Characteristic Research On Strength Of Cement Improved Aeolian Sand And Deformation Of Aeolian Sand Used To Fill Subgrade For Heavy Haul Railway

Aeolian sand has been widely used in the desert highway road bed and ordinary railway subgrade as a special engineering geological material.Special physical and mechanical properties for Aeolian sand,such as poor grading?loose particles?low cohesion and so on,it is difficult to meet the requirement of bed bottom filling of subgrade for high speed railway and heavy haul railway,so research on Aeolian sand has a great significance for understanding of Aeolian sand material and engineering application.In this paper,based on the research which is key technology study of Aeolian sand filling subgrade for the heavy haul railway which is from the Nei Monggol Autonomous Region to Jiang xi Province in Maowusu sandy,laboratory soil tests are taken for Aeolian sand and cement improved Aeolian sand from test section,contrasted and analyzed the part results from laboratory of field work area and test section;used the finite difference method software FLAC3 D to analysis deformation characteristics and subgrade slope stability for the subgrade of heavy haul railway which is filled by Aeolian sand in different working condition;put forward proposals to the design and construction for the heavy haul railway,research results have certain reference for similar projects.In this paper,the main research content and achievement as following.(1)Particles analysis sampling test is taken for Aeolian sand from work area.The experimental results showed that the Aeolian sand as the poor grading of fine sand,belong to the group C packing,it is difficult to meet the requirement of bed bottom filling of subgrade for heavy haul railway,need to be modified.For Aeolian sand and cement improved Aeolian sand,through the heavy compaction test,we can come to the conclusion,the optimal moisture content of Aeolian sand is reduced with mixing cement to Aeolian sand,at the same time improve the maximum dry density.The optimal moisture content is 14% and the maximum dry density is 1.88g/cm3 for the Aeolian sand;when the cement content is 4%~8%,the optimum moisture content is 11.5%~11.5% and the maximum dry density is 1.94 g/cm3~1.97 g/cm3.(2)The unconfined compressive strength increases with the increase of cement content and compacting factor for cement improved Aeolian sand.With the cement content is 6%~8%,the strength growth is greater than the cement content is 4%~6%;with the compacting factor is 0.93~0.95,the strength growth is less than the compacting factor is 0.91~0.93;Between the unconfined compressive strength and cement content,and Between strength and compacting factor have well polynomial fitting relationship.(3)The unconfined compressive strength increases with the increase of curing age for cement improved Aeolian sand.7d strength is up to 0.67~0.86 strength of 90 d and 28 d strength is up to 0.81~0.92 strength of 90 d when the compacting factor is 0.93 and cement contents are 6%~8%;The early strength of cement improved Aeolian sand increases quickly and the late strength growth is slow;Between the unconfined compressive strength and curing age has a well power exponent fitting relationship.(4)The unconfined compressive strength increases with the increase of the cement strength grade for cement improved Aeolian sand.The cement strength grade improved from P.O32.5 to P.O42.5,with the same compacting factor(0.91~0.93)and cement content(6%~8%),strength of samples increase by 3%~20% under different curing ages.(5)The cement content is 7%~8% can be used as control standard when compacting factor is 0.95 and using the P.O32.5 cement filling the bottom layer of subgrade bed for heavy haul railway;For P.O42.5 cement,we can take 5%~6% of cement content as control standard.(6)For the subgrade of heavy haul railway which is filled by Aeolian sand,when the slope ratio of subgrade is 1:1.5 and the height of subgrade is 9.0 m,the geogrid reinforcement spacing is 0.6m and the geogrid reinforcement length is 3.0m,the cement content of cement improved Aeolian sand is 4%~8%,in these cases,the slope safety coefficients are about 1.23 and the cement content have impact on the settlement of the subgrade.(7)For the subgrade of heavy haul railway which is filled by Aeolian sand,the maximum horizontal displacement of subgrade slope increases with the increases of geogrid reinforcement spacing when using 6% of cement content to improve Aeolian sand which is used to fill the bottom layer of subgrade bed;it increases from 3.1cm to 5.2cm with the geogrid reinforcement spacing increases from 0.3m to 0.9m.The maximum horizontal displacement of subgrade slope decreases with the increases of geogrid reinforcement length;it decreases from 4.4cm to 2.1cm with the geogrid reinforcement length increases from 3.0m to 7.0m,at the same time,the slope safety coefficient increases from 1.23 to 1.48;geogrid reinforcement spacing and length have a little impact on the settlement of the subgrade.(8)For the subgrade of heavy haul railway filled by Aeolian sand,which the slope ratio is 1:1.5 and the height is 9.0 m.Considering engineering economy and construction technology,putting forward a recommend that we can use 6% of cement content to improve Aeolian sand which is used to fill the bottom layer of subgrade bed,the reinforcement length of geogrid is 4.0 m and the reinforcement spacing is 0.6 m.