Improvement Of Completely Decomposed Granite And Study On Differential Settlement Control Technology Of New And Old Subgrade Of Lian Zhu Highway

When the construction of the backbone network of the highway is basically completed,China's highway construction is about to enter the development period of the post-highway.During this period,China's new highway projects will be fewer and fewer,the reconstruction and expansion of the previous low-grade highways and highways will gradually become the norm state.Therefore,in the context of this era,the study of highway reconstruction and expansion project will be of great significance.This paper relying on the high-speed upgrade project of LianZhu,combined with the methods of indoor and outdoor tests,numerical simulations and theoretical analysis,to study the problems of improvement of completely decomposed granite subgrade filling as well as differential settlement control technology of new and old Subgrade under complex geological conditions.The main research contents of this paper and the related conclusions are as follows:Firstly,it was concluded that the soil samples of completely decomposed granite along the project line were sandy low-liquid limited clay through indoor experiments,and the CBR only meets the requirements of the subgrade(region 93)of the filling portion.The variation of elastoplastic mechanical parameters of the completely decomposed granite filler with water content and compaction were obtained by Indoor load bearing plate test and static triaxial test.Secondly,after 4% of the total cement modified soil of completely decomposed granite processing was satisfied subgrade(region 94)of the filling portion,the completely decomposed granite modified soil treated with 8%cement can be used to fill all parts of the roadbed,and the strength and stiffness of cementitious soil increases with the increase of cement content verified by tests.Thirdly,combined with specific engineering examples,the change of the humidity field inside the subgrade with time was simulated by Geostudio under the influence of long-term climate and groundwater level changes.And the results show that the humidity inside the subgrade gradually increases with time due to the influence of climate and underground water level.After about 3?5 years,the subgrade soil reaches the moisture balance and basically no longer changes.Finally,combined with specific engineering examples,use ABAQUS software to simulate the differential settlement deformation of new and old roadbed,foundation and pavement surface under the complicated construction and technical schemes under complicated geological conditions,and provided a theoretical basis for the different settlement control techology of new and old subgrade in the upgrading and transformation of low-grade highway to higher-grade highway engineering under complex geological conditions(such as soft soil,completely decomposed granite,etc.)and undesirable subgrade filling.