Fracture energy release and size effect in borehole breakout

The paper presents a simple approximate analytical solution of the remote stresses that cause the collapse of a borehole or other circular cylindrical cavity in an infinite elastic space. Regions of parallel equidistant splitting cracks are assumed to form on the sides of the cavity. Their boundary is assumed to be an ellipse of a growing horizontal axis, the other axis remaining equal to the borehole diameter. The slabs of rock between the splitting cracks are assumed to buckle as slender columns, and their post-critical stress is considered as the residual stress in the cracked rock. The buckling of these slab columns is assumed to be resisted not only by their elastic bending stiffness but also shear stresses produced on rough crack faces by relative shear displacements. The energy release from the infinite medium caused by the growth of the elliptical cracking region is evaluated according to Eschelby's theorem. This release is set equal to the energy dissipated by the formation of all the splitting cracks, which is calculated under the assumption of constant fracture energy. This yields the collapse stress as a function of the elastic moduli, fracture energy, ratio of the remote principal stresses, crack shear resistance characteristic and borehole diameter. The collapse stress as a function of crack spacing is found to have a minimum, and the correct crack spacing is determined from this minimum. For small enough diameters, the crack spacing increases as the (4/5)-power of the borehole diameter, while for large enough diameters a constant spacing is approached. In contrast to plastic solutions, the breakout stress exhibits a size effect, such that for small enough diameters the breakout stress decreases as the (? 2/5)-power of the borehole diameter, while for large enough diameters a constant limiting value is approached. Finally, some numerical estimates are given and the validity of various simplifying assumptions made is discussed.     

现代黄河三角洲粉土触变性研究及其应用

通过对现代黄河三角洲砂质粉土和粉质粘土触变性的对比试验研究，阐述了黄河口粉土的触变性。试验结果对解释粉土的失稳机制、解决工程地基的稳定性和防止地质灾害等具有重要的现实意义。     

草簇状石墨烯片限域Pd纳米粒子及其催化应用(英文)

通过氨基离子液体改性石墨烯,并将其固载于堇青石表面,作为负载型Pd催化剂的载体.所制备的Pd催化剂经加氢老化后,表面石墨烯呈草簇状结构,将Pd纳米粒子限域于片层内,有效防止了Pd的流失和团聚.在重要的工业反应对羧基苯甲醛(4-CBA)加氢中,此结构催化剂与传统的钯碳催化剂相比,表现出很好的稳定性     

云南武定迤腊厂铜矿含矿石英脉40 Ar-39Ar年龄及其意义

对武定迤腊厂铜矿成矿期石英进行了40Ar-39Ar同位素年龄测定,得到马鞍形年龄谱,坪年龄为(784.25±0.95)Ma,等时线年龄为(783.93±8.59)Ma.地质特征研究表明该矿床后期改造作用明显,并非同生沉积或成岩作用早期成矿,而与晋宁期Rodina大陆裂解有关.武定迤腊厂铜矿的形成可能是在Rodinia大陆裂解时,从深部带来大量成矿物质,改造成岩时期初始的矿化,形成矿床的叠加富集和最终定位,晋宁-澄江期是该矿床的主成矿期.     

东川桃园式铜矿Ar-Ar同位素年龄及意义

通过对东川桃园铜矿与铜矿共生石英的40Ar/39Ar同位素年龄的测定,得到马鞍形年龄谱,其坪年龄为768.43Ma±0.58Ma,等时线年龄为770.00Ma±5.44Ma。该矿床后期改造作用明显,并非同生沉积或成岩作用早期成矿,而与晋宁期Rodina大陆裂解有关。东川铜矿的形成可能是在Rodinia大陆裂解时,从深部带来大量成矿物质改造成岩时期初始的矿化,形成矿床的叠加富集和最终定位,因此,晋宁-澄江期是东川铜矿的主成矿期。     

用于新生代定年的Ar-Ar法标准样品候选样品初测结果

Ar Ar法定年的特点是必须要有一套年龄从小到大的标准样。迄今用于新生代定年的国内标准样极少。为满足新生代矿物Ar Ar法定年的需要,初选了一个标准样候选者BT 1透长石。样品总重366g,粒级6080目,纯度100%,缩分为100瓶,每瓶3 66g。Ar Ar阶段加热法初测结果为:全部12个阶段给出的总气体年龄为30 8±0 9Ma,412阶段视年龄十分接近,年龄谱平坦,对应的39Ar析出量达96%,坪年龄为29 6±0 4Ma,等时年龄为29 6±0 6Ma,MSWD=1 01。40Ar/36Ar初始值为293 6±3 9,与尼尔值295 5相当。重复测定结果为:全部气体年龄为31 0±0 9Ma(全部9个阶段),坪年龄为29 5±0 4Ma,等时年龄为29 4±0 6Ma,MSWD=1 94,40Ar/36Ar初始值为282 2±6 3。这些结果表明,BT 1透长石不含过剩氩,作为新生代定年的Ar Ar法标准样品候选者是较为理想的。     

Experimental study on reduction of U (Ⅵ) by an anaerobic bacterium, Shewanella putrefaciens: Application to sandstone-hosted interlayer oxidation-zone type uranium deposits, China

An experimental study on reduction of U (Ⅵ) by anaerobic bacteria, Shewane//a putrefaciens, is first reported here in China. The experimental conditions were: 35℃ and pH =7.0-7.4, corresponding to a physicochemical environments in which the sandstone-hosted interlayer oxidation-zone type uranium deposit formed in Northwest China's Xinjiang. Bacteria adopted in the present experiment, Shewanella putrefaciens, occur extensively in natural environment. Our study shows that nano-crystal precipitates of uraninite quickly occurred on the surface of the cells within one week. It was found that the pitchblende was characterized by a random arrangement of uraninite nanocrystals (2-4 nm) in it, significantly different from natural pitchblende in which uraninite nanocrystals are arranged in order. Finally, a possible mechanism of uranium biomineralization by microorganisms in the deposits is discussed. Our investigation may supply a technical train of thoughts for bioremediation of nuclear-contaminated water environments and for underground dissolving extraction of the sandstone-hosted uranium ores.     

太湖表层沉积物多环芳烃的空间分布、来源及其风险

随着太湖流域社会与经济的发展,多环芳烃(PAHs)在各种环境介质中逐渐累积,污染日益严重,可能对太湖生态环境及周边人体健康构成威胁。为探究太湖沉积物PAHs的来源及生态风险,于2021年12月在太湖采集30个表层沉积物样品,利用气相色谱-质谱联用仪(GC-MS)检测样品中16种PAHs含量;利用受体模型和苯并[a]芘(BaP)毒性当量法进行来源解析及生态风险评估,并将各来源贡献与毒性当量浓度相结合,量化源风险。结果表明,太湖表层沉积物中16种PAHs总含量介于124~592 ng/g之间,平均值为294 ng/g,中值为279 ng/g;高环多环芳烃(HMW PAHs)为主要组分,占∑PAHs的67%。高含量区域位于竺山湾、梅梁湾、贡湖湾和西太湖,与国内外其他湖泊沉积物相比,太湖沉积物PAHs含量处于较低水平。源解析的结果表明,太湖表层沉积物中PAHs交通排放源贡献率为29.1%、煤炭燃烧源贡献率为26.7%、生物质燃烧源贡献率为28.7%、石油源贡献率为15.6%。生态风险评价结果表明,交通排放源、生物质燃烧源、煤炭燃烧源和石油源的BaP毒性当量含量(TEQ_BaP)均值分别为19.34、17.81、16.33和9.1 ng/g,均小于70 ng/g,几乎处于无风险水平。西太湖、贡湖湾和梅梁湾的部分区域ΣTEQ_BaP大于70 ng/g属于潜在风险区,具有一定潜在毒性。在后续的污染治理中应重点关注太湖西北部地区污染物的排放。本研究可为沉积物中PAHs污染的研究提供数据支撑,为地方政府精准、高效地管控PAHs污染提供理论依据。     

茯苓酸调节AMPK/GSK-3β/Nrf2信号通路对子宫内膜异位症大鼠内膜基质细胞铁死亡的影响

目的：探索茯苓酸调节腺苷酸活化蛋白激酶（AMPK）/糖原合成酶激酶3β（GSK-3β）/核因子E2相关因子2（Nrf2）信号通路对子宫内膜异位症（EM）大鼠基质细胞铁死亡的影响。方法：将51只SD大鼠于腹腔内异位移植子宫内膜组织构建EM大鼠模型,并将其随机分为模型组、茯苓酸低剂量（3.5 mg/kg）组、茯苓酸高剂量（7.0 mg/kg）组、茯苓酸高剂量（7.0 mg/kg）+盐酸多索啡（0.2 mg/kg）组,每组各12只,另取12只SD大鼠只开腹不移植,设为假手术组,药物分组处理后测定各组大鼠异位子宫内膜体积、异位子宫内膜组织铁死亡指标［谷胱甘肽（GSH）、丙二醛（MDA）水平、铁含量］、血清及异位子宫内膜组织炎症因子［肿瘤坏死因子α（TNF-α）、白细胞介素-6（IL-6）］水平、异位子宫内膜组织铁死亡相关蛋白［长链脂酰辅酶A合成酶4（ACSL4）、环加氧酶2（PTGS2）］与AMPK/GSK-3β/Nrf2通路相关蛋白表达。原代培养EM大鼠子宫内膜基质细胞,并将其随机分为对照组、茯苓酸低浓度（40 mg/L）组、茯苓酸高浓度（80 mg/L）组、茯苓酸高浓度（80 mg/L）+盐酸多索啡（10 μmol/L）组,以药物分组处理后,以CCK-8法、流式细胞术分别测定各组细胞增殖及凋亡;以试剂盒检测各组细胞铁死亡指标GSH及MDA水平、铁含量;以免疫印迹实验检测各组细胞铁死亡相关蛋白及AMPK/GSK-3β/Nrf2通路相关蛋白表达。结果：与假手术组相比,模型组大鼠异位子宫内膜体积、MDA水平及铁含量、血清及异位子宫内膜组织TNF-α及IL-6水平、ACSL4及PTGS2蛋白表达升高（P<0.05）,GSH水平、p-AMPK/AMPK、p-GSK-3β/GSK-3β及Nrf2蛋白表达降低（P<0.05）;与模型组相比,茯苓酸低、高剂量组大鼠异位子宫内膜体积、MDA水平及铁含量、血清及异位子宫内膜组织TNF-α及IL-6水平、ACSL4及PTGS2蛋白表达降低（P<0.05）,GSH水平、p-AMPK/AMPK、p-GSK-3β/GSK-3β及Nrf2蛋白表达升高（P<0.05）,且高剂量茯苓酸作用更强;盐酸多索啡可减弱高剂量茯苓酸对EM模型大鼠的作用。与对照组相比,茯苓酸低、高浓度组大鼠子宫内膜基质细胞活力、MDA水平及铁含量、ACSL4及PTGS2蛋白表达降低（P<0.05）,凋亡率、GSH水平、p-AMPK/AMPK、p-GSK-3β/GSK-3β及Nrf2蛋白表达升高（P<0.05）,且高浓度茯苓酸作用更强;盐酸多索啡可减弱高剂量茯苓酸对EM大鼠内膜基质细胞的作用。结论：茯苓酸可减轻EM大鼠炎症及铁死亡,抑制其子宫内膜基质细胞增殖及异位内膜生长,其作用机制可能是通过激活AMPK/GSK-3β/Nrf2信号通路来实现的。     

A Case study of a snowstorm at the Great Wall Station,Antarctica

A case of a snowstorm at the Great Wall Station was studied using data of NCEP (National Centers for Environmental Prediction) analysis, in situ observations and surface weather charts. The storm occurred on August 29th,2006, and brought high winds and poor horizontal visibility to the region.It was found that the storm occurred under the synoptic situation of a high in the south and a low in the north. A low-level easterly jet from the Antarctic continent significantly decreased the air temperature and humidity.Warm air advection at high level brought sufficient vapor from lower latitudes for the snowstorm to develop.The dynamic factors relating to strong snowfall and even the developmentof a snowstorm were deep cyclonic vorticity at middle and low levels,the configuration of divergence at high level and convergence at low level, and strong verticaluplift. There was an inversion layer in the low-level atmosphere during the later phase of the storm.This vertical structure of cold air at low levels and warm air at high levels may have been important to the longevity of the snowstorm.