循环加载岩石界面滑移位移演化特征试验研究

在岩土工程实践中,岩石界面摩擦滑移会引起工程失稳问题,严重威胁着人们的生命财产安全;岩石界面的滑移问题往往处于一种往复加载状态,目前大多数学者对于岩石界面滑移问题的研究往往是在单一的加载状态下进行的,而对于往复加载状态研究较少;为了研究循环加卸载作用下界面滑移位移场演化特征,设计并开展了花岗岩试件恒定围压下的双剪模型试验研究。利用CCD相机采集界面滑移过程中的散斑图像,并利用白光数值散斑相关方法对该组花岗岩试件在实验过程中的位移场、摩擦滑移位移在循环加卸载情况下的演化特征进行研究分析。试验结果表明:①在循环加卸载作用下,随着循环次数的增加,位移场会发生明显的摩擦滑移,且当循环到一定次数,试件会发生整体黏滑现象;②随着循环次数的增加,位移场随着循环加卸载发生明显的时空演化特征,空间上存在明显的剪切位移增大和减小区域,同时随着循环次数的增加位移存在明显的累积,表现为位移演化的分区性及剪切位移场累积效应。时间上存在剪切位移演化相对于剪切应力的滞后性;③相同剪应力水平下,随着循环次数的增加,垂直位移整体趋势有所降低,界面咬合程度增加,水平滑动位移有所增加,界面分区滑动机制改变,加载端和自由端存在明显的黏滑现象;④在试件发生整体黏滑前后,剪切位移随着循环次数的增加发生不同的变化;黏滑前,随着循环次数的增加,剪切位移缓慢增大,黏滑后,随着循环次数的增加剪切位移明显增大;即黏滑前后,界面滑移速率由小变大。

Evolution characteristics of sliding displacement of rock interface under cyclic loading

In the practice of geotechnical engineering,the frictional sliding of rock interface can cause engineering instability,which seriously threatens people’s life and property safety.The slippage problem of rock interface is often in a reciprocating state.At present,most scholars are interested in rock interface slippage.The problem is often built in a single loading state,but less research is on reciprocating loading states.In order to study the evolution characteristics of interface slip field under cyclic loading,a double shear model test study of granite specimen under constant confining pressure was designed and carried out.The CCD camera was used to collect the speckle image during the interface slip process,and the evolution characteristics of the displacement field and frictional slip displacement of the granite specimen during the experimental loading were carried out by using the white light numerical speckle correlation method for research and analysis.The results show that ① under the action of cyclic loading,with the increase of the number of cycles,the displacement field will have obvious frictional slip,and when the cycle reaches a certain number of times,the overall stick slip phenomenon will occur.② With the increase of the number of cycles,the displacement field has obvious space time evolution characteristics with cyclic loading.There are obvious shear displacement increases and decreases in space,and there is obvious accumulation of displacement with the increase of the cycle number.It is represented by the zonality of displacement evolution and the cumulative effect of shear displacement field.There is hysteresis of shear displacement evolution relative to shear stress in time.③ Under the same shear stress level,as the number of cycles increases,the overall trend of vertical displacement decreases,the degree of interface occlusion increases,the horizontal sliding displacement increases,the interface partition sliding mechanism changes,and the loading end and the free end have obvious sticky sliding phenomenon.④ Before and after the overall viscosity slip of the specimen,the shear displacement varies with the increase of cycle times.Before stick slip,the shear displacement increases slowly with the increase of the number of cycles.After stick slip,the shear displacement increases obviously with the increase of the number of cycles.That is,before and after viscous slip,the interface slip rate increases slowly.