岩土材料塑性应变增量方向的确定

通过与金属材料的类比，分析了岩土材料的特征面(SMP面)的特性，提出了SMP面上的应力 决定岩土材料塑性应变增量流动方向的观点，并由此推导出计算公式. 通过增加一个材料参 数，还可以考虑存在黏聚力时的情况. 由该公式计算的塑性应变增量方向得到了 试验结果的验证. 该公式也在用变换应力修正的剑桥模型中得到应用，模型预测结果能够合理反映试验数据.

DETERMINATION OF THE DIRECTION OF PLASTIC STRAIN INCREMENT FOR GEOMATERIALS

As shown in a great amount of test results and theoretical analyses, the direction of plastic strain increment for geomaterials is different from that of stress. The direction of plastic strain increment for metals is determined by the stress on its characteristic plane--octahedral plane and it is the same as the direction of stress. Based on the analogy between geomaterials and metals as well as the concept of the characteristic plane, the direction of plastic strain increment for geomaterials can be determined by the direction of the stress on their characteristic plane (SMP plane). The equations for the determination of the direction of plastic strain increment are proposed. They can be applied to the cohesive materials by adding a material parameter. Finally these equations are validated by the test data. The proposed equations are also used in Modified Cam Clay revised by transformed stress, which can simulate the test data well.