Autogenous closure of cracks in clay during wet−dry cycles is usually observed through digital photography or x-ray, or inferred from changes in hydraulic conductivity. Samples in almost all experimental studies of clay self-sealing carry networks of cracks, making it challenging to control initial conditions of healing or to separate processes operating over a single crack from those pertaining to interaction between cracks. Furthermore, most observational studies are based on before-and-after images with little sense of the pace of crack closure. This paper reports a set of x-ray computerised tomography observations of a single artificial cylindrical hole, as a proxy for a crack, in consolidated, close-to-saturation bentonite samples, undergoing further hydration. The sample is scanned at different times and the scans analysed by image processing. The results show that water chemistry, pre-consolidation pressure and vertical boundary conditions all significantly affect the pace and extent of hole closure. The pace of hole closure is found to follow a logarithmic function when the sample is unconstrained vertically. Autogenous closure appears to be due mostly to osmotic swelling. This suggests that the latter may form the basis for developing constitutive relationships and evolution functions for sealing of cracks in swelling clay undergoing wet−dry cycles.

中文翻译：

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膨润土空腔的自体密封：X 射线计算机断层扫描研究

在干湿循环过程中粘土裂缝的自生闭合通常是通过数字摄影或 X 射线观察到的，或者从水力传导率的变化中推断出来。几乎所有粘土自密封实验研究中的样品都带有裂缝网络，这使得控制初始愈合条件或将在单个裂缝上运行的过程与有关裂缝之间相互作用的过程分开变得具有挑战性。此外，大多数观察性研究都是基于前后图像，几乎没有裂缝闭合的速度。本文报告了对单个人造圆柱孔的一组 X 射线计算机断层扫描观察，作为裂缝的代表，在经过进一步水合的固结、接近饱和的膨润土样品中。在不同时间扫描样品，并通过图像处理分析扫描结果。结果表明，水化学、预固结压力和垂直边界条件都显着影响闭孔的速度和程度。当样本在垂直方向上不受约束时，发现孔闭合的速度遵循对数函数。自体闭合似乎主要是由于渗透性肿胀。这表明后者可能构成开发本构关系和演化函数的基础，以密封经历干湿循环的膨胀粘土中的裂缝。当样本在垂直方向上不受约束时，发现孔闭合的速度遵循对数函数。自体闭合似乎主要是由于渗透性肿胀。这表明后者可能构成开发本构关系和演化函数的基础，以密封经历干湿循环的膨胀粘土中的裂缝。当样本在垂直方向上不受约束时，发现孔闭合的速度遵循对数函数。自体闭合似乎主要是由于渗透性肿胀。这表明后者可能构成开发本构关系和演化函数的基础，以密封经历干湿循环的膨胀粘土中的裂缝。