Study On The Moisture Balance And Control Of Construction Quality Of Granite Residual Soil In Guang-Fo-Zhao Expressway

Granite residual soil is often used as filling for the construction of subgrade.However,Its water stability is poor,its structure is loose,and its cohesive force is small.A large number of granites are distributed along the basement and hilly area of the Guang-Fo-Zhao Expressway,the thickness of the weathered zone of the surface granite is large.In order to fill the embankment with granite residual soil directly to ensure the long-term bearing capacity of Subgrade.In this paper,the physical and mechanical properties of granite are analyzed.The moisture regularity of the subgrade of granite residual soil and the control technology of subgrade compaction are studied,and the corresponding measures of subgrade quality control are formed.It has important theoretical and practical significance for the development of special soil subgrade design and construction technology.The main work and conclusions are as follows.Firstly,the basic soil parameters of the granite residual soil is studied.The results show that:(1)the granite residual granite joint fissures in soil,the porosity and water absorption rate are small,the expansion coefficient is different,and the natural water content is high,and the liquid plastic limit is large.(2)Based on the above analysis,through the study of the soil humidity characteristics,it is found that the overall distribution characteristics of the soil moisture in Guang-Fo-Zhao expressway are larger than those of the clay soil particles,and the moisture content of the roadbed soil is basically more than 90%.The residual volume water content of the granite residual soil sample is about 25%～30%,and the granite residual soil with large initial dry density has strong water holding capacity.(3)The saturated permeability coefficient of the soil samples with larger initial dry density is relatively small,showing a decreasing trend.Under the same dry density,the thermal conductivity of granite residual soil increases with the increase of moisture content.The volumetric specific heat of soil increases gradually with the increase of moisture content,until the soil sample tends to be saturated and stable.(4)Through the relationship between the modulus of resilience of subgrade and the change of water content,it is found that the parameters of the modulus of road base modulus in the design of pavement structure should consider the change law of the long-term modulus attenuation of the subgrade.Therefore,it is advisable to balance the corresponding modulus of the humidity as the reference value of the modulus of the pavement structure.Then,the compaction control method of granite residual soil is studied.(1)The performance and compaction control method shows that the granite residual soil in the humidity of CBR peak water content,dry density after the smallest attenuation;(2)CBR peak water content as the granite residual soil subgrade compaction water content,facilitate the construction of subgrade.(3)Through the compaction construction quality control of the roadbed test section of Guang-Fo-Zhao,the field test results show that the new technology of special soil compaction control,which aims at the maximum carrying capacity,can guarantee the quality of the subgrade construction and the performance of the road.Finally,through the comparison of indoor and field tests,a penetration of PR and CBR,deflection,bearing plate static modulus Eb,PFWD dynamic relationship between Ep modulus and degree of compaction of K,verified by the relevant department is well,indicating that DCP can be used as a valid method of determination of subgrade compaction quality.