The rapid and accurate measurement of in situ stress fields is one of the essential steps in geological engineering. Indoor acoustic emission tests and the Kaiser effect provide a promising prior peak stress measurement method. This paper aims to qualitatively explore the time delay mechanism of the Kaiser effect under uniaxial compressive stress. Acoustic emission tests were conducted with natural and water-soaked sandstone specimens to examine the time delay phenomenon of the Kaiser effect, and the typical Griffith fracture mechanics theory was adopted to explain the mechanism. The time delay of the Kaiser effect under uniaxial compressive stress was affected by the friction coefficient on the crack surfaces and the initial crack angle $$\beta$$ β . The time effect was indirectly induced by the changes in the friction coefficient on the crack surfaces, and the friction coefficient was controlled by the water content in the rock specimen. A higher initial friction coefficient led to an earlier and easier time delay of the Kaiser effect. Consequently, from the aspect of the Kaiser effect, it was suggested that when testing in situ stress, measures should be taken to maintain the original moisture contents in the rock cores after they are drilled underground. Otherwise, the in situ stress should be tested within 7 days.

中文翻译：

---

单轴压应力条件下砂岩中Kaiser效应的延时机制

快速准确地测量地应力场是地质工程中必不可少的步骤之一。室内声发射测试和凯撒效应提供了一种很有前途的先验峰值应力测量方法。本文旨在定性地探讨单轴压应力下Kaiser效应的时滞机制。对天然砂岩和水浸砂岩试样进行声发射试验，考察了Kaiser效应的时滞现象，并采用典型的格里菲斯断裂力学理论对其机理进行解释。单轴压应力下Kaiser效应的时间延迟受裂纹表面摩擦系数和初始裂纹角β的影响。时间效应是由裂纹表面摩擦系数的变化间接引起的，摩擦系数由岩石试样中的含水量控制。较高的初始摩擦系数导致更早、更容易延迟凯撒效应。因此，从Kaiser效应的角度，建议在进行地应力测试时，应采取措施保持岩心钻入地下后的原始含水量。否则，应在 7 天内测试原位应力。建议在进行地应力测试时，应采取措施保持岩心钻入地下后保持原来的含水量。否则，应在 7 天内测试原位应力。建议在进行地应力测试时，应采取措施保持岩心钻入地下后保持原来的含水量。否则，应在 7 天内测试原位应力。