鄂尔多斯盆地西部侏罗系煤储层特征及有利区预测

在系统采集样品的基础上,通过对煤样的煤质、煤岩显微组分、煤相、煤岩显微裂隙分析及孔隙度和压汞孔隙结构测试,研究了鄂尔多斯盆地西部的煤层气储层物性特征,并采用多层次模糊数学评价方法,预测了煤层气资源分布的有利区。结果表明,该区侏罗系煤储层具有较强的生气潜力和储气能力,孔隙系统具双峰分布特点,以微孔-小孔和大孔为主,其中二道岭-汝箕沟地区具备"小而肥"的资源优势,是该区煤层气勘探开发的最有利目标区。      

瑞利阻尼对砂土场地非线性地震响应的影响分析

在地震荷载作用下,自由场地会产生土体侧向变形和地表响应放大现象。由于土体的高度非线性,计算自由场地地震响应时,不同的阻尼比及剪切模量取值是造成其计算结果与试验结果相差较大的原因之一。目前动力计算常采用瑞利阻尼方法,其系数取值会在一定程度上影响计算结果。选用两模态简化瑞利阻尼系数计算方法,分析土体阻尼比及控制频率的取值对计算结果的影响,对比离心机模型试验,利用开源有限元平台OpenSees,采用适合于土体动力分析的多屈服面本构模型(PDMY),建立剪切梁模型模拟三维自由场地,并分析瑞利阻尼参数对自由场地地震响应和侧向变形计算结果的影响。结果表明,针对相对密度为60%的Nevada干砂,阻尼比为4%、控制频率比为5时,场地响应计算结果与试验结果较为符合。综合分析显示场地非线性响应时域计算时,应特别注意选用的瑞利阻尼参数值。     

Present-Day Crustal Vertical Motion Around the Ordos Block Constrained by Precise Leveling and GPS Data

Precise leveling data observed in the period of 1970–2014 around the Ordos block were collected and processed to estimate present-day crustal vertical movement. Vertical rates of 6 GPS sites were employed as a priori constraints to define the reference frame. The velocity field shows that the interior of the Ordos block moves upward at a rate of 3 mm/a as a stable block. With respect to the central Ordos, the grabens and rifts around the Ordos block are undergoing subsidence, while the northeastern and southwestern Ordos uplift at the average rates of 2 and 1 mm/a, respectively. To the southeastern margin of the Ordos block, the Weihe and southern Shanxi grabens are subsiding at the rates of 4–6 mm/a. The subsidence of the Shanxi graben indicates that the graben is experiencing extensional movement on a long timescale. To the northwestern margin of the Ordos block, the Hetao and Yinchuan rifts are subsiding at the rates of 2–3 mm/a. A 2-D buried faulting model is used to infer the normal or reverse dip-slip rates. Our solution shows that most of the normal slip rates along the faults in the grabens and rifts are ~2 mm/a.     

京西盆岭构造区积累库仑破裂应力变化对强震的影响

Since 231 B. C.,a total of 15 M6.0 - 7.5 earthquakes have been recorded in the west Beijing basin-range tectonic region( 38.3°- 41.5° E,112°- 116.2° N),a region mainly under the action of tensional normal faulting. In this paper,we calculate the Coulomb stress change of each earthquake and the cumulative Coulomb stress change,and on this basis we analyze the stress triggering of strong earthquakes. The research shows that there are 10 of 14 earthquakes that occurred in the trigger zones,in which the Coulomb stress change is positive,and the trigger rate is 71%. The positive areas of cumulative Coulomb stress change caused by these 15 earthquakes are: middle of northern Liulengshan fault,Northern Huaizhuo basin fault,Xinbaoan-Shacheng fault,Sangganhe fault and Southern Yuxian basin fault. This necessarily increases the seismic risk of these faults and can be used as a reference for future seismic risk analysis in this area.     

Tomographic inversion of near-surface <Emphasis Type="Italic">Q</Emphasis> factor by combining surface and cross-hole seismic surveys

The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer. We present a new geometry that can be used to acquire field data by combining surface and cross-hole surveys to decrease the effect of geophone coupling on Q estimation. In this study, we drilled number of receiver holes around the source hole, each hole has different depth and each geophone is placed geophones into the bottom of each receiver hole to avoid the effect of geophone coupling with the borehole wall on Q estimation in conventional cross-hole seismic surveys. We also propose a novel tomographic inversion of the Q factor without the effect of the source signature, and examine its stability and reliability using synthetic data. We estimate the Q factors of the near-surface layer in two different frequency bands using field data acquired in the Dagang Oilfield. The results show that seismic absorption in the near-surface layer is much greater than that in the subsurface strata. Thus, it is of critical practical importance to enhance the seismic solution by compensating for near-surface absorption. In addition, we derive different Q factors from two frequency bands, which can be treated, to some extent, as evidence of a frequency-dependent Q.     

Three-dimensional admittance analysis of lithospheric elastic thickness over the Louisville Ridge

Using bathymetry and altimetric gravity anomalies, a 1° 9 1° lithospheric effective elastic thickness(Te) model over the Louisville Ridge and its adjacent regions is calculated using the moving window admittance technique. For comparison, three bathymetry models are used: general bathymetric charts of the oceans, SIO V15.1,and BAT_VGG. The results show that BAT_VGG is more suitable for calculating T e than the other two models. T e along the Louisville Ridge was re-evaluated. The southeast of the ridge has a medium Te of 10–20 km, while Te increases dramatically seaward of the Tonga-Kermadec trench as a result of the collision of the Pacific and IndoAustralian plates.     

基于耦合欧拉-拉格朗日法充灌袋挤淤过程的有限元研究

在含水率大、承载能力低的软土地基上,利用充灌砂袋进行挤淤置换的方法工艺简单、施工方便、处理效果明显,已经广泛地应用在建造围埝和修筑道路中。充灌袋下沉到一定深度后,其重量与地基承载力相等,从而达到极限平衡状态。充灌袋挤淤所达到的深度与其高度存在一定的对应关系,在工程中确定此关系十分重要。通过3组不同宽度的挤淤模型试验,得到充灌袋下沉量与充灌袋高度的曲线关系、淤泥的位移特性及隆起量。利用ABAQUS中耦合欧拉-拉格朗日法（CEL法）,将充灌袋和淤泥分别用拉格朗日体和欧拉体描述,模拟充灌袋挤淤下沉的过程,将模拟得到的充灌袋下沉深度和高度的关系、淤泥的位移特点与试验结果以及理论公式进行对比。结果表明,CEL法模拟得到的结果与试验结果、理论解具有很好的吻合性,说明利用CEL法可以较好地模拟充灌袋的挤淤问题。     

Natural Radioactivity at the Sin Quyen Iron-Oxide-Copper-Gold Deposit in North Vietnam

The field radiometric and laboratory measurements were performed at the Sin Quyen copper deposit in North Vietnam. The field gamma-ray spectrometry indicated the concentration of uranium ranging from 5.5 to 87 ppm, thorium from 5.6 to 33.2 ppm, and potassium from 0.3 to 4.7%. The measured dose rates ranged from 115 to 582 nGy/h, the highest doses being at the copper ore. Concentrations in the solid samples were in the range of 20–1700 Bq/kg for uranium, 20–92.7 Bq/kg for thorium, and 7–1345 Bq/kg for potassium. The calculated doses were from 22 to 896 nGy/h; both measured and calculated dose rates are mostly related to uranium. Concentrations of radium in water samples were below 0.17 Bq/L. Uranium in water samples was significantly higher than the hydrogeological background; the maximum of 13 Bq/L was at the waste zone pool, but neither radium nor uranium were present in tap water. Radon concentration in the dwelling air was from 42 to 278 Bq/m³ for ²²²Rn and from 8 to 193 Bq/m³ for ²²⁰Rn. The estimated committed dose rates were principally related to ²²²Rn concentration and ranged from 1.1 to 8.1 mSv/y.     

开采上保护层对巨厚砾岩诱发冲击矿压的减冲机制分析

为研究开采上保护层对巨厚砾岩断裂诱发冲击的防治作用,根据跃进煤矿25采区的地质条件和采掘条件,将25110工作面下巷作为研究对象,从理论上分析了动静载叠加诱发冲击矿压的机制以及开采上保护层后的防冲原理,数值模拟研究了未开采上保护时和开采上保护层后在同等强度的动载扰动应力的影响下巷道底板的位移、速度、应力以及塑性区的变化规律,进行相似模拟试验研究了人工震源的作用下未开采上保护时和开采上保护层后巷道底板的加速度和动应力响应规律。结果表明,上保护层开采后能够有效地释放围岩内部的高应力,且采空区顶板自然垮落,形成的软弱松散岩层结构,能够更好地起到对动载扰动应力波的衰减作用,从而降低了冲击矿压发生的可能,一定程度上能够较好地防治冲击矿压。研究成果对巨厚砾岩下冲击矿压的防治具有一定指导意义。