Study On The Mechanical Properties Of New Type Joints For Composite Segment In Shield Tunnel

Shield tunneling is faced with the increasingly complicated situations such as large buried depth,long hole line,high ground stress,strong karst formation and so on.Composite segment has been applied to practical engineering because of its excellent mechanical properties such as high strength and stiffness.In order to give full play to the advantages of composite segment in the structural form and mechanical properties,some new joints have been developed and put into use.However,the new joints of composite segment are mostly composed of structures with complex structure and high machining accuracy.The factors that affect the mechanical properties of new joints include not only the contents of the traditional joints,but also the unique characteristics of the new joints.Therefore,it is necessary to establish a new type of composite segment joint that can truly reflect its mechanical properties and be convenient for designers and researchers to use.On this basis,the influencing factors of the mechanical properties of the new joint can be studied and discussed in detail.Based on the elastic-plastic mechanics and damage mechanics theory,numerical models of anchor joint and FRP-Key joint for composite segment were established by finite element software ABAQUS combined with the existing experimental results.At first,the rationality and validity of the models were verified.On this basis,the influence of the roughness and size error of key components on the mechanical properties of the anchor joint was studied.The difference between the working principle of the its assembly and tensioning process was investigated.The range of error allowed by its normal work was analyzed.And parameters standard for different types of anchor joint were obtained.In addition,the effects of material strength,the distance between the lower edge of the tenon and grooves,the size and layout of the joint,the axial force and supporting condition of the segment on the mechanical properties of FRP-Key joint were investigated.The failure modes and damage paths of FRP-Key joints under various factors were discussed.The influence of various factors on the ultimate bearing capacity and displacement of FRP-Key joint with segment under shear action was analyzed.The optimal arrangement of FRP-Key joints under specific conditions was proposed.The results show that processing technology is an important factor affecting the mechanical properties of anchor joint.Higher machining accuracy is required to ensure its normal work.The bearing capacity of FRP-Key joint increases with the increase of material strength,joint size and the edge margin of mortise and tenon in a certain range.Changing its layout is an effective way to improve the mechanical properties of FRP-Key joint.Finally,the numerical model and related parameter setting method presented in this paper can provide theoretical basis and technical support for the development and application of other new type joints.