Abstract

In NGI-type simple shear apparatus, including recently developed NGI-type bi-directional simple shear apparatus, the complete stress state is unknown which limited the interpretation of test results. This study compares the stress state of NGI-type simple shear test obtained by two methods, the stress state determined by an empirical method using test data, and stress state determined by measured values in a corresponding DEM test. Results showed that (1) stress state obtained by the two methods shows good agreement, especially at simple initial stress conditions. (2) due to the underestimation of constant k, minor principle stress and horizontal stress interpreted by the empirical method are higher than that in DEM test, and noncoaxiality interpreted by the empirical method are lower than that in DEM test. It is recommended that before determining the stress state of NGI-type bi-directional drained simple shear tests, it is needed to perform a test and corresponding DEM test under simple stress condition. The empirical equations for horizontal stress, especially the constant k should be validated and corrected for the tested soil before interpreting the stress state.

摘要

在 NGI 型简单剪切装置中，包括最近开发的 NGI 型双向简单剪切装置，完整的应力状态是未知的，这限制了对测试结果的解释。本研究比较了通过两种方法获得的 NGI 型简单剪切试验的应力状态，即通过使用试验数据的经验方法确定的应力状态，以及由相应 DEM 测试中的测量值确定的应力状态。结果表明，(1)两种方法得到的应力状态具有较好的一致性，尤其是在简单的初始应力条件下。(2) 由于对常数k的低估，经验法解释的次主应力和水平应力高于DEM试验，经验法解释的非同轴度低于DEM试验。建议在确定NGI型双向排水简单剪切试验的应力状态之前，需要在简单应力条件下进行试验和相应的DEM试验。水平应力的经验方程，特别是常数 k 应在解释应力状态之前验证和校正被测土壤。