多年冻土区活动层冻融状况及土壤水分运移特征

利用位于典型多年冻土区的唐古拉综合观测场2007年9月1日—2008年9月1日实测活动层剖面土壤温度和水分数据,对多年冻土区活动层的冻结融化规律进行研究;同时,对冻融过程中的活动层土壤液态水含量的变化特征进行分析,探讨了活动层内部土壤水分分布特征及其运移特点对活动层冻结融化过程的影响. 结果表明：活动层融化过程从表层开始向下层土壤发展,冻结过程则会出现双向冻结现象. 一个完整的年冻融循环中活动层冻结过程耗时要远远小于融化过程. 活动层土壤经过一个冻融循环,土壤水分整体呈现下移的趋势,土壤水分逐步运移至多年冻土上限附近积累. 同时,土壤水分含量和运移特征会对活动层冻融过程产生显著的影响.     

Genetic algorithm for fitting a mixed Bingham distribution to 3D orientations: a tool for the statistical and paleostress analyses of fracture orientations

The clustering of fracture orientations is important for tectonic studies and for geotechnical engineering. In this study, a real‐coded genetic algorithm was adopted to fitting a mixed Bingham distribution to orientation data by maximizing the log‐likelihood function of the distribution. The maximization is a difficult problem, because the function has multimodality and singularity. It was found that the algorithm was effective for this problem. Given the orientations of dilational fractures, the present method determines not only the stress axes and stress ratio of each of the fracture groups but also the maximum non‐dimensionalized fluid pressure at the time of their formation. In addition, the software calculates the 95 % error ellipses of the concentration axes. The present method found that the orientations of ore veins of the Akenobe Mine, SW Japan, should be partitioned into three clusters. It is shown that two of the groups had distinctive Zn and Sn contents, and that the ore fluids had overpressures only slightly greater than the minimum principal stress at the time of the deposition of Zn‐ and Sn‐rich veins.     

THE THEORETICAL STUDY ON THE LAWS OF DRAG REDUCTION BY AERATION IN OPEN CHANNEL 1

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俯冲带库仑楔形体力学

楔形体理论研究楔形体在底部摩擦力、重力和边界外力共同作用下内部的应力状态,有助于我们定量分析断层强度和岩石性质与楔形体稳定状态之间的关系.本文首先简要介绍基于不同楔形体材料而得出的应力解析解.然后介绍基于理想弹塑性材料的俯冲带库仑楔应力解析解.最后介绍基于该解析解而提出的动态库仑楔形体理论.俯冲带地震反射剖面数据表明,弧前靠近海沟部分地表坡度比较陡,其内部经历复杂永久塑性变形（称为外部楔形体,outer wedge）.而靠近内陆部分地表坡度比较平缓,反射剖面显示沉积层呈水平规则分布,常伴随沉积盆地（称为内部楔形体,inner wedge）.动态库仑楔形体理论认为弧前这种地表形态和内部构造特征的不同,可能反映了断层面摩擦性质的差异性.内部楔形体对应于断层面上的生震带,在地震周期可能主要经历弹性变形.而外部楔形体对应于断层面上的无震蠕滑部分,在地震发生时可能产生塑性破坏、永久变形.

     

由环境应力值寻找地震危险区的尝试

作者根据位错理论,采用二维矩形破裂模式,在导出了平均震源速度谱的基础上,导出了用地震波计算环境剪应力τ_0的公式。计算了1987—1991年中国和邻区大约1000多次4级以上中强地震的环境剪应力值τ_0,并把τ_0≥10MPa的地震看作是高剪应力值地震。自1987—1991年5年内,我国及邻区共发生M_s≥6.0的强震45次,和160余次高剪应力中强地震(M=4.0-5.0,τ_0≥10MPa),大约有1/4的强震和1/3的高应力值地震发生在台湾地区。说明台湾地区是一个高地震活动区和高应力值地区。新疆的喀什—乌恰—乌什地区也是高地震活动区和高应力值地区。我们对发生在其地区的强震,向前追溯了环境应力值τ_0的变化。发现有11个强震事件(约占全部事件80%)在震前1—5年内,在以强震为圆心,半径为200km范围内(个别略远),均有1—2个或多个高应力值地震出现。说明当高应力值地震发生时,该地区环境应力在增高,它可以作为将要发生强震的前兆。据此,推测了今后3年内大陆强震发生的可能地区是:①中印缅三国边境地区;②西藏波密地区;③青海北部到宁夏北部地区;④新疆伊宁地区;⑤纵贯新青藏90°E±2°线地带;⑥晋北忻州地区;⑦苏北及黄海地区;⑧山东长岛地区。     

汾渭地震带强震震源参数的确定

目的是计算汾渭地震强震的震源参数。所用的方法是根据断裂力学的有关公式分析断裂扩展过程中应力和位移的变化,计算结果表明地震多数是在低初始应用作用下发生的（大约１００×１０＾５Ｐａ）,而且该方法在原理上是可行的。     

哈尔滨-齐齐哈尔客运专线路基防冻工程模型试验研究

季节冻土地区修筑铁路客运专线面临着严重的路基冻胀问题,为研究保温板（XPS）在季节冻土地区路基工程中的防冻胀效果,开展了室内模型试验研究. 试验结果表明：经过2个周期的试验,保温板上下温差十分明显,保温板上下温差在负温期高于正温期,保温板下土体冻结速率随保温板厚度的增加而减小. 30 cm保温板下黄土的含水率随冻融过程呈单一变化规律,其他3个试验模型土体含水率在冻结开始时先减小,冻结结束时增大,最终保持稳定的趋势. 4个试验模型中的下层土体冻胀量均远大于上层土体,无保温板黄土试验模型冻胀量远大于其他3个保温板试验模型;AB料冻胀量随保温板厚度的增加而减小,AB料冻胀率远小于黄土冻胀率. 因此,在季节冻土地区路基设计中宜采用保温板路基,路基填料优先采用AB料.     

重金属胁迫下四种红树植物幼苗生理响应特征

研究了四种红树植物红海榄、秋茄、木榄、角果木幼苗在不同浓度重金属水溶液胁迫28天后的生理生化指标变化特征,包括可溶性蛋白含量、超氧化物歧化酶（superoxide dismutase, SOD）、过氧化物酶（peroxidase, POD）活性和氧化损伤标志物丙二醛（malondialdehyde, MDA）含量。研究结果表明四种植物叶片内的SOD、POD活性均呈现出先升高后下降趋势,10倍重金属水溶液中的红海榄,5倍重金属水溶液中的秋茄和木榄,以及1倍重金属水溶液中的角果木具有较好的抗氧化酶活性,能有效清除活性氧,减小氧化损伤。在同等浓度重金属水溶液处理下,MDA含量结果显示红海榄受损程度最轻,秋茄、木榄受损程度居中,角果木受损程度最重。红海榄抗重金属胁迫能力强于秋茄、木榄,角果木抗重金属能力最弱。上述四种红树植物对重金属的抗性结果说明红树科植物具有较强的抗污染能力,这对于我国红树林生态修复与保护具有重要的指导意义。     

Effects of differing coverage of moss‐dominated soil crusts on hydrological processes and implications for disturbance in the Mu Us Sandland,China

To study the effects of biological soil crusts (BSCs) on hydrological processes and their implications for disturbance in the Mu Us Sandland, the water infiltration, evaporation and soil moisture of high coverage (100% BSCs), middle coverage (40% BSCs) and low coverage (0% BSCs, bare sand) of moss‐dominated crusts were conducted in this study, respectively. The conclusions are as follows: (1) the main effects of moss‐dominated crusts in the Mu Us Sandland on the infiltration of rainwater were to reduce the infiltration depths and to retain the limited rainwater in shallow soil; (2) moss‐dominated crusts have no significant effects on daily evaporation when the volumetric water content at 4 cm depth in 100% BSCs (VWC4) was over 24.7%, on enhanced daily evaporation when the VWC4 ranged from 6.5% to 24.7% and on reduced daily evaporation when the VWC4 was less than 6.5%; and (3) decreasing the coverage of moss‐dominated crusts (from 100% to 40%) did not significantly change its effects on infiltration, evaporation and soil moisture. Our results demonstrated that for the growth and regeneration of shrubs, which were dominated by Artemisia ordosica in the Mu Us Sandland, high coverage of moss‐dominated crusts has negative effects on hydrological processes, and these negative effects could not be significantly reduced by decreasing the coverage of moss‐dominated crusts from 100% to 40%. Therefore, for the sustained and healthy development of shrub communities in the Mu Us Sandland, it is necessary to take appropriate measures for the well‐developed BSCs in the sites with high vegetation coverage in the rainy season. Copyright © 2015 John Wiley & Sons, Ltd.