求翻译：损伤变量在本质上是一个热力学的内变量，无法通过试验精确测量或是比较困难，但考虑到事物相关性，损伤必然会引起一些诸如几何尺寸、弹性模量和电阻率等的外部变量的变化，所以考虑在实际应用中可以通过某些特定的表示方式来间接地表示损伤变量的值，用以描述损伤的程度。但由于岩体本身和损伤特性的复杂性，选择一种既在理论上科学严谨又在工程上方便实用的损伤检测方法目前还比较困难。迄今为止，岩石损伤检测的技术涉及光、电、声、磁测量等各种方法。是什么意思？

The damage variable is essentially a thermodynamic internal variables, accurate measurement can not test more difficult, but takes into account the correlation, the damage will inevitably cause some changes in external variables such as geometry, elastic modulus, and resistivity Therefore, consider

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Damage variable is essentially a thermodynamic variables, not through the accurate measurement of the test or difficult, but taking into account the relationship between things, modulus of elasticity of damage must be caused by some, such as geometric dimensions, and resistivity changes in external