Study On Road Performance Of Saline Soil With Lime And Jute Fiber

A large area of saline soil is distributed in the western part of Jilin Province.As a special soil,saline soil will cause various forms of road diseases such as salt expansion,collapse,frost heaving and frost boiling on roads and railways.The engineering properties exhibited by saline soil make it unsuitable for direct use as a roadbed filler.While in the western part of Jilin Province,high quality fillers are extremely scarce.Therefore,it is particularly important to take measures to improve the pavement performance of saline soils and make their performance meet the standard requirements.This paper takes the representative saline soil of the Sahara dry soil in Tongyu County,western Jilin Province as the research object,and improves the properties of this saline soil by lime and sisal fiber.Through the unconfined compressive strength test of saline soil,the effects of water content,lime content,fiber content and fiber length on soil strength were studied.At the same time,the three-factor and three-level orthogonal experiments were carried out with lime content,fiber content and fiber length,and the optimal combination was obtained.At the same time,based on the test results,the optimal combination and undisturbed soil were selected for the bearing ratio(CBR)test,the triaxial test under the freeze-thaw cycle and the unconfined compressive strength test.The main research results of this paper can be summarized as follows:(1)Experimental study on the basic mechanical properties and physical properties of the test soil samples.The total salt content of the test soil samples was0.389%,which was named as medium-saline soil.It could not be directly used as roadbed filling according to the specifications.(2)The best mix proportion of lime-fiber modified saline soil was obtained by three-factor and three-level orthogonal test: lime content was 10%,fiber length was1.5cm,and fiber content was 0.9%.The unconfined compressive strength of lime-fiber modified saline soil under the best mix proportion was 2.81 MPa,whichhas an increase of 2.20 MPa and an increase of 361% in strength compared with the unconfined compressive strength of undisturbed soil.(3)According to the experimental results,the cohesion of lime-fiber modified fibrous reinforcement soil was 147.49 kPa and the internal friction angle was 29.32°.The cohesion increased by 70% compared with the undisturbed soil and the internal friction angle increased by 23%.After 9 freeze-thaw cycles,the lime-fiber modified fibrous reinforcement soil has a cohesion of 117.62 kPa and an internal friction angle of 32.60°.The cohesion was 84.76% higher than that of the undisturbed soil and the internal friction angle was increased by 13.08%.(4)After one,three,six,and nine freeze-thaw cycles,the unconfined compressive strength attenuation rates of undisturbed soils were 10.21%,21.36,28.79%,and 32.53%,respectively.The unconfined compressive strength attenuation rates of lime-fiber modified saline soil were 6.75%,15.46%,21.94%,and 24.18%,respectively.The attenuation rate of unconfined compressive strength of lime-fiber modified saline soil is smaller than that of undisturbed soil,indicating that adding lime and sisal fiber to saline soil can improve the frost resistance of saline soil.After 9freeze-thaw cycles,the unconfined compressive strength of lime-fiber modified saline soil was 2.14 MPa,1.73 MPa higher than undisturbed soil,and the strength increased by 421%.(5)CBR test was carried out on undisturbed soil and lime-fiber modified saline soil.The CBR value of lime-fiber modified saline soil was 13.78,and the CBR value of undisturbed soil was 1.23.The CBR value increased by 1020%,and the CBR value of the lime-fiber modified saline soil meets the filling requirements of all grades of highways in the specification.