| In the process of road construction in China,the backfilling engineering of structures such as abutments and fertilizer tanks faces severe differential settlement problems caused by difficult control of backfilling quality,which threatens the service life of roads and driving safety.Foamed lightweight soil,as a new backfill material that can be filled and compacted by itself,has high surface flatness after pouring,adjustable density and strength,and it is efficient in construction as while as effectively controlling the differential settlement after construction.However,the high cost and large carbon dioxide emissions limit its large-scale application in road engineering.On the other hand,China lacks effective means of reusing the sintered dust generated by steel smelting every year.Massive accumulation not only causes waste of land resources but also causes serious pollution to the environment.In view of the above problems,the sintered dust as the main raw material was used to carry out research and development of new green solid waste foamed lightweight materials.Based on the physical and chemical characteristics of sintered dust and the factors affecting the performance of foam light soil,the optimization and modification methods are proposed,and the mechanical properties,durability and dynamic properties of foam light soil based on dust removal ash were systematically studied.The main conclusions of the study were as follows:(1)Based on the synergistic effect of sintered dust,slag powder and cement multicomponent components,the compressive strength of sintered dust foamed lightweight soil can be increased by 43%.A variety of modified reagents developed in the laboratory can effectively improve the hydrophobicity of dust removal ash particles,optimize the internal pore structure of foamed lightweight soil,and improve the mechanical properties and water stability of sintered dust foamed lightweight soil.The modification effect is optimal when the amount of modified reagent A was 0.4%of dust removal ash mass,the amount of modified reagent B was 20%of foaming agent mass,and the amount of modified reagent C was 0.5%of cementitious material mass.(2)The mechanical properties of sintered dust foamed lightweight soil were positively correlated with the density,and negatively correlated with the amount of the sintered dust.The 28d unconfined compressive strength of 600kg/m3～1200kg/m3 foamed lightweight soil was 1.06MPa～8.06MPa,softening coefficient was 0.665～0.958,water absorption was 35.4%～7.9%,and compression modulus was 105.1MPa～244.5MPa.When the natural settlement,apparent density and compressive strength were taken as the pouring quality control indicators,the maximum single pouring height of dust removal ash based foamed lightweight soil was 1.2m,and the engineering adaptability was good.(3)The mass and moisture content of sintered dust foamed lightweight soil increased rapidly in the early stage of dry wet cycle,and then tended to be stable.The higher the density of foam light soil was,the faster it reached a stable state,and the stronger the ability to resist dry wet cycle.The strength ratio of 600kg/m3～1200kg/m3 foamed lightweight soil after dry wet cycle was 69.5%～94.3%,and the water content was 38.3%～9%;When the sintered dust foamed lightweight soil was used as backfill material in areas with dry wet cycles,it was recommended to control the density not less than 800kg/m3.If the design density was less than 800kg/m3,the dust content should be controlled less than 30%.(4)The wet mass of foamed lightweight soil increased first and then decreased with the increase of freeze-thaw cycles;The strength ratio of 600kg/m3～1200kg/m3 foamed lightweight soil after freeze-thaw cycle was 66.3%～93.3%,and the mass change rate is 96.5%～96.7%;When dust removal ash based foam light soil was used as backfill material in areas where freezing thawing cycles occur,the mix proportion scheme with density≤600kg/m3 and dust removal ash content>30%should be avoided.(5)The dynamic resilient modulus of foamed lightweight soil increased with the increase of specimen density and stress level.The dynamic resilient modulus of foamed lightweight soil under the natural state of 600kg/m3～1200kg/m3 was between 455MPa～859MPa,and the modulus after saturation was between 387MPa～785MPa,which was far greater than the requirements of subgrade dynamic resilient modulus.(6)The permanent strain of foamed lightweight soil increased with the increase of loading stress level.Under natural conditions,the permanent strain of specimens tended to be stable during cyclic loading,the permanent strain was within 0.12%,and the allowable dynamic stress level was 0.6qu;After being saturated with water,the dynamic performance of the specimen decreases,and the allowable dynamic stress level was 0.3qu.When the dynamic stress level was higher than 0.3qu,the permanent strain development mode was plastic creep or incremental failure,which did not meet the usage requirements.Therefore,when using in high water level sections,water isolation and drainage measures should be taken,and the dynamic stress level should be controlled to be not exceed 0.3qu... |
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