Continuous measurement of whole‐tree water balance for studying urban tree transpiration          下载免费PDF全文

Takashi Asawa  Tomoki Kiyono  Akira Hoyano 《水文研究》2017,31(17):3056-3068

Street and garden trees in urban areas are often exposed to advection of strong vapour pressure deficit (VPD) air that can raise the whole‐tree transpiration rate (E_T), known as the oasis effect. However, urban trees tend to have small soil volume compared with natural conditions, and so they are believed to strongly regulate stomata. E_T characteristics of such urban trees have not been well understood because of a lack of reliable measurement methods. Therefore, we propose a novel weighing lysimeter method and investigate the whole‐tree water balance of an isolated container‐grown Zelkova serrata to examine (a) which biotic and abiotic factors determine E_T and (b) which spatial and temporal information is needed to predict E_T under urban conditions. Whole‐tree water balance and environmental conditions were measured from 2010 to 2012. Although leaf area substantially increased in the study period, daily E_T did not vary much. E_T increased with VPD almost linearly in 2010 but showed saturation in 2011 and 2012. Root water uptake lagged E_T by 40 min in 2012. These results suggest that the small planter box interfered with root growth and that hydraulic supply capacities did not increase sufficiently to support leaf area increase. From analysis of water balance, we believe that neglecting soil drought effects on street trees without irrigation in Japan will overestimate E_T over 4–5 sunny days at the longest. This is unlike previous studies of forest.  相似文献   

Stable isotopes of precipitation and spring waters reveal an altitude effect in the Anti‐Lebanon Mountains,Syria          下载免费PDF全文

Paul Koeniger  Mathias Toll  Thomas Himmelsbach 《水文研究》2016,30(16):2851-2860

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长江漫滩区深大异形基坑施工对紧邻特大型桥梁影响及变形控制研究     

史建升  徐源  李慧  阎长虹  侯珏  俞良晨  赵华新  崔王洪  徐成华  刘刚 《地质论评》2024,70(1):2024010005-2024010005

随着地下空间资源的开发利用,越来越多深基坑呈现出开挖深、规模大、形状不规则等特点,其支护结构设计复杂,施工难度大,具有明显的空间效应。本文以南京地铁某基坑工程为例,分析基坑施工对邻近桥梁的影响。其场区位于长江下游漫滩相二元结构地层分布地段,上部软土层厚度大,下部承压含水层地下水位高、水量丰富,地质条件复杂,该基坑为典型的深大异形基坑,距离某大桥的双曲拱引桥仅为7. 2 m,由于之前桥梁已遭受其他地下工程施工产生的较大变形,所以后续工程对其影响变形控制要求极高。为此,该车站基坑支护结构设计基于地下空间实际功能采用设置分隔墙分区开挖及MJS超深工法墙综合变形控制方案。本文通过有限元数值模拟计算,开展复杂环境下基坑开挖引起的围护结构及桥梁桩基的变形预测分析,计算结果显示,该深大狭长异形基坑开挖对邻近桥梁沉降变形影响显著,通过设置分隔墙分区开挖及MJS工法墙进行变形控制,能够较好地控制基坑的空间效应,减少“长边效应”、“异形效应”等对桥梁沉降变形的影响。通过现场基坑开挖过程实际监测结果,验证这一综合变形控制方案的可行性。该研究成果对于类似复杂地质条件下深大狭长异形基坑的支护及施工设计具有很好的借鉴意义。  相似文献   

Simulation of spatially correlated earthquake ground motions for engineering purposes   总被引：4，自引：4，他引：0  

Yongxin Wu  Yufeng Gao  Dayong Li 《地震工程与工程振动(英文版)》2011,10(2):163-173

A new model to simulate spatially correlated earthquake ground motions is developed. In the model, the main factors that characterize three distinct effects of spatial variability, namely, the incoherency effect, the wave-passage effect and the site-response effect, are taken into account, and corresponding terms/parameters are incorporated into the well known model of uniform ground motions. Some of these terms/parameters can be determined by the root operation, and others can be calculated directly. The proposed model is fi rst verif ied theoretically, and examples of ground motion simulations are provided as a further illustration. It is proven that the ensemble expected value and the ensemble auto-/cross-spectral density functions of the simulated ground motions are identical to the target spectral density functions. The proposed model can also be used to simulate other correlated stochastic processes, such as wave and wind loads.  相似文献   

高山峡谷场地地震动水平峰值加速度传播特性研究     

张玉敏  李幻  朱泽奇 《世界地震工程》2011,27(3)

建立了高山峡谷场地的动力计算模型,分析了攀枝花地震动作用下场地水平峰值加速度(HPA)的衰减效应,研究了不同参数对场地HPA传播特性的影响。数值分析结果表明:HPA随深度增加而衰减,HPA在坡脚处比在峡谷处要低一些;在山顶处有放大效应,但放大系数比实际震害要小一些;HPA衰减程度随着阻尼比和模型深度的增加而增加,随着坡比增加而减小,且不受输入地震动峰值加速度影响;在不同频谱特性地震动作用下,当地震波的卓越频率接近计算模型的自振频率时,场地衰减程度会随之增大。  相似文献   

Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages   总被引：1，自引：0，他引：1  

Woodrow B. Thompson  Carol B. Griggs  Norton G. Miller  Robert E. Nelson  Thomas K. Weddle  Taylor M. Kilian   《Quaternary Research》2011,75(3):552-565

Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 ± 31 to 11,650 ± 50 ¹⁴C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520 + 95/−20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 ± 65 ¹⁴C yr BP (Mytilus edulis) and 12,800 ± 55 ¹⁴C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England.  相似文献   

广元上寺剖面下三叠统飞仙关组风暴岩:巨型季风体制下的极端气候事件?   总被引：2，自引：0，他引：2  

曾德勇  时志强  张华  安红艳  张慧娟 《沉积学报》2011,29(3):440-448

早三叠世扬子地台位于特提斯东北缘,研究者根据大量地质证据和模拟实验证实该时期巨型季风强度最大,且控制了整个泛大陆和周边海域的气候循环.笔者于川西北广元上寺剖面下三叠统中发现一套保存完好的风暴岩,其发育于飞仙关组下部,风暴沉积特征明显,风暴侵蚀构造、风暴撕裂构造和层理构造发育;根据沉积构造、岩石性质等识别了Sa-Sb-S...  相似文献   

空气潜孔锤钻进技术在豫西抗旱找水打井施工中的应用          下载免费PDF全文

陈鑫发  牛建设 《探矿工程》2011,38(10):37-39

空气潜孔锤在豫西山区、严重缺水的基岩地区抗旱找水打井施工中发挥出了优越性。介绍了空气潜孔锤钻进技术工艺在豫西抗旱找水打井工程施工中的实际应用及其操作要点、钻进技术优势。同时分别对断裂破碎带地层和较完整地层中的空气潜孔锤钻进技术的应用效果进行了深入探讨和总结。  相似文献   

煤矸石回填地基的环境效应研究     

李树志  白国良  田迎斌 《西安地质学院学报》2011,(4):412-415,420

为了弄清楚煤矸石回填地基对复垦区的环境效应,以开滦矿区吕家坨复垦新村为例,介绍了地基回填煤矸石工艺,分析了煤矸石化学成分及其含量;采用室内淋溶实验,对pH、总硬度（CaCO3）、F^-、SO4^2-、Pb、Cd和Cr^6＋浓度等地下水环境质量指标进行分析,探讨了煤矸石回填地基对水环境的影响;讨论了煤矸石回填地基对大气质量的影响;参照《城市放射性废物管理办法》规定,评价了回填地基煤矸石的放射性对人体健康的危害。结果表明：通过现场振动压实试验确定了回填地基分层充填、分层振动压实参数及碾压趟数,确定按照煤矸石与土体积之比5：2进行回填,若回填一层厚500mm煤矸石,则要回填一层厚200mm粉煤灰或土,地表覆土厚度确定为0．5m;煤矸石中SiO2和Al2O3含量较高,属基性岩类,同时煤矸石含有炭、铝和CaO等物质,易发生水解和风化等现象;地基分层回填压实的复垦工艺减少了煤矸石中有害物质的释放量,降低了污染物的迁移速度,不会对水环境造成污染;地基回填煤矸石也显著减少粉尘和有害气体的排放量,降低对大气的污染;研究区煤矸石不属于放射性废物,不会影响人体健康,可作为建筑材料使用。  相似文献   

Research for time-temperature equivalence effect of rock (I):Theory research   总被引：1，自引：1，他引：0  

LIU Quan-sheng  ZHU Yuan-guang 《岩土力学》2011,32(3):641-646

In order to know about the rheological properties of rock in a long range of the time scale,method of increasing temperature was brought forward to accelerate the rheological process of rock,which could extend the time scale of experimental test data.Firstly,based on the generalized linear viscoelastic constitutive equation with temperature variable,the creep behavior of rock was divided into three types according to the different strain dependences of the time,that is,Hookean deformation,Newtonian flow,and retarded elasticity.Then the general equivalence relationship between time parameter and temperature parameter was derived for each type of strain.Finally,the relation between time parameter and temperature parameter in the whole creep was considered and the general theory of time-temperature equivalence effect(TTEE) of rock was established.This research reveals: ①The temperature effect on the instantaneous strain could be modified through vertical shift.②The key point of the TTEE of Newtonian flow depends on whether in the study of linear viscoelastic behavior of rock change of temperature is completely equivalent to a shift of the logarithmic time scale or not.③By plotting the results of a creep experiment performed at different temperatures and comparing the curves obtained,one can decide whether the rock considered have TTEE.④The TTEE of the whole creep should satisfy that the horizontal shift function of Newtonian flow and retarded elasticity is consentaneous.  相似文献