Deformation And Stability Control Technology Of High Fill Slope Subgrade In Nanshan District

In the construction of expressways in southwest mountainous areas,high-fill slope subgrade is frequently encountered,and large deformation and instability of the subgrade occur during the construction and operation periods.In view of this problem,this thesis takes the Yiyi Expressway project as the background and takes the "Yiyi Expressway Project Sixth Lot"(K63+713-K83+269)as the object,through literature review,laboratory tests and numerical simulations,the deformation and stability of the subgrade during the construction period and operation period are studied,and the control measures of the high-fill slope subgrade are summarized and proposed,and the main conclusions are as follows:(1)The physical property test results show that the liquid limit of the basement soil is 60.1%,and the plastic limit is 34.9%,which is a high liquid limit clay;XRD test analysis showed that the main components were illite and quartz;The maximum dry density was 1.52g/cm3 and the optimal water content was 24.7%.The water absorption test showed that the water content of soil samples in the early stage of water absorption increased rapidly,and the water content of soil samples in the later stage increased slowly.The shear test showed that with the increase of compaction,the shear strength also increased,and with the increase of water absorption time,the shear strength decreased.The compression test shows that the compression modulus increases with the increase of compaction.Therefore,the compaction degree of the foundation can be improved in the project,the water absorption capacity of the foundation can be reduced,and the shear strength and compression modulus can be improved.(2)Through the numerical simulation of the construction period of the high-fill slope subgrade,the effects of four factors such as basement slope,basement soil thickness,compaction degree and water content on the deformation and stability of the subgrade were analyzed.The results show that the maximum horizontal displacement of the subgrade is distributed in the area near the foot of the slope under the subgrade,and the maximum settlement is distributed in the area near the right shoulder of the subgrade.In terms of the stability of the subgrade,the high-fill slope subgrade during the construction period was in a stable state,and the slope slope and water content had a greater impact on the stability of the subgrade,followed by the degree of compaction,and the thickness had the least effect on the stability of the subgrade.(3)Consider the influence of vehicle load and horizontal seismic load on the deformation and stability of subgrade during the operation period of high-fill slope subgrade.The numerical results analysis showed that the maximum horizontal displacement and settlement increased by only 13.3mm and 13.9mm under vehicle load,and the stability safety factor decreased by only 0.02;under the vehicle and horizontal seismic load,the maximum horizontal displacement and settlement increased by 211.4mm and 28.3mm,and the stability safety factor was 1.05,and the roadbed was in an unstable state,indicating that the horizontal seismic load had a great influence on the stability of the roadbed.(4)Based on the above research conclusions and literature review,the basic principles of high-fill slope subgrade engineering treatment are summarized and extracted,and the prevention and control measures of high-fill slope subgrade are summarized from the aspects of interception drainage,mechanical balance and foundation improvement,so as to provide reference for the prevention and control of high-fill slope subgrade in southwest mountainous areas.