基于多跨单向板力学模型的管幕冻结法隧道初期支护参数优化方法

Optimization Method of Initial Support Parameters of Tunnel by Pipe Curtain Freezing Method Based on the Mechanical Model of Multi-span One-way Slab

管幕冻结法是一种在复杂水文条件下能够较好地控制地层沉降和涌水风险的新型工法,目前在管幕冻结法隧道设计中未考虑管幕-冻结圈承载力与隧道初期支护承载力的匹配问题,导致初期支护设计偏保守,使得初期支护钢架布置密,施工效率低,因此,需要进行初期支护优化研究。以隧道下穿秦淮新河段为依托工程,首先基于多跨单向板力学模型考虑等距钢架对上部冻结圈的支撑作用,求解组合结构内力;其次按照组合梁模型求解组合结构应力,并按照强度控制计算最大允许钢架间距;最后采用数值模拟,对初期支护参数优化进行研究。结果表明:本工程中最大允许钢架间距由中性轴以下部分混凝土强度控制,为2~3 m;拱架刚度对衬砌变形及应力影响较大,提升拱架刚度对于改善初期支护应力状态具有良好效果;综合考虑冻结圈和衬砌的变形和应力,得到适用于本工程的初期支护优化参数。

The Freeze-Sealing Pipe Roof(FSPR)is a new type of construction method suitable for controlling surface settlement and water gushing risks under complex hydrological conditions.At present,the matching between the bearing capacity of the tube curtain-freezing ring and the initial support bearing capacity of the tunnel is not considered in the tunnel design of the tube curtain freezing method,which leads to the conservative design of the initial support,the dense arrangement of the initial support steel frame,and the low construction efficiency.Therefore,it is necessary to study the parameters of primary support.First of all,based on the project with tunnel passing through the Qinhuaixin River,the internal force of the composite structure is solved by considering the supporting effect of the equidistant steel frame on the upper freezing ring based on the multi-span unidirectional plate mechanical model.Secondly,the stress of composite structure is solved according to the composite beam model,and the maximum allowable steel frame spacing is calculated according to the strength control.Finally,numerical simulation is used to study the optimization of initial support parameters.Results show that the maximum allowable steel frame spacing in this project is controlled by the concrete strength below the neutral axis,which is 2~3 m;different I-steel models have great influence on lining deformation and stress,and the improvement of I-steel model has good control and improvement effect on initial support stress state.Considering the deformation and stress of freezing ring and lining,the initial support optimization parameters suitable for this project are obtained.