| The double carbon strategy about reducing energy consumption and carbon emissions of the whole life cycle in the transportation infrastructure construction,is the important report of 2021 state council government work.At this stage,more and more mountain roads are being built in the context of the rapid development of urbanization and gradual reduction of the poor-rich disparities.The problem of differential settlement and large-area depression deformation is particularly prominent in the embankment engineering built on the soil-rock composite foundation.The reinforced soil structure can be applied in highway engineering to control the differential settlement of soil-rock composite foundation due to good flexible deformation characteristics.However,the problem of limited control effect of settlement and the problem of stress concentration are prominent.Therefore,this paper puts forward prestressed reinforced soil structure and applies it to the embankment engineering of soil-rock composite foundation,revealing the settlement deformation response and action mechanism of prestressed geosynthetic-reinforced embankment under the uniform load and the traffic load.Furthermore,the feasibility of applying the prestressed geosynthetic-reinforced embankment to the anti-impact engineering of soil-rock composite foundation in mountain area is explored,and the application of the prestressed geosynthetic-reinforced embankment in soil-rock composite foundation engineering in mountain area is further expanded.The main research contents and results include:(1)The settlement deformation control effect and settlement failure mechanism of the reinforced soil structure were explored according to the laboratory model test results.It was found that the settlement deformation control effect of reinforced soil structure was not very effective.With the increase of differential settlement,the phenomenon of "stress concentration-fracture-separation" was easy to occur,which was not conducive to structural stability.Therefore,the prestressed reinforced soil structure was proposed in this paper.The settlement deformation control effect of the prestressed reinforced soil structure was explored by the laboratory model test,and the mechanism of the prestressed reinforced soil structure controlling differential settlement was revealed.The results shown that the prestressed reinforced soil structure can give full play to the restraint effect of reinforcement,eliminate the compression settlement of filler in advance,effectively improve the phenomenon of stress concentration,and significantly improve the flexural stiffness and settlement deformation stability of the reinforced soil structure.(2)Based on the good settlement deformation control performance,the prestressed reinforced soil structure was applied to the embankment engneering of soil-rock composite foundation in mountainous areas,and the settlement test of the prestressed geosynthetic-reinforced embankment under uniform load was carried out.Combined with the test results,the mechanical response,the differential settlement control effect and the mechanism of prestressed geosynthetic-reinforced embankment were analyzed.Compared with the ordinary geosynthetic-reinforced embankment,the average settlement of prestressed geosynthetic-reinforced embankment was reduced by 55.4%,and the maximum settlement was reduced by 48.6 %.In addition,near the soil-rock composite foundation,the differential settlement of the prestressed geosynthetic-reinforced embankment was reduced by 68.2 % than the ordinary reinforced embankment,indicating that the prestressed geosynthetic-reinforced embankment had a significant control effect on the differential settlement of the soil-rock composite foundation.The additional stress of prestressed geosynthetic-reinforced embankment and its attenuation along the buried depth of the structure were smaller than that of ordinary geosynthetic-reinforced embankment,which further reflected the remarkable load transfer performance and settlement deformation control advantages of the prestressed geosynthetic-reinforced embankment.(3)Combined with the loading characteristics of the embankment,the settlement test of prestressed geosynthetic-reinforced embankment on soil-rock composite foundation under the traffic load was carried out,and the settlement deformation control effect as well as the mechanism of prestressed geosynthetic-reinforced embankment under the traffic load were explored.It was found that the differential settlement of prestressed geosynthetic-reinforced embankment was significantly smaller than that of ordinary geosynthetic-reinforced embankment,and its average settlement was 42%smaller than that of ordinary reinforced embankment,which reflected the significant differential settlement control performance of the prestressed geosynthetic-reinforced embankment.In addition,the exertion of the prestressed reinforcement effect of reinforcement not only limited the relative displacement of the filler,increased the bending stiffness of the prestressed geosynthetic-reinforced embankment,increased the diffusion range of the additional stress,but also increased the space for transmission and diffusion of upper load.Therefore,the additional stress in the prestressed geosynthetic-reinforced embankment was generally less than that in the ordinary geosynthetic-reinforced embankment,which further reflected the significant settlement deformation control advantages of the prestressed geosynthetic-reinforced embankment.Combined with the grey theory,the influence of prestress size and spacing of prestressed members on the settlement deformation control performance of the prestressed geosynthetic-reinforced embankment was analyzed.The results shown that the settlement deformation control performance of the prestressed geosynthetic-reinforced embankment was more sensitive to the spacing of prestressed members than to the prestress size.(4)The calculation methods of settlement deformation of the prestressed geosynthetic-reinforced embankment under the uniform load and the traffic load were proposed,based on the cable theory,the elastic theory,the equivalent composite stiffness and the deflection deformation range.Firstly,the effect of each component was equivalent to the force acting on the filler according to the stress-strain relationship of each component of the prestressed geosynthetic-reinforced embankment,and then the calculation method of the equivalent composite stiffness of the prestressed geosynthetic-reinforced embankment was proposed.Secondly,according to the stress and deformation of the reinforcement in the prestressed geosynthetic-reinforced embankment,combined with the cable theory,a method for calculating the deflection deformation area of the embankment was proposed,and the settlement deformation calculation under the various load conditions was further carried out.Among them,the traffic load function was modified by the time-varying characteristics of traffic load.And then,the settlement deformation calculation model of prestressed geosynthetic-reinforced embankment under the traffic load was further proposed,and its rationality was verified by the model test results.The settlement deformation calculation method of prestressed geosynthetic-reinforced embankment under the uniform load and the traffic load proposed in this paper can be used to calculate the post construction settlement of embankment and evaluate the stability of embankment,and provide a theoretical basis for the application and design of prestressed geosynthetic-reinforced embankment in soil-rock composite foundation engineering in mountainous areas.(5)Based on the good deformation control performance,the prestressed geosynthetic-reinforced embankment was further applied to the anti-impact engineering of embankment on soil-rock composite foundation,and the comparative model test study of prestressed geosynthetic-reinforced embankment and soil embankment under the impact of rockfall was carried out.The test results shown that the pit size,the duration of the impact force and the transmission rate of the impact force of the prestressed reinforced embankment were significantly smaller than that of the soil embankment under the rockfall impacting.The results showed that the prestressed geosynthetic-reinforced embankment was more conducive to the absorption,transmission and diffusion of the rockfall impact force,reflecting the remarkable impact deformation control performance of the prestressed geosynthetic-reinforced embankment.With the increase of impact times,the tensile performance and lateral restraint effect of reinforcement can be fully tapped to improve the stiffness of prestressed geosynthetic-reinforced embankment,resulting in the gradual transformation of the additional stress distribution in the embankment from "parabolic single peak" to "double peak".It can be seen that,with the outstanding performance of impact deformation resistance,the prestressed geosynthetic-reinforced embankment was an candidate of anti impact embankment engineering of soil-rock composite foundation in mountainous areas,and can be popularized and applied in mountainous areas with high rockfall disasters. |
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