Defining and selecting characteristic values of geotechnical parameters for designs to Eurocode 7

ABSTRACT

Recent geotechnical design codes (such as Eurocode 7) aim to achieve geotechnical designs with an appropriate target reliability by applying partial factors to characteristic parameter values. Development in Eurocode 7 of the definition and selection of the characteristic values is traced. A significant development occurred with the definition of the characteristic value as a cautious estimate of the value affecting the occurrence of the limit state. Statistical equations to select characteristic values are presented, including one proposed for the revised of Eurocode 7.An alternative equation reduces the amount of subjective judgement and is more likely to achieve the target reliability.     

鄂尔多斯盆地马岭油田长7致密储层古今构造应力研究

构造应力是油气运移与富集的控制因素之一,古今构造应力状态的研究对油气勘探与开发具有重要意义。利用流体包裹体测温、古地磁裂缝定向、声发射法和微地震监测、岩石压缩试验和水力压裂法分别对鄂尔多斯盆地马岭油田长7致密储层古今构造应力进行研究。结果表明:长7致密储层裂缝发育关键期为燕山运动Ⅳ幕,其水平最大主应力方向为84°,有效应力大小为44 MPa;现今水平最大主应力方向为76°,而现今水平最小主应力有效应力大小为15 MPa。     

湖泊深水重力流沉积露头精细解剖——以鄂尔多斯盆地瑶曲剖面长7油层组为例

沉积露头为精细刻画沉积体内部结构、建立准确地下地质模型发挥着不可替代的作用。本文以鄂尔多斯盆地南部瑶曲剖面长7段为例,采用地质学、野外露头沉积学方法,详细剖析了湖泊深水重力流沉积深水岩相的类型、特征、垂向组合及沉积环境。研究表明,瑶曲剖面长7段发育块状细砂岩相、鲍马序列粉砂岩相、水平纹理泥岩相、块状泥岩相、水平层理页岩相、凝灰岩相6种岩相类型,碎屑流沉积、浊流沉积、滑塌沉积、深水原地沉积、火山碎屑沉积5类沉积单元,在垂向上5类沉积单元构成了A、B、C、D 4类垂向分布形式。在此基础上,结合区域地质特征,研究认为长7段发育湖泊、水道型重力流沉积两种沉积体系。湖泊相可进一步确定为半深湖—深湖亚相,深水原地沉积微相,以D类岩相组合最为发育;水道型重力流沉积体系进一步划分为近源水道、远源水道、堤岸、前端朵体4个亚相,包含砂质碎屑流沉积、浊流沉积、滑塌沉积3个微相,近源水道+堤岸形成A类、C类、B类岩相组合,远源水道+堤岸形成B类、C类岩相组合,前端朵叶发育C类岩相组合。剖面相分析表明,研究区优质的烃源岩与重力流砂体可构成较好的"下生上储"的致密岩性油气藏。     

鄂尔多斯盆地南部长7页岩沉积特征和有机质富集因素研究

对鄂尔多斯盆地南部瑶科1（YK1）井延长组长7段页岩45件样品进行了总有机碳、Rock-Eval热解分析,并且对其中的15个样品进行了有机碳同位素组成分析、氯仿沥青“A”含量和微量元素分析。结果显示,长7段有机质丰度指标（TOC、氯仿沥青“A”、生烃潜量）之间具有良好的相关性,长73有机质丰度高于长71,长72有机质丰度最低;有机碳同位素指示长73层有机质类型好,以Ⅰ型为主,长72和长71层有机质以Ⅰ和Ⅱ型为主;氧化还原指标U/Th、δU和V/(V+Ni)值指示长7沉积时期水体整体为还原-强还原环境,其中,相比长72和长71的沉积环境,长 73的沉积环境还原性更强,可能达到厌氧、硫化细菌发育的程度。页岩中高P元素含量,指示YK1井长7段页岩沉积时期具有高古生产力特征。有机碳含量（TOC）与氧化还原指标和P元素呈良好的正相关关系,表明有机质含量的变化同时受控于古生产力高低和氧化还原的保存条件。因此,长7段页岩有机质富集模式可能属于“生产力模式”,即长7页岩有机质的富集是由于较高的初始生产力通过消耗水体中的氧气而形成易于保存有机质的缺氧环境。综合前人的页岩气研究成果,认为富有机质的长73层是鄂尔多斯盆地南部页岩气富集的最有利层段。     

恩诺沙星对脊尾白虾APND、ECOD和GST活性的影响

为研究脊尾白虾(Exopalaemon carinicauda)药物代谢酶对恩诺沙星的响应及其在恩诺沙星代谢过程中的作用,作者以10、20和40 mg/kg恩诺沙星连续投喂脊尾白虾3 d,于投喂后的第1、2天以及停止投喂药物的第1、4、8、12、24、48、72、120小时取样,测定了脊尾白虾肝胰腺、鳃和血清中的氨基比林-N-脱甲基酶(aminopyrine-N-demethylase,APND)、7-乙氧基香豆素-O-脱乙基酶(7-ethoxycoumarinO-Deethylase,ECOD)和谷胱甘肽-S-转移酶(glutathione-S-transferase,GST)的活性。结果表明:不同浓度恩诺沙星对脊尾白虾肝胰腺、鳃和血清中Ⅰ相药物代谢酶APND和ECOD活性均呈现显著抑制作用(P0.05)。投喂药物后,APND和ECOD活性呈现先下降后逐渐上升趋势,3个剂量组酶活性均在最后一次给药后8 h达到最低。与对照组相比,不同浓度恩诺沙星对各组织中Ⅱ相药物代谢酶GST活性呈现显著诱导作用(P0.05),此作用呈现先上升后下降的趋势。恩诺沙星对脊尾白虾APND、ECOD及GST活性的作用均呈现剂量依赖性。本研究表明,脊尾白虾Ⅰ相和Ⅱ相代谢酶均会对药物做出反应,可作为其养殖过程中药物代谢及适用性的指示物。     

The investigation of Baker's Hole, Northfleet, Kent, 1909-1914; the impact of collection history upon the interpretation of archaeological data

The site of Baker's Hole in the Ebbsfleet valley, Kent, is the best-known British Early Middle Palaeolithic (MIS 9-7) site, and has produced a substantial assemblage of Levallois artefacts. The history of this collection, however, has become confused over the years, with some suggestions that it was actually amassed through excavation. This paper reviews the history of investigations at the site, on the basis of archive letters and records, and demonstrates that it was clearly collected by quarry workers. This clarification has important implications for understanding human activity in the Ebbsfleet valley during late MIS 8/early MIS 7.     

Strike-slip motions in the Gulf of Siğaçik (western Turkey): Properties of the 17 October 2005 earthquake seismic sequence

The October 2005 series of earthquakes that occurred in the Gulf of Siğaçik (western Turkey) reveal the operation of pure strike-slip faults, as evidenced from the 49 focal mechanisms we determined, in a region dominated by N–S extension and bounded by well-documented graben structures. The sequence is characterized by the occurrence of three moderate size events (17 October 2005, 05:45 UTC, Mw 5.4; 17 October 2005, 09:46 UTC, Mw 5.8; and 20 October 2005, 21:40 UTC, Mw 5.8) with an eastward propagation and close spatial separation (< 6 km). We relocated over 200 aftershocks, combining phases from the Greek and Turkish seismological networks, which align roughly in a NE–SW cloud, but considerably spread after the first day of the sequence, indicating the simultaneous activation of multiple structures nearly orthogonal to the main rupture. It is hard to relate the occurrence of the events to any of the previously mapped faults in the region. The region of occurrence is a well-known geothermal area which implies that it is in a very unstable state, with the fault systems close to rupture and very sensitive to stress perturbations. Here we showed that the sequence is adequately explained by static stress triggering. It is worth noting that this sequence, though moderate in magnitudes, provides stronger evidence for the operation of sub-parallel strike-slip faults in the central Aegean Sea–western Turkey, north of the volcanic arc, which seem to be optimally oriented in the regional stress field and facilitate the Anatolia motion into the Aegean Sea.     

Alteration Information Extraction by Applying Synthesis Processing Techniques to Landsat ETM＋ Data： Case Study of Zhaoyuan Gold Mines, Shandong Province, China

Satellite remote sensing data are usually used to analyze the spatial distribution pattern of geological structures and generally serve as a significant means for the identification of alteration zones. Based on the Landsat Enhanced Thematic Mapper （ETM＋） data, which have better spectral resolution （8 bands） and spatial resolution （15 m in PAN band）, the synthesis processing techniques were presented to fulfill alteration information extraction： data preparation, vegetation indices and band ratios, and expert classifier-based classification. These techniques have been implemented in the MapGIS-RSP software （version 1.0）, developed by the Wuhan Zondy Cyber Technology Co., Ltd, China. In the study area application of extracting alteration information in the Zhaoyuan （招远） gold mines, Shandong （山东） Province, China, several hydorthermally altered zones （included two new sites） were found after satellite imagery interpretation coupled with field surveys. It is concluded that these synthesis processing techniques are useful approaches and are applicable to a wide range of gold-mineralized alteration information extraction.     

Synthetic tidal parameters for gravity over China and its neighbor area

The synthetic tidal parameters with high spatial resolution for gravity over China and its neighbor area are con- structed with Earth’s tidal model and ocean tide loading calculated using TPXO7 global ocean tide model as well as tidal data over China seas. The comparison between synthetic parameters and ones observed by spring gravime- ters at some seismic network stations and Hong Kong station and one observed by super-conducting gravimeter at Wuhan station shows that the average differences in amplitude factors and phases are smaller than 0.005 and 0.5° respectively; and that the discrepancies between observational and synthetic parameters are dependent on gravim- etric technique in that the synthetic parameters are in well agreement with the superconducting gravimetric obser- vations. This also indicates that the synthetic result is a good estimation for tidal gravity, and the numerical results in the present paper not only can provide ground and space gravimetry such as absolute gravimetry with correction model of tidal gravity, but also provide effective tidal parameters over areas where no observation is carried out.     

U–Pb and Sm–Nd geochronology of amphibolites from the Curaçá Belt, São Francisco Craton, Brazil: Tectonic implications

The Curaçá terrane is part of the Itabuna–Salvador–Curaçá (I–S–C) Paleoproterozoic orogen in the São Francisco craton, northeastern Brazil, and comprises supracrustal rocks, gneisses of their probable basement, amphibolites, and mafic-ultramafic Cu-bearing bodies (including the Caraíba Cu-Mine), all affected by D₁-D₃ deformation events associated to M₁-M₃ metamorphism under high-T granulite and amphibolite facies, and assisted by G₁-G₃ tonalitic-granodioritic-granitic intrusions. U–Pb and Sm–Nd Thermal Ionization Mass Spectrometry (TIMS) isotopic data from amphibolite, tonalite, and granite, sampled in a well-known outcrop, indicate partial reset and heterogeneous modification of the original isotopic systems, attributable to deformation and metamorphism. The ages obtained from these systems agree with each other, and also with other previously published U–Pb data, and imply that 2.6 Ga is the crystallization age of the protolith of the amphibolite. Together with key structural relationships, they also indicate a 2.08–2.05 Ga interval for M₃ metamorphism, and make even a less precise age (2.2–2.3 Ga) acceptable, as it suggests contamination in the amphibolite with material in a syn-D₂ tonalite crystallized 2248 ± 36 Ma ago. The new data demonstrate the existence of Neoarchean fragments of both oceanic and continental crusts and constrain the Archean-Paleoproterozoic development of the Curaçá belt, the I–S–C orogen, and the São Francisco craton.