Study On Parameters Of Plate-short Anchor Assembly Structure Of Repairing Cracking Lining

As the operation mileage of tunnels in China increases year by year,lining cracks as a typical tunnel disease have a serious impact on the structural stability and operational safety of existing tunnels.Therefore,it is urgent to study the repair and reinforcement methods of lining cracks.The plate-short anchor assembly structure with repairing cracked lining has the advantages of firm anchor connection,convenient prefabrication,convenient construction,etc.,and can quickly improve the bearing capacity of the crack lining.Some scholars have carried out related research on the repair method.However,the research on the plate-short anchor assembly structure is still in the preliminary stage,and the influence of related parameters on the repair effect and mechanical state of the combined structure is still unclear.This paper relies on the sub-project of the national key R&D plan “Fast minimally invasive repair technology for structural damage of existing urban tunnels”.Through data investigation and theoretical analysis,the method of repairing the lining plate-short anchor assembly structure of cracked lining is deeply studied.The finite element analysis method of the whole process simulation was carried out to study the related parameters and mechanical state of the plate short anchor combination structure.The main conclusions and results are as follows:(1)Through the analysis of the force state of the short-anchor composite structure,the calculation method of the combined structural bearing capacity of the strengthened steel plate under the condition of the secondary stress of the repaired structure is obtained,and the parameters of the short-anchor composite structure are proposed.Optimization.(2)Based on the virtual tracking element method,the finite element calculation method of the whole process of cracking-repairing in the repair of the cracked lining of the plate type short anchor combination structure is proposed,which makes the numerical simulation more in line with the engineering practice.(3)Numerical simulations were carried out for the relevant parameters of the plate short anchor combination structure and the conclusions were as follows:(1)The short anchor spacing can reduce the overall bearing capacity of the combined structure,and the densely arranged short anchor can fully exert the reinforcing effect of the repairing structure.Under the research conditions studied in this paper,the short anchor spacing should be no more than 40 cm.At the same time,the short anchor adopts the plumshaped arrangement to effectively alleviate the concentrated damage effect of the drilling on the concrete and the weak surface,so that the concrete tensile damage is apportioned,thereby improving the bearing capacity of the combined structure.(2)Short anchors play the role of connecting reinforcing steel plate and concrete in the combined structure.When the anchoring length is less than 13.5cm(30% lining thickness),the stiffness of the repaired structure is reduced,and the short-row anchors show obvious deformation tendency,and the ultimate bearing capacity of the members.Seriously reduced.At the same time,the load between the steel plate and the concrete is mainly carried by the short-row anchor away from the middle,and the short length of the inner row has little influence on the bearing capacity of the combined structure.Therefore,the length of the shortrow anchor in the combined structure should not be less than 30% of the thickness of the lining,and the shorter arrangement of the shorter inner row of the short anchor is a more ideal arrangement.(3)The thickness parameter of the steel plate in the combined structure has a direct influence on the ultimate bearing capacity of the component.When the thickness is less than 8mm,the deformation of the steel plate increases sharply due to the decrease of the stiffness,and the bearing capacity is significantly reduced.Increasing the thickness of the steel plate can effectively improve the overall rigidity of the repaired structure and the overall structure of the component.Carrying capacity.When the thickness of the steel plate is 12 mm,the effect of increasing the thickness value on the ultimate bearing capacity of the combined structure is not obvious,so the thickness of the combined structural steel plate should be 8 to 12 mm.(4)The timing of the repairing time can effectively inhibit the in-depth development of the mid-span crack and improve the ultimate bearing capacity of the component.When the midspan crack is repaired to 20% lining thickness,the residual bearing capacity of the component can not reach the bearing capacity of the complete component,so the timing of repairing the structure should be controlled before the crack depth develops to 20% of the lining thickness.