Abstract: In this paper we studied the definition and extensive characterization of geostress measurement accuracy in view of the present situation of the research field. First of all, we reviewed the geostress measurement methods, commonly used techniques, and the problems in measurement accuracy as well as their causes. From the perspective of closed-loop measurement, we gave our definitions of geostress measurement and geostress measurement accuracy. On the basis of classifying and summarizing historic researches, we presented the composition and structure of a characterization system for geostress measurement accuracy, expounded the significance of accuracy research, the difference between measurement method and measurement technology, as well as the accuracy problems. Furthermore, we presented the idea and connotations of quantitatively characterizing all factors of geostress measurement accuracy and gave the 3D physical model test device for measurement accuracy and its coordinate setting and characterization program. We also introduced the characterization formulae of all factors which include indexes of average-mode and maximum-mode in 2D and 3D measurement. In addition, we discussed the method of calculating angle error and explained the relationship between characterization modes and technical requirements. Taking the example of characterizing the measurement accuracy of the physical model test results of USBM borehole deformation gauge and CSIRO hollow inclusion strain gauge, we demonstrated the process of our extensive quantitative characterization. By comparing the characterization indexes with the original ones, we found that the overall measurement error of the single index of the maximum-mode of USBM and CSIRO is 10% and 27%, respectively. By using the present extensive characterizing method in consideration of all factors, we found that the measurement accuracy of USBM is superior to that of CSIRO.

Key words: geostress, measurement accuracy, magnitude error, angle error, single index, USBM borehole deformation gauge, CSIRO hollow inclusion strain gauge