空心包体介质参数对应变片变形和测量精度的影响分析

空心包体式孔壁应变测试中的环氧树脂和粘胶介质参与应力和变形的传递,其变化规律可用来改善介质性能或提高测量精度。给出了数值模拟物理模型校验的程序,建立了针对性数学模型,结合地应力测量精度的定量表述,获得了空心包体介质参数对应变片变形和测量精度的影响规律。结果显示:单一介质模型条件下轴向应变片随介质参数的改变其变形量变化不明显,其它应变片随介质弹性模量(E)减小或泊松比(μ)增加而变形增大,反之则结果相反;E和μ参数的单独变化对测量精度的影响＜0.5%。双介质模型多个工况的模拟结果显示随着粘胶层E增加、 μ降低至与岩体相同时,其轴向应变片变形量略增加,其它应变片变形量减小,量值误差显著降低,角度误差略有上升,该规律的技术转化可显著提升空心包体的测量精度。

Influence of Hollow Inclusion Cell’s Medium Layer on Deformation and Measurement Accuracy

The epoxy resin and glue layer of hollow inclusion cell in CSIRO test participate in the transmission of stress and deformation. The regularity results can be used to improve the properties of medium layer or to improve measurement accuracy. In this paper, a calibration procedure of numerical simulation of physical model test is presented. In association with the quantitative expression of geo-stress measurement accuracy, a suitable mathematical model is established. The influence parameters of hollow inclusion’s medium layer on deformation of strain gauge and measurement accuracy is obtained. Results reveal that in the model with single medium, the deformation of axial strain gauge is very small, and the deformations of other strain gauges increase with the rising of elastic modulus (E) or with the declining of Poisson’s ratio (μ) of the medium layer, and vice versa. The variation of E or μ poses an influence smaller than 0.5% on measurement accuracy. On the other hand in the model with double media, when E and μ of glue layer change to be the same with those of rock, the deformation of axial strain gauge increases slightly, while the deformations of other strain gauges continue to reduce, with the value of magnitude-error dropping markedly and angle error rising slightly. The technical transformation of such regularity can be used to improve the measurement accuracy of hollow inclusions.