大理岩损伤强度的识别及基于损伤控制的参数演化规律

DAMAGE STRENGTH DETERMINATION OF MARBLE AND ITS PARAMETERS EVALUATION BASED ON DAMAGE CONTROL TEST

为获取脆性岩石特征强度及破坏过程中损伤演化规律,设计能同步测试应力–应变曲线、AE声发射及岩样径向纵波波速的试验方案,并对3种不同方法确定的损伤强度值进行对比。结果表明,除AE及波速测试方法外,采用体应变(含裂纹体应变)方法可以较为准确地获取试件的特征强度值。通过定义岩石循环加卸载试验获取的不可逆裂纹应变累计值作为岩石损伤的度量,基于损伤控制试验得到锦屏大理岩破坏过程中强度和变形特性随损伤的演化规律。研究表明,随损伤变量的增加,岩石弹性模量、损伤强度和峰值强度均会下降,但随着损伤变量达到至某值后,损伤强度会发生迅速降低,而峰值强度随着损伤累积仍会保持增加然后缓慢降低;进一步分析得到内摩擦角和黏聚力随损伤变量变化规律:随着损伤的发展,黏聚力从峰值迅速下降,并很快到达残余门限值;而内摩擦角随着损伤的发展经历了先上升再降低2个过程,其中上升段是在大部分黏聚力损失后逐渐升高至峰值。研究成果对于揭示脆性岩石强度破坏机制具有重要的理论意义。

In order to obtain the reliable damage strength and the evolution regulation,an experimental scheme of synchronic testing of stress-strain curves,AE activity and velocity of P wave is proposed and carried out.Compared with the results from three different methods,besides AE and P velocity testing method,the characteristic strengths can be objectively obtained from stress-volumetric strain（including crack volumetric strain） curves.By defining the irreversibly accumulative crack strain as damage parameter from loading and unloading volumetric curves,the characteristic strength and deformational modulus evolvement process are obtained based on damage-controlled testing.The results show that the deformation modulus,crack-damage strength and peak strength are all decreasing with damage growing;however,once the damage reach to a certain degree,the damage strength promptly decrease earlier than peak strength,and the peak strength keeping on increasing with damage growing and then decreasing gradually.By further analysis,the internal friction angle and cohesion evolvement law during failure process are discovered,that is,cohesion decreases rapidly with damage growing and reach to residual;but internal friction angle experiences increasing firstly then decreasing slowly,among which the increasing period happens to the moment of most cohesion loss.All the experimental results play a significantly theoretic role in discovering the failure mechanism of brittle rock.