土钉支护弹塑性数值分析及稳定性探讨

用三维弹塑性有限元法对土钉支护进行了边开挖、边安装土钉和喷射混凝土面层的施工过程的数值模拟分析。通过一种强度折减技术探讨了土钉支护的稳定性。研究结果表明，施工过程中在不同的使用荷载作用下受力最大的土钉并不是一成不为的，因此，在土钉支护工程中不能随意地缩短某层土钉的长度。数值计算确定的潜在滑裂区和局部破坏区符合实际情况，认为钉体拔出是土钉支护最可能出现的内部失稳形式。     

跨采软岩巷道锚注支护试验研究

通过对鲍店煤矿北翼跨采软岩巷道的调查与分析，说明了巷道的破坏机理，并根据跨采软岩巷道的特点提出了各类巷道的支护技术方案。通过巷道数值模拟、相似材料模拟及井下试验应用，取得了较好的技术经济效果。     

Sea level pressure patterns associated with dry or wet monthly rainfall conditions in Turkey

Summary  Monthly rainfall totals at 7 stations across Turkey and sea level pressure (SLP) in 16 grid points in the region delimited by the 20° E and 50° E longitudes and by the 30° N and 45° N latitudes were analysed. Data were available for a period longer than sixty years. The standard deviations of SLP at each grid point for each month, were calculated and mapped. For each station, months were defined as dry or wet according to their z scores: ≤ −1.0 or ≥ 1.0 respectively. Maps showing the SLP z scores of the corresponding dry or wet months for each station were prepared. The maps, enable to distinguish between SLP patterns associated with dry or wet conditions. Furthermore, correlations between monthly rainfall in each of the stations and SLP at each grid point were performed. The correlation coefficients were mapped. (a) The variability of the SLP decreases from the Balkans towards the Arabian Peninsula and is much larger in winter as compared with summer. (b) Relationship between rainfall in Turkey and the regional SLP is large in winter and non existing in summer. (c) Pressure patterns associated with dry conditions, show usually positive SLP departures, whereas, pressure patterns associated with wet conditions show usually negative SLP departures. (d) There is a great resemblance between pressure patterns associated with wet conditions and correlation maps of the same months. Received September 4, 2000 Revised January 15, 2001     

山西沁水煤层气田采收率预测

采用地质类比、等温吸附曲线及储层数值模拟 3种方法对山西沁水煤层气田主力气层———二叠系山西组 3# 煤层、石炭系太原组 15 # 煤层的煤层气采收率进行了预测 ,结果 3# 煤层的煤层气采收率为 6 2 % ,15 # 煤层的采收率为 5 5 % ,总平均采收率为 5 9%。分析对比了这 3种方法的运用条件及优缺点 ,指出煤层气采收率的预测必须采用多种方法 ,并结合具体的煤层气地质特点进行综合分析 ,才能得出合理的结论。     

Historical pollution trends in a disturbed, estuarine sedimentary environment, SW Sweden

The objective of this article is to determine whether pollution trends can be reconstructed from sediments in the outer Göta älv estuary. Detailed interpretation of heavy metal profiles in the recent sediment, in combination with profiles of ²¹⁰Pb- and ¹³⁷Cs-activity, organic carbon content and grain size distribution, allows estimation of historical trends. This is based on the assumption that only certain intervals, which can be identified, are disturbed. The sediment data are compared with archive data on historical trends in emissions of heavy metals. Special attention is given to mercury, which shows high enrichment over long periods of time. It is found that the most polluted sediments were deposited between 1930 and 1980, but that episodic discharges have also occurred more recently. Nevertheless, the effects of remediation since the 1970s are apparent.     

Ophiolite emplacement by strike-slip tectonics between the Pontide Zone and the Sakarya Zone in northwestern Anatolia, Turkey

Northwestern Anatolia contains three main tectonic units: (a) the Pontide Zone in the north which consists mainly of the Gstanbul-Zonguldak Unit in the west and the BallLda<-Küre Unit in the east; (b) the Sakarya Zone (or Continent) in the south, which is juxtaposed against the Pontide Zone due to the closure of Paleo-Tethys prior to Late Jurassic time; and (c) the Armutlu-OvacLk Zone which appears to represent a tectonic mixture of both zones. These three major tectonic zones are presently bounded by the two branches of the North Anatolian Transform Fault. The two tectonic contacts follow older tectonic lineaments (the Western Pontide Fault) which formed during the development of the Armutlu-OvacLk Zone. Since the earliest Cretaceous, an overall extensional regime dominated the region. A transpressional tectonic regime of Coniacian/Santonian to Campanian age caused the welding of the Gstanbul-Zonguldak Unit to the Sakarya Zone by an oblique collision. In the Late Campanian, a transtensional tectonic regime developed, forming a new basin within the amalgamated tectonic mosaic. The different tectonic regimes in the region were caused by activity of the Western Pontide Fault. Most of the ophiolites within the Armutlu-OvacLk Zone belong to the Paleo-Tethyan and/or pre-Ordovician ophiolitic core of the Gstanbul-Zonguldak Unit. The Late Cretaceous ophiolites in the eastern parts of the Armutlu-OvacLk Zone were transported from Neo-Tethyan ophiolites farther east by left-lateral strike-slip faults along the Western Pontide Fault. There is insufficient evidence to indicate the presence of an ocean (Intra-Pontide Ocean) between the Gstanbul-Zonguldak Unit and the Sakarya Zone during Late Cretaceous time.     

Late orogenic crustal extension in the northern Menderes massif (western Turkey): evidence for metamorphic core complex formation

The Simav metamorphic core complex of the northern Menderes massif, western Turkey, consists of a plutonic (Tertiary) and metamorphic (Precambrian) core (footwall) separated from an allochthonous cover sequence (hanging wall) by a low-angle, ductile-to-brittle, extensional fault zone (i.e. detachment fault). The core rocks below the detachment fault are converted into mylonites with a thickness of a few hundred metres. Two main deformation events have affected the core rocks. The first deformational event (D₁) was developed within the Precambrian metamorphic rocks. The second event (D₂), associated with the Tertiary crustal extension, includes two distinct stages. Stage one is the formation of a variably developed ductile (mylonitic) deformation (D_2d) in metamorphic and granitic core rocks under greenschist facies conditions. The majority of the mylonites in the study area have foliations that strike NNW to NNE and dip SW to SE. Stretched quartz and feldspar grains define the mineral lineation trending SW-NE direction and plunging gently to SW. The kinematic indicators indicate a top-to-NE sense of shear. Stage two formation of brittle deformation (D_2b) that affected all core and cover rocks. D_2b involves the development of cataclasites and high-angle normal faults. An overall top towards the north sense of shear for the ductile (mylonitic) fabrics in the core rocks is consistent with the N-S regional extension in western Turkey.     

Ice-sheet growth and high-latitudes sea-surface temperature

The response of the LLN 2-D climate model to the insolation and CO₂ forcings during the Eemian interglacial is compared to reconstructions obtained from deep-sea cores drilled in the Norwegian Sea and in the North Atlantic. Both reconstructions and modeling results show a decrease of sea-surface temperature (SST) in the higher latitudes (70–75 °N zonal belt for the model and the Norwegian Sea for the proxy records), associated with a more moderate cooling at lower latitudes (50–55 °N and North Atlantic), at the middle of isotopic substage 5e, several millenia before the beginning of continental ice-sheet growth. Such a comparison between the simulated SST and ice volume of the Northern Hemisphere has been extended to the whole last glacial-interglacial cycle. The influence of the insolation forcing on SST and the shortcomings of the model due to its zonal character are discussed. Received: 6 July 1995/Accepted: 19 December 1995     

Modelling the ecological constraints on growth and movement of juvenile American shad (Alosa sapidissima) in the Hudson River estuary

Juvenile fishes often face conditions that force them to experience fitness trade-offs (e.g., foregoing a rich food patch because of high risk of predation). In this study, three aspects of the environment of juvenile American shad: food availability, predation risk, and “thermal risk” (defined here as the probability of the onset of adverse temperatures; ≤9°C, the temperature at which feeding ceases), are evaluated empirically with data from the Hudson River estuary in New York State. The evaluations are then used in dynamic programming models to determine when juvenile American shad should switch habitat (upper versus middle versus lower estuary), and, in combination with a simple bioenergetic model, to determine growth trajectories for fish spawned at different times in the spawning season. Comparisons of simulations with real data suggest that scenarios in which predation risk is highest in the lower river produce the most realistic patterns of habitat use. High upriver food availability in June promotes use of the upriver habitat; however, by September most size classes of fish utilize the middle estuary, and by late October, fish move to the lower estuary (even in the face of higher predation risk), due to a combination of lower food resources and thermal risks in the upper and middle estuary.     

God,thine earth is burning: Nature attitudes and the Latvian drive for independence

The dominant element in Latvian culture is nature rather than history. Latvians are as bound to place, to landscape, to particular geographies, as other peoples are bound to tribal legends and religions. Incorporation of this Baltic land into the Soviet Union in 1940 occasioned dramatic conflicts between these deeply-rooted orientations to the concrete facts of nature and the abstract formulations of Marxism-Leninism. The nature culture of Latvia, celebrated in daina, folk arts and crafts, is the bedrock on which the current independence movement has been built. Two major challenges are being addressed: the overt political one between Moscow center and the Baltic republics, and a deep intellectual conflict between the closed ideology of Marxism-Leninism and the open-ended nature and place-oriented cultures of the Baltic peoples.