盾构接收工作井围护结构附加应力计算及应用

Calculation and Application of Additional Stress on Enclosure Structure of Shield Receiving Work Shaft

为分析盾构接收对工作井围护结构附加应力的影响,以某盾构隧道工作井为依托工程,通过建立盾构接收期工作井围护结构力学模型,基于弹性力学Mindlin应力解与Sagaseta公式,提出盾构刀盘正面附加推力、盾壳与土体摩擦力、同步注浆压力及土体损失对工作井围护结构附加应力的计算方法.通过对工作井围护结构附加应力的主要影响因素进行计算分析,并结合数值模拟研究接收期工作井围护结构的力学行为,基于工程实例形成了盾构近接控制原则.研究结果表明:1)工作井围护结构附加应力的影响范围随盾构隧道直径增大而扩大,且主要发生在盾构直径的1.5倍范围圈内,盾构机所处深度对附加应力最大值具有重要影响;2)总附加应力中以正面附加推力和盾壳与土体摩擦力引起的附加应力为主,占比分别约1/3和2/3,同步注浆和土体损失引起的附加应力相比前两种可忽略不计;3)总附加应力的理论计算和数值模拟结果基本一致,验证了计算方法的合理性,同时数值模拟表明盾构接收期工作井围护结构的弯矩和变形增长了1倍左右,在盾构接收施工中应予以重视;4)基于掘进速率对工作井围护结构附加应力的计算分析结果,在工程接收关键区间(10~0环)中采取了“低推速”接收原则,保障了盾构的安全接收,可为同类工程提供参考.

To analyze the influence of shield tunneling reception on the additional stress of work shaft enclosure structure,taking a shield work shaft as the supporting engineering,a calculation method for additional stress of work shaft enclosure structure caused by bulkhead additive thrust of shield cutter head,friction force between shield shell and soil,synchronous grouting pressure and soil loss was proposed by establishing mechanical model of work shaft enclosure structure in the shield tunneling reception period,based on Mindlin stress solution of elasticity mechanics and Sagaseta formula.The main influencing factors of the additional stress of the work shaft enclosure structure were calculated and analyzed,and the mechanical behavior of the work shaft enclosure structure during receiving period was studied by numerical simulation.The principle of the shield tunneling proximity control was formed based on engineering examples.The results show that:1)the influence range of additional stress of work shaft enclosure structure increases with the increase of shield tunnel diameter and mainly occurs in the 1.5 times of shield diameter.The depth of the shield machine has an important influence on the maximum value of additional stress.2)The total additional stresses are mainly caused by frontal additional thrust and friction between shield shell and soil,accounting for about 1/3 and 2/3,respectively.The additional stresses caused by synchronous grouting and soil loss are negligible when compared with the first two.3)The theoretical calculation and numerical simulation results of total additional stress are basically the same,which verifies the reasonableness of the calculation method.At the same time,the numerical simulation shows that the bending moment and deformation of the enclosure structure of the working well during the receiving period of shield tunneling increase by about one time,which should be paid attention to in the receiving construction of shield tunneling.4)Based on the calculation and analysis results of the additional stress of the work shaft enclosure structure caused by the excavation speed,the principle of“low speed”reception is adopted in the key receiving interval of the project(10-0 rings),which ensures the safe receiving of shield and provides a reference for similar projects.