on the method of making frozen soil with large porosity soft soil samples,and obtaining the change of freezing temperature with time accords with the requirement of frozen soil sample making,as well as the relationship between the thermal conductivity and the dry density of the frozen soil with large porosity soft soil.Secondly,the indoor test is carried out,through the design of single factor test scheme and orthogonal test scheme,carrying out the unconfined uniaxial compression test of frozen soil with large porosity soft soil.The influence of water content,temperature and dry density on the strength and elastic modulus of frozen soil with large porosity soft soil is analyzed,and the relationship between various factors and the strength or elastic modulus of frozen soil with large porosity soft soil is explored.Through regression analysis,the corresponding fitting relation is obtained.And through orthogonal analysis,the relationship and significance of three factors,including water content,temperature and dry density,to the strength and elastic modulus of frozen soil with large porosity soft soil are obtained.Furthermore,the microscopic images of the frozen soil with large porosity soft soil are obtained by scanning electron microscopy,and image processing software is used to process the SEM image by the IPP,obtaining the related mesoscopic parameters,such as porosity and maximum minimum particle radius ratio,etc.It is in favor of modeling of PFC^2D and strengthening microcosmic understanding of the frozen soil with large porosity soft soil.Finally,the numerical simulation is carried out.In this paper,the particle flow software by PFC^2D is used to simulate the unconfined uniaxial compression test of frozen soil with large porosity soft soil samples with water content 30%,temperature-10?and dry density 1.37g/cm³.Compared with the indoor test results,it is proved that the PFC^2D simulation of unconfined uniaxial compression test of frozen soil with large porosity soft soil is feasible.From the microscopic point of view,the development of crack,the displacement field and stress field of sample are studied and analyzed,and the understanding of physical and mechanical characteristics of frozen soil with large porosity soft soil is strengthened.The physical and mechanical properties of frozen soil with large porosity soft soil are obtained through the relevant research and analysis in this paper.It is also understood that the law of development is basically consistent with the general frozen soil.The particle flow software by PFC^2D is successfully applied to simulate the uniaxial compression test of frozen soil with large porosity soft soil,and the understanding of physical and mechanical characteristics of frozen soil with large porosity soft soil is deepened from microscopic perspective.