基坑开挖卸荷土体的本构模型真三轴试验研究

Study on True Triaxial Experiment of Constitutive Model for Excavation Unloading Soil Mass

通过真三轴试验模拟基坑开挖过程中侧向卸荷土体的应力路径,针对武汉地区具有代表性的粉质粘土,进行了一系列真三轴排水和不排水固结剪切试验。试验分析结果表明,真三轴卸荷不排水试验的应力—应变关系曲线不符合Duncan-Zhang模型,但该试验曲线在低围压下基本符合Lade-Duncan弹塑性模型,在高围压下偏差较大;而卸荷排水试验的应力—应变关系曲线与不排水条件下Lade-Duncan弹塑性模型曲线吻合较好。由于排水试验耗时较长,因此在卸荷排水条件下的实际工程可以用不排水试验来代替,以便缩短试验时间。本文研究成果为进一步在该方面的研究和工程应用提供参考。

On the basis of the representative samples of slity clay in Wuhan, china, the lateral unloading soil＇s stress path, which is produced by excavating foundation pit engineering, is simulated through true triaxial experiment. A series of consolidated-undrained and consolidated-drained true triaxial tests were accomplished. The study results show that the curves of stress-strain obtained in the undrained test doesn＇t conform to the Duncan-Zhang model but can conform to the Lade-Duncan elastoplastic model under low confining pressure basically, and the curves are much more different from file curves calculated under high confining pressure. However the curves obtained in the drained test conform to the Lade-Duncan model well under the undrained test. Because of time-consuming of the drained test, the undrained test can take the place of it in order to shorten the test time, The results can be used for reference to further study and engineering application.