The tensile strength of volcanic rock exerts control over several key volcanic processes, including fragmentation and magma chamber rupture. Despite its importance, there is a paucity of laboratory data for the tensile strength of volcanic rocks, leading to an incomplete understanding of the influence of microstructural parameters, such as pore size and shape (factors that vary widely for volcanic rocks), on their tensile strength. To circumvent problems associated with the variability of natural samples, we provide here a systematic study in which we use elastic damage mechanics code “Rock Failure Process Analysis” to perform numerical experiments to better understand the influence of porosity, pore diameter, pore aspect ratio, and pore orientation on the tensile strength of volcanic rocks. We find that porosity and pore diameter exert a first-order control on the tensile strength of volcanic rocks, and that pore aspect ratio and orientation also influence tensile strength. Tensile strength is reduced by up to a factor of two as porosity is increased from 0.05 to 0.35 or as pore diameter is increased from 1 to 2 mm. Small, but systematic, reductions in tensile strength are observed as the angle between the loading direction and the major axis of an elliptical pore is increased from 0 to 90°. The influence of pore aspect ratio (the ratio of the minor to major axis of an ellipse) depends on the pore angle: when the pore angle is 0°, a decrease in pore aspect ratio, from 1 (a circle) to 0.2, increases the tensile strength, whereas the same decrease in pore aspect ratio does not substantially change the tensile strength when the pore angle is 90°. These latter numerical experiments show that the tensile strength of volcanic rocks can be anisotropic. Our numerical data are in broad agreement with new and compiled experimental data for the tensile strength of volcanic rocks. One of the goals of this contribution is to provide better constrained constitutive models for the tensile strength of volcanic rocks for use in volcano modelling. To this end, we present a series of theoretical and semi-empirical constitutive models that can be used to determine the tensile strength of volcanic rocks, and highlight how tensile strength estimations can influence predictions of magma overpressures and assessments of the volume and radius of a magma chamber.

火山岩的抗拉强度控制着几个关键的火山过程，包括破碎和岩浆房破裂。尽管它很重要，但关于火山岩抗拉强度的实验室数据很少，导致对微观结构参数的影响不完全了解，例如孔隙大小和形状（火山岩的因素差异很大）对其抗拉强度的影响力量。为了规避与天然样品的可变性相关的问题，我们在这里提供了一个系统的研究，其中我们使用弹性损伤力学代码“岩石破坏过程分析”进行数值实验，以更好地了解孔隙率、孔径、孔隙纵横比的影响，和孔隙取向对火山岩抗拉强度的影响。我们发现孔隙度和孔径对火山岩的抗拉强度具有一级控制作用，孔隙纵横比和取向也影响抗拉强度。当孔隙率从 0.05 增加到 0.35 或孔径从 1 毫米增加到 2 毫米时，抗拉强度最多降低两倍。当加载方向和椭圆孔的主轴之间的角度从 0° 增加到 90° 时，观察到抗拉强度的小但系统性降低。孔纵横比（椭圆的短轴与长轴之比）的影响取决于孔角：当孔角为 0° 时，孔纵横比从 1（圆形）到 0.2 的减小增加抗拉强度，而当孔角为 90°时，孔纵横比的相同减小不会显着改变拉伸强度。后面这些数值实验表明火山岩的抗拉强度可以是各向异性的。我们的数值数据与新的和汇编的火山岩抗拉强度实验数据大体一致。此贡献的目标之一是为火山岩的拉伸强度提供更好的约束本构模型，以用于火山建模。为此，我们提出了一系列可用于确定火山岩抗拉强度的理论和半经验本构模型，并强调抗拉强度估计如何影响对岩浆超压的预测以及对火山岩体积和半径的评估。岩浆房。后面这些数值实验表明火山岩的抗拉强度可以是各向异性的。我们的数值数据与新的和汇编的火山岩抗拉强度实验数据大体一致。此贡献的目标之一是为火山岩的拉伸强度提供更好的约束本构模型，以用于火山建模。为此，我们提出了一系列可用于确定火山岩抗拉强度的理论和半经验本构模型，并强调抗拉强度估计如何影响岩浆超压的预测以及对火山岩体积和半径的评估。岩浆房。后面这些数值实验表明火山岩的抗拉强度可以是各向异性的。我们的数值数据与新的和汇编的火山岩抗拉强度实验数据大体一致。此贡献的目标之一是为火山岩的拉伸强度提供更好的约束本构模型，以用于火山建模。为此，我们提出了一系列可用于确定火山岩抗拉强度的理论和半经验本构模型，并强调抗拉强度估计如何影响对岩浆超压的预测以及对火山岩体积和半径的评估。岩浆房。我们的数值数据与新的和汇编的火山岩抗拉强度实验数据大体一致。此贡献的目标之一是为火山岩的拉伸强度提供更好的约束本构模型，以用于火山建模。为此，我们提出了一系列可用于确定火山岩抗拉强度的理论和半经验本构模型，并强调抗拉强度估计如何影响对岩浆超压的预测以及对火山岩体积和半径的评估。岩浆房。我们的数值数据与新的和汇编的火山岩抗拉强度实验数据大体一致。此贡献的目标之一是为火山岩的拉伸强度提供更好的约束本构模型，以用于火山建模。为此，我们提出了一系列可用于确定火山岩抗拉强度的理论和半经验本构模型，并强调抗拉强度估计如何影响对岩浆超压的预测以及对火山岩体积和半径的评估。岩浆房。