The deformation properties of rocks ultimately become anisotropic depending on the orientations of mineral particles and sedimentary structures. Characterization of deformation anisotropy is important for accurate understanding of the deformation characteristics of structures constructed inside rocks (e.g., rock foundation and tunnel). The simplest anisotropic elastic model is transversely isotropic elasticity, and in recent years, many methods for rationally specifying this elastic constant have been proposed.

Although the most general linear elastic model for describing deformation anisotropy is orthotropic elasticity, no efficient method currently exists for determining the orthotropic elastic constants because the number of elastic constants required for the model description is extremely large. A rational determination method for orthotropic elasticity is necessary when considering application at construction sites and coupling with other phenomena such as differences in water content. In this study, a new method was developed for obtaining all 12 constants of orthotropic elasticity by three uniaxial compression tests on specimens sampled in three directions orthogonal to each other. For each specimen, the strain tensor was measured, and the strains in the elastic region were added and analyzed to identify the principal orientation of orthotropic elasticity. Thereafter, nine elastic constants are specified using the stress–strain relationship of each specimen. The methodology is described herein. The validity of the proposed method was evaluated on the basis of results from verification experiments performed with Neogene soft sedimentary rocks.

根据矿物颗粒的方向和沉积结构，岩石的变形特性最终会变得各向异性。变形各向异性的表征对于准确理解在岩石内部构造的结构（例如，岩基和隧道）的变形特征非常重要。最简单的各向异性弹性模型是横向各向同性弹性模型，近年来，人们提出了许多合理指定该弹性常数的方法。

虽然描述变形各向异性的最通用的线弹性模型是正交各向异性弹性，但由于模型描述所需的弹性常数数量非常大，目前还没有确定各向异性弹性常数的有效方法。考虑到施工现场的应用以及与含水量差异等其他现象的耦合，需要一种合理的正交各向异性弹性确定方法。在这项研究中，开发了一种新方法，通过对在彼此正交的三个方向上采样的试样进行三个单轴压缩试验，获得所有 12 个正交各向异性弹性常数。对于每个样本，测量应变张量，并添加和分析弹性区域的应变，以确定正交各向异性弹性的主要方向。此后，使用每个试样的应力-应变关系指定九个弹性常数。本文描述了该方法。根据对新近系软沉积岩进行的验证实验结果，对所提出方法的有效性进行了评估。