Experimental Study On Creep Characteristics Of Sand-mudstone Mixed Fillers With Different Mixing Ratios

In recent years,with the rapid development and progress of various aspects such as economy and society,the construction of various infrastructures in Southwest China has been in full swing,and great achievements have also been made.Due to the unique topographic features of the southwest region,this determines that a large number of fill projects will inevitably occur in the construction of large-scale and large-scale infrastructure such as airports.At the same time,due to the characteristics of wide area,large amount of engineering,and complicated construction of the airport construction,considering the economic cost of the construction,the earth-rock mixture after excavation and blasting is often used directly as fill material in airport construction.In Chengdu,Chongqing and other regions,the strata structure of sand and mudstone interbeds is widely distributed.Therefore,the sand and mudstone mixture obtained after the excavation of widely distributed sand and mudstone formations is usually directly applied to airport fill materials during the construction of airports.Due to the uneven distribution of sandstone and mudstone in the entire airport area,the mixing ratios of sand and mudstone mixed filler after blasting and excavation is also different.Sand and mudstone mixtures with different mixing ratios may exhibit different creep characteristics,and the difference in creep characteristics may cause uneven settlement and other engineering problems after the construction of the airport.This has always been the focus of attention in airport construction.Therefore,it is very important to conduct experimental research on sand and mudstone mixtures with different mixing ratios.In this context,this paper is based on the Chengdu Tianfu International Airport project,and intends to conduct experimental research on the creep characteristics of sandstone and mudstone mixed fillers mixed in different proportions.The main methods and work used by the author during the research are as follows:(1)The sample gradation was determined by experimental study.Sampling and sieving the field fillers of Chengdu New Airport,combined with the current status of the indoor test equipment,using the scale method of the mixing method to scale the field filler grading.The scale is determined after the gradation of the indoor test sample is determined Evaluation of sample grading.the gradation is good.(2)The maximum dry density and optimum water content of sand and mudstone mixed packing with different mixing ratios were studied.The compaction test was used to determine the maximum dry density and optimal water content of sand and mudstone mixtures with different mixing ratios,and to explore the effect of mudstone content on its related parameters.When the moisture content of the sample is 9.5%,the dry density of the four different ratios of sand and mudstone mixture can be close to the maximum dry density to the maximum extent,so the moisture content of the sample is set to 9.5%.As the content of mudstone increases,the optimal water content increases approximately linearly,and the maximum dry density decreases approximately linearly.(3)Experiments were conducted to study the creep characteristics of sand and mudstone fillers with different mix ratios.On the basis of the compaction test results,uniaxial lateral compression test was carried out on the sand and mudstone mixed filler samples with different mix ratios,and the stress-strain curve,strain-time curve and relevant parameters describing the compressibility obtained by the test were calculated and analyzed.And explore the correlation between mudstone content and related parameters.The sample will undergo obvious three processes of instantaneous elastic deformation,attenuation creep and steady-state creep.Sample sand: mud = 4: 6,the porosity ratio is the smallest,the compression coefficient is the smallest,the change range of the compression coefficient before and after the stress change is also the smallest,and the compressibility is the smallest;The compression coefficient is relatively large and the compression coefficient changes the most before and after the stress changes,and the compressibility is the largest.Creep characteristics can be characterized by logarithmic functions.(4)The particle fragmentation and its effect on the creep characteristics of sand-mudstone mixed packing samples with different mixing ratios were studied.The sieving test is carried out on the samples after compaction and compression during the test,and the particle breakage during the test of the sand and mudstone mixed filler samples with different mixing ratios is analyzed by comparing the gradation curves before and after the test.Based on the gradation curve,the crushing rate and mass fractal dimension are calculated,and the correlation between each parameter and mudstone content is explored.In the compaction stage,the crushing rate is maximum when the mudstone content is 60%.In the compression stage,the mudstone content is the smallest at 20% and 60%,and the crushing rate is the largest when the mudstone content is 80%.As the content of mudstone increases,the increment of the mass fractal dimension in the compression stage gradually decreases,which may be caused by the cementation of the mudstone during the long-term compression process.(5)The creep model and numerical simulation of sand-mudstone mixed packing with different mixing ratios were studied.Based on the strain-time curve obtained by the experiment,the empirical formula model and element model are used to analyze the creep characteristics of the sand and mudstone mixture,and to explore the correlation between the model parameters and the mudstone content.Using the simulation software,the sand: mud = 4: 6 sample is numerically analyzed to explore the rationality of the component model parameters and to interpret the creep deformation mechanism of the sand and mudstone mixture from a microscopic perspective.Finally,these two models are compared with each other and the author analyzed them to explore their advantages and disadvantages in the application of creep models.The creep characteristics of sand and mudstone mixed fillers can be characterized by Burgers model.The numerical simulation results also have three stages of instantaneous elastic deformation,deceleration creep,and stable creep,which are the same as the results of the indoor uniaxial compression test.