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991.
992.
团结构金矿是一个产于花岗斑岩中的大型岩金矿,由于所发现的金矿体绝大部分赋存在花岗斑岩中,因此长期以来,针对该区的找矿评价工作,均主要围绕花岗斑岩展开。本文通过对该矿区及其外围地区的矿石和岩石的稀土配分模式、硫同位素、包体测温等方面的系统分析与比较,发现该金矿床虽然在空间上与花岗斑岩关系密切,但在成因上却不相关。因此,本文对该矿床的控矿构造规律重新进行了系统分析和归纳总结,提出了火山次火山机构的内环带构造是区内金矿体最主要的控矿构造的新认识,进而指出了团结沟金矿田今后的找矿方向。 相似文献
993.
武安市团城铁矿系国有矿山,多年来为国家做出了一定的贡献;20世纪80年代以来,又对数家地方矿山进行采矿。由于采矿弃渣乱放和坑下开采造成地面沉降、塌陷、地裂缝,直接威胁着矿山的正常发展,危及周边村庄的经济、环境和民众的生命安全。通过详细的调查和实测,广泛地收集了各方面资料,因地制宜,提出以废渣部分充填地面塌陷、地裂缝;覆土造林,争取绿化面积超过90%。建设成为集典型地质灾害遗迹观察研究与生态观赏旅游为一体的绿色矿山,把矿产资源开发对环境的破坏降到最低限度,实现资源开发与生态环境的协调发展。 相似文献
994.
地震作用下边坡稳定性分析 总被引:3,自引:0,他引:3
考虑了边坡岩土体材料的动力特性以及地震特性,利用动力有限元时程分析方法对边坡在地震荷载作用下的动力特性进行了分析,采用最小平均安全系数对边坡稳定性进行了评价,并与拟静力法的结果进行了对比分析,对某具体工程实例计算结果表明该分析方法的可行性,可为地震作用下边坡工程设计工作提供一些有益的参考。 相似文献
995.
Controlling factors of loess landslides in western China 总被引:5,自引:1,他引:4
Based on detailed field data from recent geo-hazards surveys in the Loess Plateau region of western China, this study analyzes
the key factors that control loess landslides. The evolution phase of river valleys, the geological structure of slopes and
the geometry of slopes are all found to play a role in determining the occurrence, distribution and other characteristics
of loess landslides. Groundwater and vegetation also contribute to their formation. A combination of human engineering activities
and precipitation events are the principal triggering factors for the instability of loess slopes. 相似文献
996.
997.
Frontal upwelling is an important phenomenon in summer in the Yellow Sea (YS) and plays an essential role in the distribution of nutrients and biological species. In this paper, a three-dimensional hydrodynamic model is applied to investigate the characteristics and influencing factors of frontal upwelling in the YS. The results show that the strength and distribution of frontal upwelling are largely dependent on the topography and bottom temperature fronts. The frontal upwelling in the YS is stronger and narrower near the eastern coast than near the western coast due to the steeper shelf slope. Moreover, external forcings, such as the meridional wind speed and air temperature in summer and the air temperature in the preceding winter and spring, have certain influences on the strength of frontal upwelling. An increase in air temperature in the previous winter and spring weakens the frontal upwelling in summer; in contrast, an increase in air temperature in summer strengthens the frontal upwelling. When the southerly wind in summer increases, the upwelling intensifies in the western YS and weakens in the eastern YS. The air temperature influences the strength of upwelling by changing the baroclinicity in the frontal region. Furthermore, the meridional wind speed in summer affects frontal upwelling via Ekman pumping. 相似文献
998.
Fan Wei Mei Han Guangxuan Han Min Wang Lixin Tian Jiqian Zhu Xianglun Kong 《海洋学报(英文版)》2022,41(9):192-204
Coastal wetlands are located in the ecotone of interaction between the land surface and sea, and anthropogenic activities extensively interfere with these wetlands through the reclamation of large tidal wetlands and destruction of the function of the ecosystems. In this study, we investigated the dynamic evolutionary characteristics of the Bohai Rim coastal area over the past 40 years using the Modified Normalized Difference Water Index, the fractal dimension, object-oriented classification, the land-use transfer trajectory, and regression analysis. Additionally, we quantified and monitored the evolution of reclamation and analyzed the correlation between reclamation and coastal wetlands based on 99 Landsat-2, -5, and -8 images (at 60 m and 30 m spatial resolution) over the period 1980–2019. The results are as follows. (1) The coastline of the Bohai Rim increased by 1 631.2 km from 1980 to 2019 with a zigzag variation. The artificial coastline increased by 2 946.1 km, whereas the natural coastline decreased by 90%. (2) The area of man-made wetlands increased by 3 736.9 km2, the area of construction land increased by 1 008.4 km2, and the natural wetland area decreased by 66%. The decrease of tidal flats is the main contributor to the decrease of natural wetland area (takes account for 91.1%). Coastal areas are affected by intense human disturbance, which was taken place across a large area of tidal flats and caused the landscape to fragment and be more heterogeneous. The coastal zone development activities were primarily concentrated in the southern Laizhou Bay, the Yellow River Delta, the Bohai Bay, the northern Liaodong Bay, and the Pulandian Bay. The solidified shorelines and increase in sea level have resulted in intertidal wetlands decreasing and impaired wetland ecology. (3) There is a good agreement between reclamation and the size of the coastal wetlands. Both land reclamation and the reduction in coastal wetland areas are significantly related to the population size, fishery output value, and urbanization rate. In summary, human activities, such as the construction of aquaculture ponds and salt pans, industrialization, and urbanization, are the primary forces that influence the environmental changes in the coastal region. This study is beneficial for establishing and improving the systems for the rational development and utilization of natural resources, and provides theoretical references for restoring wetland ecology and managing future reclamation activities in other coastal zone-related areas. 相似文献
999.
横带髭鲷(Hapalogenys mucronatus)为我国东南沿海具有良好发展前景的养殖鱼类,目前亟待突破其规模化苗种培育的瓶颈技术问题。为探究横带髭鲷仔鱼发育阶段的摄食和生长特性,采用实验生态学方法,在水温(24±0.2)℃、盐度为26的条件下对饥饿仔鱼形态发育、生长、不可逆点及投喂状态下的摄食节律进行研究。结果表明,孵化出膜后的初孵仔鱼,3日龄开口摄食,进入混合营养期,3日龄卵黄囊消耗完毕,油球于8日龄消耗完全,混合营养期为5d。饥饿组仔鱼全长呈先增长后下降趋势,拐点出现在3日龄,在4日龄有畸形仔鱼出现。饥饿仔鱼初次摄食率为10.12%,最高初次摄食率出现在7日龄,为85.06%;PNR出现在7日龄和8日龄之间,至9日龄全部死亡。早期仔鱼(7日龄)的摄食高峰出现在7:00、11:00和15:00,晚期仔鱼(14日龄)在7:00、11:00、15:00和19:00四个时间段,摄食高峰均出现在白天,属于典型的白天摄食类型,随着仔鱼的生长发育,摄食高峰有所延长。横带髭鲷仔鱼最佳开口摄食时间在3日龄,掌握仔鱼的摄食高峰期,在此时间段驯化配合饲料,对于活体饵料向配合饲料的驯食转化具有重要实践意义。 相似文献
1000.
空心块体具有良好的阻水和促淤功能,近年来被广泛用于生态修复工程。本文结合水槽试验及Flow-3D数值模拟,分析了开敞型和半封闭型空心块体的阻水效应和泥沙淤积特性。结果表明:空心块体的开孔率对内部水流流速、紊动强度起主导作用,开孔率较小的半开敞型空心块体减速、制紊效果更强;开敞型和半封闭型空心块体近底层悬沙浓度分别增大56%和75%,两者均有利于促进泥沙在块体内部淤积,近底层水流紊动越强,泥沙淤积形态差异越大;空心块体所营造的低流速、泥沙微淤、内外连通的水沙环境是大型底栖生物的生境需求,半封闭型空心块体内部的低紊动水流结构更有利于大型底栖生物的栖息、繁衍。 相似文献