Measurement of overburden failure zones in close-multiple coal seams mining

In the Kaiping Coal field,mining of five coal seams,located within 80 m in the Kailuan Group,#5,#7,#8,#9 and#12 coal seam,is difficult due to small interburden thickness,concentrated stress distributions,high coal seam metamorphism,and complex geological conditions.By using the ZTR12 geological penetration radar(GPR)survey combined with borehole observations,the overburden caving due to mining of the five coals seams was measured.The development characteristics of full-cover rock fractures after mining were obtained from the GPR scan,which provides a measurement basis for the control of rock strata in close multiple coal seam mining.For the first time,it was found that the overburden caving pattern shows a periodic triangular caved characteristic.Furthermore,it is proposed that an upright triangular collapsed pile masonry and an inverted triangular with larger fragments piled up alternately appear in the lower gob.The research results show that the roof structure formed in the gob area can support the key overlying strata,which is beneficial to ensure the integrity and stability of the upper coal seams in multiple-seam mining of close coal seams.

Layout and support design of a coal roadway in ultra-close multiple-seams

A roadway within ultra-close multiple-seams(RUCMSs) is one of the most difficult supported coal roadways to deal with in underground coal mines. This is usually due to the unknown stress distributions, improper roadway layout, and unreasonable support parameters. In order to solve this support problem and effectively save RUCMSs from frequent and abrupt disasters(such as serious deformation of the surrounding rock, roof cave ins, and coal side collapse), a comprehensive method is adopted here which includes theoretical analysis, numerical simulation, and field monitoring. A mechanical model was constructed to determine the stress distribution in the coal pillar after two sides of a longwall panel had been mined. Based on this model, the horizontal, vertical, and tangential stress equations for the plane below the floor of the upper-left coal pillar were deduced. In addition, a typical coal mine(the Jinggonger colliery, located in Shuozhou city, Shanxi province, China) with an average distance between its 9# and 11# coal seams of less than 8.0 was chosen to conduct research on the proper layout and reasonable support required for a typical coal roadway located within coal seam 11#. Using FLAC3D(Fast Lagrangian Analysis of Continua in 3-Dimensions) numerical software, eight schemes were designed with different horizontal distances(d) between the center lines of the coal pillar and the roadway in the lower coal seam(RLCS). The simulations and detailed analysis indicate that the proper distances required are between 22.5 and 27.5 m. A total of 20 simulation schemes were used to investigate the factors influencing the support provided by the key bolts(bolt length, spacing, distance between two rows, installation angle, and pre-tightening force). The results were analyzed and used to determine reasonable values for the support parameters. Field results show that the stability and strength of the RLCS can be effectively safeguarded using a combination of researched stress distribution characteristics, proper layout of the RLCS, and correct support parameters.

近距离煤层采空区下巷道支护优化设计

针对双马一矿12201运输巷变形破坏严重的问题,结合双马一矿11号和12号近距离煤层实际赋存环境,运用FLAC3D软件分析掘巷、工作面回采围岩应力演化规律。模拟结果显示,在掘巷期间两帮出现不对称应力升高区。工作面回采稳定后,运输巷采空区帮转为应力降低区,而实体煤帮在多重扰动作用下,巷帮侧向支承压力明显升高。根据模拟结果对巷道支护进行优化设计,巷帮采用全锚索支护并且增加锚杆索支护密度。现场实测表明,两帮围岩变形100 d内稳定在300 mm,顶板变形量稳定在200 mm,优化支护方案明显减少了巷道围岩变形量,巷道锚固圈稳定,有效控制围岩变形。

New CCD photometric investigation of the early-type overcontact binary BH Cen in the young star-forming Galactic cluster IC 2944

BH Cen is a short-period early-type binary with a period of 0.792^d in the extremely young star-forming cluster IC 2944. New multi-color CCD photometric light curves in U, B, V, R and I bands are presented and are analyzed by using the Wilson-Devinney code. It is detected that BH Cen is a high-mass-ratio overcontact binary with a fill-out factor of 46.4% and a mass ratio of 0.89. The derived orbital inclination i is 88.9 degrees, indicating that it is a totally eclipsing binary and the photometric parameters can be determined reliably. By adding new eclipse times, the orbital period changes in the binary are analyzed. It is confirmed that the period of BH Cen shows a long-term increase while it undergoes a cyclic oscillation with an amplitude of A3 = 0.024 d and a period of P3 = 50.3 yr. The high mass ratio, overcontact configuration and long-term continuous increase in the orbital period all suggest that BH Cen is in the evolutionary state after the shortest-period stage of Case A mass transfer.The continuous increase in period can be explained by mass transfer from the secondary component to the primary one at a rate of˙M2 = 2.8×10^-6 M⊙per year. The cyclic change can be plausibly explained by the presence of a third body because both components in the BH Cen system are early-type stars. Its mass is determined to be no less than 2.2 M⊙ at an orbital separation of about 32.5 AU. Since no third light was found during the photometric solution, it is possible that the third body may be a candidate for a compact object.

An orbital period investigation of the Algol-type eclipsing binary VW Hydrae

Orbital period variations of the Algol-type eclipsing binary, VW Hydrae, are analyzed based on one newly determined eclipse time and the other times of light minima collected from the literature. It is discovered that the orbital period shows a continuous increase at a rate ofdP/dt = ＋6.34 × 10^-7 d yr^-1 while it undergoes a cyclic change with an amplitude of 0.0639 d and a period of 51.5 yr. After the long-term period increase and the large-amplitude period oscillation were subtracted from the O-C curve, the residuals of the photoelectric and CCD data indicate a small-amplitude cyclic variation with a period of 8.75 yr and a small amplitude of 0.0048 d. The continuous period increase indicates a conservative mass transfer at a rate of dM2/dt = 7.89 × 10^-8 M⊙ yr^-1 from the secondary to the primary. The period increase may be caused by a combination of the mass transfer from the secondary to the primary and the angular momentum transfer from the binary system to the circumbinary disk. The two cyclic period oscillations can be explained by light-travel time effects via the presence of additional bodies. The small-amplitude periodic change indicates the existence of a less massive component with mass M3 〉 0.53 M⊙, while the large-amplitude one is caused by the presence of a more massive component with mass M4 〉 2.84M⊙. The ultraviolet source in the system reported by Kviz ＆ Rufener （1987） may be one of the additional components, and it is possible that the more massive one may be an unseen neutron star or black hole. The rapid period increase and the possibility of the presence of two additional components in the binary make it a very interesting system to study. New photometric and high-resolution spectroscopic observations and a detailed investigation of those data are required in the future.

近距离煤层群协调开采支架工作阻力计算方法与系统

近距离煤层群协调开采模式下,由于煤层间的开采扰动影响,各煤层开采顶板结构特征不尽相同,因此各煤层开采支架工作阻力的计算方法也存在差异。为针对性地为各煤层开采支架额定工作阻力确定提供思路,综合应用理论分析、系统开发及现场实测方法,对各煤层开采支架工作阻力的计算方法进行了研究。主要成果有:①建立了煤层开采顶板砌体梁式、散体给定式及散体给定−砌体梁式平衡结构模型。砌体梁式平衡结构适用于未受开采扰动影响或受到的开采扰动影响较小的煤层开采;散体给定载荷平衡结构适用于煤层顶板岩层为单一岩层,且受到上部煤层开采影响的煤层开采;散体给定载荷−砌体梁式平衡结构适用于顶板岩层为多层岩层,且层间存在厚度较大,岩性较硬的岩层,同时受到上煤层开采影响岩层仍能保持连续性与完整性的煤层开采;②开发了适用于开滦集团“近距离煤层群开采覆岩破断及支架载荷评价系统”,提出了各煤层支架额定工作阻力的建议选择结果。通过各煤层开采支架压力实测,采用支架额定工作阻力经验选择结果后,各煤层开采支架载荷利用率普遍偏低,支架载荷富余量偏大。而采用各煤层支架额定工作阻力的建议选择结果后,各煤层开采支架载荷利用率明显提高。

极近距离煤层下层煤采场顶板结构与控制

为进一步发展顶板岩层控制技术,针对极近距离煤层开采时下层煤的顶板岩层结构特点,构建了"散体-块体"顶板结构模型。运用散体和块体理论,对极近距离煤层下层煤工作面下位直接顶岩层结构的稳定性进行了力学分析,揭示了下层煤开采时端面顶板冒落的机理。以下层煤顶板岩层结构和工作面支架载荷为研究对象,通过力学分析研究了工作面的支架载荷,得出了支架载荷的确定方法,在此基础上以大同矿区极近距离煤层为研究对象,通过现场实测进一步论证了该方法的客观性与实用性。

极近距离采空区下部煤层窄煤柱宽度的确定

采用数值模拟的方法,研究了极近距离煤层群下煤层工作面沿空掘巷留设不同宽度煤柱时巷道的塑性破坏、煤柱和实体煤侧垂直应力、巷道围岩变形情况。结果表明:随着煤柱宽度增加,煤柱中央的垂直应力呈现先增大、后减小趋势,其中5~7 m宽度煤柱中央的垂直应力相对较大,3~5 m宽度煤柱边缘垂直应力最小。随着煤柱宽度增加煤柱边缘垂直应力不断增大,在煤柱宽度达到7 m时最大,而实体煤侧的垂直应力相对变化不大。进一步的数值模拟研究表明,巷道的塑性破坏程度、围岩变形量在留设7~9 m煤柱时效果最佳。综合考虑得出了下煤层开采护巷窄煤柱的合理留设宽度为8 m。

极近距离煤层联合开采工作面矿压显现规律实测研究

为了掌握极近距离联合开采工作面矿压显现规律,实测了灵石煤矿极近距离9#煤与10#煤联合开采工作面的支架工作阻力,分析了进行联合开采回采工作面顶板的矿压显现规律。研究表明:进行联合开采的090105和100105回采工作面都具有明显的周期来压现象,工作面周期来压步距分别为13.4 m和10.6 m;下煤层工作面比上煤层工作面动压影响大,矿压显现更明显,下煤层工作面来压时间持续更短。为极近距离煤层联合开采矿压控制提供了重要依据。

极近距离煤层下煤层回采巷道内错布置合理错距的研究

通过理论计算和数值计算方法研究了某煤矿极近距离煤层上煤层回采后下煤层回采巷道内错式布置的合理错距,通过理论计算确定该矿下煤层回采巷道内错式布置的合理错距为大于6.31m;运用数值计算分析上煤层回采后下煤层顶板应力分布规律及下煤层回采巷道内错布置在不同位置时巷道的受力情况。确定了该矿下煤层回采巷道内错式布置的合理错距为大于等于6m。

近距离煤层同采巷道混合布置参数分析

为探讨近距离煤层同采时回采巷道的布置方式与参数,分析了近距离煤层回采巷道不同布置方式的优缺点及适用条件,根据泉店煤矿东翼11采区的地质赋存条件及矿井生产现状,确定其近距离煤层回采巷道采用混合布置方式。依据上煤层开采后采空区边缘与下煤层巷道之间的弹塑性分布区与应力梯度分布状况,以及巷道围岩表面变形量,分别确定下煤层上巷相对上煤层上巷向上平错20m,下煤层下巷相对上煤层下巷向上平错10m。在泉店煤矿东翼11采区首采面进行近距离煤层同采巷道混合布置的应用与实测,现场实测表明巷道变形量得到有效控制,说明其同采巷道布置合理。

极近距离煤层回采巷道布置方式研究

首先应用比值判别法和"三带"判别法确定煤层群采用下行开采,然后通过理论分析得出回采巷道应采用外错式布置并计算出相应外错距,借助数值模拟软件模拟了该种情况下巷道围岩应力分布特征、屈服破坏特征以及围岩移近量,最后提出了11#煤层回采巷道支护方式。

极近距离煤层上行开采相似材料模拟实验研究

采用相似材料模拟实验方法,对淮北矿业集团朔里煤矿极近距离煤层上行开采的可行性进行研究。研究表明:上覆3煤的开采对4煤未造成破坏;下伏5煤开采后形成的冒落带高度约7.7 m,4煤处于5煤开采后形成的裂缝带下位,在层间岩性、软硬岩互层结构和垮落矸石的联合作用下,4煤整体保持连续和完整,仅在5煤采空区边界上方小范围内出现纵向台阶下沉,在采取一定安全措施后不影响4煤开采,因此该矿上行开采4煤是可行的。

近距离煤层刀柱采空区下长壁采场顶板结构稳定性研究

近距离煤层的上部煤层采用刀柱采煤法回采后,下部煤层采用长壁采煤法进行回采。对于近距离煤层,随着煤层间距离的减小,上下煤层间开采的相互影响加大。通过对上部煤层残留煤柱破坏特征的数值分析,并对下部煤层工作面顶板稳定性的研究,得出了下部煤层回采工作面顶板结构的稳定性特征。

立井揭近距离多煤层瓦斯压力联合探测技术及应用

针对近距离多煤层提出了一种联合探测技术,该方法能够快速探清所有待揭煤层的赋存状况,并测出各个待揭煤层的瓦斯压力,不仅节约时间和成本,还能为揭煤过程制定安全措施及方案调整提供参考,保证了安全生产。最后利用该方法对吴家峁煤矿回风井的4#煤和5#煤进行联合前探测压,取得了良好的效果。

近距离煤层群下保护层开采卸压保护效果研究

为了防治石屏一矿近距离煤层群开采过程中存在的煤与瓦斯突出风险,运用FLAC3D数值模拟软件分析了11025下保护层开采对上覆C19主采煤层卸压保护效果。研究结果表明:平均厚度1.3 m的下保护层开采后,距离20.9 m的上覆煤层应力释放呈现很强的分区分带性,采场中部一定范围内的应力明显降低,靠近采场边缘应力增大,中心最大位移量约为440 mm。基于法向应力和膨胀变形率指标确定煤层倾向方向卸压角运输巷侧为δ1=60.4°,风巷侧为δ2=67.9°,走向方向两端卸压角δ3=δ4=58.7°。下保护层开采后,卸压范围内C19主采煤层透气性系数提高7倍,最高瓦斯抽采速率1.13 m3/min,瓦斯压力降为0,起到了良好的卸压保护效果。

近距离多煤层采动影响巷道围岩控制技术研究

为解决近距离多煤层采动影响巷道围岩控制难题,采用现场调研、工业性试验等方法,以变被动为主动控制的设计原则,采用高预紧力锚杆实现对顶板岩层的主动控制,同时采用预应力锚索及大尺寸托板构件提高护表面积,约束表层围岩变形。基于此,开发了近距离多煤层采动影响巷道围岩控制技术,实现了近距离多煤层采动影响巷道的有效控制。

近距离中厚煤层群工作面瓦斯抽采方案设计

山西某矿为高瓦斯矿井,首采区初期开采的4号煤层上邻近层为03和2号煤层采空区,下邻近层为5号和6号煤层,首采4101工作面采用"U+U"型巷道布置及通风方式,针对该工作面邻近层和开采层瓦斯浓度较高和巷道布置特点,对该工作面瓦斯抽采方案进行了合理设计,并进行了效果预期,瓦斯抽采后对保证工作面和矿井的安全生产具有重要意义。

极近距离煤层开采巷道支护技术研究

针对极近距离煤层巷道顶板破碎,支护困难的情况,以某矿实际条件为背景,确定下煤层巷道合理布置方式,依据层间距大小对巷道顶板进行分类,并对不同类型顶板给出合理支护参数,采用新的支护方案,保证了支护质量,降低了支护成本,为工作面安全生产奠定了基础。

极近距离煤层采空区下开采技术研究

本文针对极近距离煤层群采空区下煤层开采的难题,阐述了极近距离煤层研究现状,对其特点提出了采用应力改变率选取下煤层开采回采巷道合理位置的方法,并确定了不同条件下巷道的合理断面形状及合理支护方式。根据西曲矿的具体条件,建立了数值模拟模型,确定了合理的巷道位置为内错6m布置以及合理的巷道断面形状、支护方式。