TBM隧道回填层-管片受力特征模型试验研究

回填层作为围岩和管片之间的连接部分，起到稳定衬砌、传递荷载、吸收变形等作用。护盾式TBM隧道施工过程中，回填层存在未注浆松散、注浆固结两个主要状态。回填层状态不同，回填层作用及管片受力特点也不同。研究采用相似模型试验分析不同状态下的回填层作用机制，通过研究得到了以下结论：回填层未注浆松散状态下，由于碎石的径向压缩与环向移动，围岩传递到管片上的荷载量值降低且分布较为均匀，此时回填层作为“可压缩层”，具有让压和均匀荷载的作用，能明显降低管片的受力和变形；回填层注浆固结后，回填层虽然能够承担少量的荷载与变形，但承载能力有限，主要作为围岩与管片之间的“传递层”，传递荷载与变形；对于挤压性围岩护盾式TBM隧道施工可适当应用回填层未注浆时的“可压缩性”，减小施工过程中管片受力与变形；对于浅埋及地铁隧道则应尽早注浆，使衬砌与围岩形成稳定的受力体系；回填层弹性模量的增加可提高回填层-管片组合体系支护刚度，但增加效果不明显。

Model test study on stress characteristics of backfill to segment in TBM tunnel

As a connecting part between surrounding rock and the segment, the backfill layer is used to stabilise the lining, transfer the load, and absorb the deformation. During the construction of shielded TBM tunnel, the backfill layer had two main states: loosened before grouting and consolidated after grouting. The effect of the backfill layer and characteristics of the segment stress depend on the state of characteristics of segment stress. The similar model test was used to analyze the mechanism of backfill at different states, and the following conclusions were obtained. When the backfill is loosened before grouting, due to the radial compression and circumferential movement, the load value of the surrounding rock to the segment is reduced, and the distribution is more uniform. At this time, the backfill is used as the "compressible layer" to reduce pressure and to make the pressure uniform. The backfill can significantly reduce the force and deformation of the segment. When the backfill becomes consolidation after grouting, the backfill layer can bear a small amount of load and deformation, but the bearing capacity is limited. At this time, it becomes the "transfer layer" between the surrounding rock and the segment. The extrusion of the shield rock TBM tunnel construction may use the backfill compressibility before grouting, and reduce the segment force and deformation. Shallow and subway tunnels should be grouting as soon as possible, so the lining and the surrounding rock can form a stable force system. The increase of elastic modulus of the backfill layer can improve the support stiffness of the backfill to the segment system, but the effect is not obvious.