双高煤层底板注浆加固工作面突水机制及防治机理研究

发布时间：2018-06-13 05:43

本文选题：高水压 + 高地应力　；参考：《中国矿业大学(北京)》2016年博士论文

【摘要】：高地应力和高水压型“双高”煤层注浆加固后工作面突水间题在大水矿区非常典型,受多个因素影响,包括高水压、高地应力、注浆、采动和岩体性质等。本文以赵固矿区注浆加固后突水工作面为工程背景,采用理论分析、TAW-2000三轴试验机试验、二维相似模拟试验、数值模拟与现场工程试验相结合的方法,系统研究了注浆加固工作面突水机制和底板岩体注浆加固防治机理,取得了如下主要创新成果：(1)总结分析了研究区防治水环境的复杂多变特点：①煤层埋藏深度大,地应力高；②将来下水平开拓延伸,底板灰岩含水层水压高,约10MPa；③煤层底板岩体存在断层等破碎带；④个别注浆加固工作面底板出水。(2)三向应力状态条件下,注浆加固前原始岩体、破碎后加固体的力学性能有所区别。煤层开采卸压后,高水压区破碎岩体注浆加固后的突水机制直接关系矿井的安全生产。高水压区域注浆加固后的煤层底板突水与底板岩体的应力解除有着密切关系。三轴试验首先研究了高水压条件下注浆前原始岩体和注浆后加固体的力学性能,然后研究了开采导致应力状态发生变化时破碎加固岩体的力学特性和突水特征,得到以下几点结论：①设定围压25Mpa和水压6MPa条件下,对原始完整砂岩、灰岩进行三轴加载实验得到了它们的全程应力-应变曲线,此种条件下砂岩峰值强度为168MPa,灰岩峰值强度为313Mpa。实验发现围压25MPa时,峰值过后强度降低,然后达到残余强度,中间没有发生突水。岩样发生了剪切破坏,剪切破坏面清晰,而岩样顶底部面完整没有破坏,虽然岩样内部产生裂隙,由于25MPa围压和轴向加载作用6MPa水头还无法穿透顶底面完整的试件导致突水。裂隙是发生突水的重要条件, 受到围压和轴压三向应力作用,中间存在裂隙端面完整的破坏岩样在一定时间内没有发生突水。②实验发现注浆加固前后岩样的全程应力-应变曲线上升段有变化。完整试件比较致密,裂隙发育不明显,全程应力-应变曲线上升段曲线比较平滑,没有大的波动；而破裂岩体经过注浆后的全程应力-应变曲线上升段会出现一次波动,说明破碎岩体注浆加固后仍然存在一定的裂隙及孔隙。③设计围压25MPa和水压6MPa条件,比较分析了两种不同破碎度灰岩和砂岩经过加固后强度变化特点。破碎度I灰岩经过注浆加固,有效应力峰值达到105MPa,总应力达111MPa。有效应力恢复到原始完整岩块强度的33.5%。破碎度II灰岩经过注浆加固,有效应力峰值达到93MPa,总应力达99MPa。有效应力恢复到原始完整岩块强度的29.7%。破碎度I砂岩经过注浆加固,有效应力峰值达到76MPa。有效应力恢复到原始完整岩块强度的45.2%。破碎度II砂岩经过注浆加固,有效应力峰值达到68MPa。有效应力恢复到原始完整岩块强度的40.5%。④在25Mpa围压条件下,破碎岩体强度都能够得到提升；但是破碎度越大,强度的提升相比较破碎度小的岩体要低。比较破碎的灰岩和砂岩经过注浆加固后的强度发现,灰岩的注浆加固后强度高于砂岩。但是虽然原始完整灰岩岩样强度较砂岩高,强度提升比例却比砂岩小。⑤进行围压25MPa和水压6MPa条件下注浆加固岩体卸围压突水试验。保持轴向载荷18MPa不变条件下,轴向应变不变,而在围压降低的过程中水流量急剧增加,轴向应变变化不大,而径向应变明显变化。围压从15MPa降低到8MPa后,径向应变有明显增大趋势,之后又会减小到一定值,在围压反复降低到零时,径向应变均有反应,径向应变和垂直裂隙的扩展程度具有较强的相关性。试验表明,煤层底板岩体中裂隙的水流量并不是常数,其影响因素包括裂隙面应力、岩性和孔隙压力。当围压小于水压时,径向应变增大,裂隙的渗水量增大；围压较大时,软岩裂隙面渗透系数受应力的影响较大,使底板岩体具有较强的阻水能力。围压是发生突水的重要影响因素,特别是存在裂隙时,较高围压阻止垂向裂隙的扩展,而围压的解除使得突水危险性增加。⑥分析了裂隙度、波速和三轴极限强度的关系,计算比较了弹性模量和波速为参数的损伤系数。按照弹性模量计算得到破碎度I灰岩经过加固后损伤系数为0.74；破碎度II灰岩经过加固后损伤系数为0.71；破碎度I砂岩经过加固后损伤系数为0.33；破碎度II砂岩经过加固后损伤系数为0.24。按照波速方法计算破碎度I灰岩经过加固后损伤系数为0.78。破碎度II灰岩经过加固后损伤系数为0.71；破碎度I砂岩经过加固后损伤系数为0.33；破碎度II砂岩经过加固后损伤系数为0.29。两种计算方法效果相近,也验证了损伤系数越大,强度提升比例越小。(3)以孔隙裂隙弹性和比奥理论为基础,结合矿压、断裂力学和损伤力学等基本理论,以动态变化的思想和实测资料,研究分析了注浆加固前后岩体的流固耦合变形控制方程,建立了考虑损伤、注浆和采动影响的注浆加固工作面底板突水结构力学模型。①根据孔隙裂隙理论对孔隙型介质的类型进行划分,按照底板岩体的破碎度和裂隙的连通程度,将岩体划分为4种类型,分别是：I型—完整的隔水岩体、II型—非连通性裂隙岩体、III型—连通性裂隙岩体和Ⅳ型—破碎的岩体。并且分析了4种类型岩体的流固耦合方程。②注浆加固工作改变了底板岩体类型。注浆后,岩体类型高的破碎岩体转变为破碎度低的岩体。但注浆无法改变岩体内所包含岩石固有的力学性质,浆液主要通过充填破碎岩体中裂隙或孔隙,降低裂隙的连通性,从而使得岩体破碎类型降低。注浆效果理想时,无论是Ⅳ型破碎岩体、Ⅲ型破碎岩体,还是Ⅱ型较破碎岩体,都将变成完整的Ⅰ型岩体。矿井现场运用电法探测对注浆加固作用机理进行验证,探测结果显示注浆后煤层底板内富水区消失。③相似试验研究表明相比较采高4.5m和分层开采,采高6m时裂隙发育最大,裂隙数目最多,底板破坏深度最大,裂隙发育至L8灰岩,且在靠近弹簧组底界面发育有裂隙,危险程度最大。试验阐明了采动作用是工作面底板发生破坏、垂直裂隙发育、裂隙类型升高的重要原因。④实施了井下底板钻孔注水裂隙发育试验研究。通过现场注水试验发现,支承压力作用下底板岩体发生破坏,增压注水使得裂隙进一步贯通,裂隙的扩展迹线与水流方向一致。突水伴有底臌发生,而底臌破坏是底板岩体应力的显现,此显现的控制对控制突水有很大作用。底臌量在某时刻瞬间增大,底板破坏具有突变性；支护可抑制底臌,可降低变形量和涌水量。⑤相似试验和现场注水试验很好地验证了采动影响对底板岩体裂隙扩展的作用。采动作用可以改变岩体的类型,使岩体类型提升。采动作用影响下,当围岩垂向应力达到岩体裂隙的贯通破坏强度条件时(σz6]),岩体中存在的裂隙在力的作用下开始发育扩展、还会贯通；经过加固改造的岩体由于裂隙的重新发育和扩展,破碎类型升高；在煤层开采时,由于采动应力局部岩体破碎类型可能重新转变为成Ⅲ型或者Ⅳ型破碎岩体,为导水通道的形成创造条件,严重时可能发生底板突水事故。破坏多是由于剪切作用下局部岩体的岩桥破坏,因此导水通道-般表现为“小范围、垂直”特点。⑥以孔隙裂隙弹性理论为基础,结合比奥理论、损伤力学、断裂力学和矿山压力理论,推导了用波速和压缩系数表达的注浆加固前后岩体的流固耦合方程,同时得到了考虑损伤的注浆加固后岩体的各向异性本构方程,并根据断裂力学推导了裂隙扩展的破坏准则,最后建立了注浆加固工作面底板岩体“孔隙-裂隙升降型”突水结构力学模型。(4)根据现场双高矿井注浆工程套管布置密度高、长度大的特点,建立了“双高”煤层底板注浆加固套管与围岩相互作用力学模型。理论推导出套管容许的煤层底板最大的垂向位移公式。研究确定了底板注浆加固套管对底板变形的影响程度和控制机理。①建立注浆套管与围岩耦合作用模型。套管一部分处于底板破坏区,一部分处于围岩稳定区,即存在某个边界面将套管分为两段,自由段套管(底板破坏区)和固定段套管(围岩稳定区)。对某一套管,宏观上可视为杆件。固定段套管受固定端约束,自由段套管受套管下方分布力和套管上方岩体阻力作用。当套管上方阻力小于套管下方分布力时,套管发生向上弯曲变形。由于套管自身具有较高的抗弯性能会阻止底板变形。套管力学参数是可知的,容易求得套管的变形特征,然后根据作用与反作用的关系推导出底板变形特点,套管的受力变形和破坏特征是衡量底板注浆加固体变形和破坏的重要参数。②理论分析了单一套管抗弯性能。将注浆套管视为受分布力作用的一端固定的梁(S点为界),围岩稳定区内套管受固定端约束。而按照上文分析,在弹塑性极限平衡条件下,套管的底板破坏段长度和套管下方的分布力以及套管上方岩体阻力可以求得。(a)S点处产生的套管弯矩Mβ(x,y)弹塑性极限平衡临界状态下,求解了倾角为β的套管上分布的正应力在S点产生的弯矩为：(?)根据弯曲条件下正应力σ与弯矩的关系σ)=My/Iz,得到套管的弯曲强度条件(b)理论求得了套管顶端最大挠度ωA和套管顶端截面转角θA。按照悬臂梁在分布力作用下的情形计算套管顶端点A最大挠度,求得注浆套管顶端最大挠度最后得到了套管承受的底板垂向的最大变形量为：③数值模拟分别计算施加套管前、后底板破坏情况,得到以下结论。(a)无套管时,底板破坏形态符合常规数值计算结果；施加套管后,底板破坏变得不连续。由于施加套管,注浆加固体强度增大,底板破坏范围减小；但是套管与围岩连接处存在弱面,剪切作用下容易发生局部破坏。数值模拟研究表明施加套管后,注浆加固底板垂向位移相对加固前减小,说明套管的抗弯能力对底板岩体变形破坏起到抑制作用。与无套管相比,施加套管后A点位移量减少14%；B点位移量减少19.5%；C点位移量减少16.2%；D点位移量减少32.4%；E点位移量减少21.4%。套管对D点位移影响最大,D点位于破坏临界处,深度相对较大,由于施加套管直接限制了此处的变形,绝对位移量变化大。E点位于被动区,该区为底板破坏直观显现区,同时受到深部岩体影响,过渡区加固效果对该区域的变形影响很大。(b)比较分析发现套管对过渡区Ⅱ影响最大,该区域是控制底板破坏的关键区域,将套管施加在该区域能够更好地提升底板岩体抵抗变形破坏能力。虽然底板破坏显现不可避免,但由于套管的作用,强化了过渡区Ⅱ,从而可以控制底板破坏变化。
[Abstract]:High water pressure and high water pressure type "double high" coal seam grouting reinforcement is very typical in great water mining area, which is influenced by many factors, including high water pressure, high ground stress, grouting, mining and rock mass. In this paper, the water inrush face after grouting reinforcement in Zhao Gu mining area is used as the engineering background, the theoretical analysis, the TAW-2000 three axis test is adopted. The mechanism of water inrush mechanism of grouting reinforcement working face and the mechanism of grouting reinforcement for floor rock mass are studied systematically. The main achievements are as follows: (1) the complex and changeable characteristics of water control environment in the study area are summarized and analyzed: (1) the buried depth of coal seam Large, high ground stress; (2) in the future horizontal development and extension, the water pressure of the aquifer of the bottom limestone rock is high, about 10MPa; (3) there is a fracture zone in the floor rock of the coal seam; (2) under the condition of three direction stress state, the mechanical properties of the rock after the grouting are different. After loading and unloading pressure, the mechanism of water inrush after grouting reinforcement of fractured rock mass in high water pressure area is directly related to the safety of mine production. There is a close relationship between water inrush from the floor of coal seam floor after grouting and reinforcement in high water pressure area and the stress relief of rock mass. First, the mechanics of raw rock before grouting under high water pressure and the mechanics of adding solid after grouting are first studied in the three axis test. The mechanical properties and water inrush characteristics of the broken rock mass are studied when the stress state is changed, and the following conclusions are obtained: (1) under the conditions of setting up the confining pressure 25Mpa and water pressure 6MPa, the full stress strain curves of the original intact sandstone and limestone are obtained by three axis loading experiments, and the sandstone under this condition is under this condition. When the peak strength is 168MPa, the peak strength of the limestone is 313Mpa., when the confining pressure is 25MPa, the peak strength decreases after the peak pressure, then the residual strength is reached, and there is no water inrush in the middle. The rock sample has shear failure, the shear failure surface is clear, and the bottom surface of the rock sample is intact. Although the rock sample is fractured inside, it is due to the 25MPa confining pressure and the axial direction. The loading of 6MPa water head can not penetrate the complete specimen of the top and bottom and lead to water inrush. The fracture is an important condition for water inrush. It is subjected to three direction stress by confining pressure and axial pressure. There is no water inrush in the fracture surface with complete crack end face in the middle. The whole stress strain curve of rock sample before and after grouting reinforcement was found. There is a change in the rising segment of the line. The complete specimen is compact, the fracture development is not obvious, the curve of the stress strain curve of the whole course is smooth and there is no large fluctuation, but there will be a fluctuation in the rise section of the stress-strain curve of the broken rock after grouting, which indicates that there is still a certain crack and hole after the grouting reinforcement of the broken rock body. 25MPa and water pressure 6MPa conditions are designed, and the strength changes of two kinds of fractured limestone and sandstone are compared and analyzed. The fracture degree I limestone is strengthened by grouting, the peak value of effective stress reaches 105MPa, the total stress reaches the 33.5%. breakage of the original intact rock mass and the 33.5%. crushing degree II grout with the strength of the original complete rock mass. The effective stress peak reached 93MPa, the effective stress reached 93MPa, the total stress reached 99MPa., the effective stress was restored to the strength of the original complete rock, the 29.7%. breakage I sandstone was strengthened by grouting, the effective stress peak reached the 45.2%. breakage of the original complete rock mass, the effective stress was recovered to the original complete rock strength, and the sandstone was strengthened by grouting, the effective stress peak reached 68MPa.. The effect is restored to 40.5%. of the strength of the original intact rock block. The strength of the broken rock mass can be promoted under the condition of 25Mpa confining pressure; but the greater the degree of breakage, the lower the strength of the rock mass which is smaller than the broken degree. The strength of the crushed limestone and sandstone after the grouting reinforcement is found, and the strength of the grout after the grouting is higher than that of the rock. However, although the strength of the original complete limestone is higher than that of sandstone, the ratio of strength to strength is smaller than that of sandstone. 5. Under the confining pressure 25MPa and water pressure 6MPa, the rock mass unloading test of rock mass unloading was carried out. The axial strain remained unchanged under the condition of constant axial load 18MPa, while the water flow increased sharply in the process of reducing the confining pressure, and the axial stress should be in the axial direction. When the confining pressure is reduced from 15MPa to 8MPa, the radial strain increases obviously and then decreases to a certain value. The radial strain has a reaction when the confining pressure is repeatedly reduced to zero. The radial strain and the extension of the vertical fissure have a strong correlation. The water flow of the fissure is not constant, and its influencing factors include the stress, lithology and pore pressure in the fissure surface. When the confining pressure is less than the water pressure, the radial strain increases, the seepage water of the fissure increases, and the seepage coefficient of the crack surface of the soft rock is greatly influenced by the stress when the confining pressure is large, and the rock mass has a strong water resistance ability. Confining pressure is water inrush. Important influence factors, especially in the existence of fissures, the high confining pressure prevents the expansion of the vertical fissure, and the lifting of the confining pressure increases the danger of water inrush. 6. The relationship between the crack degree, the wave velocity and the three axis ultimate strength is analyzed, and the damage coefficient of the elastic modulus and wave velocity is calculated and compared. The fracture degree I limestone is calculated according to the modulus of elasticity. After reinforcement, the damage coefficient is 0.74, the damage coefficient of fracture degree II limestone is 0.71, and the damage coefficient of fracture degree I sandstone is 0.33, and the damage coefficient of II sandstone is 0.24., and the damage coefficient is calculated in accordance with the wave velocity method, I limestone is strengthened and the damage coefficient is 0.78. crushing degree II limestone after reinforcement. The post damage coefficient is 0.71, and the damage coefficient of the fractured I sandstone is 0.33, and the damage coefficient of the broken II sandstone is similar to the two calculation methods of the damage coefficient 0.29.. The greater the damage coefficient, the smaller the proportion of the strength lifting. (3) based on the pore fracture elasticity and the Biot theory, combined with the ore pressure, fracture mechanics and loss. On the basis of the basic theory of mechanics of injury and other basic theories, the fluid solid coupling deformation control equation of rock mass before and after grouting reinforcement is studied and analyzed with dynamic changing thought and measured data. The mechanical model of water inrush structure in the floor of grouting reinforcement with the effects of damage, grouting and mining is established. (1) the type of pore type medium is divided according to the theory of pore fissure. According to the fracture degree of the rock mass and the connectivity of the fracture, the rock mass is divided into 4 types, namely: I type - complete watertight rock mass, II type - unconnected fractured rock mass, III - connected fractured rock mass and type IV - broken rock mass. And the fluid solid coupling equation of 4 types of rock mass is analyzed. The rock mass type has changed. After grouting, the broken rock mass of high rock mass is transformed into low crushing rock mass. But the grouting can not change the inherent mechanical properties of the rock included in the rock mass. The slurry is mainly filled by fissures or pores in the fractured rock mass, reducing the connectivity of the fractured rock and reducing the fracture type of the rock mass. The grouting effect is ideal. In the case of type IV fractured rock mass, type III fractured rock mass, or type II fractured rock mass, it will become a complete type I rock mass. The mechanism of grouting reinforcement is verified by electric method detection in mine site, and the detection results show that the water rich area in the floor of coal seam is disappeared after grouting. (3) similar experimental studies show that 4.5m and stratified opening are compared. When mining and mining, the maximum fracture development, the maximum fracture number, the maximum fracture depth, the crack growth to the L8 limestone, and the crack near the bottom of the spring group are the most dangerous. The experiment clarifies that the mining action is the important reason for the failure of the floor of the working face, the vertical fissure and the increase of the fracture type. (4) the bottom bottom is carried out. Through the field water injection test, it is found that the rock mass of the floor under the supporting pressure is destroyed by the field water injection test. The pressurized water injection makes the crack further through, and the crack extension trace is consistent with the flow direction. The water inrush is accompanied by the floor heave, and the floor heave is the manifestation of the bottom slab stress, and the control of this manifestation is controlled. Water inrush has a great effect. The floor heave increases instantaneously at a certain moment, the floor failure is catastrophic, the support can inhibit the floor heave and can reduce the amount of deformation and water inflow. 5. Similar test and field water injection test well verify the effect of the mining effect on the fracture expansion of the floor rock mass. Under the influence of mining action, when the vertical stress of the surrounding rock reaches the fracture strength condition of the fracture of rock mass (sigma z6]), the cracks in the rock mass begin to grow and expand under the action of force, and the fractured rock mass is raised because of the redevelopment and expansion of the fissure; in the mining of the coal, the mining of the coal seam is produced due to the mining. The breakage type of stress local rock mass may be changed into type III or type IV fractured rock mass, which creates conditions for the formation of water guide channel, and the water inrush accident may occur in serious case. Most of the damage is due to the rock bridge failure in the local rock mass under shear, so the water guide channel is characterized by "small range, vertical" characteristics. 6. Kong Xilie On the basis of gap elasticity theory, combining Biot theory, damage mechanics, fracture mechanics and mine pressure theory, the fluid solid coupling equation of rock mass before and after grouting with wave velocity and compression coefficient is derived, and the anisotropic constitutive equation of rock mass after grouting is obtained, and the fracture expansion is derived according to fracture mechanics. In the end, the mechanical model of water inrush structure of "pore fissure lifting type" in rock mass of grouting reinforcement working face is established. (4) according to the characteristics of high density and large length of casing arrangement in the double high mine grouting project, the mechanical model of the interaction between the casing and the surrounding rock of "double high" seam floor grouting is established. The maximum vertical displacement formula of the coal seam floor allowed by the casing pipe. The study determines the influence degree and the control mechanism of the floor grouting reinforcement casing to the floor deformation. (1) the coupling interaction model of the grouting casing and the surrounding rock is established. The casing part is in the bottom floor failure area, and some part is in the stability zone of the surrounding rock, that is, the casing is divided into a certain boundary surface. The two section, the free section casing (floor failure area) and the fixed section casing (the surrounding rock stability zone). For a certain casing, it can be considered as a member on the macro. The fixed section casing is restrained by the fixed end. The free segment casing is under the casing distribution force under the casing and the resistance of the rock mass above the casing. The casing bend upward when the resistance is less than the distribution force below the casing. Due to the high bending property of the casing itself, the deformation of the bottom plate can be prevented. The mechanical parameters of the casing are known, and the deformation characteristics of the casing can be easily obtained. Then the deformation characteristics of the bottom plate are derived according to the relationship between the action and the reaction. The stress deformation and failure characteristics of the casing are the important parameters of the grouting and the solid deformation and destruction. The bending performance of a single casing is analyzed theoretically. The grouting casing is regarded as a fixed beam with a distributed force (S point), and the casing in the stability zone of the surrounding rock is restricted by the fixed end. The length of the failure section of the casing bottom and the distribution force below the casing and the rock above the casing under the elastoplastic limit equilibrium condition are analyzed. The body resistance can be obtained. Under the critical state of the elastic plastic limit equilibrium of the casing bending moment M beta (x, y) produced at (a) S point, the bending moment of the positive stress distributed on the casing of the casing with the dip angle of beta is solved. (?) according to the relationship between the positive stress and the bending moment under the bending condition (?) =My /Iz, and the casing bending strength condition (b) theory is obtained to get the top of the casing. The maximum deflection of the end maximum deflection Omega A and the section angle of the top section of the sleeve is calculated according to the distribution force of the cantilever beam. The maximum deflection of the top point of the sleeve is calculated. The maximum deflection at the top of the casing pipe is obtained. Finally, the maximum deformation amount of the vertical vertical of the bottom plate under the casing is obtained. (3) the numerical simulation is used to calculate the failure of the back floor before the casing is applied and the failure of the rear bottom plate is calculated. The following conclusions are drawn: (a) the failure mode of the floor is in accordance with the conventional numerical calculation without casing, and the failure of the floor becomes discontinuous after applying the casing.
【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】：2016
【分类号】：TD745

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