Compression testing schemes that induce failure in rock specimens primarily through a reduction in confining stress have become increasingly common in recent years. Despite this, the interpretation of the results from such studies are fraught with complications due to the large number of factors that can influence the outcome of such tests relative to standard compression tests that follow a loading path. Among these, unloading rate is especially significant, as it has the potential to both influence peak strength and total test time (i.e. time-dependent effects). In this study, we present a framework to convert unloading rates into equivalent loading rates to facilitate comparison with standard compression test results as well as comparisons across rock types. We then present the results of a suite of 39 compression tests, including strain-controlled standard UCS and triaxial tests, constant deviatoric stress unloading triaxial tests, diagonal stress path unloading triaxial tests, and load-controlled standard triaxial tests. Based on comparison of load-controlled and strain-controlled standard compression tests, it is concluded that strain-controlled tests produce appreciably lower peak strength values, even if relevant ISRM Suggested Methods and ASTM Standards are followed in both cases. Additionally, the different control modes produce different volumetric strain responses up to the point of peak strength. A detailed comparison of load-controlled test results from standard triaxial tests and unloading triaxial tests with failure points at σ₃ ≈ 1 MPa reveals that diagonal stress path unloading tests produce comparable peak strength values to standard load-controlled tests. Although the observed trend in the constant deviatoric stress unloading triaxial test data corresponds to lower peak strength values than those obtained using standard load-controlled tests, we attribute this discrepancy to time-dependent damage effects and/or minor damage accumulation during the initial loading phase of the tests rather than to the difference in stress paths.

近年来，主要通过降低围压引起岩石试样破坏的压缩试验方案变得越来越普遍。尽管如此，与遵循加载路径的标准压缩测试相比，由于大量因素会影响此类测试的结果，因此对此类研究结果的解释充满了复杂性。其中，卸载率尤为重要，因为它有可能影响峰值强度和总测试时间（即时间相关效应）。在这项研究中，我们提出了一个将卸载率转换为等效加载率的框架，以便于与标准压缩测试结果进行比较以及跨岩石类型进行比较。然后，我们展示了一套 39 项压缩测试的结果，包括应变控制标准 UCS 和三轴试验、恒定偏应力卸载三轴试验、对角应力路径卸载三轴试验和载荷控制标准三轴试验。基于负载控制和应变控制标准压缩试验的比较，可以得出结论，应变控制试验产生明显较低的峰值强度值，即使在这两种情况下都遵循相关的 ISRM 建议方法和 ASTM 标准。此外，不同的控制模式会产生不同的体积应变响应，直至达到峰值强度。标准三轴试验和卸载三轴试验的负载控制试验结果的详细比较，失效点位于 σ 对角线应力路径卸载三轴试验和负载控制标准三轴试验。基于负载控制和应变控制标准压缩试验的比较，可以得出结论，应变控制试验产生明显较低的峰值强度值，即使在这两种情况下都遵循相关的 ISRM 建议方法和 ASTM 标准。此外，不同的控制模式会产生不同的体积应变响应，直至达到峰值强度。标准三轴试验和卸载三轴试验的负载控制试验结果的详细比较，失效点位于 σ 对角线应力路径卸载三轴试验和负载控制标准三轴试验。基于负载控制和应变控制标准压缩试验的比较，可以得出结论，应变控制试验产生明显较低的峰值强度值，即使在这两种情况下都遵循相关的 ISRM 建议方法和 ASTM 标准。此外，不同的控制模式会产生不同的体积应变响应，直至达到峰值强度。标准三轴试验和卸载三轴试验的负载控制试验结果的详细比较，失效点位于 σ 即使在这两种情况下都遵循相关的 ISRM 建议方法和 ASTM 标准。此外，不同的控制模式会产生不同的体积应变响应，直至达到峰值强度。标准三轴试验和卸载三轴试验的负载控制试验结果的详细比较，失效点位于 σ 即使在这两种情况下都遵循相关的 ISRM 建议方法和 ASTM 标准。此外，不同的控制模式会产生不同的体积应变响应，直至达到峰值强度。标准三轴试验和卸载三轴试验的负载控制试验结果的详细比较，失效点位于 σ₃  ≈ 1 MPa 表明对角线应力路径卸载测试产生的峰值强度值与标准负载控制测试相当。尽管在恒定偏应力卸载三轴试验数据中观察到的趋势对应于使用标准载荷控制试验获得的峰值强度值较低的峰值强度值，但我们将这种差异归因于时间相关的损伤效应和/或初始加载阶段的轻微损伤累积的测试，而不是应力路径的差异。