基于滑带应力和变形监测数据演变特征的滑带土大型原位剪切蠕变试验研究

Slip zone strength is the most important controlling factor in the process of landslide hazard evolution. Studying on the creep of field slip zone soil has great significance to long-term stability evaluation and forecasting of landslide. The IBIS-M system, 3D laser scanner and GPS were used to monitor three-dimensional deformation of landslide surface. The fixed inclinometer and sliding inclinometer were used to monitor the inside deformation of slip mass. The joint meter, the displacement meter, the stress gauge and total station were used to monitor the deformation and stress of slip zone soil. Analyze the temporal evolution characteristics of deformation and stress from outside to the inside of landslide and find out the real shearing strain rate and stress variation. The 50cm×50cm×40cm field shearing creep test will be carried out in the 3# and 5# branch tunnel. The nonlinear damage constitutive model of field slip zone will be established according to the content, size, morphology and directionality of gravel, the Ca2+ concentration, the pore volume and pore diameter distribution by the method of digital image processing technique and mercury injection apparatus. The relationship between internal microstructure and macroscopic physical and mechanical property of shearing creep of slip zone soil are studied. The dynamic response mechanism of shearing creep strength properties and the process of landslide deformation are revealed. The research results can provide the basic data for the development and evolution of the landslide and long-term stability analysis, and provide a scientific basis for the comprehensive management of landslide hazard.

滑带土强度是滑坡灾害孕育演化最主要的控制因素，开展原位滑带土的蠕变试验研究，对滑坡的长期稳定性评价与预报预警具有重要的意义。采用IBIS-M系统、三维激光扫描仪、GPS实时监测系统提取滑体表面岩土体变形数据，采用固定测斜仪、滑动测斜仪提取滑体内部变形数据，采用测缝计、位移计、应力计和测量机器人提取平硐内滑带变形和应力数据，剖析滑坡由表及里变形、应力时空演变特征，得出滑带土真实的剪切应变速率与应力变化。在3号、5号支洞滑带位置开展50cm×50cm×40cm原位剪切蠕变试验，研究剪切面碎石含量、大小、形态、分布和定向性，孔隙液体中Ca2+浓度，孔隙体积和孔径分布等微细观蠕变特性与宏观蠕变强度关系，建立原位滑带土的非线性损伤蠕变本构方程，揭示原位滑带土剪切蠕变强度特性与滑坡变形过程的动态响应机理。研究成果可为滑坡的发展演化和长期稳定性分析提供基础数据，为滑坡灾害的动态综合治理提供科学依据。

（1）研究了黄土坡滑坡滑带土在不同固结状态下的蠕变特性，研究结果表明：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。.（2）研究了饱和滑带土的三轴流变规律，采用GDS三轴仪开展饱和滑带土的应力松弛实验，研究不同围压和不同应变增量条件下滑带土的应力松弛特征。研究结果表明：饱和滑带土的应力松弛特征受围压、轴向应变速率、轴向应变增量、松弛时间的影响较大。根据应力松弛曲线可以分别得出滑带土的峰值强度和残余强度指标，当轴向应变接近破坏应变（15%）时随着有效围压的增加，滑带土的应力松弛量和残余应力比增加，应力松弛比减小；当轴向应变恒定时，滑带土的体积应变大于应变增加过程中的体积应变。当应变加载速率较小（0.02 mm/min）时，应变加载过程中会出现瞬时应力松弛现象。.（3）研究了含碎石滑带土大型直剪试验特征，发现随着轴压的增大、碎石粒径的增大和碎石含量的增大，抗剪强度均呈现增加的趋势。剪切面大多较光滑、平整、含水率偏高。随着碎石含量的增加、碎石粒径的增大、剪切面呈现凸凹不平的状态。.（4）通过对含碎石滑带土开展CT扫描试验，发现剪切面上的含石率低于试样平均值。剪切面上碎石的长轴分布有定向性，长轴与剪切方向呈0~15°夹角。随着剪切的进行，剪切面积减小，剪切盒前端碎石含量高于试样平均值。