循环动荷载作用下岩石动态响应分析

为研究循环动荷载作用下岩石的动态变化,利用SHPB装置对长径比为2.0的试件进行冲击作用,分析试件在0.04,0.06,0.08,0.10 MPa气压冲击用下应力-应变曲线、峰值应力、峰值应变变化情况,结果表明:随着冲击气压的增加,试件反应出的峰值应力增加,试件受首次冲击的峰值应变减小。选用0.06 MPa气压对长径比为2.2,2.4,2.6的试件进行循环冲击作用,结果表明:长径比2.0的试件平均峰值应力为70.56 MPa;长径比2.2的试件为71.15 MPa;长径比2.4的试件为83.54 MPa;长径比2.6的试件为91.09MPa,且随着长径比增加,试件所能承受的动荷载次数减少。

不同冲击荷载作用下粉砂岩动力学特性试验研究

文章以皖北某矿巷道开挖为研究背景,研究施工过程中围岩破坏机理及其动力学特性。首先采用XRD和电镜扫描相结合的微观研究手段,对巷道层位围岩粉砂岩进行微观成分分析,并在不同放大倍率下对粉砂岩内部节理及裂隙分布进行分析,最终利用Hopkinson压杆(SHPB)试验装置,分别以五组恒定冲击气压(0.2、0.25、0.3、0.35、0.4MPa)对粉砂岩进行冲击试验,得到不同气压下该巷道围岩应力——应变曲线。研究结果表明:该矿巷道层位围岩主要成分为石英(Quartz-sio2)、高砱石(Kaolinite-Al2Si2O5(OH)4)和珍珠高岭石(Nacrite-Al2Si2O5),占比分别为39.2%、41.5%、16.3%,占总成分的97%;粉砂岩的应力——应变曲线可分为弹性阶段、裂缝扩展、塑性变形和破坏四个阶段,且峰值应力与冲击气压呈正相关;试验结果合理有效,可为类似地质条件下巷道围岩动力学特性研究提供有益参考。

Dynamic response and failure behavior of rock under static-dynamic loading

Dynamic response and failure behavior of rock under static-dynamic loading were studied. The effects of initial static load on the total energy dissipated during the failure process of specimen were analyzed. To simulate the engineering situation that in-situ rock experienced and obtain the dynamic loading with an intermediate strain rate, a low cycle fatigue load with the frequency from 0.5 to 5 Hz was adopted by servo-controlled Instron material testing system. The results show that the obtained strain rate increase with the increase of load frequency. The initial static load has great influence on both the energy and dynamic response of rock. Both the energy and the maximum failure load P_f decreases with the increase of initial static load. P_f under the static-dynamic loading is larger than that under only the static loading but less than that under only the dynamic loading. The load-displacement curves become nonlinear as the pre-added static load reaches the transition point which is about one third of static strength. With the increase of initial static load, Young’s modulus decreases and poisson ratio increases. It shows that rock has a lower strength and a tendency to soften under a higher initial static load. Rock may be broken more easily static-dynamic loading than under only the dynamic loading. The proposed method is useful in the investigation of constitutive relationship and failure behavior of rock under quasi-dynamic loading.

Dynamic responses of deep underground explosions based on improved Grigorian model

It is important to investigate the dynamic behaviors of deep rocks near explosion cavity to reveal the mechanisms of deformations and fractures. Some improvements are carried out for Grigorian model with focuses on the dilation effects and the relaxation effects of deep rocks, and the high pressure equations of states with Mie-Grüneisen form are also established. Numerical calculations of free field parameters for deep underground explosions are carried out based on the user subroutines which are compiled by means of the secondary development functions of LS-DYNA9703 D software. The histories of radial stress, radial velocity and radial displacement of rock particles are obtained, and the calculation results are compared with those of U.S. Hardhat nuclear test. It is indicated that the dynamic responses of free field for deep underground explosions are well simulated based on improved Grigorian model, and the calculation results are in good agreement with the data of U.S. Hardhat nuclear test. The peak values of particle velocities are consistent with those of test, but the waveform widths and the rising times are obviously greater than those without dilation effects. The attenuation rates of particle velocities are greater than the calculation results with classic plastic model, and they are consistent with the results of Hardhat nuclear test. The attenuation behaviors and the rising times of stress waves are well shown by introducing dilation effects and relaxation effects into the calculation model. Therefore, the defects of Grigorian model are avoided. It is also indicated that the initial stress has obvious influences on the waveforms of radial stress and the radial displacements of rock particles.

多次冲击荷载对千枚岩性质影响研究

为研究千枚岩在不同形式循环冲击荷载作用下的性质变化,利用SHPB装置对千枚岩试件进行多次冲击,分别以单一恒定0.4,0.06,0.08,0.10 MPa气压以及0.04 MPa与0.08MPa气压交替、0.06 MPa与0.10 MPa气压交替循环作用试件。相比单一气压冲击,不同气压交替冲击作用对试件的应力-应变曲线的影响更为突出,曲线切线斜率变化更明显;在不同气压交替冲击作用下,岩石承受较大强度荷载的能力变弱,试件在最终破坏时产生的应变较单一冲击气压循环作用时要小;在一定冲击气压范围内不同气压交替对岩石进行冲击作用时,试件更容易失稳;对比试件的宏观破碎程度,交替气压冲击作用比单一气压冲击更为突出。