真三轴气固耦合煤体渗流试验系统的研制及应用

为了更真实地模拟煤岩在掘进巷道迎头等环境下的应力状态,研究三向应力环境下煤岩的损伤变形及瓦斯渗流情况,自主研发了真三轴气-固耦合煤体渗流试验系统。该装置主要由真三轴压力室、液压伺服系统、气体渗流系统和监测与控制系统组成,采用的试件尺寸为200 mm×100 mm×100 mm,可施加的最大轴压(?1)为70 MPa、最大侧压（?2）为35 MPa、最大侧压（?3）为10 MPa、最大瓦斯压力为6 MPa。该装置具有以下特点：(1) ?1、?2采用刚性压头加载,?3采用柔性加载,三向应力分别独立加载;(2) 设计了刚柔性压头及传压滑杆,使得?1与?2方向压头在同时加载过程中互不干扰;(3) 通过伺服液压系统控制加载功能,使得装置性能稳定,应力与位移加载精确,易于控制;(4) 气体渗流系统采用蜂窝孔对试件进行面通气,确保试件进气端瓦斯压力均匀分布;(5) 采用多种高精度传感器进行监测,实时记录煤体所受应力值、变形量及瓦斯渗流量。用两种不同应力路径下的渗流试验对该系统准确性和可靠性进行了验证,结果表明,该装置性能稳定可靠。该装置可用于揭示煤与瓦斯在三向应力条件下的耦合作用机制,为防治瓦斯灾害及研究瓦斯抽采提供了可靠的试验基础。     

宽频带静电反馈倾斜仪正交耦合误差分析

分析和计算宽频带静电反馈倾斜仪测量中正交方向上的倾斜对测量结果的影响。结果表明,正交方向的倾斜使测量结果产生误差,需对仪器加以改进,以减小正交耦合误差。     

Assessment of effectiveness of nature reserves on the Tibetan Plateau based on net primary production and the large sample comparison method

Twenty-one typical coupled large samples were chosen from areas within and surrounding nature reserves on the Tibetan Plateau using the large sample comparison method (LSCM). To evaluate the effectiveness of the nature reserves in protecting the ecological environment, the alpine grassland net primary production (NPP) of these coupled samples were compared and the differences between them before and after their establishment as protected areas were analyzed. The results showed that: (1) With respect to the alpine grassland NPP, the ecological and environmental conditions of most nature reserves were more fragile than those of the surrounding areas and also lower than the average values for the Tibetan Plateau. (2) Of the 11 typical nature reserves selected, the positive trend in the NPP for Manzetang was the most significant, whereas there was no obvious trend in Taxkorgan. With the exception of Selincuo, the annual NPP growth rate in the nature reserves covered by alpine meadow and wetland was higher than that in nature reserves consisting of alpine steppe and alpine desert. (3) There were notable findings in 21 typical coupled samples: (a) After the establishment of the nature reserves, the annual rate of increase in the NPP in 76% of samples inside nature reserves and 82% of samples inside national nature reserves was higher than that of the corresponding samples outside nature reserves. (b) The effectiveness of ecological protection of the Mid-Kunlun, Changshagongma, Zoige and Selincuo (Selin Co) nature reserves was significant; the effectiveness of protection was relatively significant in most parts of the Sanjiangyuan and Qiangtang nature reserves, whereas in south-east Manzetang and north Taxkorgan the protection effectiveness was not obvious. (c) The ecological protection effectiveness was significant in nature reserves consisting of alpine meadow, but was weak in nature reserves covered by alpine steppe. This study also shows that the advantage of large sample comparison method in evaluating regional ecology change. Careful design of the samples used, to ensure comparability between the samples, is crucial to the success of this LSCM.     

湖北省百岁人口分布与长寿区自然环境背景

基于人口普查数据,运用ArcGIS 空间分析以及SPSS 数理统计方法,对湖北省百岁人口分布与相对长寿区的自然环境背景进行研究,结果表明：过去50 a 来,湖北省百岁人口数量不断增加,百岁人口比率不断提高,但其百岁人口总数在全国的占比一直低于人口总数的占比,百岁人口比率与全国平均水平的差距越来越大;县域百岁人口比率空间差异明显,鄂北岗地稳居前茅,鄂西南山地、江汉平原、鄂东南丘陵百岁人口比率增长相对迅速;百岁人口重心向东南迁移并向省域几何中心和总人口重心靠近。湖北省的相对长寿区包括29 个县域,主要分布在鄂北岗地和江汉平原外缘的平原丘陵交错带,其自然环境背景是：气候温和、夏无酷暑、冬无严寒、雨量适中、阳光充足、空气流动性好、海拔较低、地形平缓,土壤中富含钼、锰、锌等微量元素。     

500 kV输电线路黄河大跨越塔基工程施工实践

500 kV输电线路黄河大跨越塔基工程分地下和地上两大部分,集多种施工工艺方法于一体。重点阐述了钻孔桩施工,支撑系统的选择,高桩承台模板的支护,地脚螺栓的安放和大体积承台砼的浇注等施工关键工序、技术难点和重点的具体控制方法。     

考虑渗流场作用下的隧道开挖分析

由于隧道的开挖,破坏了初始地应力场与渗流场。以圆形隧道为例,采用有限差分程序计算考虑渗流场作用时,隧道开挖后洞室周围应力场、孔隙水压力、位移场的分布情况,并对比计算了是否考虑渗流效应时位移场的差异,以及不同水位导致的位移场的不同分布状态。提出了相应的隧道防排水、设计与施工相关建议。     

Unfolding relations between land cover and farm management: high nature value assessment in complex silvo-pastoral systems

The high nature value (HNV) concept, proposed by the European Environment Agency, recognizes that specific farming systems support high biodiversity levels, mainly as a result of extensive management practices. The Portuguese montado is one of the most significant HNV systems in southern Europe. However, considering the great complexity characterizing these systems both in land management and in landscape structure, a specific context-oriented methodology to assess which montado areas are likely to be classified as HNV farmland is needed. In this sense, the aim of this study is to explore a methodological approach which makes it possible to assess land management pressures through land cover information on these complex silvo-pastoral systems. The proposed methodology was tested through a local case study in a montado area in southern Portugal, assessing the relation between management practices and a vegetation cover index. Results show that in similar montado areas different land management strategies varying in stocking density, but also in type of grazing animals and shrub control practices, configure different vegetation cycles. These results indicate there is a way to develop a straightforward methodology to assess the HNV value of Mediterranean silvo-pastoral systems based on land cover indicators. These would make it possible to assess the HNV of montado areas with direct and objective information and independent of farmer’s surveys or other farm-based data.     

Predicting the displacement of triple pendulum™ bearings in a full‐scale shaking experiment using a three‐dimensional element

The accuracy of a series spring model to predict the peak displacement and displacement history of Triple Pendulum? (TP) bearings in a strongly shaken, full‐scale building is evaluated in this paper. The series spring model was implemented as a self‐contained three‐dimensional TP bearing element in OpenSees and is now available for general use. The TP bearing element contains the option for constant friction or a generalized friction model that accounts for the effect of instantaneous velocity and compression load on the friction coefficient. Comparison between numerical simulation and experimental data of a five‐story steel moment frame building shows that the peak displacement of isolation system can generally be predicted with confidence using a constant friction coefficient model. The friction coefficient model accounting for the effect of axial load and velocity leads to minor improvement over the constant friction coefficient models in some cases. Copyright © 2013 John Wiley & Sons, Ltd.     

On topographic core-mantle coupling

Abstract

The purpose of this note is two-fold: to draw attention to a perplexing difficulty connected with topographic core-mantle coupling, and to suggest tentatively an explanation. The difficulty is an apparent conflict between the most comprehensive theory of the coupling so far attempted (Anufriev and Braginsky, 1975a, b, 1977a, b) and recent explicit calculations based on magnetic and seismic information (Speith et al., 1986). It is argued that asymmetric deviations from Anufriev and Braginsky's basically axisymmetric model of the underlying core flow are capable of resolving the difficulty.