Investigation and enhancement of stress-dependent compliance characteristics in deep in-situ stress measurements based on anelastic strain recovery (ASR) method

To accurately obtain the deep in-situ stress state during the construction of deep vertical shafts, laboratory-based Anelastic Strain Recovery (ASR) compliance experiments were conducted. The results revealed that under uniaxial loading conditions, the shear and volumetric modes of ASR compliance tend to stabilize after 48 h of unloading, and the extension of the loading time slows the rate of anelastic recovery. The ASR compliance and its ratio under different stress conditions (0.25 UCS and 0.5 UCS) varied with changes in stress. In-situ stress measurements based on the ASR method, conducted at the Sanshandao deep vertical shaft project site, showed that the ASR compliance under the 0.25 UCS stress condition provided stress values that more closely matched the results obtained from hydraulic fracturing, with the maximum principal stress deviation ranging from 0.14% to 4.1%, and the minimum principal stress deviation ranging from 0.27% to 4.57%. This study confirms that combining the depth of the sampled rock cores with in-situ stress conditions for compliance calibration can improve the accuracy of the ASR method. The findings provide foundational support for in-situ stress evaluation and rock mass stability control in similar deep strata.