岩石破坏瞬间压机-岩石系统振荡特性研究

A Study on Dynamic Response of Brittle Rock in Compression Test

岩石的单轴压缩实验是获得岩石力学特性的通用方法。虽然单轴压缩实验在岩石力学测试中被广泛引用,但始终缺少对岩石和仪器所组成系统的动态响应的认识。本文通过对川南龙马溪组高脆性页岩的单轴压缩实验,研究了破坏瞬间岩石与压机的动态相互作用。通过提取动态破坏瞬间的实验数据,分析了压机和岩石对动态破坏的响应,建立了压机岩石的全系统振荡模型,并对模型进行了求解。同时对压机岩石系统进行颗粒流建模,得到了岩石破坏瞬间的全系统声发射响应。结果表明,离散元数值模拟方法得到的压机岩石系统对岩石破坏的动态响应与实验测得的声发射动态响应相吻合,脆性岩石破坏瞬间整个系统进行横向和纵向高频阻尼振动,压机岩石系统在岩石峰值破坏时的动态声发射响应主要来自类似拨弦振动的横向振动,振动的频域特性取决于压机岩石系统的尺寸以及力学特性。

Rock compression test is a universal method of obtaining the mechanical properties of rock.The dynamic interaction between rock and test machine is not fully understood.In this study,uniaxial compression tests of brittle shale from Longmaxi Formation of south Sichuan province were conducted.The dynamic interaction between rock and the test machine was studied.The dynamic model of the oscillation of rock-machine system was established.The effects of servo system and load train stiffness on severe post-peak failure were studied on the time scale of millisecond.The essence of frequency characteristics of acoustic emission during the tests were revealed by Particle Flow Code 2D simulation and laboratory results.The acoustic characteristics of experiments confirm well to the results from the PFC simulation.The essence of frequency characteristics of acoustic emission during uniaxial compression test is the frequency spectrum of‘load train and rock’system’s response to oscillation triggered by rock failure.The spectrum is determined by elastic modulus and dimensions of both rock and load train.The results also show that in order to obtain intact post-peak curves in stress-strain curve,the load mode of the servo system should be carefully selected.This study shows some new perspectives on the dynamic interaction between rock and test machine during failure process.