Development Of Similar Material Of Collapsible Loess And Analysis On The Physical And Mechanical Properties And The Influencing Factors Of Collapsibility

So far, there haven’t so many domestic and foreign scholars who have conductedresearch work about similar material of collapsible loess used in model test, the originalmethod is still used in the experimental study on the collapsibility of loess, as a result, so thatin the laboratory test, collapsibility of loess cannot be effectively simulated and controlled,which causes some impact on the further research of loess.Aiming at the research status of geomechanical model about similar material at homeand abroad, combined with the formation mechanism and collapsible characteristics of loess,by adjusting the ratio of materials,4kinds of collapsible similar material which have the samecollapsible rule of natural loess are successfully developed, these materials are respectivelynumbered SMC-74621, SMC-85421, SMC-76511and SMC-66611. In the similar material,quartz powder, sand and salt are non viscous materials, bentonite is the main viscous material,gypsum is the supplementary cementitious material, in order to simulate the wind depositionof loess, free falling method is used to prepare the samples, the samples are dried in the ovenat temperature of50℃for24hours, under the dry condition, collapsible consolidationexperiment is conducted. Collapsibility coefficient of the similar material under differentsoaking load is acquired, the collapsible is the same with the natural loess, which candetermines that the similar materials can be used to simulate loess on collapsibility.But if the similar material is to be used in indoor test, it should not only meet therequirement of collapsibility of loess on, but also should meet the requirements of loess inother properties, such as the consistency parameter, shear strength parameter, compressionparameter and so on, in order to make sure the physical and mechanical properties of similarmaterial can also meet the requirements of loess, liquid and plastic test, direct shear test andconsolidation test of similar material are conducted to determine the physical and mechanicalparameters, the similar material that meets the requirements of physical and mechanicalparameters of loess can be judged as the similar material of collapsible loess.Through the test, specific gravity of the soil particle of the similar material of collapsibleloess is tested between2.63and2.66, which is very similar to the specific gravity of soilparticle of loess, the liquid limit is between26.3%and27.7%, plastic limit is between15.1%and16.7%, plasticity index is between10.1and12.6, on the basis of plasticity chart, it isclassified to clay soil with intermediate liquid limit, maximum dry density is between1.73and1.76g/cm3, the optimal moisture content is between15.5%and16.4%, which is veryclose to the physical parameters of loess. For the mechanical parameters, the cohesion isbetween42.67kPa and64.24kPa, internal friction angle is between23.51°and28.15°,compression coefficient is between0.40MPa-1and0.45MPa-1, which belongs to the secondary compressive soil, all of these are close to the mechanical parameters of loess, theabove data provide certain reference for future research on this kind of similar material.After the successful preparation of similar material of collapsible loess, in order tofatherly study the influencing factors of collapsibility of the similar material, based on thesimilarity of the properties of loess, similar material SMC-74621is selected as the researchobject to fatherly study the influencing factors of collapsibility, the factors mainly includesoaking load, water and so on.The conclusions of the paper are as follows:Through the development of similar material and study on the physical and mechanicalproperties, it is not only verified that free falling method can be used to simulate the winddeposition of loess that lead to collapsible structure, but also verify the feasibility of thesimilar material can be used to replace loess in geomechanical model test, making the materialof collapsibility test model can be controlled, test results have repeatability, test error causedby field sampling and indoor remodeling and filling can be reduced, which provides a newway to study the collapsible loess.In order to further understand the collapsibility of similar material of collapsible loess,through the test, influencing factors of collapsibility are analyzed, results show thatcollapsibility coefficient of similar material decreases with the increase of wetting watercontent under the condition of pre wetting, when the wetting water content is constant,collapsibility coefficient increases first and then reduces, peak value of collapsibilitycoefficient will appear, its corresponding peak load will decrease, peak value of collapsibilitycoefficient decreases with the increase of moisture content. According to the influence of eachfactor on collapsibility coefficient, it provides adjustable range in using similar material toreplace loess to conduct indoor model test of different collapsible grade.