The Mechanical Properties Of Oil Contaminated Saline Soil Treated By Lime And Fly Ash

Oil contaminated soil occurs inevitably as its exploiting,transporting and using.The oil film wraps on soil surface and the liquid oil exists between soil pores influence the mechanical and hydraulic properties of contaminated soil.Reasonable disposal of oil contaminated soil need to be solved urgently as oil contamination is un-stability and will migrate again with environment.To use oil contaminated soil for engineering,testes of compressive strength and shear strength were carried out on soil samples included oil contaminated saline soil,lime treated oil contaminated soil,lime and fly ash treated oil contaminated soil.Appropriate solidified material(fly-ash and lime)were selected by considering engineering mechanics and green development requirements.It explored the effect of oil content and environment temperature on soil mechanical properties,and summarized the strength and deformation distribution of treated oil contaminated soil.Then orthogonal t analysis method was used to obtain the optimal proportion.Results are as follows:(1)The indexes of compressive strength,cohesion and internal friction angle of soil increased firstly and then decreased oil content.Main differential stress-strain curve of oil contaminated soil presented strain softening.There was threshold of oil content for the maximum of main differential stress,a positive correlation existed as it below threshold but it just the opposite when exceeding.The failure of inclined crack and areas was intensified with increasing of oil content whether confining or unconfined condition.(2)Temperature had significant effects on mechanics properties of oil contaminated saline soil.Compressive strength of oil contaminated soil decreased with the increasing of temperature,and it reduced nearly 70% at 20 oC as to oil content of 15% comparing with un-contaminated soils.Unconfined compressive strength increased first and then decreased with the increase of oil content.There was an opposite correlation between environmental temperature and oil content at maximum strength,and it was 15,10,and 5% at 10,20 and 30 oC respectively.Damage of oil contaminated saline soils presents strain softening type with failure plane of 45°±?/2,and it was intensified with the increasing of oil content and temperature.Environmental temperature had obvious effect on the deformation of oil contaminated saline soil.(3)The unconfined compressive strength of oil contaminated soil treated by lime was increasing gradually with the increase of lime content,and it was increasing firstly and then decreasing as to oil content.The strength increasing rate became slowly with curing days.Lime had obvious effect on cohesion,but on internal friction angle.The optimal proportion was 12% lime + 5% oil + 21 curing time.(4)Combination of lime and fly ash could improve effectively the strength of oil contaminated soil,and solved the problem existed in lime treated oil contaminated soil.The compressive strength of lime-fly ash treated oil contaminated soil was closely related to oil content and it reduced gradually with the increasing of oil content.The orthogonal experiment analysis indicated that the optimal proportion was 20% fly ash + 12% lime + 5% oil + 28 curing time.