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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.

In situ stress state becomes more and more significant with in-depth research on geodynamics and energy development. However, there has not been an economic and effective method developed to determine deep three-dimensional in situ stress. The Anelastic Strain Recovery (ASR) method is a newly developed technique that can determine three-dimensional in situ stresses. After the 12 May 2008 M s 8.0 Wenchuan earthquake, the ASR method was used for the first time in mainland China to measure the in situ stresses in the WFSD scientific boreholes in Sichuan Province, China. In this paper, the basic procedure of the ASR method is introduced in detail and the compliances of ASR for boring cores are investigated. The results show that the maximum principal stress direction was NW64° at a measured depth (MD) of 1173 m (vertical depth 1151 m) in WFSD-1. The ratio of shear mode to the volume mode compliance of ASR was 2.9. And the three principal stresses at 1173 m MD in WFSD-1 are 43, 28 and 25 MPa. Combined with stress measurement results determined using other in situ measurement methods along the Longmenshan fault zone, the directions of the maximum horizontal principal stress changes from E-W to NEE-SWW to NWW-SEE when moving from NE to SW along the Longmenshan fault zone. This change is in agreement with the stress regime of the Longmenshan fault zone of the Wenchuan Earthquake, which supports a stress regime consisting predominantly of thrusts in the southwest and strike-slip in the northeast.

The experimental determination of anelastic strain recovery (ASR) compliances for three types of rocks (granite, marble, and sandstone) was performed in the laboratory. Preloading of specimens for uniaxial compression creep tests was at 50 % of the uniaxial compressive strength (UCS) for each rock type. We obtained the shear mode Jas( t ) and volumetric mode Jav( t ) ASR compliances and calculated the ratio of Jas( t ) to Jav( t ). The Kelvin model for rock rheology was then applied in numerical simulations and the results were in good agreement with the measured data for Jas( t ) and Jav( t ). These results showed that both the magnitude and rate of increase of the ASR compliances are strongly dependent on the rock type, and the values of the Jas( t )/Jav( t ) ratio for a loading of 50 % of the UCS showed a trend leading to different constants for each of the three rock types. Further experimental and numerical analyses showed approximate power-law relationships between the ASR compliances at 50 % of UCS, and both the UCS and the tangential Young’s modulus at 50 % of UCS ( E t50 ). These relationships may be useful for the preliminary estimation of ASR compliances.