地形偏压条件下隧道初始应力场及二次应力场分布特征

为获得地下偏压条件下地层初始应力场和隧道开挖后二次应力场的分布特征,根据通常的工程地质参数取值范围,设置典型值,结合理论推导,分析偏压隧道地层初始应力场与地表倾角和泊松比的关系,研究偏压隧道二次应力场沿隧道径向和切向的分布规律。研究结果表明:相对于水平地表,偏压地形改变了地层应力场的分布状态,初始应力场便存在剪应力,且随偏压角度的增大而增大,而隧道开挖后,当偏压角度大于20°时,二次应力场中便有拉应力区域出现;各特征方向应力随离隧道中心距离的增加而减小,直至2倍洞径处;30°角度偏压时的最大剪应力约为无偏压时的2倍,主要发生在拱顶、仰拱和边墙部位,应为加固处理的重点区域。

Secondary and primary stress distribution of terrain bias tunnel

In order to obtain the distribution characteristics of primary and secondary stress field in terrain bias tunnel,the relationship among primary stress field and partial pressed angle and Poisson’s ratio was analyzed,and the distribution laws of secondary stress field along the radial and tangential direction in terrain bias tunnel were studied by theoretical derivation and calculation with typical values of engineering geology.The results show that terrain bias changes the stress field condition in compaison with the horizontal ground surface;shear stress appears in primary stress field and increases with the increase of the partial pressed angle;moreover,after the tunnel excavation,tensile stress appeares in the secondary stress field when the partial pressed angle exceeds 20°,and the stress on typical direction declines with the distance from tunnel center till to 2 times of tunnel span;the maximum shear stress under 30° partial pressed angle is twice of horizontal ground surface and occurs on vault,inverted arch and side wall,so these areas should be put emphasis on reinforcement.