黄土贴坡高填方变形破坏机制研究

受地形条件限制,黄土山区贴坡高填方工程近年逐渐增多并出现了一些失稳事故,亟需对其变形破坏机制进行研究。以黄土梁地形上某机场建设工程中的失稳贴坡高填方为例,通过现场详勘与工程地质调查,分析并总结了这类边坡的结构特点及变形破坏的关键影响因素,进而针对性的开展了压实黄土增湿变形试验、Q2离石黄土高压湿陷试验、CTC及RTC路径三轴试验,结合现场资料与室内试验结果对其变形破坏机制进行了研究。结果表明:下覆地形高差导致填方厚度差异,进而引起的坡顶地面差异沉降裂缝是诱发后续变形破坏的必要条件。黄土贴坡高填方变形破坏机制可以概括为:工后土体固结沉降、填土增湿及黄土高压湿陷沉降致裂→水分沿裂缝入渗软化土体→形成中部初始滑面→前部土体加载增湿破坏→后部土体卸荷增湿破坏→锁固段土体加载增湿破坏→滑面贯通整体失稳。该结果有助于加深对贴坡高填方变形破坏演化过程的认识,可以为这类边坡的防治工作提供科学依据。

Deformation and failure mechanism of high sticking loess slope

Loess high sticking slopes have become a popular construction solution for engineering land in loess ridge landform area. The failures of those slopes have encouraged the studies on deformation and failure mechanisms of such artificial slopes. In this research, a high sticking slope failure is used as a case study. Based on the in-situ investigation and geological engineering survey, the stratigraphic structure features and impact factors of slope stability are analyzed. According to the analysis results, the corresponding laboratory tests are conducted, such as compacted loess wetting compression tests, deeply buried Q₂ loess collapsibility tests, and loess triaxial tests with CTC and RTC stress paths. The deformation and failure mechanisms of high loess sticking slopes are studied from the in-situ and laboratory test data. The results indicate that the fluctuation of bed stratum causes various fill thicknesses, which further induce differential settlements and cracking on the slope shoulder. Water infiltration into the crack will then trigger deformation and failure. The failure mode of high sticking slopes is summarized: the differential settlement induced by consolidation of compacted loess and collapse of Q₂ loess under high pressure causes cracks of slope shoulder→water infiltration into cracks softens the compacted loess→the initial sliding surface forms in the middle of slope→the front part of loess fails under wetting CTC stress path→the back part of loess fails under wetting RTC stress path→the locking section loess failes under wetting CTC stress path→the whole slope fails. These results are helpful for understanding the formation and evolution of failure of high loess sticking slopes, and may provide technical support to the treatment of loess slope stability.