横观各向同性岩体地应力计算中岩层倾角的影响

Influence of Formation Dip Angle on the Geostress Calculation of a Transversely Isotropic Rock Mass

三维地应力是地下工程结构设计、施工中的重要参数,套孔应力解除法是当今最为常用的地应力测量方法,然而它却无法考虑岩层倾角的影响,工程应用中采用的忽略或修正的处理方法必将造成较大的误差。文章根据有限单元法的计算原理,针对横观各向同性岩体,开展了岩层倾角从0°至90°变化时地应力的求解研究,以用于对横观各向同性岩体隧道工程中测得的地应力值作适当调整。研究结果表明:岩层倾角主要对垂直于钻孔平面内的正应力影响较大,其变化趋势是先增大后减小;岩层倾角为45°时影响最为明显,第一主应力误差为19.00%,第二主应力误差为10.86%,第三主应力误差为88.98%。

The 3D geostress is an important parameter in the structural design and construction of underground works. Overcoring stress relief is the most commonly used method to measure geostress at present, but it cannot take into account the influence of the formation dip angle. In engineering applications, ignoring or modifying the influence of the formation dip angle can often cause greater errors in geostress measurement. According to the calculation principle of finite element method, solutions for geostress measurement of a transversely isotropic rock mass were studied with the formation dip angle varying from 0°- 90° in order to make appropriate adjustments to the geostress values measured during tunneling. The resuhs show that the formation dip angle chiefly has a great influence on the normal stress in the plane perpendicular to the hole, with the tendency to increase at first and then decrease; and the influence is most obvious at 45° of the formation dip angle, with the errors of the first, second, and third principal stress being 19.00%, 10.86% and 88.98% respectively.