三维地应力计算模型研究

简要回顾了现有的三维地应力实测方法在实际工程应用中存在的局限性。对钻孔局部壁面应力全解除法进行了系统的研究，从理论上说明了由它确定三维地壳应力张量的可行性。采用线弹性有限元法对钻孔局部壁面应力解除过程做了数值模拟研究，分析了应力解除曲线的变化特征，给出了达到完全应力解除时解除深度和被解除岩芯直径之间的定量关系，还进一步分析了环形解除槽引起的应力集中对其附近局部孔壁应力分布的影响，从而为在钻孔孔壁的局部壁面上如何合理的布置应变计（花）提供了参考依据。最后对本课题的研究前景做了展望。

Study on a calculation model for 3D in-situ rock stress tensor

The limitations of the present 3D rock stress measurements are briefly reviewed.A linear elastic model for the determination of the 3D rock stress tensor,based on a special method for stress relief on the local surfaces of a drilled borehole wall,is researched.The six stress tensor components can be calculated from this model.Numerical simulation on the whole stress relief process by side-wall core drilling using FEM was done.The response curves of the strains versus the depth of the annular slot advance are analyzed.Quantitative relationship between the relief depth and the diameter of the rock core to be unloaded is given when the stresses stored in it are completely relieved.Arrangements of strain rosettes attached to the borehole-wall are studied,being free from the influence zone of annular slot resulting from local side-wall core drilling,thus ensuring strain-gauging accuracy.The results obtained from numerical simulation are helpful for designing prototype test or model test and further developing the new stress measuring instrument.This stress measuring method discussed in this paper has a reliable theoretical basis that can not only solve the problem of core-breaking occurring in stress relief with overcoring technique but also overcome the premise of hydraulic fracturing method-one of the principal directions of rock stress tensor should be coincident with the borehole axis.There is also no need for a pilot hole during the stress measurements.It can be anticipated to be a new way and channel for rock stress measurements.