IV级软弱围岩相似材料的试验研究

以IV级围岩为参照对象，研制可用于隧道围岩稳定性物理模型试验的软弱围岩相似材料。采用的5种原材料（重晶石粉、石膏、细砂、洗衣液和水），通过直剪试验、无侧限抗压强度试验及三轴压缩试验测得所配相似材料的强度特征和物理力学参数，包括黏聚力c、内摩擦角?、单轴抗压强度Rc、弹性模量E和泊松比?。首先，通过试验分析每种原材料的不同比例对所配相似材料强度特征及物理力学参数的影响，选择适合于模拟IV级围岩相似材料的原材料配比；其次，针对优选的材料配比所配制的相似材料，开展大量的三轴压缩试验，研究在不同围压下该相似材料的强度及其破坏特征。结果表明，含水率减少或石膏含量增加导致Rc、E和c明显增大，而?降低不明显；增加砂含量可增大E 和?，但Rc值减少；石膏含量对相似材料的脆性和延性影响最明显，而含水率对相似材料的强度影响最为突出。试验结果还表明，相似材料在低围压时呈现脆性，在高围压时呈延性；就破坏准则而言，试验所得结果小于Mohr-Coulomb准则，略大于Hoek-Brown准则，但更符合Hoek-Brown准则。研制软岩相似材料的试验数据可为下一步拟开展的隧道围岩稳定性模型试验和数值模拟提供重要的参考和依据。

Experimental study of similar material for weak surrounding rock mass of class IV

This study aimed to develop an appropriate similar material for weak surrounding rock mass which can be used in physical model test of tunnel surrounding rock mass stability. The weak surrounding rock mass of class IV has been chosen as reference prototype for our research. Five raw materials, namely, barite powder, gypsum, fine sand, laundry detergent, and water were used to produce the similar material. Direct shear tests, uniaxial compression tests and triaxial compression tests were performed to obtain strength characteristics and physico-mechanical parameters of the material, including cohesive strength c, internal friction angle ? uniaxial compressive strength Rc, elastic modulus E, Poisson ratio ?. Firstly, a large number of the above mentioned tests were carried out to analyze the impact of various proportions of each raw material on strength characteristics and physico-mechanical parameters of the similar material; thus selecting appropriate raw material proportion to simulate the weak surrounding rock mass of class IV. Secondly, strength characteristics and failure behavior of the similar material which had been developed with selected raw material proportion, is further studied by a large numbers of triaxial compression tests under various confining pressures. The results indicate that, either decreasing water content or increasing gypsum content can lead to an obvious increase in Rc, E and c, along with a slight decrease in ?. On the other hand, the mounting of fine sand content resulted in an increase of E and ?, while Rc value decreased. In addition, while gypsum content turned out to be the most important factor affecting the brittle and ductile characteristics of similar material; water content affected the strength of such material significantly. The results also show that the developed material presents brittleness under low confining pressure, and becomes more ductile with the increase of confining pressure. Furthermore, failure data of the material are smaller than that calculated from linear Mohr-Coulomb failure criterion and slightly higher than that of nonlinear Hoek-Brown failure criterion. However, similar material obeys far better the Hoek-Brown criterion. The results of this study will be very useful for future research on tunnel surrounding rock mass stability in physical model tests, as well as in numerical simulations.