采动条件下拱形裂隙类岩体破坏机理及模型研究

发布时间：2018-04-20 00:05

本文选题：煤矿开采 + 贯通破坏　；参考：《中国矿业大学(北京)》2017年博士论文

【摘要】：本文围绕采动条件下覆岩破坏及裂隙演化机理这一科学问题展开了研究,通过现场实测、理论分析、物理模型试验、数值模拟和实验室试验等方法,对采动条件下拱形裂隙类岩体破坏机理及其模型进行了研究,提出了采动过程中覆岩随着矿压显现而形成拱形裂隙的理念,提出了三角拱形和“W”拱形两类裂隙简化模型,并构建了与矿压显现相结合的解释采动覆岩拱形裂隙空间展布、衍生特征及动态发育的三角拱形裂隙演化模型和“W”拱形裂隙演化模型;建立了初始拱形裂隙损伤开采模型和无初始损伤开采相似材料对比模型,对采动覆岩裂隙形态变化、分形及沉降特征进行了研究,并对演化模型进行了验证;结合UDEC数值模拟方法,构建了与相似材料模型一致的模型及其他两个考虑裂隙拱前后倾角、拱形裂隙层数因素的模型,归纳了不同初始拱形预制裂隙分布特征对覆岩采动裂隙演化影响的规律;通过制备四类裂隙形态、六组倾角范围的预制拱形裂隙类岩石试件,对其在单轴压缩加载条件下的破坏行为及模式进行了试验研究,揭示了三角拱形裂隙和“W”拱形裂隙随裂隙倾角变化对类岩石试件的强度与弹性模量、起裂扩展贯通裂纹形态与倾角的影响规律,对于地下工程开挖中地质灾害的预测与防治,具有一定的参考价值和实践意义。本文的主要研究成果如下:(1)通过转龙湾煤矿顶板拱形裂隙发育形态实测,获得工作面顶板裂隙发育形态为拱形,呈现工作面中间最高,工作面两侧最低的特征,提出了两类采动裂隙的简化模型,即三角拱形(Λ)与W拱形(W);提出了与矿压显现相结合的解释采动覆岩拱形裂隙空间展布、衍生特征及动态发育的三角拱形裂隙演化模型和“W”拱形裂隙演化模型,并结合提出的两裂隙演化模型,归纳了随着来压步距而发展的覆岩采动裂隙动态演化过程、形态变化、形成时间及发育规律;提出了采动过程覆岩主要导水裂隙通道形成规律,根据建立的裂隙演化模型,推断主要导水裂隙通道是煤层开挖过程中沿着工作面推进方向的两个端点向上延伸位置及开挖空间中间位置上方的一次来压步距裂隙拱。(2)相似材料模拟实验中,预制拱形裂隙的开采模型内部纵向裂隙发育更为密集,具有更加明显地、有规律地拱形裂隙动态发育趋势,随着工作面逐渐推进,裂隙朝着推进方向以“拱形”发育,并逐层向上闭合拱形,而后继续延展、连通已存在的小的次生裂隙拱形成新阶段的裂隙拱,小拱形裂隙逐渐向前向上发展形成大裂隙拱;损伤模型的沉降曲线极不规则,越接近开采初始端沉降中心点越多,煤层上覆岩体由下而上,随距离煤层顶板高度的增加,上覆岩层沉降量逐渐缩小,各沉降曲线中心点依次沿着推进方向偏移;而无初始损伤开采模型的沉降中心点相对较集中;在开采初期(开挖60 m之前)损伤模型的纵向裂隙密度明显高于无损模型,而在开采后期(开挖60 m~80 m)其与无损模型保持几近相同的裂隙密度。(3)建立了具有不同初始拱形预制裂隙分布特征的UDEC数值模拟模型,发现损伤开采模型随着工作面推进,内部纵向裂隙发育明显,裂隙形态以有规律的小“三角形”或小“拱形”来推进,形成的裂隙整体形态则经历着由起初的“等腰三角形”-随着开采倾斜于切眼的“斜三角形”-采后压实稳定的“拱形”;随着预制裂隙角度的降低模型展现出更好的裂隙发育范围和内部裂隙发育程度,裂隙发育更为紊乱、复杂,裂隙向上扩展趋势越来越不明显,形态上由“高瘦”拱形向“矮胖”拱形过渡,在一定的尺度范围内,同一阶段两拱形预制裂隙倾角大、倾角差值大及上下相邻两阶段预制裂隙的间距略大有利于覆岩裂隙的纵向扩展,而且,双阶段损伤模型比单阶段模型具有更好的拱形裂隙发育趋势,开采空间覆岩拱形裂隙层数越多越有利于其拱形趋势的扩展延伸。(4)四类裂隙系列试件中裂隙汇合(即TA和W)或低角度的裂隙倾角都会增加其塑性变形能力,试件中两预制裂隙倾角一侧高角度会使其在应力应变曲线前期受裂隙形态、汇合等因素的影响程度大幅度的降低,裂隙倾角对其影响占主导地位,裂隙的汇合会造成裂隙岩体抵抗变形能力略微降低,而形态上的差异,即“W”拱形裂隙在两侧“V”形的影响下其抵抗变形能力明显的降低了,可知若是采动覆岩中两侧“V”形裂隙汇合后将极易破坏;通过比较分析各系列损伤试件峰值强度及弹性模量,获知“W”拱形裂隙系列对裂隙岩体峰值强度降低程度远大于三角拱形,远比裂隙汇合带来的影响严重,对于预制裂隙试件中同一倾角随形态变化的峰值强度,六组裂隙倾角试件分别在I、STA、TA、SW、W下的峰值强度变化基本呈现出随着形态变化依次递减的趋势,各形态对峰值强度降低程度从小到大依次为ISTATASWW;而对于预制裂隙试件中同一倾角的随形态变化的弹性模量,六组裂隙倾角试件随着形态变化也呈现出大体递减的趋势,但不如峰值强度趋势明显,而各形态对弹性模量降低程度与其相同;拱形裂隙试件两裂隙倾角总和相同的情况下,其差值越大,峰值强度及弹性模量相对越低。(5)获得了含四类预制裂隙试件的峰值强度与完整试件的峰值强度之比(/JP P??)、弹性模量与完整试件的弹性模量之比(/JP PE E)与裂隙倾角影响系数k关系的经验公式,当量化峰值强度随着倾角影响系数的递增呈现出非常好的线性递减关系;通过统计裂隙试件起裂、峰值破坏的强度与时间,提出了STA、TA、SW、W四类裂隙系列试件的稳定裂隙发展阶段和非稳定裂隙发展阶段界限范围;归纳了不同初始损伤试件裂纹起裂、扩展、贯通破坏倾角及迹线形态变化规律,发现对于两条未汇合的拱形裂隙(STA系列),两裂隙倾角不同很有可能会引起其中倾角较小的裂隙发育更为剧烈,并以其为主导引起裂纹继续向上扩展,同时扩宽了向下发育的裂隙,并且裂隙倾角越大或两倾角差值越大,这种效果越明显;对于两条已汇合的拱形裂隙(TA系列),其中低倾角的裂隙尖端是破坏的薄弱区域,应力多沿此区域释放,使得交汇的顶点产生的裂纹继续整体保持沿低倾角裂隙倾向于另一侧发展趋势;对于两个未汇合(SW)或已汇合(W)的相同形态的“V”形裂隙,沿其中低倾角裂隙起裂及扩展的趋势仍很明显,另外SW系列中随着裂隙倾角增加,裂隙相互交汇并向上扩展的趋势愈加明显,低倾角裂隙多朝向垂直于主应力方向。
[Abstract]:This paper focuses on the scientific problem of overlying rock failure and fracture evolution mechanism under the mining conditions. Through the field measurement, theoretical analysis, physical model test, numerical simulation and laboratory test, the failure mechanism and model of the arch fractured rock mass under the mining condition are studied, and the overlying rock is put forward in the process of mining. With the idea of forming the arch fissures, the triangle arch and the "W" arch shape simplified models were put forward, and the evolution model of the trigonometric arch fracture and the "W" arch fracture evolution model, which were combined with the ore pressure manifestation, were constructed to explain the spatial distribution of the arch fissures in the mining overlying rock, the derivation characteristics and dynamic development of the arch fissure and the "W" arch fracture. The fracture damage mining model of the beginning arch and the comparison model of similar material without initial damage mining are used to study the fracture morphology, fractal and settlement characteristics of the mining overlying rock, and the evolution model is verified. Combined with the UDEC numerical simulation method, a model consistent with the similar material model and the other two other fracture arches are built. The rule of the influence of the distribution characteristics of different initial arch prefabricated fissures on the fracture evolution of the overlying mining is summed up, and the damage behavior and model of the prefabricated arch fractured rock specimens under the uniaxial compression loading condition are tested and studied by the preparation of four types of fracture morphology and six groups of dip angles. The influence of the triangle arch fracture and the "W" arch crack to the strength and elastic modulus of the rock specimen, the influence law of the crack morphology and dip angle of the crack growth and penetration are revealed. It is of certain reference value and practical significance for the prediction and prevention of geological disasters in the excavation of underground engineering. The results are as follows: (1) through the measurement of the shape of the arch fissures on the roof of the Longwan coal mine, the shape of the crack development in the roof of the working face is arched, showing the highest middle working face and the lowest characteristics on both sides of the working face. The simplified model of two kinds of mining cracks, namely the triangle arch (a) and the W arch (W), is put forward, and the interpretation of the combination with the mineral pressure is put forward. The dynamic evolution process, shape change, formation time and development law of overlying strata, which are developed with the two fissure evolution model, are summed up with the proposed two fracture evolution model. According to the established fracture evolution model, it is concluded that the main water guide fissure channel is an upward extension position of two endpoints along the direction of the coal seam excavation and the one step pressure step distance from the middle position of the excavation space in the process of coal seam excavation. (2) a similar material simulation experiment. The longitudinal fissure development of the prefabricated arch fracture model is more densely developed, and it has a more obvious trend of dynamic development of the arch fracture. With the gradual advance of the working face, the crack is developed in the direction of "arch" in the direction of propulsion, and the arch is closed to the upper level, and then it continues to extend, connecting the small secondary fissure arches. In the new stage, the fracture arch of the small arch is gradually developed forward to form a large fracture arch. The settlement curve of the damage model is very irregular. The more the settlement center point is closer to the initial end of the mining, the overlying rock in the coal seam is up to the bottom, with the increase of the height of the roof of the coal seam, the subsidence of the overlying strata is gradually reduced, and the center points of each settlement curve depend on the center point of the settlement. The center point of the subsidence is relatively concentrated without the initial damage mining model, and the longitudinal fissure density of the damage model is obviously higher than that of the lossless model in the early stage of mining (60 m before excavation), while in the later period of mining (60 m~80 m excavation) it is almost identical to the nondestructive model. (3) it has different initial conditions. The UDEC numerical simulation model of the distribution characteristics of the pre arch prefabricated fissures shows that the damage mining model develops with the working face, and the internal longitudinal fissure development is obvious. The fracture morphology is propelled by the regular small "triangle" or the small "arch". The formation of the whole fracture form is experienced by the initial "isosceles triangle" - with the mining inclination. The "oblique triangle" inclined to the cutting of the eye is the "arch" which is stable after mining. With the reduction of the prefabricated crack angle, the model shows a better range of fracture development and the degree of internal fissure development. The fracture development is more disorganized and complex, and the upward trend of fracture upward is becoming more and more unobvious, and the shape is from "thin" arch to "stout" arch form. In a certain scale, in a certain scale, the two arch prefabricated fissure inclination is large, the angle difference is large and the spacing of the prefabricated fissures in the upper and lower adjacent two stages is slightly extended, and the double stage damage model has a better arch fracture development trend than the single stage model, and the arch fracture of the overlying rock is exploited. The more the number of layers is more beneficial to the expansion and extension of the arch trend. (4) the plastic deformation ability of the fracture confluence (TA and W) or the low angle of the crack will increase the plastic deformation ability. The high angle of the two prefabricated fissure angle in the specimen will be affected by the fracture shape at the early stage of the stress-strain curve, and the influence degree of the confluence is great. With the decrease of the amplitude, the influence of the fracture angle is dominant. The confluence of the fissure will cause a slight decrease in the ability to resist the deformation of the fractured rock mass, but the difference in shape is that the resistance to deformation of the "W" arch crack is obviously reduced under the influence of "V" shape on both sides. It is known that if the "V" fissures on both sides of the mining overlying rock are converged, By comparing and analyzing the peak strength and modulus of elasticity of each series of damage specimens, it is known that the reduction of the peak strength of the fractured rock mass of the "W" arch fracture series is far greater than that of the triangle arch, and the influence of the far ratio of the fracture confluence is serious. For the peak strength of the same dip with the shape change in the prefabricated fracture specimens, the six groups of fissures are tilted. The variation of the peak strength of the angular test parts at I, STA, TA, SW and W showed a trend of decreasing in turn, and the decrease degree of the peak intensity from small to large in each form was ISTATASWW, while the six groups of fracture angles were changed with the morphologic change of the same dip in the prefabricated fissures. There is a tendency to decrease generally, but it is not as obvious as the peak intensity trend, and the degree of the modulus is the same as that of the modulus of elasticity; the greater the difference value, the lower the peak strength and the modulus of elasticity in the case of the two fracture angle of the arch fracture specimen. (5) the peak strength and the complete test of the four types of prefabricated crack specimens are obtained. The peak strength ratio (/JP P?), the empirical formula of the relationship between the modulus of elasticity and the modulus of elasticity of the complete specimen (/JP PE E) and the influence coefficient K of the fracture angle, when the quantitative peak intensity increases with the increase of the inclination influence coefficient, it presents a very good linear decreasing relation; the strength and time of the peak damage through the statistical fracture test. The stable fissure development stage and the boundary range of unstable fissure development stage of four kinds of fracture series of STA, TA, SW, W are put forward, and the crack initiation, expansion, penetration angle and trace form change of different initial damage specimens are summed up, and it is found that the two fissure dip angles are different for two non confluence arch fractures (STA Series). It can cause a more intense development of the smaller slit, which leads to the continuous upward expansion of the crack and the widening of the downward developing fissure, and the greater the slit angle or the greater the difference of the two dip angle, the more obvious the effect is. For the two confluence arch fissures (TA series), the tip of the low dip angle is broken. In the bad weak region, the stress is released along this area, making the cracks at the vertex of the intersection maintain a trend along the other side, and the tendency to crack and expand along the low inclination crack is still obvious for two SW or W confluence (W) fissures with the same shape, and the other SW system Along with the increase of crack dip angle, the trend of fracture convergence and upward expansion is more obvious. The low dip fissure is oriented toward the direction of principal stress.

【学位授予单位】：中国矿业大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TD325

【参考文献】