甘肃永靖黑方台地区滑坡形成的黄土时效特性

An analysis of the time-dependent properties of loess in the formation of landslides at Heifangtai area, Yongjing County, Gansu Province

甘肃黑方台地区是中国滑坡预测预报研究和实践的热点地区,开展黄土时效特性试验是进行滑坡预测预报的基础。以黑方台原状黄土为研究对象,开展了2个含水量、4个围压、八级偏应力水平下的黄土三轴固结排水蠕变试验,研究了黑方台黄土的粘-弹-塑性变形破坏规律。蠕变试验结果表明,相同含水量和围压下,偏应力越大时,黄土的蠕变变形量越大;围压和偏应力水平一定时,含水量越高,蠕变越容易,蠕变量越大;黄土具有显著的非线性粘-弹-塑性变形特征。分析认为黑方台黄土普遍表现出稳定型和渐变型的变形特征,进行该地区滑坡预测预报是有科学基础的。以试验数据为基础,采用幂函数和对数函数分别拟合得到黄土的蠕变模型。建议采用对数型经验方程进行黑方台黄土斜坡长期稳定性分析和滑坡预测预报。

Heifangtai area of Gansu Province is the hotspot for landslide prediction research and application. Tests of the time-dependent properties of loess are the basis of landslide prediction. Taking undisturbed loess in Heifangtai as the study object, the authors conducted consolidated and drained trixial creep tests of loess under the conditions of two water content values, four confining pressures and eight levels of axial stresses. With these tests, the visco-elastic plastic deformation and failure laws of loess in Heifangtai were studied. The creep test results demonstrate that, under the same water content and compression pressure, creep deformation increases as axial stress increases. When compression pressure and axial stress are stable, creep deformation increases as water content increases. Loess is characterized by obvious non-linear visco-elastic plastic deformation. The analyses show that Heifangtai loess generally shows stable and progressive deformation characteristics, suggesting that there exist scientific foundations for landslide prediction. Based on test data, the authors adopted both power and logarithmic functions to get fitting creep models of loess. It is recommended that logarithmic empirical function be used to carry out the analysis of long term stability of loess slopes and the prediction of landslides.