应变速率对注浆体力学特性影响规律

为研究微震荷载作用下注浆加固体力学特性,以裂隙倾角30°、宽度4 mm的红砂岩裂隙注浆体为研究对象,借助岩石三轴伺服压力机进行变应变速率(10^-5 ~5×10^-3 s^-1)单轴压缩试验；然后从能量耗散、裂纹扩展及破坏形态等3个方面,分析变应变速率对注浆体力学特性的影响规律及机理. 研究表明:随着应变速率的增加,注浆体的峰值强度、弹性模量均随之而增大；且峰值强度与应变速率呈指数函数关系变化；注浆体受应变速率影响的响应分为敏感应变速率阶段和滞缓应变速率阶段,主要差异在于峰值强度变化率和弹性模量变化率；随着应变速率的增大,注浆体的总能量在增大；压密阶段是影响不同应变速率下注浆体力学特性的主要阶段；敏感应变速率阶段和滞缓应变率阶段中的压密阶段主要区别在于积散比大小,积散比进一步决定产生裂纹的多少和分布区域与规律；耗散能密度对注浆体破坏脱落面积以及粒径分布影响较大,耗散能密度越大,碎块越以大块为主(粒径大的比率逐渐增加),滞缓应变率阶段耗散能密度较敏感应变率阶段大,其破碎块体较敏感应变率阶段大. 研究在裂隙注浆加固体的变应变速率影响下力学特性,从能理原理、分形理论角度得到了其影响机理.

Influence of strain rate on mechanical properties of grouting body

To study the mechanical properties of grouting body under microseismic loads, the grouting in red sandstone fissure with a fracture angle of 30° and a width of 4 mm was taken as the research object, and the uniaxial compression test was carried out by rock three-axis servo press at different strain rates (10^-5-5×10^-3 s^-1). Then, from the three aspects of energy principle, crack propagation mechanism, and final failure morphology, the influence law and mechanism of variable strain rate on the mechanical properties of grouting were analyzed. Research shows that with the increase of strain rate, the peak strength and elastic modulus of the grouting body increased, and the peak intensity and strain rate changed exponentially. The response of the grouting body affected by strain rate was divided into sensitive strain rate stage and slow strain rate stage, and the main difference was in the peak strength change rate and elastic modulus change rate. As the strain rate increased, the total energy of the grouting body increased. The compaction phase was the main phase affecting the mechanical properties of the grouting body under different strain rates. The main difference between the compaction phase in the sensitive strain rate stage and the slow strain rate stage was in the dispersion ratio, which further determined the number of cracks and the distribution area and its law. The dissipated energy density had a great influence on the failure area and the particle size distribution of the grouting body, where the greater the dissipated energy density was, the greater the proportion of large fragments was (the proportion of larger particle size increased gradually). The dissipated energy density in the slow strain rate stage was larger than that in the sensitive strain rate stage, so the fragments were larger than those in the sensitive strain rate stage. By analyzing the mechanical properties of the grouting in fractured zone under the influence of variable strain rate, the influence mechanism was obtained from the perspectives of energy theory and fractal theory.