四川广元千佛崖石窟造像表面风化的环境地质问题分析     

宗静婷  王淑丽  张忠永 《地球科学与环境学报》2011,33(2):185-190

采用温湿度测试、石窟造像渗水实验、石窟造像吸水的红外成像、岩石特征分析等手段,对四川广元千佛崖石窟造像表面及其周围环境进行监测,以及对石窟造像岩石特征进行分析.结果表明:进深较大的窟室内外存在2℃～4℃的温差,岩石0～40 mm深度范围内温度与外界气温存在显著相关性;石窟造像岩石主要成分为长石、石英、黑云母及黏土矿物,...  相似文献   

中国黄土¹⁰Be记录中的古地磁场变化     

杜雅娟  周卫健  鲜锋  孔祥辉  康志海 《地球科学》2013,38(3):482-488

因受气候因素的强烈影响,中国黄土10Be记录无法直接用于示踪地磁场变化,需开展信号分离研究.针对黄土10Be示踪古地磁场的复杂性和存在的关键问题,结合分离黄土10Be浓度所包含的气候因素和地磁场因素的数理分析方法发展历史,分析了各种方法的优缺点.在原有方法的基础上,引入主成分分析法对洛川和西峰2个黄土剖面的10Be记录进行主成分提取,进一步剔除了残差中可能存在的少量气候因素、噪声等随机信号,定量重建了130ka以来的大气10Be产率,与以往方法相比较取得了更优的结果.将主成分分析应用于复杂地质信号的分离,将有助于解决地质或其他信号分离的难题.  相似文献   

西安地热水资源保护与管理的思考     

李印  李雪静 《地下水》2013,(1):50-52

西安地区蕴藏有丰富的地热水资源,充分挖掘、发挥地热水资源的综合效益不仅能有效缓解区内能源供需矛盾,而且有益于区内环境保护,实现经济的科学、可持续发展。近年来,行政监管不力导致过度开采地热水并进而引发地裂缝和地面沉降等问题。同时,西安地区在开发利用地热水中还存在粗放式利用,浪费严重及随意排放地热水尾水等问题。解决西安地区的地热水问题首先应该加强行政监管力度,其次要依法管理,最后还要实施统一的地热水资源勘查与评价以及综合利用研发。  相似文献   

美国技术标准用弦线模量对我国技术更新的启示   总被引：1，自引：1，他引：0  

焦五一  赵树德  郭志恭  罗笃敬  朱书勤  马怀栓 《岩土力学》2009,30(Z2):105-109

用弦线模量计算地基变形是中国的原始自主创新。它改正了压缩模量和各种计算模型存在的问题,所以对计算结果有很大的改进。它依据土性物理指标用软件计算,是各种计算方法中最简单的方法。用于地基设计规范能够实现以变形控制设计的目标;用于黄土地区建筑规范,能够依据基础面积、基底压力、相邻基础影响等条件,并考虑地区差异、土性的微结构差异等条件真实地计算不同类型黄土的湿陷量,实现定量评价黄土湿陷性的目标。在中国对弦线模量研究的同时,美国在金属材料非线弹性变形计算中也研究并已经在其技术标准中采用了弦线模量代替杨氏模量,中国的同类标准也引用了它。这对在我国地基规范中采用弦线模量法进行技术更新,应该具有重要的启示作用。在简要介绍弦线模量法主要情况的基础上,进一步阐明这一观点。  相似文献   

盾构隧道管片衬砌的平板壳-弹性铰-地基系统模型   总被引：8，自引：3，他引：5  

胡志平  罗丽娟  蔡志勇 《岩土力学》2005,26(9):1403-1408

从Reissner-Mindlin板单元入手,研究了盾构隧道管片衬砌结构之间的连接特征及土层与管片衬砌结构的共同作用,提出了盾构隧道管片衬砌结构的平板壳-弹性铰-地基系统模型,在此基础上研制了相应的有限元计算程序。该模型考虑了管片衬砌本身的弯曲、剪切和薄膜作用,考虑了纵向接缝在正负弯矩作用下的转动刚度差异和环向结缝对结构刚度的削弱作用,以及土层与衬砌结构的共同作用。能解决盾构隧道管片衬砌结构的三维受力分析,并能计算出结构的内力和变形,弥补了二维计算模型的某些不足。验证了程序的可靠性,最后给出了工程算例的三维计算分析结果。  相似文献   

煤的等温吸附实验中各因素影响分析   总被引：10，自引：0，他引：10  

张庆玲  崔永君  曹利戈 《煤田地质与勘探》2004,32(2):16-19

为完善煤的等温吸附实验方法,本文系统研究了粒度、压力、温度、平衡时间等对不同变质程度煤吸附性能的影响;分析了各因素对等温吸附实验结果的影响原因;确定了实验的最佳条件,并以此为依据建立了煤的等温吸附实验方法的主要技术参数。   相似文献   

GIS支持下的澜沧江流域云南段土壤侵蚀空间分析   总被引：23，自引：5，他引：18  

姚华荣  杨志峰  崔保山 《地理研究》2006,25(3):421-429

利用ArcView3.2和ARC/INF08.1软件,通过图层叠加、统计分析和缓冲区分析等,提取西南纵向岭谷区澜沧江流域云南段的不同类型和强度的土壤侵蚀与地形坡度、土地利用/土地覆盖现状、土壤类型和分布、大雨日数以及河流、道路两侧的缓冲区等的相应数据,计算出土壤侵蚀综合度。结果表明,研究区不同坡度等级中,15°²5°坡度上的土壤侵蚀最强,其次为8°¹5°坡地和4°⁸°坡地;>25°坡地上则较小;不同用地类型的土壤侵蚀程度不同,总体上,旱耕坡地的土壤侵蚀较草地严重,而草地又较林地严重;在各种土壤类型中,黄壤和石灰土的土壤侵蚀最为突出,其次为红壤、黄棕壤和南方水稻土等;河流两侧和道路两侧的土壤侵蚀都较整个流域要严重,而河流两侧又略重于道路两侧;当多年平均大雨日数小于20日时,土壤侵蚀程度基本上随大雨日数的增加而增加;当大雨日数大于20日时,土壤侵蚀程度反而较小,原因在于前期大雨冲刷侵蚀,带走了地表的疏松物质。研究结果可为有针对性地防治水土流失、减少河流泥沙和水库淤积提供依据。  相似文献   

晚上新世以来菲律宾海盆XT4孔黏土矿物特征及其古环境意义     

丁雪  胡邦琦  徐方建  郭建卫  崔汝勇  易亮 《海洋地质与第四纪地质》2021,41(1):42-51

菲律宾海是典型风尘汇聚区,菲律宾海远离吕宋岛的深海沉积物是重建构造尺度亚洲风尘演化历史的良好载体.选取菲律宾海盆XT4孔沉积物开展了黏土矿物研究,并结合前人研究成果,在明确该孔黏土矿物来源的基础上,探讨了晚上新世以来亚洲风尘的演化历史及其可能的影响机制.菲律宾海盆XT4孔黏土矿物以伊利石为主,平均含量为39％,蒙脱石含...  相似文献   

Acyclic isoprenoid biomarkers and evolution of biosynthetic pathways in green microalgae of the genus Botryococcus     

《Organic Geochemistry》2014

Acyclic isoprenoids were among the earliest lipids on Earth and today > 30,000 isoprenoid-derived compounds are known, testifying to the remarkable diversification in isoprenoid biosynthetic pathways over time. Many of the isoprenoids have proven to be useful biomarkers in geochemical studies and evidence from sedimentary studies has the potential to provide a timeline for the evolution of different types of isoprenoid biosynthesis. A single green microalgal species termed Botryococcus braunii has been recognised as a major contributor of organic matter to sediments as old as the Precambrian. Modern studies of the taxonomy of B. braunii using molecular biology techniques have shown that the major clades identified from 18S rRNA gene sequences correspond to races A, B, L and S, which are defined on the basis of their hydrocarbon composition. The biosynthetic pathways by which C₃₀–C₃₇ botryococcenes are produced by the B race have now been shown to be due to a duplication of the squalene synthase gene, followed by subsequent changes to the genes, such that one pathway leads to the production of the C₃₀ botryococcene and the other to squalene. Both products are then methylated to produce botryococcenes and methylated squalenes having higher carbon numbers. The mode of biosynthesis of lycopadiene in race L is unclear, but may involve coupling of two C₂₀ phytyl diphosphates. From an examination of the geological record of botryococcenes and lycopadiene it seems likely that these pathways probably evolved early in the Eocene (ca. 55 Ma) and thus are more recently evolved than the genes for highly branched isoprenoid (HBI) alkenes first produced by diatoms about 92 Ma ago. Botryococcane produced from botryococcenes and a monoaromatic hydrocarbon produced from lycopadiene-related lipids, presumably under anoxic conditions, show promise as age diagnostic biomarkers. In view of these results, it seems likely that the Botryococcus species recorded in sediments predating the Eocene lacked the ability to produce botryococcenes or lycopadiene, but nonetheless still contained polymeric non-isoprenoid alkyl chains in the form of an algaenan which on preservation gave rise to a multitude of organic rich rocks.  相似文献   

Climatic changes indicated by trace elements in the Chagelebulu Stratigraphic Section,Badain Jaran Desert,China, since 150 kyr B.P.     

Yi Yang  Bao-sheng Li  Shi-fan Qiu  Zheng Wu  Quan-zhou Gao  Yun-zhuo Li 《Geochemistry International》2008,46(1):96-103

This paper analyzes the contents of 16 trace elements in the strata of the Chagelebulu Stratigraphic Section, Badain Jaran Desert, since 150 kyr B.P. and discovered that both the contents of the relatively stable elements, such as P, Mn, Zr, Cr, Pb, Rb, Nb, Y, and the relatively active elements, such as V, Sr, Ni, Cu, Zn, As fluctuated with the sedimentary cycles composed of 25 aeolian dune sands, loess, paleosols, lacustrine facies, alluvial, and colluvial sandy gravels, showing 25 cycles of low-high variation and a fluctuant jagged graph of chemical elements’ migration and accumulation. The lower contents of the elements in the aeolian sands show the erosion, migration and deposition of wind power in a cold and arid climate. The relative accumulation of sandy-gravel layers, especially the lacustrine facies, loess, and paleosols correlates with the section’s position in the special depression relief with a background of warm and humid climate. The above-mentioned variational characteristics were mainly caused by 25 cycles of arid-cold, windy, and warm-humid climatic fluctuation on the southern fringe of the Badain Jaran Desert since 150 kyr B.P. The essential reason bears a relationship with the back and force swing of the East Asia winter monsoon and summer monsoon influenced by climatic vicissitudes during the glacial and interglacial periods.  相似文献