含水煤样动静组合加载力学响应试验研究

发布时间：2018-05-11 20:01

本文选题：岩石力学 + 霍普金森压杆　；参考：《河南理工大学》2016年博士论文

【摘要】：冲击地压是影响煤矿安全生产的重大灾害之一。冲击地压的形成常以震源冲击应力波的方式通过煤岩介质传递至采掘空间,造成冲击地压事故,煤层注水是冲击地压防治常用方法之一,静载型冲击地压煤层注水使冲击倾向性降低,但深部煤层常处于动静组合加载的应力环境下,含水煤层的应力波传播衰减、强度、能量耗散的强弱机理尚不清楚,含水煤样冲击动力响应是冲击地压防治亟待解决的理论问题。利用RMT-150C和改进SHPB系统进行了煤样静载、动静组合加载试验,探讨了不同含水煤样的动态强度、失稳破坏、应力波衰减、能量耗散、损伤断裂等特征,主要结论及认识如下:(1)采用RMT-150C伺服试验系统对自然、饱水3d、7d煤样进行单轴和三轴抗压强度的静载试验,单轴及三轴抗压强度随饱水时间增加而逐渐降低;三轴压缩作用下自然和饱水7d煤样的应力-应变曲线峰后差异较明显,自然状态煤样峰后应力跌落速度较快(脆性破坏特征),饱水7d煤样峰后应力跌落较为缓慢(塑性破坏特征);基于微元强度服从Weibull分布,建立了单轴压缩含水煤样的统计损伤本构模型,并进行验证。(2)探讨了异形冲头法消除弥散效应和应力均匀问题,确定煤样动态加载尺寸为φ50mm×30mm;饱水后煤样横波传播速度基本不变,纵波传播速度增加明显,应力波衰减系数减小;利用改进SHPB系统对自然、饱水3d、饱水7d煤样分别进行了一维动静组合加载试验,煤样的动态应力-应变曲线特征与静载差异较大,煤样动态强度随饱水时间增加逐渐降低,但弹性模量少量升高,动态强度与弹性模量高于静载强度及弹性模量;针对预加静载对煤样裂隙发展影响,将煤样裂隙分为裂隙压缩稳定阶段、裂隙急剧扩展阶段、裂隙贯通阶段;煤样的动态强度呈现先升高后降低的趋势,轴向预静载大于静载强度的50%-52%(临界静载点)后,一维动静组合动态强度开始下降。(3)三维动静组合加载的相同围压不同轴压试验中,轴向静载在煤样弹性范围内其动态强度随轴向静载增加而增加,饱水7d煤样的动态强度比自然状态煤样有不同程度的增高,与静载、一维动静组合加载结果相反;相同轴压不同围压加载时,随着围压增大自然和饱水7d煤样的动态强度均有增大,弹性模量也相应增加;对一维、三维动静组合加载煤样的应力-应变曲线特征分为4个阶段:压密阶段、弹性阶段、裂纹扩展阶段、卸载阶段。(4)运用断裂损伤力学理论,分析了裂隙尖端应力场演化特征,建立了静载、动静组合加载条件下含水张开翼型裂纹模型;分析了裂隙水压作用下煤样裂隙动态起始、传播与止裂判据,建立了静载、单独动载、动静组合加载条件下含水煤样的抗压强度数学表达式,并探讨了含水煤样及岩石类材料动态抗压强度增加或降低的原因;确定了一维动静组合加载含水煤样损伤变量,建立了含水和动静组合加载条件下煤样的本构模型,并对模型进行验证。(5)一维动静组合加载自然煤样破坏所需时间大于饱水煤样破坏需要时间,煤样破碎颗粒随饱水时间增长而逐渐变小;相同含水试样破坏失稳耗散能量越大,破碎块度越小,分形维数越大;自然煤样分形维数小于饱水3d、7d,分维数随着能耗密度的增加而提高,能耗密度与分形维数增幅均呈正相关;相同能耗密度随饱水时间增长粒度逐渐减小,能耗密度与破碎粒度呈负相关,二者具有良好线性关系,水作用对试样粒径影响显著。
[Abstract]:The impact ground pressure is one of the major disasters that affect the safety of production in coal mines. The formation of rock impact pressure is often passed through the coal rock medium through the source impact stress wave to the excavation space, causing the rockburst accident. The coal seam flooding is one of the commonly used methods for the prevention and control of the impact ground pressure. Under the stress environment of combined loading and static loading, the stress wave propagation attenuation, strength and energy dissipation mechanism of the water bearing coal seam are still unclear. The impact dynamic response of the water bearing coal sample is a theoretical problem to be solved urgently. The static load and static combined loading test of coal samples are carried out with the RMT-150C and the improved SHPB system. The characteristics of dynamic strength, instability and failure, stress wave attenuation, energy dissipation and damage fracture are discussed. The main conclusions and understanding are as follows: (1) the RMT-150C servo test system is used to carry out static load tests on natural, saturated 3D and 7d coal samples with uniaxial and three axis compressive strength, and the uniaxial and three axis compressive strength increases with the filling time. Gradually decreasing, the stress strain curve of natural and full water 7d coal samples under three axis compression has obvious difference after peak stress strain curve peak, and the stress drop velocity after coal sample peak in natural state is faster (brittle failure characteristic), and the stress drop of 7D coal sample is slow after the peak of full water (the characteristic of plastic failure), and the strength of micro element is subordinate to Weibull distribution, and the uniaxial compression is established. The statistical damage constitutive model of coal water samples is verified. (2) the problem of eliminating dispersion and stress uniformity is discussed. The dynamic loading size of coal samples is determined to be 50mm x 30mm; the transverse wave propagation velocity of coal sample after full water is basically unchanged, the propagation velocity of longitudinal wave increases obviously, and the attenuation coefficient of stress wave decreases; and the improved SHPB system is used to self control. The dynamic stress strain curve of coal sample is different from static load, and the dynamic strength of coal sample decreases gradually with the increase of water filling time, but the modulus of elasticity increases slightly, and the dynamic strength and modulus of elasticity are higher than static load and elastic modulus, and the preloading static load is on the basis of preloading static load on 3D. The coal sample cracks are divided into the stage of fracture compression stability, the sharp expansion stage and the fracture penetration stage, the dynamic strength of coal sample increases first and then decreases, and the dynamic strength of one dimension dynamic static combination begins to decline after the axial static load is larger than the static load strength of 50%-52% (critical static load point). (3) three dimensional dynamic and static combination In the same confining pressure test, the dynamic strength of the axial static load increases with the axial static load in the elastic range of the coal sample, and the dynamic strength of the 7d coal sample is higher than that of the natural coal sample. It is opposite to the static load, the one dimensional static combined loading result, and the confining pressure increases with the same axial pressure. The dynamic strength of natural and full water 7d coal samples increased and the modulus of elasticity increased correspondingly. The stress strain curves of one dimension, three-dimensional dynamic combined loading coal samples were divided into 4 stages: compaction stage, elastic stage, crack growth stage, unloading stage. (4) the fracture damage mechanics theory was used to analyze the evolution characteristics of the stress field at the crack tip. The crack model of water opening airfoil under static loading and static combined loading was established, and the dynamic initiation, propagation and crack arrest criteria of coal samples under the action of fracture water pressure were analyzed. The mathematical expression of compressive strength of water bearing coal samples under static load, single dynamic load and static combined loading condition was established, and the dynamic behavior of water bearing coal samples and rock like materials was discussed. The reason for increasing or decreasing the compressive strength; determining the damage variable of one dimensional static combined loading water bearing coal sample, establishing the constitutive model of coal samples under the combined loading condition of water and static and static loading, and verifying the model. (5) the time required for the destruction of natural coal sample with one dimension static combined loading is greater than that of the coal sample destruction time and the broken coal particles The fractal dimension of natural coal sample is smaller and the fractal dimension is smaller than that of 3D, 7d, the fractal dimension increases with the increase of energy consumption density, and the energy density is positively correlated with the increase of fractal dimension, and the same energy density increases with the filling time. The length of granularity gradually decreases, and the energy consumption density is negatively correlated with the particle size. The two have a good linear relationship, and the effect of water on the particle size is significant.

【学位授予单位】：河南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TD324

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