内蒙克什克腾旗上新世含圆球形钙质结核古沙丘的发现

本文报到首次在赤峰北部之西拉木伦河南岸百岔河玄武岩之上发现了上新世中晚期的古沙丘, 证明赤峰北部百岔河谷地区在上新世中晚期也具有形成古沙丘的较干旱和强劲风力的条件, 与现今其附近地区(在汉诺坝组组成的高台地及西拉木伦河谷中)较广泛地发育的草丛沙丘的状况十分相似。同时, 在古沙丘中发现球度极好的钙质结核, 其成岩作用与古气候变化意义有待进一步研究。     

灵台风尘堆积中钙质结核的地球化学研究

通过对甘肃灵台风成黄土－古土壤－红粘土序列中钙质结核的野外分布及形态特征观察,并对主元素和微量元素进行化学分析,发现结核中氧化物活动给分和惰性组分含量的比值在剖面中自下而上逐渐变大,反映了结核形成时其上覆土层所经历的淋溶程度逐渐增强;而ＭｇＯ含量校正后的ＭｇＯ／Ｃａｏ比值则逐渐减小,批示结核形成时环境温度逐渐降低。灵台剖面自下而上不同层位结核中Ｓｒ／Ｂａ比值及ＣａＣＯ３含量的变化同氧化物含量及比值     

北美西部内陆海盆Niobrara组的钙质超微化石及其环境意义——Ⅰ：钙质超微化石及其分带

北美西部内陆海盆上白垩统Niobrara组中的钙质超微化石十分丰富,且多保存良好,呈现典型的晚白垩世远洋钙质超微化石组合面貌,经系统鉴定,计有60属100余种和亚种。为适应不同的环境,Kansas西部和South Dakota东部的钙质超微化石组合面貌稍有不同。经与白垩纪颗石藻化石带对比,可将Kansas西部的Niobrara组划分为6个化石带(CC13～CC18)和8个亚带,其中,根据本文研究地区的化石序列,CC15和CC16带被进一步划分。根据与同一剖面所建立的无脊椎动物化石带对比,钙质超微化石CC17带的时代被重新厘定,即该带应始于中Santonian的晚期,结束于晚Santonian的早期,并据此将Santoniatr／Campanian的界线划在CC18带之内。     

Late Barremian to early Aptian calcareous nannofossil paleoceanography and paleoecology from the Ocean Drilling Program Hole 641C (Galicia Margin)

Calcareous nannofossil assemblages at Site 641C (Galicia Margin, North Atlantic) were investigated in order to determine changes in fertility and temperature of surface waters. Taxa such as Zeughrabdotus spp. <3.5 μm, Biscutum constans, Discorhabdus rotatorius and Diazomatolithus lehmanii, which thrived in higher fertility conditions, are particularly abundant across the CM0 interval as opposed to those with oligotrophic affinities such as Watznaueria spp. and Nannoconus spp., which are generally reduced in abundance. The abundances of nannoconids are much lower than those observed in Tethyan sections, indicating higher fertility conditions. Slumpings and low recovery prevent the identification of the onset of the “nannoconid crisis”, but a sharp drop in nannoconid abundances, observed prior to the CM0 interval, correlates with the “nannoconid decline” observed in several Tethys sections.The normalized ratio between low and high fertility taxa (Fertility Index) was used to characterize the nannofossil assemblages in terms of productivity changes. The highest values of the Fertility Index were observed across magnetic chron CM0. The paucity of cold water taxa such as Seribiscutum spp. and Repagulum parvidentatum suggests warm water conditions throughout the deposition of upper Barremian–lower Aptian sediments on the Galicia Margin.     

Late Oligocene Sedimentary Hiatus in Deep Sea Area of South China Sea, Result of Calcareous Nannofossils from ODP Site 1148

In order to determine the age of the sedimentary hiatus and its geological significance, a study of the calcareous nannofossil biostratigraphy was carried out. Detailed strutigraphical data of the Late Oligocene-Eariy Miocene diagnostic species thus obtained. The nannofossil zonation of this interval was subdivided and the Oligocene-Miocene boundary was further determined. Several last Late Oligocene events were recognized, indicating a long-term sedimentary hiatus in the uppermost Upper Oligocene.The time span of the hiatus was estimated for about 2.2 Ma, at least from 23. 9 to 26. 1 Ma. The lithological and geophysical data from Site 1148 indicate some abrupt sedimentary changes that occurred below and above the hiatus. This hiatus at Site 1148 was probably related to the tectonic change, a major ridg ejmnp during the seafloor spreading in the Late Oligocene South China Sea.     

石灰岩地区种植龙须草生态经济效益分析

本文采用定性与定量相结合的方法,研究与探讨了石灰岩地区种植龙须草的生态、经济效益。研究结果表 明,在土壤瘠薄、水土流失严重、土地生产力极其低下的石灰岩地区,种植龙须草不仅能获得较好的生态效益,而且 也能取得良好的经济效益,从而促进地方经济的快速发展。     

钙质砂中锚定板的极限抗拔力计算

采用室内足尺寸模型试验研究钙质砂中锚板的抗拔破坏面形状,并将破坏模式分为浅埋型、过渡型及深埋型。采用极限平衡理论得到三种不同的破坏模式的极限抗拔力计算公式。     

Shearing response of geotextile-reinforced calcareous soils using monotonic triaxial tests

Abstract

Different types of geosynthetic reinforcements have been widely used for improving shear strength of soil materials in recent decades. In this study, two different calcareous soils reinforced by geotextile layers were evaluated by monotonic compression triaxial tests. The calcareous soils were obtained from Hormuz Island and Boushehr Port located in the north coast of the Persian Gulf. Different reconstituted samples were prepared at dense conditions with and without geotextile layers and consolidated under different effective confining pressures ranging from 100 to 600?kPa. Different layers of reinforcements including one, two and three geotextile layers were placed in the reinforced samples and sheared under drained condition. The results show that confining pressure has a significant effect on the efficiency of reinforcements. Evidently, increasing the reinforcement layers decreased the particle breakage of the calcareous soils used in this study.     

基于三维数字图像相关技术钙质砂颗粒运动行为试验研究

桩基附近土颗粒的运动行为与宏观力学表现密切相关,对揭示界面剪切机制具有重要意义。利用自主研制的大型直剪仪,结合三维数字图像相关技术（3D-DIC）全场位移测量分析系统,开展了钢−钙质砂界面循环剪切试验,研究了界面附近砂颗粒的运动行为演化规律。结果表明：界面峰值剪切应力和发挥的界面摩擦角随循环次数的增大而增加,体变特性以剪缩为主;钙质砂颗粒左右移动的幅度与距界面的垂直距离成反比,钙质砂颗粒的位置随循环次数的增大逐渐向正剪切方向移动,试验结束时上剪切盒左侧区域的钙质砂颗粒向正剪切方向移动的距离最大;钙质砂颗粒在单个循环内出现有规律的上下移动,向下移动的幅值更大,位于上层的钙质砂颗粒向下移动的位移值大于下层;钙质砂颗粒的运动速度在沿单方向剪切时,呈现出慢−快−慢的变化规律,位于上剪切盒右侧区域的钙质砂的体变特性较左侧区域更显著;网格位移值和缺失数量随循环次数的增大而增加,在试验后期趋于稳定,试验结束时的破碎带厚度为 6.21 mm。     

波浪荷载作用下饱和钙质砂孔压特性及累积损失能量试验研究

钙质砂是一种海洋生物成因土,为我国南海岛礁吹填的主要材料。研究其动力特性对开发南海资源意义重大。实际工程中,钙质砂主要受到幅值和主应力方向均变化的波浪荷载作用,其作用效果与一般定轴剪切试验有较大不同。因此,利用空心圆柱扭剪仪模拟波浪荷载,开展一系列饱和钙质砂的不排水试验,重点研究循环应力比CSR和相对密实度Dr对钙质砂孔压特性的影响,并与石英砂对比分析,发现颗粒形态差异导致了两类砂土不同的孔压发展模式。同时,引入能量法,初步探究钙质砂累积损失能量变化规律。在此基础上,建立了考虑不同相对密实度的钙质砂孔压-累积损失能量模式。