黄土路堑边坡变形破坏机理的三轴试验研究

通过原状黄土的减压三轴压缩试验,研究了黄土边坡不同深度不同含水量土体的应力-应变关系,并与原状黄土的常规三轴试验结果进行了比较,发现减压三轴试验能合理地模拟和解释开挖卸荷作用下黄土边坡土体的变形与破坏过程。试验结果表明:坡脚开挖卸荷时,黄土边坡中浅层非饱和黄土易出现应变软化或塑性流动,强度较低,易产生较大变形,而深层饱和黄土仅在高围压下发生应变硬化,强度增加,在中低围压时均发生应变软化现象。分析认为黄土边坡特殊的工程地质条件,使得黄土边坡的特定部位在开挖卸荷作用下常形成了不利于土体稳定的含水量和围压组合,导致坡体特定部位的土体变形破坏,进而诱发边坡的变形破坏;开挖卸荷作用下黄土边坡变形破坏的力学机制应为蠕滑-压致拉裂或"牵引式滑坡"。

TRIAXIAL TEST STUDY ON THE DEFORMATION AND FAILURE MECHANISM OF LOESS CUT SLOPE

The stress-strain relationship of loess with different depth and water content of loess slope is studied with the reduced triaxial compress test of undisturbed loess and compared with the results of conventional triaxial compress test of undisturbed loess. It is pointed that the deformation and failure process of loess slope under excavation and unloading can be reasonably explained by the reduced triaxial compress test. The test results show that the surface unsaturated loess of loess slope with toe excavation is easy to appear strain softening or plastic flow, and strength reduction, the deep layer saturated loess appears strain softening under the condition of mid-lower confining pressure and strain hardening and strength increase under high confining pressure. Then, based on the results of reduced triaxial compress test, deformation mechanism analysis of loess cut slope is made. It is considered that the particular engineering geological conditions of loess slope leads to a disadvantageous combination of water content and confining pressure to the strength of soil. Then the disadvantageous combination causes deformation and failure of soil mass and slope. The deformation and failure mechanism of loess slope under excavation belongs to creeping slide and crack arising from pressing or retrogressive slide.