岩质边坡物理模型试验相似材料研究

Research on Similar Materials for Physical Model Tests of Rock Slopes

岩质边坡物理模型试验中相似材料的选取与制作,通常只是考虑密度、粘聚力、内摩擦角和弹性模量参数在数值上的相似关系,并未考虑相似材料是否能够再现复杂应力条件下岩石的强度和变形特性.为了解决这一问题,通过统计分析汶川地震所诱发滑坡的地层岩性,选取其中常见的石英岩和砂岩作为沉积岩原型;确定相似材料制备的主要控制指标以及试样成型方法,并分别采用两种常用的地质模型相似材料制备方法,在实验室制备其三轴压缩试验标准试样;开展两种相似材料标准试样的三轴压缩试验,研究其在不同围压条件下的应力应变特性与破坏模式.试验结果表明:不同围压条件下,实验室制备的两种相似材料标准试样在剪切破坏之前的应力应变曲线变化规律同实际的岩石原型相符,表现为线弹性关系;相似材料标准试样所受围压与其单轴抗压强度的比值不同的情况下,试样剪切破坏时所受偏应力与其单轴抗压强度的比值与实际岩石原型三轴试验中的比值相近,但相似材料试样的破坏应变均小于实际岩石原型的破坏应变.

In the selection and manufacture of similar materials for physical model tests of rock slopes,only the similarities in the magnitudes of density, cohesion, internal friction angle and elastic modulus were generally taken into consideration. The ability of the obtained similar materials to reproduce the strength and deformation behaviors of rock masses under complicated stress conditions was typically not considered. First,limestone and sandstone were herein selected as sedimentary rock prototypes, according to the stratigraphy of Wenchuan earthquake-induced landslides. After the primary control indexes and manufacturing process were determined, two common configuration methods for similar materials in geological models were used to manufacture the standard samples for triaxial compression tests. Finally,static triaxial compression tests of the standard samples were conducted to study the stress-strain behaviors and failure modes of two similar materials under various confining pressures. The experimental results indicated that, before the shear failure of standard samples, the stress-strain curves of two similar materials were observed to have a linear elastic relationship under the different confining pressures, and were in accordance with those of the actual rocks. When shear failure of standard samples occurred under different ratios of confining pressure to uniaxial compression strength,the ratios of the deviatoric stresses acting on the samples to the corresponding uniaxial compression strengths were close to those of the actual rocks,whereas the failure strains of similar materials were less than those of the actual rocks.