In situ stress state and strength in mudrocks
In situ stress state and strength in mudrocks
复制标题
泥岩中的地应力状态和强度
DOI：
10.1002/2016jb012855
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Brian Fahy
中科院分区：
文献类型：
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作者：
B. Casey;J. Germaine;P. Flemings;Brian Fahy
单轴应变条件下埋藏的泥岩的应力状态是通过对来自不同地质背景的水饱和再沉积泥岩进行大量的实验室三轴试验来定义的。在正常单轴压缩（由K0NC），临界状态摩擦角，在不排水加载过程中的抗剪强度的水平应力之间的独特的关系。在0.1至100 MPa的有效应力范围内进行试验。富含蒙皂石的泥岩随着有效应力的增加而显示出更快的剪切强度降低，这与水平应力的更快增加相对应。在这项研究中发现的水平应力和临界状态摩擦角之间的关系与Jâky（1948）的著名相关性相比毫不逊色，该相关性是针对非常低的应力开发的，即使摩擦角值低至11°。一个泥岩的结果表明，这种关系也适用于泥岩剪切卸载（超固结）状态。摩擦角和K0NC之间的相关性与试验压缩阶段施加的应力路径无关。然而，不排水条件下的剪切情况并非如此，并且需要应用产生单轴压缩的应力路径来测量可靠的剪切强度。K0NC和强度特性的系统变化反映了泥岩屈服面的形状和方向随有效应力水平的总体变化。本研究结果有助于估算泥岩的地应力状态和强度特性，这将对一系列地球科学和工程问题产生重要影响。
The stress state of mudrocks buried under uniaxial strain conditions is defined through a large number of laboratory triaxial tests performed on water‐saturated resedimented mudrocks from a diverse set of geologic backgrounds. Unique relationships are found between the horizontal stresses that develop during normal uniaxial compression (given by K0NC), critical state friction angle, and shear strength during undrained loading. Tests were performed over the effective stress range of 0.1 to 100 MPa. Smectite‐rich mudrocks display a more rapid reduction in shear strength with increasing effective stress, which corresponds with a more rapid increase in horizontal stresses. The relationship between horizontal stresses and critical state friction angle found in this study compares favorably with the well‐known correlation of Jâky (1948), which was developed for very low stresses, even for friction angle values as low as 11°. Results for one mudrock suggest that this relationship also applies to mudrocks sheared from an unloaded (overconsolidated) state. The correlation between friction angle and K0NC is independent of the stress path applied during the compression phase of a test. This is not the case for shearing under undrained conditions, however, and the application of a stress path that produces uniaxial compression is necessary to measure a reliable shear strength. Systematic variations in K0NC and strength properties reflect an overall change in the shape and orientation of a mudrock's yield surface with effective stress level. The results of this study can aid in estimating the in situ stress state and strength properties of mudrocks, and this will have significant impact on a range of geoscience and engineering problems.