砂板互层岩体中隧道围岩力学特性研究

通过建立可反映互层岩体中砂岩与板岩组成、岩层倾角、岩层走向等因素变化对岩体变形影响的互层岩体本构模型,研究了砂板互层岩体中隧道围岩的力学特性。研究结果表明:岩体中板岩体积含量越高,围岩最大变形及破坏范围越大,隧道周边围岩变形不对称性也越明显,板岩结构面的内摩擦角大小对岩体变形及破坏范围影响很大,板岩沿结构面破坏为砂板互层岩体的主要破坏形式之一;砂板互层岩体的倾角变化将影响隧道周边围岩变形的对称性及破坏区域的分布,倾角在40°～60°时,围岩变形的不对称性最明显,板岩含量较高时,砂板互层岩体的最大变形随倾角的增大而降低;岩层的走向与洞轴线交角越大,围岩变形越小,隧道周边围岩变形也越趋于对称,在陡倾砂板互层岩体中,洞轴线应尽可能沿与岩层走向大角度相交的方向布置以利于围岩的稳定;随着埋深的增加,围岩变形及破坏范围均增长,因岩层倾角、走向变化引起的隧道周边围岩变形不对称性也越明显。

Study on Mechanical Properties of Surrounding Rock for Tunnels in Rock Mass of Interbedded Sandstone and Slate

A constitutive model for rock mass of interbedded sandstone and slate, in which the influence of combinations of sandstone and slate in rock mass, and dip angle of rock mass and bedding strike were taken into account, was proposed. Based on the model, mechanical properties of surrounding rock for tunnels in interbedded sandstone and slate were studied. The results show that (1) The more slate content in rock mass is, the more the maximum displacement and failure range of the tunnel surrounding rock are, and the more unsymmetrical the deformation of surrounding rock is. The variation of the internal friction angle of structural plane in slate has significant influence on the displacement and failure range of surrounding rock, which shows that one of the main failure features is the failure of structural planes in slate. (2) The variation of the dip angle of rock mass is of great influence on the symmetry of deformation and failure range of surrounding rock. The distinct asymmetry of deformation of surrounding rock happens when the dip angle is in the range from 40° to 60°. The maximum displacement of the tunnel surrounding rock decreases with the increase of the dip angle when slate content is more than sandstone in rock mass. (3) With the increase of the angle between the bedding strike and tunnel axis orientation, the deformation of surrounding rock decreases and tends to symmetry. In rock mass of interbedded sandstone and slate with steep dip angle, the angle between tunnel axis orientation and bedding strike should be designed as large as possible for the stability of surrounding rock. (4) As the tunnel depth increases, the displacement and failure range of surrounding rock increase. At the same time, the asymmetry of deformation of surrounding rock induced by the variation of dip angle and bedding strike becomes more distinct.