切坡卸载下原状黄土裂隙宏细观损伤规律研究

Study on Laws of Macro-&Micro-damage at Undisturbed Loess Fissures under Cut Slope Unloading

黄土崩塌是一种危害性极大的地质灾害,而黄土节理裂隙发育是引起黄土崩塌的最主要原因。针对切坡卸载对黄土边坡节理裂隙发展的影响,选取富县Q_(2)原状黄土,通过常规三轴仪模拟边坡开挖,结合CT扫描图像定性、定量分析及图像二值化处理,研究原状黄土损伤过程。宏观试验结果表明:侧向速率和卸荷幅度对原状黄土的节理裂隙发育有较大影响;卸荷速率越大,土样内部裂隙就越多,土样也更容易破坏;侧向卸荷幅度越大,土体内部节理裂隙发育越明显,土样的破坏也从微小的裂隙变化转变为瞬间破坏。细观试验结果表明:卸荷速率和幅度越大,CT扫描阴影区域越大,土样越容易破坏。定量分析结果表明:卸荷幅度对土样结构影响最为显著。

Loess collapse is a kind of extremely harmful geological disaster,and the development of loess joint fracture is the most important cause.With regard to the influence of slope cutting unloading on the joint fracture development in loess slope,undisturbed loess Q_(2)at Fuxian was selected to simulate the slope excavation with conventional triaxial instrument,and then according to the qualitative and quantitative analysis of CT scan images and the image binarization processing,the damage process of undisturbed loess was studied.The result of macroscopic test shows that,the lateral rate and unloading amplitude have large impact on the joint fracture development in undisturbed loess;the greater the unloading rate,the more fractures inside the soil sample,thus the soil sample is easier to be destroyed;the greater the lateral unloading amplitude,the more obvious development of joint fracture inside the soil sample,and the soil sample failure changes from micro fracture to instantaneous destruction.The result of microscopic test shows that the greater the unloading rate and amplitude,the larger the shadow area of CT scan,and the soil sample is easier to be destroyed.The result of quantitative analysis shows that the unloading amplitude has the most significant impact on the structure of soil sample.