The flux profile of a blowing sand cloud: a wind tunnel investigation

The flux profile of a blowing sand cloud, or the variation of blown sand flux with height, is the reflection of blown sand particles that move in different trajectories, and also the basis for checking drifting sand. Here we report the wind tunnel results of systematic tests of the flux profiles of different sized sands at different free-stream wind velocities. The results reveal that within the 60-cm near-surface layer, the decay of blown sand flux with height can be expressed by an exponential function: q_h=aexp(−h/b), where, q_h is the blown sand transport rate at height h, a and b are parameters that vary with wind velocity and sand size. The significance of coefficient a and b in the function is defined: a represents the transport rate in true creep and b implies the relative decay rate with height of the blown sand transport rate. The true creep fraction, the ratio of the sand transported on the surface (h=0) to the total transport varies widely, decreasing with both sand size and wind speed. The flux profiles are converted to straight lines by plotting sand transport rate, q_h, on a log-scale. The slope of the straight lines that represents the relative decay rate with height of sand transport rate decreases with an increase in free-stream wind velocity and sand grain size, implying that relatively more of the blown sand is transported to greater heights as grain size and wind speed increase. The average saltating height represented by the height where 50% of the cumulative flux percentage occurs increases with both wind speed and grain size, implying that saltation becomes more intense as grain size and/or wind velocity increase.     

应用定量颗粒荧光技术研究低渗致密油藏成藏特征——以鄂尔多斯盆地西缘长8段为例

鄂尔多斯盆地西缘地区经历了较为复杂的构造演化,油气成藏特征与盆地内部相比存在较大差异.利用流体包裹体观察、统计和定量颗粒荧光技术(QGF和QGF-E)开展了西缘南段长8油藏详细分析.结果表明:油气包裹体荧光显示本地原油成熟度不高,包裹体丰度GOI及定量荧光数值均不大,研究区整体含油显示级别和含油饱和度均低于湖盆内部,其...     

利用GPS数据分析四川“Y”型构造区地壳运动状态

四川地区地质构造复杂,地壳活动剧烈,为了深入揭示该区“Y”型构造区地壳1999年以来近20年的动态演化规律,基于1999—2017年7期GPS数据,解算各周期网格速度场、应变率场,研究地壳应变场演化过程。结果表明：①2008年以前的3期GPS速度场相对稳定,汶川地震后,速度场变化最大的龙门山断裂带由4.0—5.0 mm/a增至8.0—10.0 mm/a;②汶川震后,“Y”型构造区最大剪应变高值区出现在汶川以东,由2.0×10^-8/a增到22.0×10^-8/a;龙门山断裂带以SE或SEE向主压应变为主,变化速率约5.0×10^-8/a—12.0×10^-8/a,鲜水河断裂由震前NS向主拉应变转为震后EW向主压应变,安宁河断裂东侧由震前SE向主压应变6.0×10^-8/a减至震后的2.0×10^-8/a;面膨胀结果显示,由震前低密度梯度带瞬间变为平行于龙门山断裂带走向的高密度变化区,且存在以金川至都江堰、北川至青川为条带的2个正负交替过渡区;③汶川地震发生压应力释放后,该区SEE向压性特征又逐渐增强,且持续至2017年,释放了龙门山断裂带地壳内部SEE向压应力多年累积能量,但汶川地震对鲜水河断裂与安宁河断裂的整体运动状态则无明显触发作用。     

基于图形解算的玻璃幕墙支柱施工测量方法探讨

随着建筑物结构设计复杂程度的提高,研究新的施工放样方法,提供多样的施工途径,以应对复杂多变的建筑结构设计至关重要。提出基于图形解算的支柱施工测量方法,采用常规测量获取建筑物关键部位坐标,经过二元一次多项式趋势面拟合、B样条曲线拟合、基于特征的关键点解算等步骤完成施工放样,并以体育馆为例进行验证,其精度可满足施工要求。     

管道穿越采空区沉陷监测方法初探

长距离油气管道运行压力大,沿线地质、地理、生态环境复杂。由于成本控制、地理环境等因素,油气管道常常不可避免地铺设在矿山采空区上。针对油气管道穿越煤层采空区受地表沉陷灾害的威胁这一问题,对矿山采空区沉陷监测的几种方法进行了比较,分析了它们的优势及不足,对矿山沉陷监测方法的选择和保护油气管道的正常运营具有指导意义。     

断层活动协调比计算方法的改进及震例分析

根据断层活动协调比的概念,讨论了起算点对协调比计算结果的影响,提出了移动窗计算断层活动协调比的方法以及离散度评定指标.震例分析结果表明,丽江7.0级地震前丽江场地断层活动协调比数值变化范围较大,分布较离散;震后数值相对稳定,离散度较低.反映了在孕震阶段断层的应变积累以及由其引起的3分量运动相互协调性较差;震后断层处于自由活动状态,积累的应变能得到释放,3分量运动相互协调一致.目前丽江场地断层活动协调比数值离散度处于低值,断层应变积累处于较低水平.     

Effectiveness of a new organic polymer sand-fixing agent on sand fixation

Sand erosion due to wind is a serious problem in the relatively arid and semiarid areas. A new organic polymer sand-fixing agent (PVIN), polymerized by the monomer of vinyl acetate, initiator and cross-linking agent, is introduced in this study. To understand the effect of PVIN on sand fixation, the strength test, water-retaining test and wind erosion test were performed. The results indicated that the presence of PVIN could improve the structural strength, water retaining and anti-wind erosion ability. When the sand-fixing agent was applied on the sand surface, the crust in surface layer was produced. The structural strength variations determined by micropenetrometer indicated that the specimens treated with concentrations of 1, 3, 5, 10, and 20% PVIN have produced the crusts with thickness being approximately 1, 2, 4–5, 5, and 5–6 mm and the strength being around 1, 4.5, 18, 26 and 41, respectively. This crust has a good water-absorption, water-retaining and anti-evaporation properties. It can also improve the anti-wind erosion ability, and also prevent the loose sand surface from forming a sand dune in the wind erosion conditions. Additionally, this sand-fixing agent has a low cost, it is easier to produce and apply and also produces no additional pollution. Therefore, this can be considered as an ideal soil-fixing agents to control sand erosion in the relatively arid and semiarid areas.     

Mineralogy and geochemistry of gold-bearing arsenian pyrite from the Shuiyindong Carlin-type gold deposit, Guizhou, China: implications for gold depositional processes

Arsenian pyrite in the Shuiyindong Carlin-type gold deposit in Guizhou, China, is the major host for gold with 300 to 4,000 ppm Au and 0.65 to 14.1 wt.% As. Electron miroprobe data show a negative correlation of As and S in arsenian pyrite, which is consistent with the substitution of As for S in the pyrite structure. The relatively homogeneous distribution of gold in arsenian pyrite and a positive correlation of As and Au, with Au/As ratios below the solubility limit of gold in arsenian pyrite, suggest that invisible gold is likely present as Au¹⁺ in a structurally bound Au complex in arsenian pyrite. Geochemical modeling using the laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis of fluid inclusions for the major ore forming stage shows that the dominant Au species were Au(HS)₂⁻ (77%) and AuHS_(aq)⁰ (23%). Gold-hydroxyl and Gold-chloride complexes were negligible. The ore fluid was undersaturated with respect to native Au, with a saturation index of −3.8. The predominant As species was H₃AsO₃⁰ _(aq). Pyrite in the Shuiyindong deposit shows chemical zonation with rims richer in As and Au than cores, reflecting the chemical evolution of the ore-bearing fluids. The early ore fluids had relatively high activities of As and Au, to deposit unzoned and zoned arsenian pyrite that host most gold in the deposit. The ore fluids then became depleted in Au and As and formed As-poor pyrite overgrowth rims on gold-bearing arsenian pyrite. Arsenopyrite overgrowth aggregates on arsenian pyrite indicate a late fluid with relatively high activity of As. The lack of evidence of boiling and the low iron content of fluid inclusions in quartz, suggest that iron in arsenian pyrite was most likely derived from dissolution of ferroan minerals in the host rocks, with sulfidation of the dissolved iron by H₂S-rich ore fluids being the most important mechanism of gold deposition in the Shuiyindong Carlin-type deposit.     

新城金矿主成矿期构造应力场对矿体倾伏、侧伏、富矿柱的控制及成矿深度的估算

成矿构造应力场研究是控矿构造研究、认识矿体空间展布形态、位置、预测及布置探矿设计的基础。依据弹性力学和莫尔库仑剪切破裂理论,推导出形成共轭及在剪切构造带内形成羽列、雁列等构造应力场的产状和形成羽列、雁列主应力大小的数学解析表达式,进而应用计算机对新城金矿床主矿体进行了测算。结果显示：该矿主容矿构造是在NNW向缓倾拉张主应力、NE向陡倾主压应力、焦家构造带平面呈右行扭动下形成的。NWW向中间主应力控制新城Ⅰ号主矿体在NW向倾斜平面上延深的长轴方向。该轴在水平面上投影的倾伏向为281°,与水平面的夹角倾伏角为26°,在N40°E纵投影面上向SW侧伏,侧伏角为45°,富矿柱产状亦与中间主应力轴产状一致。在已获取容矿构造产状基础上,据相关岩石力学性质测试成果,分析并建立了主容矿羽列与控制剪切构造带两者的力学关系和剪切破裂方程式。联立解出成矿应力场的最大和最小主应力的量值,再由陡倾主应力大小估算出该矿头部的成矿深度在2 750 m左右。     

藻源性湖泛发生过程CDOM变化对水色的影响

利用Y-型沉积物再悬浮发生装置模拟湖泛发生过程,分析其中有色可溶性有机物(CDOM)的变化特征及其对水色的影响.结果表明,藻类死亡过程消耗大量的氧气,水中溶解氧在短时间内消失殆尽,形成厌氧环境;并同时分解产生大量CDOM,使得水中CDOM显著增多.前期阶段,CDOM浓度随时间一直升高,第6 d时CDOM浓度达到峰值,CDOM在443 nm处的吸收系数a_g(443)为4.48 m^-1.水体黑度值(FeS浓度)呈先增大后减小的趋势,最大值0.35mmol/L同样出现在第6 d,整个过程中,CDOM浓度和黑度值变化趋势一致,a_g(443)与水体黑度呈显著正相关.利用Hydrolight和CIE颜色匹配函数模拟不同梯度的CDOM对水色的影响,发现随a_g(443)增大,水体颜色也逐渐由绿色转为棕色,整体向长波方向移动,水色逐渐变暗.因此,可以认为CDOM浓度变化是引起湖泛水体发黑的重要原因之一,可作为定量监测湖泛强度的指示性参数.