关键词: 岩性, 断面形状, 深部硬岩隧洞, 板裂失稳, 真三轴试验

Abstract:

To explore the influence of the lithology and cross-section shape on spalling failure properties of deep hard rock tunnels, indoor true triaxial tests on spalling failure were performed. Firstly, two types of rock samples (marble and granite) and two typical cross-section shapes (high side wall gate arch shape and horseshoe shape) samples in practical applications were selected. Then, the failure characteristics under the influence of different lithology and cross-section shapes were analyzed from the three aspects including spalling failure mode, spalling rock plate characteristics, and the characteristic stress during spalling. Finally, numerical simulation was conducted to explore the corresponding displacement and stress distribution characteristics during the development and propagation of the cracks. Furthermore, the spalling failure characteristics of deep hard rock tunnels were investigated. The results indicated that the slab peeling and opening failure phenomenon for the marble sample was more significant than the granite one in terms of spalling failure mode during the test process. Moreover, the cross-sectional contour range involved in spalling failure for the horseshoe shape sample was smaller than the high-side wall gate arch shape. Different lithologies presented different flaked rock slab shapes for different flaked rock slab characteristics. Compared with the high-side wall gate shape, the flaked rock slabs near the outer layer relevant to the curved wall arch sample were more slender. For the characteristic stress during spalling, the granite sample had a larger threshold at the beginning of the spalling and a faster rate for the evolution process of the spalling failure compared with the marble one. Furthermore, compared with the horseshoe shape sample, the characteristic stresses of the high-side wall gate arch sample were higher from the beginning of plate cracking to the occurrence of obvious plate cracking failure. The area with large displacement in the numerical simulation was mainly observed on the side wall of the hole. The farther away from the side wall, the smaller the displacement. Moreover, the major reason the spalling occurs can be attributed to the tangential stress concentration.

Key words: lithology, cross-section shape, deep hard rock tunnel, spalling failure, true triaxial test