我国华北型煤田受底板水害威胁的煤炭资源储量达570亿吨，而华北型煤田浅部的上组煤已开采殆尽，深部或下组煤开采突水威胁日益突出，如何实现受承压水威胁的煤炭资源的安全回采是目前我国煤炭行业亟待解决的重大难题之一。为此，本文以煤层底板水害超前区域治理关键注浆参数控制机制为研究对象，采用室内试验、数值模拟、相似模拟、理论推导、统计分析等研究方法和手段，对煤层采动底板加载-卸荷应力路径的损伤突水机理、岩溶裂隙承压含水层水平孔注浆浆液扩散规律、底板灰岩劈裂注浆裂隙起裂机制、煤层底板水害超前区域注浆治理关键控制因素和方法进行研究，取得了如下主要结论：

（1）采用采动数值模拟计算、岩石力学室内试验和理论扰动程度分析，揭示了煤层采动过程中底板主应力状态转换特征、失稳的滞后效应和突变特征，建立了采动底板加载-卸荷主应力转换与水压共同作用下的理论损伤突水判据。

采场底板沿着回采方向呈现周期性的加载-卸荷的应力路径过程，但加载-卸荷程度随深度增加而减弱。进尺与采宽相等时，底板岩层最大主应力在采动加载后由水平方向转换为垂直方向、卸荷后又从垂直方向转换为水平方向。采动过程中最大与最小主应力差值曲线呈现由“双峰”到“单峰”再到“平顶”的变化特征，沿煤层方向差值波动幅度随着深度的增加而降低，差值大小在煤壁附近和采空区下方均增大；在卸荷试验中，环向约束的解除直接促进了试样扩容发展。试样在卸压后存在明显的损伤累积过程，致使试样存在失稳滞后效应。试样失稳时产生应力跌落现象，且跌落速度随孔压增大而降低。细观揭示了采动底板加载-卸荷应力路径下损伤失稳的滞后效应和突变特征；理论建立了基于孔隙水压不为0的采动应力扰动系数（k_3d）、水压作用裂隙起裂判别指标（k_w）、采动后岩体失稳判别指标（k_i）之积的底板岩层采动应力扰动强度指标（k），提出了k＞1的采动底板加载-卸荷应力路径下的突水判据。

（2）采用承压倾斜裂隙浆液辐向扩散理论模型构建和解析的方法，揭示了水平孔在承压倾斜裂隙中注浆浆液扩散呈现左右沿中心垂线对称、钻孔上下非对称的近似椭圆形态的变化规律。

在承压倾斜裂隙中，浆液自重在水平注浆孔上方裂隙和下方裂隙中分别起到阻力和动力作用、静水压力均起到阻力作用；考虑浆液自重、裂隙倾角、静水压力、浆液粘度、辐向扩散等因素，构建了岩溶裂隙承压含水层水平孔注浆浆液扩散受力模型，建立了承压倾斜裂隙水平注浆孔牛顿流体和粘时变流体浆液辐向扩散形态迹线控制方程；在不同注浆压力、裂隙倾角（除水平外）和开度、浆液水灰比下，承压倾斜裂隙水平孔注浆浆液扩散迹线形态呈沿中心垂线左右对称、沿水平孔上下裂隙非对称的近似椭圆形态，上方裂隙扩散迹线的中心位置呈微凹分布特征，相同时刻浆液扩散距离最大值和最小值分别在辐向角0°和180°位置。浆液扩散迹线范围随注浆压力、裂隙开度、浆液水灰比的增加而增大，且下方裂隙增加幅度大于上方裂隙。浆液扩散迹线范围在下方和上方裂隙中随裂隙倾角增加分别增大和减小。

（3）采用颗粒元数值模拟计算，结合真三轴应力状态下劈裂注浆相似材料物理模型试验，系统揭示了不同影响因素下预制裂隙和弱面劈裂注浆裂隙起裂机制。

在不同水灰比浆液、地应力水平、弱面和裂隙倾角、开度条件下劈裂注浆起裂压力变化规律：预制弱面和裂隙的起裂压力随浆液水灰比、最大与最小主应力差值、弱面和裂隙开度增加而减小，随弱面和裂隙与最大主应力夹角增加而增加；弱面条件下的起裂压力均随着弱面与基质强度比的降低而降低，当弱面强度较高时，起裂压力大于裂隙条件下的起裂压力。相同工况下，二次起裂压力均大于初次起裂压力，二次起裂压力随最小主应力降低而降低，但二次起裂压力降低幅度要高于初次起裂压力降低幅度；劈裂注浆起裂裂隙延展变化规律：注浆孔在弱面中部或两端时，裂隙均在钻孔周围弱面强度较低处起裂，而后沿最大主应力方向延展。注浆孔在裂隙中部时，裂隙在预制裂隙尖端起裂，而后沿最大主应力方向延展。起裂裂隙扩展路径基于弱面、裂隙左右呈非对称形态。

（4）基于显微CT扫描、室内试验、统计分析和数值计算等方法对浆液水灰比和材料选配、注浆终结压力、水平孔间距和布设方位、稳压时间等进行研究，揭示了煤层底板超前区域注浆浆液扩散关键控制因素，形成了相应控制方法。

建立了煤层底板岩溶裂隙含水层超前区域注浆浆液扩散控制因素和方法体系，包括基于灰岩宏观垂向渗透性发育特征和细观空隙定量参数等因素相结合的注浆材料粒径选配的宏细观确定方法，提出了基于底板承压水作用下起裂判据的水泥基浆液强度的确定方法，基于不同条件下水平孔倾斜单裂隙浆液扩散距离、注浆设备额定工作能力和岩体起裂压力等因素的注浆终结压力、稳压时间和钻孔间距的确定方法，基于水平钻孔轨迹与最大主应力方向垂直、与最小主应力方向平行的钻孔方向布设原则，基于调控浆液水灰比、注浆压力和注浆时间等因素达到注浆终结压力和稳压时间标准的浆液扩散控制方法。

North China type coalfield in our country under the threat of bottom water disasters of coal resources reserves of 57 billion tons, and is on the north China type coal field of the shallow coal mining, deep or group of coal mining underwater inrush threat increasingly prominent, how to implement under the threat of confined water safety mining of coal resources is one of the major problems urgently to be solved in the coal industry in our country. Therefore, this paper takes the preact grouting control mechanism of confined fissure aquifer of coal seam floor as the research object, adopts laboratory test, numerical simulation, similarity simulation, theoretical derivation, statistical analysis, and other research methods and means. The damage and water inrush mechanism of load-unloading stress path of coal seam mining floor, diffusion law of grouting grout in the horizontal hole of the confined aquifer in karst fissure, fracture initiation mechanism of split grouting in floor limestone, control factors, and methods of advance grouting grout diffusion in karst fissure aquifer are studied, and the following main conclusions are obtained:

(1) Based on the macroscopic numerical simulation calculation, microscopic laboratory test, and theoretical disturbance degree analysis, this paper reveals the characteristics of the state transformation of the principal stress of the floor, the hysteresis effect, and the abrupt change of the instability in the process of coal mining, and establishes the theoretical damage criterion of water inrush under the combined action of the principal stress transformation of the mining-unloading floor and water pressure.

The maximum principal stress of floor rock stratum changes from horizontal direction to vertical direction after mining loading, and from vertical direction to horizontal direction after unloading. In the mining process, the curve of the difference between the maximum and minimum principal stresses shows the variation characteristics from "double peak" to "single peak" and then to "flat roof". The fluctuation amplitude of the difference along the coal seam decreases with the increase of depth, and the difference increases near the coal wall and below the goaf; In the unloading test, the release of circumferential constraint directly promotes the development of sample expansion. There is an obvious damage accumulation process after pressure relief, resulting in the instability lag effect of the sample. The stress drop occurs when the sample is unstable, and the drop speed decreases with the increase of pore pressure. It reveals the lag effect and catastrophe characteristics of damage and instability under the loading-unloading stress path of the mining floor from the mesoscopic view; The mining stress disturbance intensity index (k) of floor rock stratum based on the product of mining stress disturbance coefficient (k_3d), fracture generation discrimination index (k_w) underwater pressure and rock mass instability discrimination index (k_i) after mining is established theoretically, and the mining floor water inrush criterion of k>1 is proposed.

(2) Based on the theoretical model construction and analysis of radial diffusion of grout in confined inclined fractures, the variation law of grout diffusion of grouting in horizontal holes in confined inclined fractures is revealed, which is symmetrical along the center perpendicular line from the left to right, and asymmetric above and below the borehole.

In the pressure bearing inclined crack, the self-weight of slurry plays the role of resistance and power in the crack above and below the horizontal grouting hole respectively, and the hydrostatic pressure plays the role of resistance; Considering the factors such as slurry self-weight, fracture inclination, hydrostatic pressure, slurry viscosity and radial diffusion, the stress model of grouting slurry diffusion in horizontal hole of karst fracture confined aquifer is constructed, and the trace control equations of Newtonian fluid and viscous time-varying fluid slurry radial diffusion in horizontal hole of confined inclined fracture are established; Under different grouting pressure, crack inclination (except horizontal) and opening, and slurry water-cement ratio, the shape of grouting slurry diffusion trace in horizontal hole of pressure bearing inclined crack is an approximate elliptical shape, which is symmetrical left and right along the central vertical line and asymmetric along the upper and lower cracks of horizontal hole, and the central position of the upper crack diffusion trace is slightly concave. At the same time, the maximum and minimum values of slurry diffusion distance are at the radial angle of 0° and 180° respectively. The range of slurry diffusion trace increases with the increase of grouting pressure, crack opening, and slurry water-cement ratio and the increased range of lower cracks is greater than that of upper cracks. The range of slurry diffusion trace increases and decreases with the increase of fracture inclination in the lower and upper fractures, respectively.

(3) Based on particle element numerical simulation of split grouting and physical model test of similar materials under true triaxial stress, the initiation mechanism of prefabricated cracks and weak surface split grouting cracks under different influencing factors was systematically revealed.

Under the conditions of different water-cement ratio, grout, in-situ stress level, weak surface and crack inclination and opening, the variation law of fracturing grouting initiation pressure: the fracturing pressure of prefabricated weak surface and crack decreases with the increase of grout water-cement ratio, the difference between the maximum and minimum principal stress, weak surface and crack opening, and increases with the increase of the angle between the weak surface and crack and maximum principal stress; The initiation pressure under the condition of the weak surface decreases with the decrease of the strength ratio of weak surface to the matrix. When the strength of the weak surface is high, the initiation pressure is greater than that under the condition of fracture. Under the same working conditions, the secondary initiation pressure is greater than the primary initiation pressure, and the secondary initiation pressure decreases with the decrease of the minimum principal stress, but the reduction range of the second initiation pressure is higher than that of the primary initiation pressure; Variation law of crack extension of splitting grouting: when the grouting hole is in the middle or both ends of the weak surface, the crack starts at the place with low strength of the weak surface around the drilling hole, and then extends along the direction of maximum principal stress. When the grouting hole is in the middle of the crack, the crack starts at the tip of the prefabricated crack and then extends along the direction of the maximum principal stress. The crack initiation crack propagation path is based on the weak surface, and the crack is asymmetric on the left and right.

(4) Based on microscopic CT scans, laboratory tests, statistical analysis, and numerical calculation methods of slurry water-cement ratio and end material selection, grouting pressure, horizontal hole spacing, and layout position, pressure holding time, such as study, reveals the coal floor karst fissure aquifer advanced grout diffusion controlling factors, grout diffusion control method is proposed.

The control factors and method system of grouting slurry diffusion in the leading area of the karst fissure aquifer in the coal seam floor are established. It includes the macroscopic and mesoscopic determination method of grouting material particle size selection based on the combination of macroscopic and vertical permeability development characteristics of limestone and mesoscopic void quantitative parameters. It includes the determination method of cement-based slurry strength based on the Cracking Criterion under the action of confined water on the floor is proposed. It includes the determination method of grouting end pressure, pressure stabilizing time, and drilling spacing based on the factors such as the slurry diffusion distance of inclined single crack of the horizontal hole under different conditions, the rated working capacity of grouting equipment, and the rock mass cracking pressure. It includes the layout principle of the drilling direction based on the horizontal drilling track perpendicular to the direction of the maximum principal stress and parallels to the direction of the minimum principal stress. It includes the slurry diffusion control method based on adjusting and controlling the water-cement ratio of slurry, grouting pressure, and grouting time to meet the standards of grouting end pressure and pressure stabilization time.