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Journal of Geographical Sciences - Rapid economic development and human activities have severely affected ecosystem function. Analysis of the spatial distribution of areas of rapid urbanization is... 相似文献
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"活地"是宗教的传奇,而由于以往知识与技术的限制以及宗教圣地的"不可侵犯性","活地"也成了大自然的千年未解之谜。通过现场考察和资料调研,明晰了"活地"所在地区的地质构造特征。采用高频率表面波监测、分析技术,通过现场试验,研究了"活地"附近地表浅层岩土体分布情况。采用图像分析技术,经室内试验研究得出了"活地"及周围地区出露岩石的矿物组成。最终,对于"活地"的成因提出以下看法:1.否定了地下深层生长性岩脉诱发"活地"现象的观点;2.膨胀岩及膨胀土吸水膨胀对"活地"的隆升有一定作用,但这不是"活地"的主要诱因;3.提出"活地"是岩石风化作用及特殊地理环境综合作用结果的观点:风化作用使岩体疏松、体积增大,地面隆起;两侧山体运动对其交界处岩石产生挤压作用,为"活地"的持续隆升提供动力源。 相似文献
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基于WRF(Weather Research and Forecasting)模式及其3DVAR(3-Dimentional Variational)资料同化系统,采用36 km、12 km 、4 km三层嵌套网格进行逐3 h资料同化和快速更新循环预报,对2011年5月8日鲁中一次局地大暴雨过程进行了资料同化敏感性试验。试验结果表明,地面观测资料同化和快速更新循环对本次降水的预报起到了关键性作用。在快速更新循环预报时不同化地面观测资料,或同化全部观测资料进行冷启动预报,模式均不能预报出山东的降水。同化地面观测资料后,显著改进了模式降水落区预报。地面观测资料同化可以影响到700 hPa高度以上温压湿风要素的变化,从而改变了大气初始场的温湿结构,导致模式预报的700 hPa附近高空大气湿度和热力不稳定增强,700 hPa以下低层风场更强,850 hPa鲁中以南风速较无观测资料同化的偏强2~4 m·s-1,低层风场的动力作用触发高空的不稳定大气,降水出现在山东。 相似文献
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Acta Geotechnica - In this study, the distinct element method (DEM) was employed to numerically explore the mechanical responses of granular soils and to extract key components for an elastoplastic... 相似文献
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土地问题是城镇化建设的一个突出问题。目前城镇化进程中还存在依赖土地程度过高、土地闲置、浪费、利用率偏低、城乡用地不能统筹、管理粗放等问题。新型城镇化要走集约、智能、绿色、低碳的道路,由速度扩张向质量提升转型,这就要求城镇化进程中土地规划要更加科学、土地利用要更加节约集约,土地管理要更加精细。 相似文献
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The construction of quasirectangular tunnels at shallow depths is becoming increasingly common in urban areas to efficiently utilize underground space and reduce the need for backfilling. To clarify the mechanical mechanism of the stresses and displacements around the tunnels, this study proposes analytical solutions that precisely account for quasirectangular tunnel shapes, the ground surface, the tunnel depth, and the ground's elastic/viscoelastic properties. The Schwarz alternating method combined with complex variable theory is employed to derive the elastic solution, and convergent and highly accurate solutions are obtained by superposing the solutions in the alternating iterations. Based on the solution and the extended corresponding principle for the viscoelastic problem, the time-dependent analytical solutions for the displacement are obtained for the ground assuming any viscoelastic model. The analytical solutions agree well with the finite element method (FEM) numerical results for models that are completely consistent, and qualitatively agree with field data. Furthermore, based on the stress solution combined with the Mohr-Coulomb failure criterion, the predicted initial plastic zone and propagation directions around the tunnels are qualitatively consistent with those determined by the limit analysis. A parametric study is performed to investigate the influences of the rectangular/quasirectangular tunnel shape, burial depth, and supporting pressure on the ground stresses and displacements. 相似文献
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