不同固结状态下黄土坡滑坡滑带土的蠕变试验研究

An experimental study of creep characteristics of sliding zone soil of Huangtupo landslide under different consolidation stresses

为了研究黄土坡滑坡滑带土在不同固结状态下的蠕变特性,首先采用单向加载、加载—卸载、加载—卸载—再加载的方式分别固结滑带土,然后开展滑带土在不同固结状态下的剪切蠕变试验。试验结果表明:滑带土初始孔隙比为0.49,压缩系数a1-2介于0.37~0.45 MPa-1之间,属中等压缩性土;滑带土在单向加载至上覆压力后的孔隙比最大,压缩量最小,加载—卸载至上覆压力后的孔隙比最小,压缩量最大,加载—卸载—再加载至上覆压力后的孔隙比和压缩量介于二者之间。对于初始状态相同的滑带土,在经历不同加载—卸载—再加载固结状态后,在正应力和水平剪应力相同条件下,单向加载后的蠕变剪切应变最大,加载—卸载后的蠕变剪切应变最小,说明滑带土的剪切蠕变特性与加载路径和加载后的孔隙比密切相关。采用Burgers模型拟合蠕变试验数据,得出了不同固结状态下Maxwell模型和Kelvin模型的蠕变参数,拟合曲线和试验曲线能够很好地吻合,说明Burgers模型能够较好地反映滑带土在不同固结状态下的蠕变特性。

In order to study the creep characteristics of the sliding zone soil of the Huangtupo landslide under different consolidation stresses,the unidirectional load,load-unload,load-unload-reload tests were used to consolidate the sliding zone soil,and then the shear creep tests of the sliding zone soils in different consolidation states were carried out.The experimental results showed that the initial void ratio of the sliding zone soil was 0.49 and the compressibility coefficient a1-2 was between 0.37 and 0.45 MPa-1,belonging to the moderate compressibility soil.After unidirectional loading to the predetermined pressure,the void ratio of sliding zone soil reached to the maximum and the compression amount the minimum.After loading-unloading to the predetermined pressure,the void ratio of sliding zone soil was the minimum and the compression amount the maximum.The void ratio and compression amount after loading-unloading-reloading to the predetermined pressure was somewhere in the middle.For the same initial state sliding zone soil,after different loading-unloading consolidation states,under the same normal stress and shear stress level,the creep shear strain of unidirectional loading was the largest,but the creep shear strain of loading-unloading was the minimum.The creep shear characteristics of sliding zone soil were closely related with the loading state and the void ratio after loading.The Burgers model was used to fit the creep test data and the creep parameters of Maxwell model and Kelvin model were obtained.The fitting and test curves were in good agreement,which indicates that Burgers model can reflect the creep characteristics of sliding zone soil under different consolidation stresses.