Research On The Theory And Application Of The Conical Cutterhead Of Shield Machine

Shield is a kind of underground engineering mechanical equipment for full face construction in soil dominated stratum.Its cutterhead structure is the key component to realize the stability of the excavation face and tunnel excavation.With the construction of urban subway,some engineering technical problems arise,such as the poor tunneling performance of shield in sand gravel,gravel,pile foundation,ancient tree root and other strata.In order to improve the geological adaptability of cutterhead,the Cutterhead of shield is studied from the structural shape.In this paper,the theory and application of the conical cutter head are studied.First of all,the theoretical calculation model of the two key driving parameters of the conical cutterhead shield,thrust and torque,is established and deduced,and the reliability and applicability of the theoretical model are verified.Secondly,through the static analysis of the cutterhead,the change rule of the rigidity and the strength of the cutterhead under the same working condition with the change of the cone angle of the cutterhead is studied,and the dynamic simulation model of the shield tunneling process is established to study the soil flow and the pressure difference in the sealed cabin under different cutterhead conditions.Furthermore,the feasibility and superiority of the application of the theory of conical cutter head are discussed.It pro vides theoretical basis and reference for the design and application of the conical cutter head structure of shield.The main work contents of this paper are as follows:(1)Summarized the application and development history of shield in China and the research status of shield cutter head adaptability,structural design,thrust and torque calculation model at home and abroad;summarized the shield structure composition,operation principle and classification,and introduce and analyze cutterhead system structure,cutters layout and other functional structures in detail.(2)According to the earth pressure theory,the theoretical models of thrust and torque of the conical cutterhead shield are established by using the mechanical and mathematical methods.The driving resistance of cutterhead during normal shield tunneling is refined,that is,the driving resistance produced by earth pressure of cutterhead excavation face,the friction resistance between cutterhead side and soil,the friction resistance between spoke side and residual soil,and the resistance produced when cutters penetrates into soil.Through the systematic analysis of the components of the thrust and torque of the cutter head,the theoretical calculation formulas of the components of the thrust and torque of the conical cutterhead shield are derived.Based on the shield and geological parameters of two kinds of shield construction examples,the theoretical model of thrust and torque calculation of the conical cutter head shield is checked,and the results meet the empirical requirements,which provides a good theoretical basis for the thrust and torque design and calculation of the conical cutter head shield.(3)By using three-dimensional modeling and finite element analysis software,the static analysis of cutterhead with different cone angles is carried out under three working conditions,to explore the influence and change rule of the cone angle of cutterhead on the rigidity and strength of cutterhead,and then to optimize the cone angle of cutterhead;the dynamic simulation of the normal tunneling process of shield is also carried out,and the soil flow condition in the sealed cabin when the conical cutterhead is compared with the plane cutterhead.By monitoring the pressure before and after different cutterhead,the relationship between the taper angle of cutterhead and the pressure difference before and after cutterhead is analyzed.