岩石锚固界面剪切流变试验及模型研究

SHEAR CREEP EXPERIMENTS FOR ANCHORAGE INTERFACE MECHANICS AND NONLINEAR RHEOLOGICAL MODEL OF ROCKS

大量的试验和工程实践表明:锚固系统的失效多是发生在岩土体和注浆体的锚固界面上。为此开展锚固系统界面力学特性的剪切流变试验,以研究注浆体与岩石交界面的受力机制以及锚杆锚固力在界面剪切流变过程中的变化特征。通过试验表明:在剪切面方向,随着时间的增长,同级剪应力荷载水平下剪切变形有所增加;当剪切应力水平较低时,试样剪切流变表现出初期和稳态流变,当剪切应力值超过某一界限时,剪切流变还表现出加速流变破坏阶段;随着流变时间的增加,锚杆轴向应变值有一定的增加,锚固力呈现缓慢回升的趋势;在此基础上,提出一种基于经验的非线性剪切流变模型,该模型特别考虑法向应力对剪切流变的影响,并将流变模型参数定义成剪应力水平的函数,从而能很好地描述剪切流变的初期、稳态和加速流变整个过程;为进一步验证锚固界面本构模型的正确性,采用此界面流变模型对试样3进行数值仿真的剪切流变试验51h,计算结果与试验数据非常接近,表明采用此模型是合理而有效的。

Based on a large amount of tests and engineering practices, it is shown that the failure of anchorage system takes place at the interface between anchorage body and rock-soil; so it is necessary to carry out shear rheological experiments for interface mechanics of anchorage system in order to study the mechanism of grout-rock interface and the change characteristics of anchorage force during the rheological period. The results of experiments show that the shear rheological strain grows with time at the certain shear stress level, and grows sharply when shear stress level rises. Under the condition of low shear stress level, the initial rheological stage and steady-state creep stage occurs; however, the accelerating rheological stage will turn up when shear stress exceeds a certain value. With the increment of shear rheology, axial rheological strain of the anchor enhances a little and the anchorage force grows slowly. On the basis of experiment, a nonlinear empirical rheological constitutive model which has a continuous formulation is proposed, which is more reasonable because of its consideration of normal stress and its ability of describing the whole theological process including primary theological deformation, secondary rheological deformation and accelerating rheological deformation. For further research on feasibility of the anchorage interface rheological constitutive model, a numerical test is carried out to simulate a shear rheological experiment of sample 3 for 51 hours. It is shown that the results of numerical simulation test coincide very well with that of shear rheological experiment, so it is indicated that the proposed nonlinear rheological model is available.