某铁路隧道涌水量预测与分析

为进行某铁路隧道的设计与施工,获取相关的水文地质参数,进行了3个钻孔的抽水试验,以获取相关的水文地质参数。运用地下水径流模数法、大气降雨入渗法和地下水动力学法对隧道涌水量进行了计算,计算结果显示：地下径流模数法的计算值偏小,降水入渗法的计算值适中,地下水动力学法的精度较高,但计算的涌水量值较大;三种方法比较,决定结果采用大值,即涌水量正常值取6150m^3/d,最大涌水量值取9770m^3/d。提出了采用双向自流排水,适当布设施工监控设备的工程建议。     

相对位移反分析的DFP优化方法及其工程应用

洞室围岩的某些参数,如弹性模量、强度参数等,对地下洞室的施工和设计具有极其重要的作用,直接进行这些参数的现场测量势必要耗费大量的物资和精力,在这种背景下,位移反分析的工程应用具有很重要的理论和实用价值。但洞室工程中大量不确定性因素的存在使得监测结果不可避免地存在随机性,有时会使得变形监测结果产生较大的误差,甚至失真。因此以监测结果的绝对值所反演得到的参数可能是错误的。在这种情况下,以监测数据的相对值进行参数反演在一定程度上可以消除测量误差。基于相对位移的随机反分析法并结合DFP优化算法开发了基于相对位移的随机反分析法,将其应用于一具体洞室工程中反演其弹性模量取得了较为理想的效果。     

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。     

三江造山带玉峰寺深埋隧道岩爆危险性综合评价

深埋隧道的岩爆机理和岩爆预报预测一直是工程地质和岩石力学的热点和难点问题,已成为困扰地下工程发展的瓶颈之一。以滇藏铁路穿越三江造山带玉龙雪山南段的玉峰寺深埋隧道方案为例,在野外工程地质调查的基础上,对影响隧道岩爆的相关因素进行了系统分析。根据岩石力学试验、地应力分析和数值模拟计算结果,采用多种判据对玉峰寺隧道岩爆危险性进行了分析预测和综合评价。研究结果对于地质构造复杂区深埋隧道规划设计和岩爆灾害防治具有一定指导意义。     

三维坑道直流聚焦法超前探测技术

对坑道超前探测方法中的三维坑道直流聚焦法的电极组合作了研究.计算、分析了2个同性点电源的电流分布规律,指出由于电流的相互排斥作用,电流密度在这两个点电源的中垂线下一定深度处产生最大值,这个深度与这两个点源之间的距离成正比.基于上述理由,设计出3种电极组合:四点电源、五点电源和九点电源布极方式.用三维有限单元数值模拟的方法计算了上述3种电极系的空间电位分布,发现九点电源方式对电流聚束效果较好,而且当主电极电流小于屏蔽电极电流时效果最好.     

Research on wind-induced responses of a large-scale membrane structure

The wind-induced responses of a large-scale membrane structure, Expo Boulevard, are evaluated in this study. To obtain the wind pressure distribution on the roof surface, a wind tunnel test is performed. A brief analysis of wind pressure on the membrane roof is conducted first and then an analysis of the wind-induced responses of the structure is carried out using a numerical integral method in the time domain. In the process of calculation, the geometrical nonlinearity is taken into account. Results indicate that mean, RSM and peak values of the structure responses increase nonlinearly while the approaching flow velocity increases. Strong nonlinear characteristics are observed in the displacement responses, whereas the responses of nodal stress and cable axial force show minimal nonlinear properties when the membrane structure is subjected to wind loads. Different values of the damping ratio only have a minimal impact on the RSM response of the structure because the background component is a dominant part of the total dynamic response and the resonant component is too small. As the damping ratio increases from 0.02 to 0.05, the RMS responses of vertical displacement, nodal stress and cable axial force decrease by 8.1%, 6.7% and 17.9%, respectively. Since the mean component plays a significant role in the wind-induced response, the values of the gust response factor are not high for Expo Boulevard.     

Water temperature dynamics in High Arctic river basins

Despite the high sensitivity of polar regions to climate change and the strong influence of temperature upon ecosystem processes, contemporary understanding of water temperature dynamics in Arctic river systems is limited. This research gap was addressed by exploring high‐resolution water column thermal regimes for glacier‐fed and non‐glacial rivers at eight sites across Svalbard during the 2010 melt season. Mean water column temperatures in glacier‐fed rivers (0.3–3.2 °C) were lowest and least variable near the glacier terminus but increased downstream (0.7–2.3 °C km^–1). Non‐glacial rivers, where discharge was sourced primarily from snowmelt runoff, were warmer (mean: 2.9–5.7 °C) and more variable, indicating increased water residence times in shallow alluvial zones and increased potential for atmospheric influence. Mean summer water temperature and the magnitude of daily thermal variation were similar to those of some Alaskan Arctic rivers but low at all sites when compared with alpine glacierized environments at lower latitudes. Thermal regimes were correlated strongly (p < 0.01) with incoming short‐wave radiation, air temperature, and river discharge. Principal drivers of thermal variability were inferred to be (i) water source (i.e. glacier melt, snowmelt, groundwater); (ii) exposure time to the atmosphere; (iii) prevailing meteorological conditions; (iv) river discharge; (v) runoff interaction with permafrost and buried ice; and (vi) basin‐specific geomorphological features (e.g. channel morphology). These results provide insight into the potential changes in high‐latitude river systems in the context of projected warming in polar regions. We hypothesize that warmer and more variable temperature regimes may prevail in the future as the proportion of bulk discharge sourced from glacial meltwater declines and rivers undergo a progressive shift towards snow water and groundwater sources. Importantly, such changes could have implications for aquatic species diversity and abundance and influence rates of ecosystem functioning in high‐latitude river systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Decreasing trend of sediment transfer function of the Upper Yellow River,China, in response to human activity and climate change

Abstract

An index (F_s) for sediment transfer function is introduced, based on the sediment budget at the channel scale. The purpose of this study is two-fold: to gain a deeper insight into how F_s is influenced by natural and human factors, and to provide some new knowledge for decision making in the management of the Upper Yellow River, China. Since 1960, the F_s of the Lanzhou to Toudaoguai reach of the Upper Yellow River shows a decreasing trend. At the drainage basin level, the decreased F_s can be explained by changes in precipitation and air temperature, as well as by a number of variables describing human activity, such as reservoir regulation, water diversion, and soil and water conservation. The higher temperature reduces the transfer function, while the larger runoff coefficient increases it. At the channel level, the decreased F_s can be explained by a number of variables of flow and sediment input. Three countermeasures for restoration of the F_s are suggested.

Editor Z.W. Kundzewicz     

Illegal Farmland Conversion in China's Urban Periphery: Local Regime and National Transitions

Through a case study in a village located in suburban Haikou City, Hainan Province, this article suggests the existence of a local development regime that exercises illegal farmland conversion in China's urban periphery. This regime consists not only of state officials and business investors, but also of local farmers anxious for off-farm employment. Our study highlights the broad transitions that led to the rise of local development regimes in China's urban periphery. These transitions include (1) the development of the local state, (2) farmers' changing relations with local authorities, and (3) the asymmetrical liberalization of land transaction rights in rural and urban areas. Whereas the state government still manages to intervene in the local conversion of farmland, such intervention is increasingly ineffective as economic liberalization intensifies. A series of potential policies are recommended to protect farmland and agricultural livelihoods in the context of rapid urbanization.     

Korea: A Cartographic History

Abstract