Study On The Impact And Settlement Control Technology Of Shield Tunnel Through Existing Buildings

With the development of urbanization,the construction industry has developed rapidly,so the demand for concrete continues to increase,and a large amount of abandoned concrete is produced.The construction industry is faced with the great challenge of insufficient resources and environmental pollution.Not only the issues of land occupation and environmental pollution caused by mismanaging of waste concrete but also the shortage of sand and gravel resources can be addressed through the recycled concrete technology,which plays an important role in sustainable development of construction sector.However,the performances of recycled concrete feature a less regularity and are worse than ordinary concrete’s,and thus these limit the large-scale application in projects.Given such situations,it is necessary that mechanical properties of recycled concrete should be systematic researched to supply references for its high-performance and large-scale application.The dissertation shows researches of influences on recycled concrete strength by the way of orthogonal test,and a neural network model for strength prediction of recycled concrete has been constructed on the basis of results.In addition to these figures,the transformation law of mechanical properties of recycled concrete has been analyzed by experiments of modulus of elasticity,axial compressive strength and flexural strength.All the data form the theoretical foundation of adjustment of the strength of recycled concrete in the project.Followings are the processes and results:(1)The influence factors of recycled concrete strength were studied by orthogonal test.Aggregate gradation,replacement rate of recycled aggregate,water-cement ratio and cement incorporation ratio were found out to explain how and how much the influence did on compressive strength of recycled concrete,and even the optimal mix ratio was proposed.Based on the experimental data,a neural network model for strength prediction of recycled concrete was established.Consequently,compared with other factors,both the replacement rate of recycled aggregate and the water-cement ratio impact the strength much more.Type I aggregate gradation,30% of the replacement rate of recycled aggregate,water cement ratio 0.40,and cement incorporation ratio 0.22,which is the best mix proportion.(2)The deformation performance of recycled concrete was studied by elastic modulus test.The influence of the replacement rate of recycled aggregate and curing age on elastic modulus and stress-strain curve shape of recycled concrete was analyzed.The result indicates that if the replacement rate of recycled aggregate increases,the elastic modulus will fall while the peak strain of stress-strain curve will rise.As the curing age prolonging,the elastic modulus will go up while the peak strain of stress-strain curve will decline.(3)Compressive strength of recycled concrete was studied by axial compressive strength test.The qualitative relationship between the axial compressive strength of recycled concrete and the replacement rate and curing age of recycled aggregate was clear,and the time-varying prediction equation of axial compressive strength of recycled concrete was further established based on the replacement rate and curing age of recycled aggregate:(?)The average relative error of this equation is 2.48%,and the linear correlation coefficient is greater than 0.98,which can accurately predict the axial compressive strength of recycled concrete.(4)The tensile strength of recycled concrete was studied by flexural strength test.The change law between the variation of flexural strength of recycled concrete and replacement rate and curing age of recycled aggregate was defined.The results show that reducing the replacement rate of recycled aggregate and extending the curing age are beneficial to the growth of the flexural strength,and the growth rate of late flexural strength of recycled concrete is positively correlated with the replacement rate of recycled aggregate.Compared with normal concrete,the 7d age coefficient of recycled concrete with 100% of the replacement rate of recycled aggregate decreases by 24%.