Overlying strata movement rules and safety mining technology for the shallow depth seam proximity beneath a room mining goaf

Aiming at the shallow depth seam proximity beneath a room mining goaf, due to that the shallow depth seam is exploited using the longwall mining and overlain by thin bedrock and thick loose sands, many accidents are likely to occur, including roof structure instability, roof step subsidence, damages of shield supports, and the face bumps triggered by the large area roof weighting, resulting in serious threats to the safety of underground miners and equipment. This paper analyses the overlying strata movement rules for the shallow seams using the physical simulation, the 3DEC numerical simulation and the field measurements. The results show that, in shallow seam mining, the overburden movement forms caved zone and fractured zone, the cracks develop continuously and reach the surface with the face advancing, and the development of surface cracks generally goes through four stages. With the application of loose blasting of residual pillars, reasonable mining height, and roof support and management, the safe, efficient and high recovery rate mining has been achieved in the shallow depth seam proximity beneath a room mining goaf.

Hydrogeochemistry of karst underground waters at shallow depth in Guiyang City, Guizhou Province

The aim of this study is to shed light on the hydrogeochemical characteristics of karst underground waters at shallow depth in Guiyang City, Guizhou Province with an emphasis on the geochemistry of major elements. Guiyang City bears abundant underground waters and it is also an important representative of the karst areas throughout the world. Ca+{2+} and Mg+{2+} are the dominant cations, accounting for 81%-{99.7%} of the total, and HCO+--3 and SO+{2-}-4 are the dominant anions. Weathering of limestones and dolostones is the most important factor controlling the hydrogeochemistry of underground waters, and weathering of sulfate and evaporite rocks is less important. Moreover, the precipitation and human activities also have a definite influence on the hydrogeochemistry of underground waters in the region studied.

Design of Foundations Built on a Shallow Depth (Less than 4 m) of Egyptian Macro-Porous Collapsible Soils

It is nowadays well reported that collapsible soils spread in many countries, including United States, Russia, China, South America (e.g. Brazil), South and North Africa (e.g. Egypt, Algeria), Middle East (e.g. Saudi Arabia) and many countries in Eastern Europe. In general, collapsible soils are located in arid and semi-arid regions around the world. This special type of soil is characterized by abrupt reduction in strength, excessive and sudden settlement when it becomes wet leading to failure of the structure. Construction on such a kind of soil is one of the prominent problems in geotechnical engineering. The main objectives of this study are reporting geological and geotechnical zonation maps for potentially collapsible soils in inhabited areas in Egypt. Furthermore, a design technique for foundations built on a shallow depth of Egyptian macro-porous collapsible soils (less than 4 m) is developed. The design method includes a design chart for soil collapse field classification in terms of the most governing parameters, a method for foundation settlement estimation based on a correlation between the wetting-induced collapse strain and the applied pressure, and a design practice to guide practicing engineers to select the appropriate foundation system to construct on such soil with a great degree of confidence and safety.

Correction for Depth Biases to Shallow Water Multibeam Bathymetric Data

Vertical errors often present in multibeam swath bathymetric data. They are mainly sourced by sound refraction, internal wave disturbance, imperfect tide correction, transducer mounting, long period heave, static draft change, dynamic squat and dynamic motion residuals, etc. Although they can be partly removed or reduced by specific algorithms, the synthesized depth biases are unavoidable and sometimes have an important influence on high precise utilization of the final bathymetric data. In order to. confidently identify the decimeter-level changes in seabed morphology by MBES, we must remove or weaken depth biases and improve the precision of multibeam bathymetry further. The fixed-interval profiles that are perpendicular to the vessel track are generated to adjust depth biases between swaths. We present a kind of postprocessing method to minimize the depth biases by the histogram of cumulative depth biases. The datum line in each profile can be obtained by the maximum value of histogram. The corrections of depth biases can be calculated according to the datum line. And then the quality of final bathymetry can be improved by the corrections. The method is verified by a field test.

深、浅部煤层气地质条件差异性及其形成机制

深部煤层气资源丰富、开发前景广阔,但对其与浅部煤层气地质条件的内在联系研究尚不够深入。从煤层形成演化角度出发,以鄂尔多斯盆地上古生界煤层为例,总结了煤层深埋深藏型、深埋浅藏型及浅埋浅藏型3种埋深演化模式。系统分析了深部和浅部煤层在温压条件与含气性、地应力与渗透率特征、变质程度与含水性等方面的差异性及其形成机制。研究指出,受埋深与演化过程影响,深部和浅部煤储层温度最多相差100℃以上,储层压力最大相差40 MPa左右,导致由浅部向深部,气体赋存状态以吸附气为主转变为吸附气与游离气共存,地应力场由水平应力主导转化为垂向应力主导,煤储层孔隙率、渗透率及含水性逐渐降低。明确了深部煤层气的典型特点,即:在高温高压条件下,以吸附态和游离态共存于一定深度以下煤储层中的甲烷气体,该类煤储层在垂向应力为主导的作用下,孔裂隙空间极度压缩,含水极少且矿化度极高,内生微裂隙为主要渗流通道。基于含气性临界深度和地应力场转换深度的不一致性,指出浅部向深部煤层演化过程中存在过渡区,该区内呈现出非典型深部煤层气的特点,或深部煤层气和浅部煤层气地质条件共存的情况,在勘探开发过程中,应具体分析,制定针对性开发方案,以实现浅部与深部煤层气的高效协同开发。

浅埋深中厚煤层预掘回撤通道支护技术研究与应用

为进一步提高综采工作面末采回撤速度、确保设备回撤空间,采用理论计算、现场试验相结合的方法对浅埋深中厚煤层预掘回撤通道支护技术进行初步研究,建立了工作面残余煤柱承载力学模型,理论分析得知残余煤柱宽度对煤柱承载性能的时空演化规律具有重要影响,末采期间残余窄煤柱出现区域性脆性破坏失稳状态是导致超前采动应力、顶板岩层断裂线前移的主要原因。现场试验末采段残余煤柱宽度约5 m时,整条窄煤柱在多重载荷作用下发生屈服,进而呈现大面积失稳破碎状态,巷内支护体承载受力急剧增加,锚索最大受力约为225 kN,最大顶底板移近量出现在通道中部靠工作面侧,约为100 mm,结果表明,采用高预应力强力锚杆(索)联合支护结构配合垛式支架外部支撑,可有效控制末采期间预掘回撤通道顶底板之间的闭合位移,为类似条件下预掘回撤通道支护提供工程借鉴。

浅海环境中用于目标深度属性判别的线谱起伏特征量分析

浅海环境中目标辐射线谱的起伏特征可用于水面、水下目标深度属性判别.已有研究未给出表征水面、水下线谱起伏差异的物理量性质,导致利用不同物理量进行目标深度属性判别时性能不佳.针对这一问题,本文从声源深度起伏所导致的线谱起伏出发,采用微分方法与统计方法对线谱起伏规律进行分析,研究了线谱起伏产生的物理机理,得到了适合用于水面、水下目标深度属性判别的物理量.首先,分别推导了复声压实部、声功率与声压幅值关于声源深度的导数关系式,得到了以上三种物理量在声源深度起伏时的起伏大小;其次,利用仿真实验数据从接收深度、声源水平距离、线谱频率等层面对理论推导进行验证,并对线谱的归一化起伏特征进行了分析.最后,利用海试数据验证了相关结论.结果表明,当声源的深度起伏时,水面、水下线谱的起伏差异源自各阶模态的相互作用.声源频率、声源水平距离、接收深度三种因素决定了模态间相互作用的性质.声压幅值适用于构建目标深度属性判别特征量,可用于表征低频线谱的强度起伏差异.数值仿真和海试数据处理结果表明,相较于声压实部和声功率,利用声压幅值构建的归一化水面、水下目标深度属性判别特征量具有更优性能.

麻地梁煤矿首采综放面收作期间防灭火技术研究

麻地梁煤矿507首采面是采用放顶方法开采埋藏浅特厚的长焰煤,漏风严重,丢煤多,尤其在工作面收作期间未进行放顶,采空区遗煤量更大。另外,工作面未采阶段推进速度慢,遗煤氧化时间长,极易引起采空区煤自然发火。针对以上情况,采取注氮降氧、高位钻孔注浆和注高固水材料覆盖隔氧、堵漏控风等的综合防灭火措施,保证了该工作面支架的安全撤出,为类似回采条件的工作面收作期间的防灭火提供参考。

超浅埋小净距隧道洞口段安全评估及钢栈桥工艺

针对隧道出口段存在超浅埋、小净距与下穿既有公路的特殊性,为了确保上覆既有公路正常通车下隧道出口段安全施工,研发了在既有公路路面上钢栈桥架越隧道拱顶的新工艺及钢栈桥设计参数,首次提出了路面钢栈桥与拱顶保护壳复合式立体式隧道洞口段掘进安全防护体系.采用MidasGTSNX软件,对钢栈桥设置的合理性和有效性进行了仿真模拟,结果显示,路面存在车辆荷载前提下,钢栈桥的设置能有效减小围岩塑性区的分布面积,显著降低拱顶沉降,保持围岩稳定.实践表明:在既有公路路面上设置钢栈桥,能保证既有公路正常通车条件下的超浅埋与小净距下穿隧道的安全掘进,本研究结果对类似隧道工程洞口段安全施工有重要的借鉴意义.

浅层大位移井表层钻井的关键技术与应用

采用海水进行表层钻进已成为海上常规井、定向井常规技术,在大位移井中也通常采用海水深钻技术实现表层安全、高效钻进。对于浅层大位移井表层采用海水钻井技术尚未成熟,恩平油田浅层大位移井表层钻井面临地层松软、隔水导管窜漏、井眼轨迹难控制、井眼清洁效果不佳、易形成键槽、滑动钻进托压、下套管摩阻大、固井水泥返高把握难度大等问题。针对这些问题,通过井身结构、定向钻具组合、钻井参数、钻井液作业措施、顶驱下套管技术、固井施工方案等优选与优化,形成一套适用于恩平油田浅层大位移井表层海水钻井配套技术,对于其他海上油田的浅层大位移井表层钻井有借鉴和指导意义。

浅埋深复杂条件巷道围岩变形规律及稳定性分析

浅埋深条件下巷道掘进矿压显现规律复杂,加之在风氧化带、季节性河流和公路下伏巷道掘进,巷道围岩稳定性控制更为困难。为较好地掌握浅埋深复杂条件巷道掘进围岩变形破坏规律,采用普氏平衡拱理论和数值模拟对巷道掘进后的围岩变形破坏规律进行了分析研究,研究结果表明:巷道顶底部为卸压区,顶部影响范围小于30m,风氧化带、季节性河流和公路下伏巷道掘进不对地面产生影响,可满足巷道掘进施工的安全性。研究成果可为类似条件巷道合理布置提供依据。

浅海地震采集缆—源空间组合对激发子波特性的影响分析

地震资料分辨率低是当前渤海油田深层地震勘探面临的突出问题,而改善该问题首先须在地震采集尤其是震源设计方面寻求突破,但鲜有针对渤海浅水条件下的拖缆与震源空间组合研究的报道。为此,首先分析了渤海浅水条件下气枪脉冲的传播特征,确定了影响气枪脉冲传播的主要因素;再基于非理想气体条件气枪子波模型对浅水条件下单枪子波进行模拟,研究了考虑缆鬼波时子波及其频谱特征,提出采用考虑缆鬼波的子波对震源性能进行评价的方法;然后以渤海油田渤中地区实际地理和地质条件为基础,设计了不同缆—源沉放深度组合、震源平面展布的模拟试验,系统分析了渤海浅水条件下拖缆、震源空间组合对子波及其频谱的影响规律;最后将文中总结的规律认识和震源设计技术应用于渤中二次数据采集,并对比该区新、老三维拖缆单炮数据,验证了所提方法的正确性,对渤海浅水区气枪震源的优化设计及评价具有指导意义。

某压缩空气储能电站浅埋盐穴稳定性研究

国内许多盐穴难以满足压缩空气储能电站的改造要求,新建盐穴成为未来压缩空气储能电站储气库的重点目标。以安徽省某拟开采浅埋盐矿作为实例,建立水溶开采后盐腔计算模型。基于该矿区具有浅埋深与大倾角的地质特点,分析盐层倾角和埋深对盐腔变形和体积收缩的影响规律。研究结果表明:盐层倾角为20°时,盐腔的稳定性较差,矿区拟建盐腔埋深达到500 m后,腔体蠕变5 a后体积收缩超过安全限值。

Structure and deformation measurements of shallow overburden during top coal caving longwall mining

Mining induced pressures are strong and overburden failure areas are large in top coal caving longwall mining, which constrains high production and safety mining. By employing the combination of the full view borehole photography technique and the seismic CT scanner technique, the deformation and failure of overlying strata of fully mechanized caving face in shallow coal seam were studied and the failure development of overburden was determined. Results show that the full view borehole photography can reveal the characteristics of strata, and the seismic CT scanner can reflect the characteristics of strata between the boreholes. The combined measurement technique can effectively determine the height of fractured and caved zones. The top end of the caved zone in Yangwangou coal mine employing the top coal caving longwall mining was at the depth of 171 m and fractured zone was at the depth of 106-110 m. The results provide a theoretic foundation for controlling the overburden strata in the shallow buried top coal caving panel.

A THIRD GENERATION SHALLOW WATER WAVE NUMERICAL MODEL-YE-WAM

This paper pnesents a third gneration shallow Whter disode spedtal wave nbotal medeIYE-WAM based on the spedtal action balance equation. The mode accounts for all edevan effectsof currents on waves, incuding tmpotally and spatialy varying depth and current inded refraction,sttalning and fequency shift and also explidtly takeS into aanunt all source terms, speclally adePth-limited breaking dheipation. In addition, an energy forcing scheme is propond and applied to themode’s open boundaries to areUn for the propagution of sedIs into the study spstem The upwinddiffeIenng scheme and a standard hybrid diffdrencing scheme for the propagaion terrn and a simpleEuler method for the source teme are employed.

Stability characteristics of shallow landslide triggered by rainfall

Rainfall induced shallow landslides are known to be extremely dangerous since the sliding mass can propagate quickly and travel far from the source. Although the sliding mechanism in sloping ground is simple to understand, the problem may be complicated by unsaturated transient water flow. The flow behavior of rainwater in unsaturated sloping ground and the consequent factor of safety must be clearly understood to assess slope stability under rainfall conditions. A series of laboratory experiments was conducted to examine the critical hydrological states so that assessment of slope stability under rainfall condition can be performed. Based on the test results, a unique relationship between critical hydrological states, rainfall intensity, and soil properties was formulated. Sequential stability analysis provided insights into the stability of slopes subjected to variations in soil properties, slope angles and rainfall intensities, and the consequent variation in the depth of the failure plane, vital in landslide risk assessment, was determined through this analysis.The variation of rainfall intensity was found to strongly affect the depth of the failure plane in cohesionless sloping ground. Furthermore, the influence of rainfall intensity on the depth of the failure plane may be alleviated by a small magnitude of cohesive strength. The results of this study will reinforce knowledge of landslide behavior and help to improve mitigation measures in susceptible areas.

Some evidences for earthquake occurrence in the shallow crust in some areas of North China and Southwest China

The parameters of hypocentral location are important fundamental data for the study of seismology and the earth interior physics; among them, the focal depth is a very important one but can hardly be measured with higher precision. With the increase of seismic stations in number, the heightening of observation quality and the improvement of determination method, such a situation has been changed much. In this paper, the results of hypocentral location and re-location by 7 small-aperture digital seismic station networks at Tangshan, Zhangbei and Huailai of Hebei Province, Datong of Shanxi Province and Jianchuan, Luquan and Yao'an of Yunnan Province are used. Using these results together with those of focal depth inversion by far-field data of some individual large shocks in corresponding areas and those re-determined by the Linfen telemetered seismic network of Shanxi Province, a comparison with the results of focal depth determination in the past earthquake catalogues is made. It is found out that the focal depths determined by the small-aperture seismic networks are basically distributed in the range from the earth surface to ten-odd kilometers underground. In contrast, the focal depths determined in the past are mostly distributed at the depth range from the earth surface to 30 km underground. Besides, there is a difference of 50% to 100% between the average values of the two cases, which is quite an obvious one. From the result of analysis, it is considered that the results determined by the small-aperture seismic networks may be closer to the reality of focal depths distribution. That is to say, earthquakes in the above-mentioned areas should be distributed in the shallow part of the crust. The causes that lead to the above situation are discussed preliminarily, and some suggestions and measures for improving the precision of focal depth determination are put forward.

Transformation of Wave Energy Spectrum in Shallow Water

Combined with irregular wave-maker, the growing process of Wave Energy Spectrum in shallow water can be studied in wind wave channel on different water depth conditions, and its transformation characteristics and rules can be obtained.

Statistical Analysis on Depth Distribution Model of Earthquake Hypocenters

In order to improve reliability of probabilistic seismic hazard analysis, shallow earthquake (depth <70 km) data, recorded with orientation precision grades 1 and 2 by modern instrument and containing depth information after 1970, are selected as statistical samples, meanwhile, North China seismic region, Central China seismic region, South China seismic region, Xinjiang seismic region and Qinghai-Xizang Plateau seismic region are chosen as statistical units to study the depth distribution characteristics of shallow earthquakes. Considering the differences of depth distribution characteristics of earthquakes with different magnitudes, the following magnitude intervals are adopted to analyze earthquakes with different magnitude scales, respectively: M S=2.0～2.9, M S=3.0～3.9, M S=4.0～4.9, M S=5.0～5.9 and M S=6.0～6.9. The results show that hypocenter depths are normally distributed by and large around the mean depth of the corresponding seismic region. The probabilistic distribution curves of earthquake depth in West China are wider than those in East China. The probabilistic distribution deviation, σ, of West China is greater than those of East China, that is, earthquakes in West China have a wider range in terms of depth. There is also a tendency that the absolute value of mean hypocenter depth increases with the magnitude by and large.

浅埋不等跨隧道围岩压力计算方法与影响规律研究

为研究不等跨隧道围岩压力,构建不等跨隧道破坏模式,基于极限上限法推导不等跨隧道围岩压力,并进行验证对比;分析不等跨隧道围岩压力分布特征,最后就相关影响因素做参数分析。结果表明:两隧道内侧围岩压力比外侧大;小跨洞竖向围岩压力大于大跨洞相应侧的值;两洞不等跨时的围岩压力比等跨时的大。随着相对跨度增大,两隧道之间的围岩压力差异增大,且大跨洞将承受更多的围岩压力。在浅埋条件下,埋深对围岩压力的影响较大。大跨隧道围岩压力随着小跨隧道埋深增大而逐渐减小;小跨隧道围岩压力则随着埋深增大而增大。竖向平均围岩压力随着两洞净距的增大呈现先增大后减小。围岩压力随GSI、m_(i)、σ_(ci)值(Hoek-Brown准则相关参数)的增大而减小。不等跨隧道应结合其相对跨度大小、两洞埋深等条件,根据所受围岩压力不同而采取不对称支护。