Study On Deformation Characteristics Of Coarse-Grained Chlorine Saline Soil Subgrade In Alpine Salt Lake Area Under Traffic Load

Chaerhan Salt Lake area of Qinghai Tibet Plateau has typical alpine arid climate,which is the most widely distributed area of chlorine saline soil within the radiation of the "Belt and Road".With the further promotion of New Western Development under construction of transportation power,the scale of transport infrastructure construction in this area has gradually expanded.Under the influence of long-term traffic load and climate warming,as well as and the wetting trend of climate in the Qinghai Tibet Plateau,large number of subgrade diseases exist in this area.For example,the mudding,sink and uneven settlement caused by the poor engineering characteristics of chlorine saline soil appear on the roads in the Alpine Salt Lake area,which seriously threatens the long-term stability and operation safety of the roads in the Salt Lake area seriously.Therefore,the research on the deformation characteristics of chloride saline soil subgrade in Alpine Salt Lake area under traffic load has important theoretical significance and engineering practicalce values.Based on the Sebei-Chaerhan highway in the Alpine Salt Lake area,though the research methods of field investigation,field test,laboratory test,physical model test and numerical simulation,this thesis systematically studies investigate the the engineering geological characteristics of the chlorine saline soil,dynamic plastic cumulative deformation of coarsegrained saline soil filler,microstructure features,strength deterioration mechanism and dynamic response properties of saline soil subgrade.through the research methods of field investigation,field test,laboratory test,physical model test,and numerical simulation,The main research contents and results are as follows:Based on the summary of geological survey data and field investigation,combined with laboratory tests,the landform,hydrogeological characteristics,and physical and chemical properties of saline soil along the highway in Chaerhan Salt Lake area were analyzed,and the collapse deformation characteristics of coarse-grained chlorine saline soil filler were clarified by field immersion load test and laboratory collapsibility test.(2)Using GDS two-way vibration triaxial test system,the cumulative strain,damping ratio,and dynamic modulus of coarse-grained chlorine saline soil filler under different water content,salt content,freeze-thaw cycle times,dynamic stress amplitude,loading times,and confining pressure were studied.The dynamic stress threshold for evaluating the critical state of soil was given,and the cumulative strain prediction model of coarse-grained chlorine saline soil subgrade filler under the influence of different environmental factors was established.(3)The dynamic triaxial tests under different moisture content,salt content,freeze-thaw cycle,and traffic load were carried out by orthogonal design method,the cumulative strain under multiple interactive factors were studied,and the influence degree of various factors was obtained.Combined with CT detection under typical working conditions,the characteristics of microstructure change were studied,and the strength deterioration mechanism of the long-term deformation and coarse-grained chlorine saline soil subgrade filler was revealed.(4)Based on the self-developed DLFTC(dynamic load and freeze-thaw cycle)model test system in the Alpine Salt Lake area,the physical model tests of subgrade deformation of large-scale coarse-grained chlorine saline soil with the filler moisture content of 6.8%,7.5%and 8.5% were carried out respectively,the variation law of dynamic stress,dynamic strain and modulus of subgrade structure with vehicle load,loading times and loading frequency under traffic load and the freeze-thaw cycle was revealed.The deformation range of coarsegrained chloride saline soil subgrade under different working conditions was given.(5)The three-dimensional finite element model was established by using the ABAQUS software,the settlement law and dynamic response of coarse-grained chlorine saline soil subgrade under traffic load under different working conditions are numerically analyzed,and the distribution range of subgrade dynamic stress and the depth of subgrade working area under the influence of different vehicle speed,overload rate and load times were expounded.Combined with the cumulative deformation prediction model of coarse-grained chloride saline soil under traffic load,the long-term deformation of subgrade under different environmental factors and traffic loads was obtained.The research results of this paper not only provide effective technical support for the construction of Shicha highway,but also provide a reference for the subgrade design of similar projects and the revision of relevant specifications in the future.