工作面支承压力分布的研究

为了研究采场支承压力,运用FLAC3D软件建立工作面开采数值模拟模型,研究了工作面前支承压力分布形态及应力峰值的位置,通过与理论计算、现场实测的结果相比较,得出数值模拟、理论分析、现场实测的结果是基本一致的,提出了采场前支承压力的计算方法,对井下工作面超前支护距离设计具有借鉴意义。     

基于微震成像的采煤工作面应力异常监测

为了实现对深井采煤工作面的冲击地压灾害预防,采用微震走时成像技术,监测采煤工作面的应力异常.根据系统要求布置传感器台网,实现工作面全覆盖;采用层状模型分析地震波传播路径,计算地震波传播速度,利用子空间分阶段求解的方法进行反演,实现对监测区域的地震波走时层析成像;结合地震波速度和岩石所受应力的关系,达到研究采煤工作面应力异常的动态分布及变化特征的目的.试验结果表明：工作面推进时,煤层顶板高应力异常达到最大,工作面前方的高应力异常区动态变化范围较大,工作面后方存在较稳定的地震波低速异常,利用微震成像技术可以有效地监测地震波速度异常区域的范围及变化特征.     

孤岛煤柱下底板岩体损伤过程与分区破坏特征分析

以回坡底煤矿为工程背景,分别建立了工作面前方支承压力扰动阶段和采空区压实稳定阶段的底板力学模型.基于相关力学模型,通过理论计算分别得到了支承压力扰动阶段、底板卸压阶段和采空区压实稳定阶段的底板岩体破坏特征.计算结果表明:在工作面前方支承压力扰动阶段,仅在工作面外侧底板岩体发生了破坏;在底板卸压阶段,工作面底板岩体发生了...     

孤岛工作面窄煤柱沿空掘巷围岩变形控制

基于淮南矿区某矿17238孤岛工作面回风平巷具体地质条件,采用FLAC3D数值模拟软件对孤岛面沿空掘巷超前支承压力分布特征进行了分析.结果表明:孤岛工作面沿空掘巷的超前支承压力最大峰值明显大于常规工作面沿空掘巷,应力集中系数是常规工作面沿空掘巷的1.84倍.为研究沿空掘巷顶板"小结构"的稳定性,构建了孤岛面窄煤柱沿空掘巷围岩结构力学模型,揭示了孤岛面窄煤柱沿空掘巷围岩控制机理,提出了具有针对性的围岩变形控制对策.现场工程实践应用表明:巷道采用重新优化设计后的支护方案效果较好,巷道两帮及顶底板相对变形量与优化前相比分别减少约55%及50%,孤岛面窄煤柱沿空掘巷围岩变形得到有效控制.     

承压含水层上协调开采底板岩体采动影响规律的观测研究

承压含不层上近距离煤层协调开采是以防止底板突水为目的，减轻底板采动影响程度的特殊开采方法，本根据实际观测资料，论述了通过调控协调开采步距，使下层工作面的超前支承压力与上层工作面应力释放区的张应力迭加，达到支承压力与张应力相对消减，最大限度地减轻工作面底板岩体采动影响程度。     

推采陷落柱工作面支承压力状态演变规律研究

针对工作面推采陷落柱时面临的矿压威胁,充分考虑陷落柱的形成过程及其围岩地质特征,构建了陷落柱"四带"地质力学模型,并运用理论分析、数值模拟和相似模拟相结合的方法就推采陷落柱工作面支承压力演变规律进行了系统性研究.结果表明:陷落柱诱发的围岩应力在水平方向上可划分为柱体低应力带、柱边应力降低带、外围应力升高带和原岩应力稳定带;当工作面靠近及推过陷落柱时,均会产生采场超前支承压力与陷落柱应力四带耦合现象,其支承压力演变过程可分为耦合发生、耦合增强、柱体吸收、二次耦合和耦合渐散5个阶段;而推采陷落柱工作面的矿压规律与支承压力状态演变及岩体性质结合紧密.靠近陷落柱时,叠合高应力集聚的破碎顶板使支架承受更大载荷.推进陷落柱时,虽然柱体内的低应力起点使柱体区域应力呈一般水平,但陷落柱作为一个整体易沿弱面发生溃泄,尤其对于弱胶结松散陷落柱,矿压显现更加明显.     

不等长工作面覆岩破坏规律的数值模拟分析

针对不等长工作面煤层开采日渐增多的现状,采用数值模拟与理论分析相结合的方法,对采场覆岩的破坏特征及支承压力的分布状态进行系统研究,并相应模拟出工作面前方应力场与位移场的演化规律。结果表明：工作面自开切眼开始向前推移,推进到工作面“见方”期或斜长的整数倍位置时,顶板活动剧烈,覆岩空间结构发生新旧更替,形成了“0”型破断区;不等长工作面推进过程中岩层运移极不规则,推进距离在衔接面前后20～30m的范围内,应力波动较大,数值变化明显;回采期间支承压力对覆岩活动产生了重要影响,其大小约为水平应力的1．5～2倍;就采动过程中竖向位移的变化而言,巷帮移近量远大于顶底板变形量,故工程实践中应特别注意对巷帮及顶板的加固和维护。     

掘进工作面前方力学场动态耦合演化规律

以登槽煤矿为试验矿井,采用现场试验和数值模拟方法对掘进工作面前方力学场进行动态观测分析和模拟,获得了力学场的分布规律,揭示了不同力学场之间耦合演化控制机理。结果显示:分步匀速掘进的煤层巷道前方瓦斯压力呈现典型的三带特征,循环向前推移,瓦斯压力场对地应力场具有一致的动态耦合响应特征;卸压区瓦斯压力场响应滞后地应力场1~2 m,压力升高带和原始压力带基本一致;工作面前方的地应力峰值随工作面推进呈波浪式向前移动,且峰值应力逐渐增大至临界值;瓦斯压力分布受地应力大小、煤体结构和掘进速度影响。     

采动影响下断层冲击矿压危险性研究

采用FLAC5.02D数值模拟软件模拟了煤层开采过程中断层对矿山压力分布的影响.研究了不同断层倾角、断层强度、断层落差、老顶厚度和老顶强度下,工作面支承压力峰值变化规律.结果表明,工作面由断层上盘向断层推进:支承压力峰值随断层倾角减小而减小,当断层倾角为30°时,应力峰值降为60.92MPa,甚至会小于无断层影响下的63.18MPa;当老顶厚度超过20m,应力峰值迅速降为51.53MPa.而工作面由断层下盘向断层推进:应力峰值随着老顶强度的增大先迅速增大为89.34MPa,当老顶强度超过40GPa后,应力峰值基本保持不变.当工作面由断层下盘向断层推进时冲击危险性均比工作面由上盘向断层推进时的高.     

固体充填体压实特征下岩层移动规律研究

基于充填材料压实特性试验,结合具体工程实例,推导出充填体弹性模量与垂直应变之间的关系,利用FLAC3D软件内置FISH语言,编制相应的充填体非线性压实程序,准确地模拟矸石充填采空区后上覆岩层移动规律.研究结果表明:充填采煤工作面顶板下沉量随着工作面的推进而逐渐增大,整体以缓慢弯曲下沉为主,没有出现激增的现象;超前支撑应力分布与垮落法开采相似,其超前支承应力峰值及影响范围均要比垮落法开采低;矸石充填体内部应力呈现"拱形"分布,随着工作面的推进,矸石充填体内部应力逐步升高,增幅逐渐减小.现场实测数据与数值模拟结果基本吻合,验证了研究成果的科学性.     

Analysis of insidious fault activation and water inrush from the mining floor

Based on the stress field distribution rule of the mining floor under abutment pressure, we have established a simplified mechanical model, which contains multiple factors relating to activation and evolution of insidious water-conductive faults. The influence of normal and shear stresses on fault activation and effective shear stress distribution in the fault plane was acquired under mining conditions. Using fracture mechanics theory to calculate the stress intensity factor of an insidious fault front, we have derived the criterion for main fault activation. Results indicate that during the whole working face advance, transpressions are exerted on fault planes twice successively in opposite directions. In most cases, the second transpression is more likely to lead to fault activation. Activation is influenced by many factors, predominant among which are: burial depth of the insidious fault, friction angle of the fault plane, face advance direction and pore water pressure. Steep fault planes are more easily activated to induce a sustained water inrush in the face.     

Abutment pressure distribution for longwall face mining through abandoned roadways

Abutment pressure distribution is different when a longwall panel is passing through the abandoned gate roads in a damaged coal seam. According to the geological condition of panel E13103 in Cuijiazhai Coal Mine in China, theoretical analysis and finite element numerical simulation were used to determine the front pressure distribution characteristics when the longwall face is 70, 50, 30, 20, 10, and 5 m from the abandoned roadways. The research results show that the influence range of abutment pressure is 40 to 45 m outby the face, and the peak value of front abutment pressure is related to the distance between the face and abandoned roadways. When the distance between the longwall face and abandoned roadways is reduced from 50 to 10 m, the front abutment pressure peak value kept increasing. When the distance is 10 m, it has reached the maximum. The peak value is located in 5 to 6 m outby the faceline. When the distance between the longwall face and abandoned roadways is reduced from 10 to 5 m, the front abutment pressure sharply decreases, the intact coal yields and is even in plastic state. The peak value transfers to the other side of the abandoned roadways. The research results provide a theoretical basis for determining the advance support distance of two roadways in the panel and the reinforcement for face stability when the longwall face is passing through the abandoned roadways.     

Analytical solutions of hard roof's bending moment,deflection and energy under the front abutment pressure before periodic weighting

The distribution of front abutment pressure is closely related to the force,deformation and energy distribution of hard roof before periodic weighting. So it is necessary to carry out research on the relationship between them. According to front abutment pressure distribution feature,using the location of peak front abutment pressure as the dividing point,coal seam is divided into two parts along the direction of mining: the yield zone that is the area between the faceline and the point where the maximum front abutment pressure occurs,and the elastic zone that is the part before the point of peak front abutment pressure. The proposed mechanical model of unit width hard roof at the panel center before periodic weighting consists of five parts including the yield zone. All parameters of the deflection equations for each of the five parts that satisfy the continuity conditions and natural boundary conditions are obtained by using the Matlab software. The continuous curves of front abutment pressure,deflection,bending moment and bending strain energy density distribution of hard roof are obtained by iterative approximation method,and the relationship between the yield zone width and the above curves are analyzed in detailed.     

Measurements of in situ stress and mining-induced stress in Beiminghe Iron Mine of China

In order to obtain the distribution rules of in situ stress and mining-induced stress of Beiminghe Iron Mine, the stress relief method by overcoring was used to measure the in situ stress, and the MC type bore-hole stress gauge was adopted to measure the mining-induced stress. In the in situ stress measuring, the technique of improved hollow inclusion cells was adopted, which can realize complete temperature compensation. Based on the measuring results, the distribution model of in situ stress was established and analyzed. The in situ stress measuring result shows that the maximum horizontal stress is 1.75–2.45 times of vertical stress and almost 1.83 times of the minimum horizontal stress in this mineral field. And the mining-induced stress measuring result shows that, according to the magnitude of front abutment pressure the stress region can be separated into stress-relaxed area, stress-concentrated area and initial stress area. At the −50 m mining level of this mine, the range of stress-relaxed area is 0–3 m before mining face; the range of stress-concentrated area is 3–55 m before mining face, and the maximum mining-induced stress is 16.5–17.5 MPa, which is 15–20 m from the mining face. The coefficient of stress concentration is 1.85. Foundation item: Projects(10702072, 10632100) supported by the National Nature Science Foundation of China     

Side abutment pressure distribution by field measurement

Given the 7123 working face in the Qidong Coal Mine of the Wanbei Mining Group, nine dynamic roof monitors were installed in the crossheading to measure the amount and velocity of roof convergence in different positions and at different times and three steel bored stress sensors were installed in the return airway to measure rock stress at depth. On the basis of this arrangement, the rule of change of the distribution of the side abutment pressure with the advance of the working face and movement of overlying strata was studied. The rule of change and the stability of rock stress at depth were measured. Secondly, the affected area and stability time of the side abutment pressure were also studied. The results show that: 1) During working, the face advanced distance was from 157 m to 99 m, the process was not effected by mining induced pressure. When the distance was 82 m, the position of peak stress was 5 m away from the coal wall. When the distance was 37 m, the position of peak stress away from the coal wall was about 15 m to 20 m and finally reached a steady state; 2) the time and the range of the peak of side rock pressure obtained from stress sensors were consistent with the results from the dynamic roof monitors; 3) the position of the peak pressure was 25 m away from the coal wall.     

综放回采巷道围岩力学特征实测研究

通过对综放面回采巷道围岩的深部位移、表面位移、应力分布以及支架荷载的实测分析，得出综放面回采巷道围岩力学特征分布规律．研究表明，临近工作面巷道围岩处于支承压力降低区，支架荷载下降，但支架和围岩变形最剧烈，表明巷道围岩处于岩石峰后的力学状态．围岩变形主要发生支承压力影响区，合理的巷道支护应能控制采动影响剧烈阶段的围岩变形，顺槽支护设计理念应从载荷控制向变形控制转变．     

Formation and evolution of gas flow channels in the abutment pressure area

The permeability of coal ahead of the working face obviously changes dues to changes in abutment pressure. The formation and evolution of gas flow channels within the abutment pressure area was studied by analyzing the fracture extension mechanism and fracture development in different zones of the abutment pressure area. Fracture and damage mechanics theory is used to understand the observations. The following two techniques were used to understand the evolution of gas flow channels: field observation of the characteristic fractures at different positions relative to the working face and fluorescence micrographs of prepared coal samples. Bending tensile fractures develop along an approximately vertical direction that forms a microscopic network of channels in areas of stress concentration. The abutment pressure affects the local stress and, hence, the local gas conduction. The fractures induced by large deformation and plastic flow form macroscopically networked channels in the reduced stress area. Closer to the working face the gas flow channels evolve from microscopic to macroscopic and from isolated to network. Gas permeability continuously increases during this time. This is corroborated by field observations of the displacement of top coal and the gas flow from gas extraction drillings.     

Floor stress evolution laws and its effect on stability of floor roadway

According to the distribution of abutment stress in a stope, this research established the mechanical model of mining abutment pressure transmission in floor base on the theory of semi-infinite plate body in elasticity. This study takes the 762 working face of Haizi Coal Mine as a case in point, and analyzed the dynamic evolution law of seam floor stress during the mining process. With an organic combination of the mining floor stress and surrounding rock stress, the study obtained the change laws of the maximum principle stress and the minimum one for the floor roadway surrounding rock when mining the upper working face. Considering the non-constant pressure force state and the cracks revolution mechanisms of floor roadway surrounding rock, the research built the mechanical model of roadway stress. Simulation results verify the reliability of the above conclusions. Moreover, this model could provide the theoretical basis and technical support for controlling floor roadway surrounding rock.     

煤巷掘进工作面中高压注水措施消突机理研究

以现场实测数据为基础,利用ANSYS有限元分析软件,对中高压注水措施实施前后的掘进工作面前方煤体的应力分布、力学性质、瓦斯运移进行数值模拟,并研究了中高压注水措施的消突机理.