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231.
High buildings or architectural complex in urban areas remarkably distort the urban surface wind fields. As the air flow approaches,local strong wind may appear around the buildings. The strong wind makes the pedestrians on sidewalks, entrances and terrace very uncomfortable and causes the pedestrian level wind environment problem. In this studies, hot-wire wind measurement, wind scouring in wind tunnel and numerical computation were carried out to evaluate the wind environment of tall buildings in the prevailing flow conditions in Beijing areas. The results obtained by three techniques were compared and mutually verified. The conclusions drawn from three approaches agree with each other. Also the advantages and limitations of each method were analyzed. It is suggested that the combination of different techniques may produce better assessment of wind environment around high buildings. 相似文献
232.
Intrusion and its implication for subsidence: A case from the Baiyun Sag, on the northern margin of the South China Sea 总被引:12,自引:0,他引:12
We develop a series of simple numerical models to explain the anomalous subsidence and deposition phenomena on the northern continental margin of the South China Sea, in particular in the Baiyun Sag. The results suggest that a short-period high rate deposition of around 17 Ma is related to a rapid subsidence event, which may be due to episodic emplacement of a dense intrusion. Necking and gravity models indicate that in the basement of the Baiyun Sag, there is a dense zone that is 100–200 kg/m3 more dense than the surrounding country rock. Considering its high magnetic intensity and regional igneous activity, the dense zone is thought to be related to a phase of basalt intrusion that may have taken place around 17 Ma. Thermal and subsidence models indicate that a hot denser intrusion can cause significant subsidence immediately after the intrusion. The subsidence rate then slows down with cooling, thus becoming consistent with the observed subsidence curves at around 17 Ma. The results also indicate that the lithospheric strength under the Baiyun Sag is negligible, and that the high-velocity layer in the lowermost crust may be not an original part of the pre-rift crust. Instead, it is thought to be underplated intrusion emplaced at around 30 Ma when the continental margin broke up. 相似文献
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The influence of cavern’s span on surrounding rock classification is getting more and more recognition along with large span underground working’s increasingly coming forth. The authors analyse the timbering expense of cavern in jointed rock mass, the radius of plastic loosened zone and the size effect of macroscopical mechanical parameters of rock mass. Based on the complexion of depressing of surrounding rock’s stability due to increment of cavern’s span, the authors pinpoint attaching importance to the influence of cavern’s span on surrounding rock classification; and suggest reckoning the factor of cavern’s span in surrounding rock classification scientifically by studying the size effect of rock mass’s physico-mechanical parameters. 相似文献
236.
阐述了非开挖技术在上海的发展轨迹、应用现状和战略思考,并以翔实和权威的资料论证了有关论点,对全国非开挖技术发展有关情况也有概括性的介绍 相似文献
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Bin Chen 《Geochimica et cosmochimica acta》2005,69(22):5387-5388
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Piecewise prediction model for watershed‐scale erosion and sediment yield of individual rainfall events on the Loess Plateau,China
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Yu Guo‐Qiang Zhang Mao‐Sheng Li Zhan‐Bin Li Peng Zhang Xia Cheng Sheng‐Dong 《水文研究》2014,28(21):5322-5336
Establishing a universal watershed‐scale erosion and sediment yield prediction model represents a frontier field in erosion and soil/water conservation. The research presented here was conducted on the Chabagou watershed, which is located in the first sub‐region of the hill‐gully area of the Loess Plateau, China. A back‐propagation artificial neural model for watershed‐scale erosion and sediment yield was established, with the accuracy of the model, then compared with that of multiple linear regression. The sensitivity degree of various factors to erosion and sediment yield was quantitatively analysed using the default factor test. On the basis of the sensitive factors and the fractal information dimension, the piecewise prediction model for erosion and sediment yield of individual rainfall events was established and further verified. The results revealed the back‐propagation artificial neural network model to perform better than the multiple linear regression model in terms of predicting the erosion modulus, with the former able to effectively characterize dynamic changes in sediment yield under comprehensive factor conditions. The sensitivity of runoff erosion power and runoff depth to the erosion and sediment yield associated with individual rainfall events was found to be related to the complexity of surface topography. The characteristics of such a hydrological response are thus closely related to topography. When the fractal information dimension is greater than the topographic threshold, the accuracy of prediction using runoff erosion power is higher than that of using runoff depth. In contrast, when the fractal information dimension is smaller than the topographic threshold, the accuracy of prediction using runoff depth is higher than that of using runoff erosion power. The developed piecewise prediction model for watershed‐scale erosion and sediment yield of individual rainfall events, which introduces runoff erosion power and runoff depth using the fractal information dimension as a boundary, can be considered feasible and reliable and has a high prediction accuracy. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献