斜腿夹角对V形墩连续刚构桥地震响应的影响研究          下载免费PDF全文

台玉吉  惠迎新  金宝宏 《世界地震工程》2019,35(2):186-192

为研究斜腿夹角对V形墩连续刚构桥地震响应的影响及合理斜腿夹角角度,以一座典型V形墩预应力混凝土连续刚构桥为研究对象,采用有限元分析方法研究了斜腿夹角θ对桥梁内力及位移的影响,得出了θ对结构地震响应的影响规律和变化曲线。研究结果表明:随着斜腿夹角的增加,在纵向地震力作用下,墩底纵向弯矩逐渐减小,墩顶和主梁墩顶支撑处纵向弯矩逐渐增大;在横向地震力作用下,跨中横向弯矩逐渐减小,墩底横向弯矩逐渐增大,墩顶横向弯矩基本不变;在竖向地震力作用下,墩底和墩顶竖向弯矩逐渐增大,主梁支撑处竖向弯矩逐渐减小;斜腿夹角对纵向或横向地震力作用下结构位移影响不大,对竖向地震力作用下的位移影响较大。在满足静力设计的前提下,当两斜腿夹角为90°时,结构地震响应相对较小,受力合理性最优。研究成果可为该类桥梁的抗震设计与斜腿夹角角度选取提供参考和依据。  相似文献   

我国三北地区的植物固沙   总被引：11，自引：3，他引：8  

刘媖心 《中国沙漠》1988,8(4):11-18

本文提出三北地区影响植物固沙的自然特征, 论述了机械固沙、灌溉与植物固沙的关系, 植被盖度与栽植密度的关系, 人工植被演替及其控制, 植物固沙的指标、固沙植物种的选择与配置, 固沙植物的引种及其限制因子, 并按等雨量线将植物固沙划分为四个区。  相似文献   

Evaluating the long-term ecohydrological suitability of restoration efforts in a typical watershed of the Loess Plateau     

Miao Sun  Chengsheng Yan  Nana Zhao  Xining Zhao  Xuerui Gao  Yingxin Lian  Yujie Yuan  Hao Yang 《水文研究》2021,35(9):e14362

The vegetation growth of the Loess Plateau is often restricted by water, which seriously threatens the water sustainability of regional ecosystem. In order to clarify the relationship between supply and demand of vegetation water use after Grain for Green Project, this study selected Malian River Basin as the research area and calculated the vegetation water use and water demand using the eco-hydrological model. The results showed that the annual water demand of the basin was 570 mm, while the average annual water supply was only 294 mm, accounting only for 52.0% of the demand. From 2000 to 2018, the temporal and spatial matching degree of water supply and demand in the Malian River Basin were 0.63 and 0.65, respectively. On the whole, the water resources in Malian River Basin can basically support the growth of vegetation, but in some areas are not sustainable. Water resources in the southern region can only barely maintain the normal growth of vegetation under the current conditions, so it is not recommended to carry out new plantation in this area. The evaluation of matching degree in the northern from January to April is poor, so it is necessary to appropriately reduce the planting area of economic crops and replace it with planting herbaceous plants with small water consumption in Spring. Compared with the current conditions, under the future climate scenarios of ssp126 and ssp585, the Malian River Basin will show a trend of warming and humidification. The temporal matching degree of water supply and demand also significantly improved to 0.83 and 0.92, indicating that even if the planting structure did not change significantly, water supply would gradually meet the needs of vegetation. The study results can provide the basis for formulating more scientific and reasonable vegetation restoration policies.  相似文献   

伊犁河谷一次极端强降水事件水汽特征分析     

刘晶  周玉淑  杨莲梅  张迎新 《大气科学》2019,43(5):959-974

2016年7月31日至8月1日,新疆伊犁河谷发生了一次极端强降水事件,多站突破降水极值。利用NCEP/NCAR 1°×1°和2.5°×2.5°再分析资料、中国地面卫星雷达三源融合逐小时降水产品、新疆地区常规观测资料、基于地基GPS观测的大气可降水量资料及基于拉格朗日方法的HYSPLIT轨迹模式结果,通过对水汽输送流函数、势函数、水汽输送轨迹和暴雨区水汽收支计算,结合伊犁河谷GPS观测分析,揭示了此次强降水期间的大尺度水汽输送、辐合特征及伊犁河谷局地水汽变化特点。结果表明:（1）强降水期间大西洋及红海均对伊犁河谷的水汽供应具有贡献,河谷处于水汽通量辐合区,向西开口的地形辐合和抬升为局地暴雨的发生提供有利的动力辐合条件。低纬度印度夏季风环流和中纬度大西洋向东输送的气流共同构成伊犁河谷极端降水天气的水汽输送通道,其中印度夏季风西南水汽输送主要集中在对流层低层,对流层中层水汽的输送以大西洋向东气流和低槽自身水汽输送为主。（2）HYSPLIT模拟结果表明暴雨区3000 m中纬度偏西路径的水汽输送最为强盛,偏南路径水汽源于阿拉伯海,对流层底层偏西、偏东路径和中层偏北路径水汽通过垂直运动补充对流层低层的水汽;5000 m水汽输送轨迹以偏西路径和低槽自身携带的水汽为主。（3）降水期间水汽集中在对流层低层,通过垂直输送项向高层输送;强降水时段暴雨区对流层低层南边界水汽流入量迅速增强,中高层水汽流入主要集中在西边界。（4）降水前槽前西南气流造成伊犁河谷测站GPS-PWV明显跃升,强降水时段受印度西南季风影响,测站PWV快速增高并维持,局地GPS-PWV的增加与大尺度水汽输送辐合增强有关。  相似文献   

胶东水旺庄金矿床成矿机制:来自S-H-O同位素和流体包裹体的制约          下载免费PDF全文

李杰  张丽鹏  宋明春  梁金龙  李世勇  宋英昕  鲍中义  丁正江 《地球科学》2021,46(5):1569-1584

为探讨胶东水旺庄金矿床成因,对载金黄铁矿和石英进行了S-H-O同位素组成及流体包裹体的测试分析,研究表明:黄铁矿δ34S介于7.0‰~8.5‰,流体的δD介于-91.7‰~-82.6‰,δ18O介于2.6‰~5.6‰,发育气-液两相流体包裹体、含CO₂流体包裹体和含子矿物流体包裹体等3类,流体盐度介于1.2%~13.8%（NaCl_eq）,均一温度主要集中于290~350 ℃,成矿期流体为中高温、低盐度的H₂O-CO₂-NaCl±CH₄体系,具有深部岩浆来源特征.流体的不混溶或沸腾作用导致了金的沉淀富集.受中生代太平洋板块俯冲及后撤影响,胶东地区发生了大规模岩浆活动和强烈的地壳隆升,所产生的热隆-伸展构造为该区大规模金矿集中爆发成矿提供了有利条件.在主拆离断层中主要形成破碎带蚀变岩型金矿床,在主拆离断层下盘主要形成石英脉型金矿床.   相似文献   

Experimental Study on Water‐rock Reactions with CO2 Fluid in a Deep Sandstone Formation under High Temperature and Pressure     

LI Chengze  CHEN Guojun  LI Chao  TIAN Bing  SUN Rui  SU Long  LU Yingxin  WANG Lijuan 《《地质学报》英文版》2021,95(1):268-279

Qiongdongnan Basin has a tectonic geological background of high temperature and high pressure in a deep reservoir setting,with mantle-derived CO2.A water-rock reaction device was used under high temperature and high pressure conditions,in conjunction with scanning electron microscope(SEM)observations,to carry out an experimental study of the diagenetic reaction between sandstone at depth and CO2-rich fluid,which is of great significance for revealing the dissolution of deep clastic rock reservoirs and the developmental mechanism of secondary pores,promoting deep oil and gas exploration.In this study,the experimental scheme of the water-rock reaction system was designed according to the parameters of the diagenetic background of the deep sandstone reservoir in the Qiongdongnan Basin.Three groups of single mineral samples were prepared in this experiment,including K-feldspar samples,albite samples and calcite samples.Using CO2 as a reaction solution,a series of diagenetic reaction simulation experiments were carried out in a semi-closed high temperature and high pressure simulation system.A field emission scanning electron microscope(SEM)was used to observe the microscopic appearance of the mineral samples after the water-rock reaction,the characteristics of dissolution under high temperature and high pressure,as well as the development of secondary pores.The experimental results showed that the CO2-rich fluid has an obvious dissolution effect on K-feldspar,albite and calcite under high temperature and high pressure.For the three minerals,the main temperature and pressure window for dissolution ranged from 150℃to 300℃and 45 MPa to 60 MPa.Scanning electron microscope observations revealed that the dissolution effect of K-feldspar is most obvious under conditions of 150℃and 45 MPa,in contrast to conditions of200℃and 50 MPa for albite and calcite.Through the comparative analysis of experimental conditions and procedures,a coupling effect occurred between the temperature and pressure change and the dissolution strength and calcite.Under high temperature and high pressure,pressure changed the solubility of CO2,furthermore,the dissolution effect and strength of the sandstone components were also affected.The experiment revealed that high temperature and high pressure conditions with CO2-rich fluid has a significant dissolution effect on aluminosilicate minerals and is conducive to the formation of secondary pores and effective reservoirs.Going forward with the above understanding has important implications for the promotion of deep oil and gas exploration.  相似文献   

基于GIS的煤层顶板含水层富水性评价     

姚星  侯恩科  牛超  严迎新  周竹峰 《中国煤炭地质》2021,(3):20-24

为减少单一赋权法在评价含水层富水性方面的不足,以韩家湾煤矿为例,在综合分析矿井地质、水文地质条件的基础上,选取含水层的厚度、岩心采取率、砂岩粒度指数、砂地比以及砂泥交互层数作为影响富水性的主控因素,分别利用模糊层次分析法、CRITIC法获得各主控因素的主、客观权重,通过博弈集合理论得到综合权重,进而基于GIS平台对含水层的富水性进行分区评价。结合钻孔单位涌水量、矿井出水点的分布结果对含水层的富水性分区结果进行验证。结果表明:研究区富水性整体呈现由中部向两侧逐渐减弱的趋势,该模型的评价结果与实际情况相吻合。  相似文献   

应用GPS可降水量分析河北省一次回流降雪天气     

李国翠  张迎新  李国平  赵卫亮 《气象科技》2012,40(6):990-995

利用地基GPS反演的可降水量资料、地面加密自动站和常规天气资料,对2011年2月发生在河北省的一次回流降雪天气过程进行了分析.结果表明:①降雪过程前期,GPS可降水量由西南向东北逐渐增大,后期自北向南减小,与西南暖湿气流的输送和地面冷高压的南压对应.②第1阶段降雪的主要影响系统为高空槽,GPS可降水量不断增加,对应的实际降水也是先增后减;第2阶段的降雪主要表现为回流降雪,降雪前期GPS可降水量迅速增长,实际降水出现在GPS可降水量峰值及下降阶段.随着地面冷高压逐渐南压,GPS可降水量逐渐下降,实际降水也逐渐减弱至停止.③在探空层结曲线上,高湿层位于地面附近和700 hPa附近,而二者之间的近地层存在着低湿层.  相似文献   

湿位涡在"96.8"特大暴雨过程中的应用分析   总被引：1，自引：6，他引：1  

张迎新  胡欣  张守保 《气象科技》2004,32(Z1):25-28

1996年 8月 3～ 5日受减弱的 96 0 8号台风低压影响 ,河北省境内出现了自“6 3 8”以来的特大暴雨过程 (简称“96 8”特大暴雨 ) ,暴雨落区覆盖了太行山的东、西两侧。文中利用非静力中尺度模式MM5和常规观测资料运算结果 ,根据倾斜涡度发展理论 ,对台风减弱低压在北方产生强降水的“96 8”暴雨过程进行分析 ,发现湿位涡这一综合物理量对此类暴雨具有较好的指示意义 ,MPV1小于 0且MPV2大于 0的区域对应暴雨区。  相似文献   

独龙族聚居区农牧业开发     

高应新 《山地学报》1995,(4)

独龙族聚居区即独龙江乡，是个边远少数民族特困山区，位于滇西北．乡内山高谷深，未通公路，土地面积１９９４（ｋｍ）￣２；１９９０年全乡独龙族人口３９９５人，占全国独龙族人口的７１．１％。农牧业是当地的两个支柱产业，在保护生态环境的前提下，采取择优开发自然资源、力争粮食生产自求平衡、开拓商品生产面向市场等措施，以不断提高农牧业开发的经济效益．  相似文献