An approximation to the reliability of series geotechnical systems using a linearization approach

A method based on the linearization of the limit state functions (LSFs) is applied to evaluate the reliability of series geotechnical systems. The approach only needs information provided by first order reliability method (FORM) results: the vector of reliability indices, β, of the LSFs composing the system; and their correlation matrix, R. Two common geotechnical problems—the stability of a slope in layered soil and a circular tunnel in rock—are employed to demonstrate the simplicity, accuracy and efficiency of the suggested procedure, and advantages of the linearization approach with respect to alternative computational tools are discussed. It is also found that, if necessary, the second order reliability method (SORM)—that approximates the true LSF better than FORM—can be employed to compute better estimations of the system’s reliability.     

新疆塔里木盆地温宿凸起石油地质条件新认识

为了弄清塔里木盆地温宿凸起构造演化、油源条件及圈闭类型等关键地质问题,通过石油地质条件综合分析,结合样品测试分析,查清了温宿地区油气成藏的关键因素,提出了石油地质条件新认识。结果表明:温宿凸起为一个继承性发育的古隆起,构造演化主要经历了4个发展阶段;温宿凸起油气藏类型以构造-岩性型为主;温宿凸起不发育烃源岩,但发育沟通拜城富烃凹陷的高效输导体系;温宿凸起新近系吉迪克组油气藏类型以构造-岩性型为主;油气的生成、运移、聚集主要发生在新近纪-第四纪,具有明显的晚期复式成藏特点;优越的盖层条件是温宿吉迪克组油气藏形成的重要因素。     

Jurassic uplift and erosion of the northeast Queensland continental margin: evidence from (U–Th)/He thermochronology combined with U–Pb detrital zircon age spectra

Abstract

The Jurassic–Cretaceous Great Artesian Basin is the most extensive, and largest volume, sedimentary feature of continental Australia. The source of its mud-dominated Cretaceous infill is attributed largely to contemporary magmatism along the continental margin to the east, but the source of its Jurassic infill, dominated by quartz sandstone, remains unconstrained. This paper investigates the question of a Jurassic sediment source for the northern part of the basin. Jurassic uplift and exhumation of the continental margin crustal sector to the east provided the primary Jurassic sediment source. (U–Th)/He data are presented for zircon and apatite from Pennsylvanian to mid Permian granitoids of the Kennedy Igneous Association distributed within the northern Tasmanides between the Townsville and Cairns regions and for coeval granites of the Urannha batholith from the Mount Carlton district (N Bowen Basin), also within the northern Tasmanides. The data from zircon indicate widespread Jurassic exhumation of a crustal tract located to the east of the northern Great Artesian Basin and largely occupied by rocks of the Tasmanides. Detrital zircon age spectra for samples of the Jurassic Hutton and Blantyre sandstones from the northeastern margin of the Great Artesian Basin show their derivation to be largely from rocks of the northern Tasmanides. In combination, the detrital age spectra and (U–Th)/He data from zircon indicate exhumation owing to uplift generating appreciable physiographic relief along the north Queensland continental margin during the Jurassic, shedding sediment westward into the Great Artesian Basin during its early development. A portion of (U–Th)/He data for zircon are consistent with late Permian–mid Triassic exhumation within the Tasmanides, attributable to the influence of the Hunter--Bowen Orogeny. Evidence of Cretaceous and Paleocene exhumation episodes is also indicated for some samples, mainly by apatite (U–Th)/He analysis, consistent with data previously published from fission track studies. Overall, new data from the present study reveal that the exhumation related to Jurassic regional uplift and the subsequent erosional reworking of the northeast Australian continental margin is critical for the evolution and development of the northern side of the Great Artesian Basin in eastern Australia. Apart from this, another two previously suggested Permian–Triassic and Cretaceous exhumation and uplift episodes along the northeast Australian continental margin are also confirmed by the dataset of this study.

1. KEY POINTS

2. U–Pb detrital zircon ages of sandstone samples from the northeastern Eromanga Basin reveal Paleozoic (480–280 Ma) and Proterozoic (1800–1400 Ma) age clusters.

3. (U–Th)/He zircon and apatite dating results of granitoids samples from Cairns, Townsville and the Mount Carlton districts are dominated by Jurassic (198–164 Ma) and Permian–Triassic (272–238 Ma) age clusters.

4. Combination of above two datasets proves the regional uplift-driving Jurassic exhumation episode in the northeast Australian continental is vital for the development of the northern Great Artesian Basin.

     

Efficient system reliability analysis of rock slopes based on Subset simulation

How to efficiently assess the system reliability of rock slopes is still challenging. This is because when the probability of failure is low, a large number of deterministic slope stability analyses are required. Based on Subset simulation, this paper proposes an efficient approach for the system reliability analysis of rock slopes. The correlations among multiple potential failure modes are properly accounted for with the aid of the “max” and “min” functions. A benchmark rock slope and a real engineered rock slope with multiple correlated failure modes are used to demonstrate the effectiveness of the proposed approach.     

Social geology — integrating sustainability concepts into Earth sciences

Most geologists would argue that geoscientific knowledge, experience, and guidance is critical for addressing many of society’s most acute environmental challenges, yet few geologists are directly engaged in current discourses around sustainable development. That is surprising given that several attributes make modern geoscience well placed to make critical contributions to contemporary sustainability thinking. Here, we argue that if geoscientists are to make our know-how relevant to sustainability science, two aspects seem clear. Firstly, the geoscience community needs to substantially broaden its constituency, not only forging interdisciplinary links with other environmental disciplines but also drawing from the human and behavioral sciences. Secondly, the principles and practices of ‘sustainability’ need to be explicitly integrated into geoscience education, training and continued professional development.     

楚雄盆地上三叠统储集体成因类型及几何模式

楚雄盆地经历多期构造变形.晚三叠世,盆地北部由盆底扇深水环境过渡到沿岸砂坝和三角洲环境.该时期形成辫状河道砂、砾岩体、滨滩砂岩体,河口坝砂岩体和分流河道充填砂岩体四类储集体,构成三种相结合,即扇储集体、三角洲前缘储集体和三角洲平原储集体,几何形态对应为透镜状、带状和不规则状.     

美国长期生态学研究网络的战略规划——走向综合科学的未来

从2004年11月起至今,美国长期生态学研究网络在美国国家科学基金会的资助下,为未来(几)十年的综合和网络层面研究进行了战略规划.规划的最终目标是形成一个新的长期生态学研究(LTER)网络层面科学计划,并通过1个科学课题组、7个网络科学工作组和一系列研讨会来进行.在制定和完善科学计划的过程中,规划行动获得了LTER网络层面科学的跨学科问题、概念框架、基本科学问题、社会与环境综合科学动议、网络计算机基础设施的战略规划、教育与宣传战略规划等重大科学产出.规划的意义在于它告诉了怎样走向LTER的未来--网络层面综合科学,因而有利于LTER及长期生态研究的发展,并可为CERN等其他长期生态学研究网络的规划与发展提供启示.     

燕山西段及太行山区长城系底界的讨论

对燕山型长城系底部层位存在有不同的认识 ,从含钾盆地、大红峪海侵超覆、团山子组海进或海退的问题提出长城系底部地层属于大红峪组的观点。大红峪期时 ,燕山地区只存在一个含钾盆地 ,造成多层含钾页岩沉积 ,而串岭沟组不含钾。以前所划各组段的海侵超覆实为大红峪组的海侵超覆 ,是兴城运动在燕山西段的反映 ,其底部有明显的相变特征。由此把燕山西段及太行山区长城系底部层位重新划为大红峪组 ,则团山子组存在的不协调现象也就迎刃而解。同时还认为昌平德胜口剖面与青龙大杖子剖面几可逐层对比 ,阳原牛坊沟剖面与代表“青龙上升”的剖面相似 ,上述剖面应是大红峪海侵在燕山东西段的反映     

榆次西窑饮用天然矿泉水的形成条件及水质特征

矿泉水赋存于沁水向斜北部东翼三叠系砂页岩地层中，１９８７年和１９９３年经山西地矿局和地矿部组织鉴定，水质符合《饮用天然矿泉水》国家标准（ＧＢ８５３７－８７），属含锶－偏硅酸重碳酸－钠钙型矿泉水。Ｙｈ＿１、井、Ｋ＿１井均已开发利用，生产瓶装天然矿泉水和矿泉水系列饮料。