龙门山北段千枚岩强度及变形特性对比试验研究

对成兰铁路龙门山北段隧道群4种典型千枚岩进行不同加载方位角的强度和变形特性对比试验研究,研究结果表明:加载方位角和岩石矿物成分严重影响千枚岩变形特性,并与围压水平有关。千枚岩单轴抗压强度随方位角变化呈"U"型的各向异性特征,所试验的4种千枚岩各向异性率由大至小对比关系为:HPMPQPCP。试样一般在峰值应力前产生扩容现象,扩容起始应力和形式与加载方位角或层理发育程度相关。三轴压缩试验中,千枚岩垂直层理加载时的峰值强度、长期强度和残余强度比平行层理加载明显偏高,并随围压水平增加而增大。千枚岩不同加载方位角下单轴压缩试验破坏模式归纳为4种:层理面滑移剪切破坏、压拉剪切破坏、张拉破坏、复合破坏。

Comparative tests on strength and deformation of phyllite of northern tunnels of Longmen Mountains

The experimental tests are carried out on the strength and deformation characteristics of four typical rock samples of phyllite taken from the northern tunnels of Longmen Mountains of the Chengdou-Lanzhou Railway. The results show that the deformation of the phyllite is strongly influenced by the loading angles related to the beddings and the mineral components of the rocks as well as the confining pressure in 3-D compression. The uniaxial compressive strength of the phyllite changes with the changing of the loading angles, showing a “U” type and typical anisotropic behaviour. The anisotropic intensity of the four phyllite samples can be queued as follows: HP>MP>QP>CP. Dilation appears in the rock samples generally before the peak stress of the loading, and the starting stress and the formation of rock dilatancy are related with the loading angle as well as the development degree of the beddings. In the triaxial compressive tests, both the peak strength and the residual strength of the samples along the loading axis perpendicular to the beddings are remarkably higher than those parallel to the beddings, and the differences increase with the increase of the confining pressure. The failure modes of phyllite samples with different loading angles are classified into 4 types: bedding plane slip shear failure, tension shear failure, tensile failure and composite failure.