砾石覆盖对边界层风速梯度的影响

通过莫高窟窟顶野外风洞实验对不同覆盖度砾石床面风速梯度的变化规律进行了研究。结果表明,床面砾石平均高度以下风速梯度随砾石覆盖度变化比较杂乱,而砾石平均高度以上风速梯度随覆盖度增加呈现出有规律的变化。从覆盖度5%到35%风速逐渐减小, 40%~80%趋于稳定,35%最小。据此,大气边界层可明显分为两层,约以砾石平均高度为界,下层定义为粗糙亚层,上层定义为惯性亚层。粗糙亚层风速梯度随砾石间距高度比D/H值的变化同样比较杂乱;惯性亚层风速梯度随砾石间距高度比D/H值的变化规律比较一致:风速在D/H值0.3~1.5段趋于稳定,2.0~4.0段风速逐渐增大,1.5处风速最小。另外,对砾石床面不同高度阻风效应的计算表明,砾石床面的阻风作用在砾石床面表面附近最强(0.75 H~1.1 H),粗糙亚层阻风作用随高度增大而增大,惯性亚层阻风作用随高度增大逐渐减小。该粒径砾石阻风效应最优间距高度比D/H值为1.5,最优间距为3 cm,最优覆盖度为35%,为砾石防沙工程的铺设提供了一定的参考作用。     

抗高温泡沫钻井液体系评价研究

高频钻井液压力波信息传输技术传输速率高,是实现自动化、智能化钻井的关键技术之一,由于高频钻井液压力波在传输过程中存在较大的衰减,阻碍了该技术的现场应用,探明其衰减规律对于高速传输技术开发具有重要意义。在假设同一钻柱截面钻井液压力相等且钻井液流速存在径向分布的基础上,基于二维轴对称瞬态流动理论,采用小信号分析方法,综合考虑了压力波信号参数、钻柱尺寸及钻井液参数的影响,建立了高频钻井液压力波衰减模型并给出了适用条件。最后采用地面实验验证了该模型的正确性。随后分析钻井液压力波频率、压力波传输距离、钻井液密度及黏度、钻柱内径对高频压力波衰减的影响。结果表明：高频钻井液压力波幅值衰减量随钻井液压力波频率、压力波传输距离及钻井液黏度的增加而增大,且变化规律为指数型;幅值衰减量受频率影响最大,并随钻井液密度及钻柱内径增加逐渐减小。本研究可为高频钻井液压力波信息传输技术研发提供理论指导。

     

用地面湿度参量计算我国整层大气可降水量及有效水汽含量方法的研究

根据1993年我国28个台站地面及高空气象要素资料,拟合出这28个台站所在地区整层大气可降水量同地面湿度参量(地面水汽压、地面露点)关系的经验表达式,并且在此基础上,通过引进地理纬度ψ和海拔高度H两个参量,将经验系数参数化,建立起由地面湿度参量计算整层大气可降水量的经验计算模式.另外还拟合出这些地区整层大气有效水汽含量同可降水量关系的经验表达式,提出一个先由地面湿度参量计算整层大气可降水量,再由此计算出整层大气有效水汽含量的方法.     

中国北方山区的土地压力及其缓解途径:21个小流域的经验分析(英文)

Land pressure and adaptation are the main factors determining environmental degradation in most of China’s mountainous regions. Little attention so far has been paid to the adaptation strategies based on evaluation of land pressure in these regions. We evaluated the grain production pressure and economic development pressure for 21 small watersheds undergoing soil conservation measures in the northern mountainous region of China, compared the evaluation results with actual production for each of the watersheds, and analyzed the adaptation strategies. The results imply that land pressure was spatially heterogeneous among the sample watersheds, but there was a balancing trend between land pressure and productive capacity for each watershed. Under rising pressure, these watersheds developed a variety of adaptation strategies such as labor migration, increasing fruit and nut production, and expanding rural tourism if possible. These strategies result from evolution of the market economy in China, and persistent development of the national economy determines the variation of environment in these mountainous regions.     

The distribution of radiogenic heat production as a function of depth in the Sierra Nevada Batholith, California

Geochemical analyses and geobarometric determinations have been combined to create a depth vs. radiogenic heat production database for the Sierra Nevada batholith, California. This database shows that mean heat production values first increase, then decrease, with increasing depth. Heat production is 2 μW/m³ within the 3-km-thick volcanic pile at the top of the batholith, below which it increases to an average value of 3.5 μW/m³ at 5.5 km depth, then decreases to 0.5–1 μW/m³ at 15 km depth and remains at these values through the entire crust below 15 km. Below the crust, from depths of 40–125 km, the batholith's root and mantle wedge that coevolved beneath the batholith appears to have an average radiogenic heat production rate of 0.14 μW/m³. This is higher than the rates from most published xenolith studies, but reasonable given the presence of crustal components in the arc root assemblages. The pattern of radiogenic heat production interpreted from the depth vs. heat production database is not consistent with the downward-decreasing exponential distribution predicted from modeling of surface heat flow data. The interpreted distribution predicts a reasonable range of geothermal gradients and shows that essentially all of the present day surface heat flow from the Sierra Nevada could be generated within the 35 km thick crust. This requires a very low heat flux from the mantle, which is consistent with a model of cessation of Sierran magmatism during Laramide flat-slab subduction, followed by conductive cooling of the upper mantle for 70 m.y. The heat production variation with depth is principally due to large variations in uranium and thorium concentration; potassium is less variable in concentration within the Sierran crust, and produces relatively little of the heat in high heat production rocks. Because silica content is relatively constant through the upper 30 km of the Sierran batholith, while U, Th, and K concentrations are highly variable, radiogenic heat production does not vary directly with silica content.     

剪切带倾角尺度律与局部化启动跳跃稳定研究

研究了剪切带倾角是如何依赖于岩样高度以及剪切带的不稳定性。建立了准脆性材料试件剪切带倾角尺度效应模型,得到了剪切带倾角尺度效应的解析解,且与实验结果比较相符。研究结果表明:剪切带倾角随着试件高度的增加而增加,但其增加幅逐渐减缓,最终趋于稳定值。笔者还对剪应变局部化启动、跳跃和稳定进行了理论分析,解释了实验所观测到的剪切带跳跃现象和砂岩岩样应变局部化较煤样滞后的原因。剪应变局部化是否发生跳跃,关键取决于全程应力-应变曲线软化段是否存在拐点。对于没有拐点的情形,宏观剪切带图案不跳跃。局部化是导致准脆性材料试件剪切带倾角尺度效应的原因。     

深埋顶管顶力理论计算与实测分析

针对管幕预筑法中深埋顶管顶力进行理论和实测分析。顶管顶力与垂直土压力密切相关。参照隧道开挖中垂直土压力的计算方法,常用的垂直土压力计算理论有：普氏理论和太沙基理论。在详细分析了这两种垂直土压力计算理论的适用性和缺陷之后,结合普氏理论和太沙基理论,提出了改进的垂直土压力计算理论公式,并编写MATLAB程序计算改进理论公式的数值解。改进理论既考虑了土拱效应,又考虑了拱下土体的挟持力,更符合实际土体变形情况。将普氏理论、太沙基理论和改进的理论应用于沈阳地铁新乐遗址站管幕预筑法顶管工程中,计算不同深度的两根大埋深管道顶力,并把计算与实测结果进行比较,发现普氏理论和太沙基理论计算结果都远大于实测值,改进理论计算结果稍大于实测值,更适合于深埋顶管顶力估算。     

东海地区高压-超高压变质带中变质橄榄岩及其原岩和成因类型的判别——以PP1孔和PP3孔为例

本文在总结全球地幔橄榄岩岩石学和地球化学特征的基础上,首次提出了一个用于判别HPUHP变质带中变质橄榄岩原岩及其成因类型的判别图解。该图主要由镁铁总量MgO+（%）和一个参数m+f/si比值构成。另用Al2O3和CaO分别与MgO+（%）制成两个辅助图解,以示方辉橄榄岩和二辉橄榄岩之间在Al2O3和CaO含量上的分界。通过原岩判别结果和研究表明,PP3孔和PP1孔两者在变质组合、原岩成因类型、地球化学和变质条件方面存在一系列的重大差异。分别代表来自两种极端的地球化学类型和两种不同大地构造环境的UHP变质体。PP3钻孔以Ol+Gt+Cpx+Opx+Sp为变质矿物共生组合的含石榴石纯橄岩,其原岩系来自地幔残余成因的方辉橄榄岩遭受UHP变质作用的产物,它以成分高度均一,富Mg（Mg’=92）,极端亏损不相容元素REE（∑REE<1×10-6可称为超亏损型）为特征。在变质相中仍保留原岩的残余矿物铬尖晶石（Sp）,其成分显示蛇绿岩地幔橄榄岩的成分趋势。并出现以Gt和Sp共存相为特征的变质相。据实验结果（klemme,2004）表明该共存相的稳定域的PT条件CrSp可达7Gpa,T1400℃,即形成于200km的地幔深度。综合研究显示该孔变质橄榄岩原岩（方辉橄榄岩）具有大洋岩石圈地幔残余成因的某些印记,而不是同深度原生地幔岩相转变的产物。PP1孔变质橄榄岩是由无水矿物相（Ol+Opx+Cpx+Gt）+含水矿物相（Phl±Chu）组成的石榴石橄榄岩杂岩,其原岩来自两种不同成因的超镁铁岩系列：一为具地幔成因的方辉橄榄岩二辉橄榄岩系列（可能相当于地幔楔中的Al型橄榄岩）,另一部分（少数）来自具岩浆成因的超镁铁岩系列（纯橄岩—异剥橄榄岩—辉石岩组合,可能相当于A2型橄榄岩）。该套变质橄榄岩,以成分高度不均一,极端富集REE（∑REE平均>20×10-6可称为超富集型）和大离子亲石元素（K、Ba、Rb）为特征。这种异常现象并不反映其原岩原有的地球化学特征,它可能是由于在俯冲过程中受到陆壳物质的污染,或壳幔相互作用所致。据该孔变质相中缺乏Sp相,而以Gt为标志的变质相的事实,推断其形成的压力条件应>7Gpa, 即形成的深度应大于200km。上述研究表明在苏鲁UHP变质带中,不仅有来自大陆地幔楔中的地幔残余的UHP变质体,而且首次提出有可能来自大陆俯冲前锋具大洋岩石圈地幔性质的（蛇绿岩型地幔残片）变质体存在,这对揭示该区UHP变质带的形成和演化过程提供了新的信息。     

Calculating Method and Verification of Wave Pressure Distribution on the Breast Wall of Mound Breakwater

In this paper, the calculating charts and formulae about wave pressure on the breast wall are derived with seven parameters on the basis of physical model study. The verification shows that the charts agree with the example, and are adopted in the Specifications of Fishery Harbours Breakwater by the Ministry of Agricultures.     

钻孔压灌粉煤灰混凝土桩复合地基的应用研究

通过工程实例，介绍了钻孔压灌粉煤灰混凝土桩的施工技术，说明了其施工工艺及特点，并利用6组静荷载试验成果，对粉煤灰混凝土桩复合地基的承载力特性进行了分析。