湿陷性黄土边坡预应力锚索耐久性与改善措施研究          下载免费PDF全文

郭红东  白杨  畅才源 《甘肃地质》2021,(2):59-65

随着预应力锚索在湿陷性黄土边坡加固工程中的广泛应用,其耐久性问题就变得日益突出,湿陷性黄土边坡预应力锚索出现了较多因预应力损失而引起的失效事故。基于湿陷性黄土边坡预应力锚索运行现状进行研究,研究表明:黄土腐蚀性对边坡预应力锚索耐久性影响微弱,黄土湿陷性和地质条件变化对边坡预应力锚索耐久性影响显著;通过采用加强排水措施、提升浅部注浆工艺和注重运行维护等措施可以改善湿陷性黄土边坡预应力锚索耐久性;改善后的预应力锚索在监测期内处于平稳波动的服役状态,运行效果良好。本研究以期为湿陷性黄土边坡预应力锚索的设计、施工和运行维护等提供借鉴。  相似文献   

Origin of calcium in aerosols over the western North Pacific     

T. Suzuki  S. Tsunogai 《Journal of Atmospheric Chemistry》1988,6(4):363-374

Weekly aerosol samples were collected from March 1981 to June 1983 at the six stations in the western North Pacific region and analyzed for Ca and Na. By coupling data with those previously reported for Al (Tsunogai et al., 1985), the following results and conclusion have been obtained. There was a positive correlation between the atmospheric concentration of Al and the concentration of nonsea salt Ca (nssCa). The nssCa/Al ratios from the six stations, however, considerably varied (from 0.84±0.36 to 3.00±1.91), and the ratios were usally larger than those of the crustal average or of usual soil in Japan. The Ca/Al ratios of Asian desert soil and loess vary from 0.52 to 1.29, which are similar to the nssCa/Al ratios of aerosols in the surface air over the western North Pacific region except at Onna, Okinawa. The exception may be due to a local effect of coral. These results suggest that a large part of nonsea salt Ca in the surface air over the western North Pacific is derived from arid regions in Asia and that the nssCa/Al ratio in aerosol varies with that of the source material.  相似文献   

周口店新发现距今11～1.9万年的洞穴堆积层的成因及年代学研究     

田明中  曹伯勋 《现代地质》1993,7(4):421-427

本文对周口店新发现距今11～1.9万年的东岭子洞穴堆积物进行了成因研究,认为该套堆积物并非全属岩溶堆积物,其中也有风成黄土沉积。应用古地磁、热发光及铀系法等年代学方法测定,认为这套堆积为距今11～1.9万年间沉积,弥补了周口店地区近5万年的晚更新世洞穴地层空缺,是一个含有丰富地质事件的晚更新世洞穴地层剖面。  相似文献   

A geomagnetic event recorded in loess deposits of the Tönchesberg (Germany): identification of the Blake magnetic polarity episode     

Jan Reinders  Ulrich Hambach 《Geophysical Journal International》1995,122(2):407-418

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Rock-magnetic proxies of climate change in the loess-palaeosol sequences of the western Loess Plateau of China   总被引：5，自引：0，他引：5  

Christopher P. Hunt  Subir K. Banerjee  Jiamao Han  Peter A. Solheid  Eric Oches  Weiwei Sun  Tungsheng Liu 《Geophysical Journal International》1995,123(1):232-244

Results of the first detailed study of the climate proxy record in the loess-palaeosol sequence at Xining-one of the few palaeoclimate sites in the currently arid western Loess Plateau of China-illustrate the importance of making many types of rock-magnetic measurements other than susceptibility. A multiparameter approach yielded confirmation that here, as elsewhere in the Loess Plateau, the susceptibility enhancement in palaeosols was caused primarily by ultrafine magnetite and maghaemite. Nevertheless, magnetic enhancement was caused not exclusively by changes in relative grain size, but also by variations in concentration and mineralogy of the magnetic fraction.
The effects of concentration variations were removed through normalization of susceptibility and anhysteretic remanence with saturation magnetization and saturation remanence, respectively. the resulting signal was ascribed more confidently to variation in magnetic grain size, which in turn was interpreted as a better proxy of pedogenesis than simple susceptibility. Variations in magnetic mineralogy were also determined to constrain interpretations further. the data were then used to discuss climate history at Xining. Finally, results from Xining were compared with other western sites and contrasted with eastern sites.
In summary: (1) data is presented from a new Loess Plateau site which also appears to yield a global climate signal; (2) a demonstration is made of a more rock-magnetically robust way to separate concentration, composition and grain-size controls on susceptibility and other magnetic parameters; and (3) models are provided for inter-regional comparisons of palaeoclimate proxy records.  相似文献   

过去2．5百万年间黄土与深海古气候变化周期的对比分析   总被引：6，自引：0，他引：6       下载免费PDF全文

余志伟 《地球物理学报》1994,37(1):128-131

过去２．５Ｍａ间宝鸡黄土粒度记录和深海氧同位素曲线的Ｆｏｕｒｉｅｒ功率谱分析结果表明：在１．６Ｍａ以上部分，两者的周期性相当一致；但在２．５-１．６Ｍａ时段，两者的周期记录差异很大．深海氧同位素曲线记录的全球大陆冰量变化周期以与地轴倾斜度有关的０．０４１Ｍａ为主，而黄土粒度曲线记录的内陆风力强度变化周期则以与偏心率有关的０．４Ｍａ和０．１Ｍａ为主．造成这种异同的原因是：在２．５-１．６Ｍａ时段，内陆风力强度变化主要受地球轨道变化驱动，而从１．６Ｍａ前开始，转而主要受全球大陆冰量变化驱动．  相似文献   

SOIL SHEAR STRENGTH: AN INDICATOR FOR ERODIBILITY OF THE LOESS SOILS   总被引：1，自引：0，他引：1  

WANG Guiping  WEI Zhongping  ZHANG Zhiguo 《国际泥沙研究》1994,(1)

ＳＯＩＬＳＨＥＡＲＳＴＲＥＮＧＴＨ：ＡＮＩＮＤＩＣＡＴＯＲＦＯＲＥＲＯＤＩＢＩＬＩＴＹＯＦＴＨＥＬＯＥＳＳＳＯＩＬＳＷＡＮＧＧｕｉｐｉｎｇ；ＷＥＩＺｈｏｎｇｐｉｎｇａｎｄＺＨＡＮＧＺｈｉｇｕｏＡｂｓｔｒａｃｔ：ＦｉｅｌｄｅｘｐｅｒｉｍｅｎｔＳｕｎｄｅ...  相似文献   

安太堡露天煤矿排土场基底黄土的微结构演化与弱层的形成机理          下载免费PDF全文

陈敏 《地质论评》1995,41(6):571-576

本文根据安太堡露天煤矿排土场基底黄土的粘土矿物组成的微结构及其在分级荷载下微结构变化的研究，论述了排土场基底黄土内弱层的形成机理，提出弱层是在上覆排土压力下由于黄土的微结构变化而形成的演化弱层。并指出弱层的形成是导致排土场失稳滑坡的主要控制因素，这种弱层在新排土场设计时期并不存在，极具隐蔽性，但在设计时必须考虑在排土增至一定高度后，弱层的形成对排土场稳定性的影响，否则必将会存在重大滑坡隐患。  相似文献   

豫西东部黄土工程特性研究     

王现国 《水文地质工程地质》2005,32(2):58-61

豫西东部堆积了第四纪不同时期的风成黄土及冲积、冲洪积黄土状土,全新统黄土、上更新统黄土具有湿陷性,为弱—中等湿陷。中更新统黄土一般不具有湿陷性。黄土的微观结构与土的形成时代、成因类型关系密切,全新统黄土颗粒间为开放或次开放式架空结构,具有较高的湿陷性,上更新统黄土接近接触式胶结,存在粒间架空孔隙,潜在弱—中等湿陷性;中更新统黄土为不等粒基底胶结结构,存在骨架接触式孔隙,一般不具有湿陷性;同时,黄土的渗透性又具有各向异性。  相似文献   

黄土剖面中赤铁矿和针铁矿的定量分析与气候干湿变化研究   总被引：2，自引：6，他引：2  

季峻峰  陈骏  W.Balsam  刘连文  陈旸  赵良  周玮 《第四纪研究》2007,27(2):221-229

为了了解黄土剖面中赤铁矿和针铁矿的分布特征,文章采用对铁氧化物矿物灵敏的漫反射光谱法(DRS),开展了赤铁矿和针铁矿的鉴定和测定研究,提出了定量分析赤铁矿和针铁矿含量的DRS新方法.选择天然典型黄土和古土壤样品,首先采用柠檬酸盐-重碳酸盐-连二亚硫酸盐(CBD)方法去除其中成壤成因的铁氧化物矿物,以其为基体配制含不同赤铁矿和针铁矿的系列标样,然后进行DRS测试和多元逐步回归分析,分别建立测定赤铁矿和针铁矿含量的校准方程并加以检验.利用DRS方法,分析了多个黄土剖面的赤铁矿和针铁矿含量,发现黄土-古土壤剖面的赤铁矿/针铁矿比值可作为东亚季风干/湿变化的敏感指标.该比值较高时反映了干燥土壤环境,而较低时指示了潮湿土壤环境.对灵台和洛川剖面中赤铁矿/针铁矿比值的分析,初步揭示了2.6Ma年以来黄土高原东亚季风阶段性变强的特征.  相似文献