点荷载作用下岩石记忆效应试验研究
(江西理工大学建筑与测绘工程学院， 江西赣州市 341000)
中图分类号：TD315 文献标识码：A 文章编号：1005—2763(2008)02—0018—03
Testing Study on Memorizing Effect of Rock under Point Loading
Jin Jiefang , Zhao Kui ,Liu Mingsong ,Xu Zhenhua
(School of Architectural and Surveying Engineering,Jiangxi University of Science and Technology ,Ganzhou, Jiangxi 341000 , China)
Abstract：Graded cyclic loading test was made on granite and sandstone samples by point load tester and strain meter , and then the changing laws among load , strain , Poissons ratio , damage factor and acoustic emission( AE) for the cyclic loading test on thesamples were analyzed in detail, the relations between various parameters and accumulative AE counts on different level loading were obtained , on basis of the theory of statistics , the veracity andstability of different parameters to memorize their previous greatest value were estimated. The results showed that under point loading three rock samples had obvious memorizing effect , and load parameter was better than other parameters in the veracityand stability of memory.
Key Words：Rock，Point load，Memorizing effect，Acoustic emission，Mechanics parameters
0 引 言
岩石的Kaiser效应就是岩石对先前应力的记忆能力，即所谓的岩石应力记忆效应。将此概念延伸到其他力学参数，国内外学者利用声发射技术通过研究发现，不同的岩石对先期最大应变、弹性模量、泊松比和损伤因子都有不同的记忆效应[1-3]。目前对岩石记忆效应研究大都还是基于单轴压缩室内试验。在压力机上进行岩石记忆效应研究对岩样要求比较高，不能进行现场大量试验研究，限制了对岩石记忆效应的广泛研究和实际应用；小型点荷载试验装置是便携式的，可带到岩土工程现场进行试验，这是点荷载试验能够广泛采用的重要原因。点荷载试验的另一个重要优点是对试件的要求不严格，不需要像做抗压强度试验那样精心准备试件。最好的试件就是直径为25-100mm的岩芯，没有岩芯时，石块也可以。因此，利用点荷载仪进行大量的现场试验，研究点荷载作用下岩石记忆效应，为岩石记忆效应研究的提供了一个新思路。
通过选用不同矿山的岩样结合应变仪进行点荷载声发射试验，并对这些岩样进行循环加载，人为地给岩石制造一些“先期应力和应变”。试验表明，点荷载作用下岩石声发射能够反映岩石先前的所受载荷，即对先期载荷、应变等具有一定的记忆效应。
