隧道纤维混凝土二衬承载机理及受力计算方法研究

Study on bearing mechanism and stress calculation method of tunnel secondary lining of fiber reinforced concrete

充分考虑和发挥纤维混凝土的韧性性能是目前隧道二衬结构设计的热点和难点。通过素混凝土、钢纤维及玄武岩纤维混凝土的室内试验发现:纤维的掺入,对混凝土的增韧效果远超增强效果。基于纤维混凝土优异的韧性特征,将纤维混凝土二衬裂缝视为塑性铰,提出隧道纤维混凝土二衬的承载机理:围压作用下,衬砌出现第一个塑性铰,随着围压继续增大,塑性铰发生转动并引起更多塑性铰出现,至结构由超静定变为可转动机构时,二衬结构破坏。基于此,探讨了隧道纤维混凝土二衬裂后结构受力计算方法,推导了相应的计算公式,并通过模型试验予以验证。研究成果可为纤维混凝土在地下工程中的推广应用提供理论支撑。

Sufficient exploitation of the toughness of fiber reinforced concrete is the hot and difficult topic for the design of tunnel second lining. Based on the laboratory tests on plain concrete, steel fiber reinforced concrete and basalt fiber reinforced concrete, it is found that the addition of fibers has a far better impact on the toughness of concrete than the strength of concrete. In view of the excellent toughness of fiber reinforced concrete, the cracks of secondary lining of fiber reinforced concrete are regarded as plastic hinges, and the bearing mechanism of tunnel secondary lining of fiber reinforced concrete is proposed. Under the confining pressure, the first plastic hinge occurs in the lining, and with the increase of the confining pressure, the plastic hinges may rotate, which further lead to the occurrence of more plastic hinges. When the structure transforms from the statically indeterminate state to a rotating mechanism, the secondary lining structure is damaged. Furthermore, the stress calculation method for the cracked tunnel secondary lining of fiber reinforced concrete is discussed, and then the calculation formula is derived and validated based on model tests. Research results can be referred for popularization and application of fiber reinforced concrete to underground engineering.