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71.
杨梅洲大桥22~#索塔位于水陆交界处且溶洞地质发育,论述在复杂环境下钻孔灌注桩的成桩要点,以保证桩基施工安全、经济、高效。主要研究内容包括搭设锁口钢管桩围堰施工平台,优化围堰内群桩施工顺序以及在溶洞发育条件下改善钻孔成桩技术。研究成果对类似工程施工具有重要的参考借鉴意义。  相似文献   
72.
新一代全空间信息系统提出了新的空间数据模型——多粒度时空对象模型,多粒度时空实体对象通过唯一实体标识、多元特征信息记录空间实体,能够较好地支持空间实体的空间和语义表达。矢量地图数据作为现有重要的基础地理空间数据,记录了地理实体具体属性和位置信息,为实体对象生成提供了强大的基础数据支持。本文提出了路网矢量地图数据生成实体道路对象的研究方法,通过地图数据特征分析、实体对象生成策略和关键技术研究、实体对象转换3个方面对矢量地图数据的实体对象生成展开研究,实验表明:本文提出的实体对象转换方法为矢量地图数据生成实体对象提供了一个可行的解决方案。  相似文献   
73.
In this study, analytical solutions for tide-induced pore pressure, seepage force and water inflow into a subaqueous drained tunnel are developed. The results are compared with numerical solutions from a commercial software. The effects of the soil permeability, shear modulus, lining thickness and buried depth of the tunnel on tide-induced pore pressure, seepage force and water inflow are discussed. Larger tide-induced pore pressure and seepage force are obtained for smaller tunnel depth and higher soil permeability. The phase lags of the maximal tide-induced pore pressure at different depths are determined and investigated.  相似文献   
74.
山东邹平青山下亚组玄武安山岩源区性质及成因   总被引:1,自引:0,他引:1  
本文通过岩石的显微观察、全岩元素地球化学及Sr-Nd-Pb同位素组成等综合研究,参照前人的研究成果,探讨邹平火山岩盆地内青山下亚组玄武安山岩的岩石地球化学性质、物质来源及岩石成因。研究表明,岩石富钠、富镁,具有大离子亲石元素(Rb、Sr、Ba)和轻稀土元素(LREE)富集,高场强元素(Nb、Ta、Ti)相对亏损的地球化学特征。全岩Sr同位素初始比值(87 Sr/86 Sr)i为0.705674~0.705876;全岩Nd同位素初始比值εNd(t)为-10.0~-10.2,Nd同位素二阶段模式年龄T2DM为1.74~1.75Ga;全岩铅同位素初始比值(206Pb/204Pb)i介于16.917~17.095之间,(207Pb/204Pb)i介于15.306~15.396之间,(208Pb/204Pb)i介于36.750~37.208之间;较低的Sr-Nd初始比值及较均一的低放射性铅同位素组成,可能为EMI型富集地幔的部分熔融所致。晚中生代加厚的华北岩石圈发生大规模拆沉作用,拆沉的大陆中下地壳部分熔融形成富硅熔体与古生代岩石圈地幔相互作用形成富集地幔,随后在岩石圈伸展与区域热异常作用下减压部分熔融,形成的玄武安山质岩浆沿着深大构造侵入地壳上部或喷发至地表,形成青山下亚组玄武安山岩,但是岩浆上侵过程中地壳物质混染不强。该研究对深化鲁西地区晚中生代构造-岩浆作用的认识有一定的理论意义。  相似文献   
75.
Zhou  Jiajin  Yu  Jianlin  Gong  Xiaonan  El Naggar  M. Hesham  Zhang  Rihong 《Acta Geotechnica》2020,15(11):3271-3282
Acta Geotechnica - The pre-bored grouted planted (PGP) pile is a composite pile consisting of a precast concrete pile and the cemented soil around the pile. Thus, the PGP pile shaft capacity is...  相似文献   
76.
Luo  Zhanyou  Tao  Yanli  Gong  Xiaonan  Zou  Baoping 《Acta Geotechnica》2020,15(8):2367-2377

Shielding effects have a significant influence on the estimation of soil displacements for jacked piles, which have received minimal attention in previous studies. To include the shielding effects, a novel model was established for the soil compacting displacements of two jacked piles based on the strain path method and the source–sink method. The corresponding closed-form analytical expressions were also derived. Soil compacting displacements were calculated using the proposed method and the previous method, which disregard the shielding effects. The results showed that the soil displacements obtained based on the shielding effects are larger than those obtained when the effects are disregarded in the frontal direction, whereas the opposite results are obtained in the dorsal direction. The shielding effects have significant influence on the soil displacements in the frontal direction and those in the dorsal direction. Consequently, shielding effects should be included in the calculations of soil compacting displacements in the frontal and dorsal directions. An in situ test was also performed to investigate the reasonability of the proposed approach. Computed displacements were compared with the measured data. The results showed that the proposed model effectively predicts practical displacements, which demonstrates the validity of the proposed model. Further research is needed to verify the practicality of the described method.

  相似文献   
77.
对国内外提供遥感影像数据的主要网站进行了调查与分析,总结归纳出网站所提供影像的主要数据特点及数据使用方法。为广大遥感影像用户获取网络遥感影像资源提供便利。  相似文献   
78.
许刚  朱振国  解晓南 《湖泊科学》2004,16(2):150-157
近10年来,太湖流域上游地区经济发展逐步趋于活跃,受此影响,区域人口-资源、环境-发展(PRED)出现了新的特点与趋势。基于上游地区土地利用/覆被变化对流域整体水环境与生态安全格局所具有的重要意义,本文选择安吉县作为典型案例,分析其区域土地利用的基本特征,土地利用变化与景观格局动态的过程,以及驱动因素与机制,由此揭示山区土地利用/覆被变化的一般性规律,为太湖流域上游地区经济发展与土地利用、环境保护相互协调,提供决策借鉴与依据。  相似文献   
79.
The choice of a river training strategy is extremely important for the Lower Yellow River (LYR). Currently, the wide-river training strategy applies in the training of the LYR. However, remarkable changes in the hydrological processes in the Yellow River basin, as well as immediate pressure from socio-economic development in the Yellow River basin, make it necessary to consider if there is a possibility to change the river training strategy from wide-river training to narrow-river training. This research investigates the impacts of different river training strategies on the LYR through numerical simulations. A one-dimensional (1-D) model was used to simulate the fluvial processes for the future 50 years and a three-dimensional (3-D) model was applied to study typical floods. The study focused on river morphology, the results show that if the present decreasing trend in both water discharge and sediment load persists, the deposition rate in the LYR will further decrease no matter what strategy is applied. Especially, narrow-river training can achieve the aim to increase the sediment transport capacity in the LYR compared with wide-river training. However, if the incoming water and sediment load recovers to the mean level of the last century, main channel shrinkage due to sedimentation inevitably occurs for both wide-river and narrow-river training. Most importantly, this study shows that narrow-river training reduces the deposition amount over the whole LYR, but it provides little help in alleviating the development of the “suspended river”. Instead, narrow-river training can cause aggradation in the transitional reach where the river pattern changes from highly wandering to meandering, further worsening the “hump deposition” there. Because of uncertainty regarding future changes in hydrological processes in the Yellow River basin, and the lack of feasible engineering measures to mitigate “suspended river” and “hump deposition” problems in the LYR, caution should be exercised with respect to changes in the river training strategy for the LYR.  相似文献   
80.
基于文献计量方法的国内外城市更新比较研究   总被引:1,自引:1,他引:0  
孙威  王晓楠  盛科荣 《地理科学》2020,40(8):1300-1309
采用文献计量方法,利用Citespace工具对国内外城市更新研究进行知识图谱分析,从演化过程、发文期刊和研究机构的特征、研究热点等方面对比国内外城市更新研究的差异。研究表明:① 国内外城市更新研究的发文量呈现波动上升的趋势,在快速发展阶段尤为显著,每年发文量分别达到117篇和238篇;② 研究文献多集中在城市规划、区域研究、城市设计、建筑学等期刊。相对于国外,国内发文期刊更集中。国内排名前10的期刊发文量占比达46.65%,国外仅29.84%;③ 国内外的研究机构间初步形成合作网络,但网络联系与合作程度依然较低。相对于国外,国内研究机构间联系更紧密。④ 国外研究热点集中在伙伴关系与公众参与、绅士化、可持续发展、城市转型和文化创意等方面,国内研究热点体现在旧城改造与房地产开发、历史街区和工业遗产的保护与更新、广州?深圳城市更新的探索与实践、公众参与的初步探讨等方面。  相似文献   
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