某抽水蓄能电站PD_6平洞超挖调查与评价

本文通过某抽水蓄能电站输水隧洞的勘探平洞 PD6 的超挖测绘调查 ,分析了平洞超挖块体的边界条件 ,确定了超挖块体的类型及其特征 ,利用自编计算程序 ,评价了各类型超挖块体的体积及其分布模型。这对于地下洞室超挖的评价方法以及工程建设中地下洞室稳定性评价以及加固处理具有一定指导意义。     

Seismic evaluation of an existing complex RC building

The seismic evaluation of existing buildings is a more difficult task than the seismic design of new buildings. Non-linear methods are needed if realistic results are to be obtained. However, the application to real complex structures of various evaluation procedures, which have usually been tested on highly idealized structural models, is by no means straightforward. In the paper, a practice-oriented procedure for the seismic evaluation of building structures, based on the N2 method, is presented, together with the application of this method to an existing multi-storey reinforced concrete building. This building, which is asymmetric in plan and irregular in elevation, consists of structural walls and frames. It was designed in 1962 for gravity loads and a minimum horizontal loading (2% of the total weight). The main results presented in terms of the global and local seismic demands are compared with the results of non-linear dynamic response-history analyses. As expected, the structure would fail if subjected to the design seismic action according to Eurocode 8. The shear capacity of the structural walls is the most critical. If the shear capacity of these elements was adequate, the structure would be able to survive the design ground motion according to Eurocode 8, in spite of the very low level of design horizontal forces. The applied approach proved to be a feasible tool for the seismic evaluation of complex structures. However, due to the large randomness and uncertainty which are involved in the determination of both the seismic demand and the seismic capacity, only rough estimates of the seismic behaviour of such structures can be obtained.     

Adjustments by the Charwell River, New Zealand, to uplift and climatic changes

Major climatic changes and rapid local and regional tectonic movements were common in New Zealand during the late Quaternary and caused a diversity of adjustments in the drainage-basin and piedmont reaches of the Charwell River, which are separated by the Hope Fault. The onset of semi-arid, frigid climates during the latest Pleistocene probably greatly increased hillslope sediment yields in a periglacial environment, and the piedmont reach aggraded as much as 42 m on top of a broad strath. With the return of humid, mesic climates in the Holocene sediment yields decreased as dense forests again mantled the slopes, and the piedmont reach degraded as mush as 81 m. Dating of eleven cut-and-strath terraces by radiocarbon-calibrated weathering rind measurements on greyawake cobbles shows the degradation rates varied greatly during the last 14 ka (1 ka = 1000 yr). Initial degradation rates of < 4 m ka⁻¹ increased to 30 m ka ⁻¹ by 6 ka ago during a mid-Holocene climatic optimum. Since 4 ka ago degradation rates have been only 1.2 m ka⁻¹, comparable to uplift rates in the piedmont reach inferred from marine-terrace studies, and the river is again cutting a broad strath. Each broad strath represents equilibrium conditions attained by this powerful stream during interglacial times despite episodes of being overwhelmed by climatically induced sediment-yield increases during full-glacial climates and having to maintain a long-term degradation rate equal to the uplift rate.The 75–81 m of degradation since formation of the latest Pleistocene fill-terrace tread is the sum of the amount of late Pleistocene valley-floor aggradation and the amount of regional uplift that occurred between the estimated times of major strath formation at about 30 and 0 ka. The 39 m of tectonically induced degradation below the pre-aggradation strath is sufficiently large that post-30 ka uplift may have doubled Holocene degradation rates.Each of the eleven degradation terraces represents pauses of a few centuries in Holocene downcutting. Brief equilibrium conditions were attained by streambed armoring and concurrent growth of riparian plants; both processes progressively increased hydraulic roughness and the shear stresses needed to entrain streambed materials. Occasional floods, possibly from rare cyclones derived from tropical moisture sources, destroyed streambed armor and channel downcutting was renewed. Thus the formation of eleven equilibrium terraces can be accounted for without postulating additional tectonic perturbations or secular climatic changes.     

地面核磁共振技术勘查西北干旱浅层地下水效果浅析

地面核磁共振技术勘查地下水是一种新的应用领域,该技术是目前国际上唯一的能直接进行地下水勘查的技术.我所自一九九九年引进法国Numis仪器以来,先后在陕西黄土区、宁南黄土区等地开展寻找不同类型浅层地下水的试验工作,取得了一定的野外成果.本文是在分析总结这些成果的基础上,针对存在的问题如强干扰背景下勘查结果的可靠性,同一测点"8”字型与"正方形”发射线框二者勘查结果比较等方面进行探讨分析.     

Trace metals and radionuclides reveal sediment sources and accumulation rates in Jordan Cove, Connecticut

Many small estuaries are influenced by flow restrictions resulting from transportation rights-of-way and other causes. The biogeochemical functioning and history of such systems can be evaluated through study of their sediments. Ten long and six short cores were collected from the length of Jordan Cove, Connecticut, a Long Island Sound subestuary, and analyzed for stratigraphy, radionuclides (¹⁴C, ²¹⁰Pb, ²²⁶Ra, ¹³⁷Cs, and ⁶⁰Co), and metals (Ag, Cd, Cu, Pb, Zn, Fe, and Al). For at least 3,800 yr, rising sea level has gradually inundated Jordan Cove, filling it with mud similar to that currently being deposited there. Long-term sediment accumulation in the cove averaged close to 0.1 cm yr⁻¹ over the last three millennia. Recent sediment accumulation rates decrease inland from 0.84 cm yr⁻¹ to 0.40 cm yr⁻¹, and are slightly faster than relative sea-level rise at this site (0.3 cm yr⁻¹). Similarity of depth distributions of trace metals was used to confirm relative sediment accumulation rates. ⁶⁰Co and Ag are derived from sources outside the cove and its watershed, presumably the Millstone nuclear power plant and regional contaminated sediments, respectively. The combined data suggest that Long Island Sound is an important source of sediment to the cove; a minor part of total sediment is supplied from the local watershed. Trace metal levels are strongly correlated with Fe but not with either organic matter or Al. Sediment quality has declined in the cove over the past 60 yr, but only slightly. Cu, Pb, and Zn data correlate strongly with Fe but not with either organic matter or aluminum. Ratios of Ag to Fe and to trace metals suggest that Ag in the cove is derived almost entirely from Long Island Sound. This result supports the notion that Fenormalized Ag can serve as a better tracer of some kinds of contamination than more common and abundant metals, like Cu, Pb, and Zn. *** DIRECT SUPPORT *** A01BY085 00008     

Early Carboniferous (Viséan) emplacement of the collisional Kłodzko–Złoty Stok granitoids (Sudetes, SW Poland): constraints from geochemical data and zircon U–Pb ages

Sensitive high-resolution ion microprobe zircon U–Pb dating and geochemical data of igneous rocks from the composite K?odzko–Z?oty Stok (KZS) Granite Pluton, Sudetic Block, indicate that the granitoids represent an Early Carboniferous Viséan phase of Variscan metaluminous, high-K, I-type, syn-collisional granite magmatism within the Saxothuringian Zone of the Central European Variscides. Igneous zircon records hypabyssal magmatism that produced various granitoids and lamprophyre (spessartite) emplaced from ca. 340 to 331 Ma. The KZS granitoids have compositions ranging from granodiorite to monzonite, low A/CNK ratios (<1), and are associated with abundant mafic members. Most of them are alkaline, highly potassic, and moderately evolved. The major and trace element contents of the KZS granitoids suggest geochemical heterogeneity, and the hybrid nature of magmas derived from a range of sources in the middle crust, with a strong input of material from the upper mantle. Mixing of magmas of mantle origin with high-K material from partly melted continental crust was probably a more important factor than fractional crystallization, in controlling the evolution of the magmas. The mean Pb–U ages of the main population of igneous zircon from a quartz monzodiorite (?elazno) and hornblende monzonite (Droszków) are 340.2 ± 2.5 Ma and 339.5 ± 3.1 Ma, respectively. A slightly younger biotite-hornblende granodiorite from Chwalis?aw, 336.7 ± 2.5 Ma, was cut by a spessartite dyke at 333.1 ± 3.1 Ma. This indicates that mafic magmas were immediately intruded into fractured, probably incompletely solidified, granodiorites. The lamprophyric dyke also contains igneous zircon of Neoproterozoic age, 566.3 ± 6.4 Ma, typical of the crust in the Saxothuringian Zone. Tonalite from Ptasznik Hill near Droszków is of similar age to the spessartite, 331.5 ± 2.6 Ma. High REE contents in the tonalite and its igneous zircon indicate advanced differentiation of granitic magma, producing a more leucocratic melt associated with post-magmatic activity including abundant late crosscutting pegmatites and quartz veins, and contact metasomatic mineralization. The KZS granitoids have rather similar petrographic and geochemical characteristics to granitoids from other parts of the Central European Variscides, where a thickened orogenic root caused a substantial rise in crustal temperatures, producing granitoid magmas closely correlated with regional tectonic activity between the Saxothuringian and Brunovistulia Terranes at the NE margin of the Bohemian Massif.     

气候变化背景下珠江流域极端洪水事件的变化趋势

根据1951-2010年珠江流域23个典型断面流量资料,用P-III型分布曲线拟合洪水系列进行频率计算,分析了珠江流域极端洪水事件的变化趋势。结果表明：1980年以来,珠江流域极端洪水事件发生的频次明显增加,尤其是自1990年以来增加趋势显著;1981-2010年较1951-1980年珠江流域约70%典型断面极端洪水事件呈增加趋势,主要分布在西江、北江、粤西;而近30%的典型断面呈减少趋势,主要分布在东江和桂南。     

The seismic hazard assessment of the Dead Sea rift, Jordan

The Dead Sea fault system and its branching faults represent one of the most tectonically active regions in the Middle East. The aim of this study is to highlight the degree of hazards related to the earthquake activities associated with the Dead Sea rift, in terms of speculating the possible future earthquakes. The present investigation mainly is based on available data and vertical crustal modeling of Jordan and the Dead Sea model for the Dead Sea basin with particular emphasis of the recent earthquake activities, which occurred on December 31st, 2003 (Mc = 3.7), February 11th, 2004 (strongest Mc = 4.9 R), and March 15th, 2004 (Mc = 4). The present research examines the location of the strong events and correlates them with the various tectonic elements in the area. The source mechanism of the main shock and the aftershock events is also examined. The analyses were based on the available short period seismogram data, which was recorded at the Natural Resources Authority of Jordan, Seismological Observatory. The seismic energy appears to have migrated from the south to the north during the period from December 31st up to March 12th, where the released seismic energy showed a migration character to the southern block of the eastern side of the Dead Sea, which led the seismic event to occur on March 15th.     

The carboniferous lithostratigraphy of Southeast County Limerick,Ireland, and the origin of the shannon trough

The Carboniferous succession in southeast County Limerick, on the southeastern margin of the Shannon Trough, is Courceyan to mid-Namurian in age and over 1900 m thick. The lithostratigraphy is described in detail. Its most important aspect is the presence of two thick volcanic sequences, a Chadian one of the alkali basalt to trachyte suite and one of Asbian age dominated by limburgites and ankaramites. The associated Dinantian carbonates are of shelf or ramp facies throughout, and no fundamental division into shelf and basin facies occurs as in the Dublin and Craven Basins in early Viséan times. Rapid differential subsidence between this area and the Shannon Estuary began during deposition of the late Courceyan to early Chadian Waulsortian facies but was less marked in the remaining Viséan when much of the volcanic topography was preserved by rapid basinal subsidence. There was basinal inversion in the late Dinantian to lower Namurian, followed by renewed subsidence in mid-Namurian times. This contrasts with the continuous rapid subsidence of the area further west on the Shannon Estuary. This behaviour, together with a comparison of that of nearby Carboniferous basins such as the Dublin, South Munster, and Craven Basins, which lack substantial volcanic sequences, suggests an origin in a transtensional regime rather than one of simple crustal stretching.