柱状节理玄武岩隧洞破坏模式及其力学机制模拟

柱状节理岩体由于其内部赋存大量的隐节理面,开挖卸荷后极易出现隐节理面开裂松弛等特征,导致其破坏模式异于一般岩体。其破坏模式主要受到异常发育的节理面和较高地应力的共同作用影响。由于柱状节理岩体节理面发育,岩体结构控制型破坏占主要部分,包括单临空面节理面滑移(塌方)、多临空面节理面滑移(塌方)、与错动带、断层等弱面相组合的坍塌等破坏模式;应力控制型破坏主要为河谷侧顶拱喷层开裂;应力-结构面型破坏主要为岩性交界处的节理岩体塌落等。柱状节理岩体表层主要发生柱内竖直隐节理面和柱间节理面的拉破坏,而围岩内部的柱状节理主要发生柱间节理面的剪切破坏。因此,现场柱状节理的支护也应主要包括两个方面:以喷射混凝土钢纤维来阻止柱状节理岩体表层的张性开裂,以系统锚杆来控制柱状节理岩体内部的剪切破坏。

Failure mode of columnar jointed basalt tunnel and its mechanism simulation

There are many hidden joint planes in columnar jointed rock mass. The failure mode of columnar jointed rock mass is different from that of ordinary rock mass due to the crack of hidden joint plane. Its failure mode is mainly influenced by the extremely developed joint and high geostress. Because of the extremely developed joint in columnar jointed rock mass, the failure mode controlled by rock mass structure is the main part of damage mode, which includes joints plane slip (collapse) under single free face, joint plane slip (collapse) under multiple free faces, joint collapse combined with dislocation interface and fault, etc. The failure mode controlled by geostress is the second part of damage mode, which includes concrete layer cracking at crown of valley side. The failure mode controlled by the combination of geostress and rock mass structure is the third part of damage mode, which includes jointed rock mass caving at the lithologic boundary, etc. The failure mode at the surface of columnar jointed rock mass is tension cracking of the joint between columns and joint inside the column. Shear cracking of the joint between columns mainly happens in the surrounding rock. So the corresponding support of columnar jointed rock mass should mainly include two aspects: the shotcrete with steel fiber is mainly to prevent the tensile cracking at the surface of columnar jointed rock mass, and the anchor system is mainly to control the shear failure inside the columnar jointed rock mass.