隧道可缩工字钢拱架让压规律模型试验研究

Model Experimental Study on the Yielding Law of the Tunnel Contractible I-beam Arch

为研究软岩隧道可缩工字钢拱架让压装置的缩动规律,在侧压大拱压小的对称荷载(侧压比为1.5)和左拱腰偏压荷载两种工况下,进行室内整榀可缩工字钢拱架模型加载试验,分析其让压装置的让压过程及拱架变形等规律。结果表明:可缩工字钢拱架在两种工况下的让压过程可划分为弹性变形阶段、适应荷载-变形协调阶段、稳定让压阶段、荷载-让压变形同步增加阶段和让压完成后刚性阶段,其中稳定让压阶段,荷载呈现出小范围“增荷—卸荷—再增荷”的让压特点。稳定让压阶段、荷载-让压变形同步增加阶段的转折点可作为可缩工字钢拱架让压装置的增阻时机,并提出了相应的判断参数k。让压装置位移和拱架关键位置变形随总荷载的增加具有较高的同步性。在左拱腰偏压工况下拱顶让压装置产生平面外的错动变形,而其边墙处的让压装置和侧压大拱压小工况下的全部让压装置均未发生此类错动变形。研究成果提供了可缩工字钢拱架在侧压力大以及偏压荷载下让压缩动规律的新认识,可为在高地应力软岩隧道现场应用时提供一定的指导意义。

In order to study the load-bearing performance of the contractible I-beam arches in soft rock tunnels and the laws of yielding device movement, indoor model loading tests of the contractible I-beam arches are carried out under two conditions of symmetric loading with large lateral pressure and small arch pressure(lateral pressure coefficient is 1.5) and loading with left arch web bias pressure to analyze the force performance and shrinkage displacement laws. The results show that the stress deformation process of the contractible I-beam arch under the two working conditions can be divided into elastic deformation phase, adaptive load-deformation coordination phase, stable yielding phase, load yielding deformation simultaneous increase phase and rigid phase after yielding. In the stabilization stage, the load shows a small range of “load increase-unload-load increase again” pressure yielding characteristics. The turning point of the stable yielding phase and load-yielding deformation simultaneous increase phase can be used as the time to increase the resistance of the contractible I-beam arch yielding device, and then the corresponding judgment parameter k is proposed. The deformation of the key position of the arch has high synchronization with the retraction of the yielding device with the increase of the total load. Out of plane misalignment deformation of the vault yielding device occurs under left arch web bias pressure working condition, while all yielding devices under large lateral pressure and small arch pressure working condition are not deformed. The research results provide a new understanding of the contractible I-beam arch under large lateral pressure and bias pressure working condition, which can provide some guidance for the field application in high ground stress and soft rock tunnels.