首页|低频扰动下高应力砂岩非线性动态力学响应特征

低频扰动下高应力砂岩非线性动态力学响应特征

扫码查看
受煤矿残采区上行开采扰动影响,层间岩层在高静应力和低频扰动荷载耦合作用下的失稳是引发遗煤资源复采动力灾害的主要原因之一。为研究低频扰动荷载作用下高应力状态岩石的动态响应特征,以煤系地层砂岩为研究对象,基于自主研发的动静载耦合电液伺服试验机,开展不同幅值低频扰动荷载(5 Hz)作用下高应力砂岩(80%单轴抗压强度(UCS))动态单轴压缩试验,揭示了低频扰动下高应力砂岩的裂纹演化规律、渐进损伤行为和非线性动态响应特征。结果表明:①小幅扰动荷载作用过程中高应力状态砂岩并不会失稳,80%UCS预静载状态下诱使砂岩发生破坏的低频扰动幅值门槛值为 15%UCS,在越过应力门槛值的扰动荷载作用过程中,高应力砂岩破坏前的扰动荷载循环周期数随幅值增大指数型衰减。②在砂岩内部随机分布的微裂纹萌生和渐进扩展影响下,动态割线模量、峰值应变、耗散能密度和声发射b值随扰动荷载作用时间的非线性演化特征显著。③指数型应变演化曲线在砂岩破坏前有明显的拐点,可以作为低频扰动下高应力砂岩动态破坏的前兆信息,用于相应动力灾害预警。④在越过门槛值的低频扰动荷载作用过程中,动态割线模量演化曲线近似指数型衰减,且非线性拟合参数可以用以量化割线模量劣化速率,砂岩的割线模量劣化速率随幅值线性递增非线性变化。⑤扰动荷载作用初期的上升时间和幅值的比值(RA)可以用于砂岩动态破坏超前预测,相应地,扰动荷载作用过程中RA的突增可以作为砂岩动态破坏的前兆预警信息。未越过门槛值的低频扰动荷载作用过程中,砂岩微破裂以张拉或混合破裂为主,剪切破裂占比仅为 12。15%;幅值为 15%UCS、20%UCS和 25%UCS的扰动荷载作用过程中,剪切破裂占比分别为37。17%、52。75%和53。62%,随扰动荷载幅值增大对数型增加。
Nonlinear mechanical dynamic response characteristics of high stress sandstone subject to low frequency disturbance
The mechanical response characteristics of rock under low-frequency perturbation loads and high-stress condi-tions are important factors affecting the stability of interlayer rock in the goaf during upward mining.Taking the coal-bear-ing sedimentary rock sandstone as the research object,the dynamic uniaxial compression tests were conducted on high-stress sandstone(80%UCS)under low-frequency perturbation loads(5 Hz)using a self-developed dynamic-static coupled electro-hydraulic servo testing machine.The progressive damage behavior and nonlinear mechanical dynamic response characteristics of high-stress rock under low-frequency perturbations were revealed.The results are as follows:①During the process of small amplitude low-frequency disturbance load,high-stress sandstone does not experience dynamic failure,the threshold value of low-frequency disturbance load amplitude to induce sandstone damage is 15%UCS.Under the ac-tion of low-frequency disturbance load above the threshold value,the number of disturbance load cycles before the failure of high-stress sandstone decreases exponentially with the increase of amplitude.②The progressive initiation and accumu-lation of randomly distributed microcracks within the sandstone,as well as their gradual extension,significantly affect the nonlinear evolution characteristics of dynamic secant modulus,strain peak,plastic deformation,dissipated energy density,and b-value.③During the low-frequency perturbation process,the b-value and dissipated energy density exhibit a three-stage evolution characteristic consistent with the strain.The exponential strain evolution curve has a distinct inflection point before the failure of the sandstone,which can serve as a precursor information of dynamic failure under low-fre-quency perturbations and be used for corresponding dynamic disaster warnings.④During the low-frequency perturbation load process beyond the threshold,the dynamic secant modulus evolution curve approximates an exponential decay.The parameters in the nonlinear fitting relationship can be used to quantify the degradation rate of the elastic modulus.And the degradation rate of secant modulus of sandstone changes nonlinearly with the increase of amplitude.⑤The magnitude of the RA value in the initial stage of disturbance load can be used to predict the dynamic failure of sandstone in advance.Correspondingly,the sudden increase of RA during the low-frequency disturbance load process can serve as a precursor warning of dynamic instability of high stress sandstone.During the process of small-amplitude disturbance load below the threshold value,the microcracks mainly undergo tensile or mixed fracture,with shear fracture accounting for only 12.15%.During the low-frequency disturbance load processes with amplitudes of 15%UCS,20%UCS,and 25%UCS,the shear fracture accounts for 37.17%,52.75%,and 53.62%respectively.The proportion of shear fractures exhibits a logarithmic increase with the increase of amplitude.

low frequency disturbancehigh stressprogressive damage behaviornonlinear response characteristics

文晓泽、冯国瑞、郭军、王朋飞、白锦文、钱瑞鹏、于露杨、张洁、张鹏飞

展开 >

太原理工大学矿业工程学院,山西太原 030024

矿山岩层控制及灾害防控山西省重点实验室,山西太原 030024

山西焦煤集团有限责任公司,山西太原 030024

清华大学水沙科学与水利水电工程国家重点实验室,北京 100084

展开 >

低频扰动 高应力 渐进损伤 非线性响应

2024

煤炭学报
中国煤炭学会

煤炭学报

CSTPCD北大核心
影响因子:3.013
ISSN:0253-9993
年,卷(期):2024.49(9)