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61.
Numerical study of dewatering in a large deep foundation pit 总被引:2,自引:1,他引:1
Jianxiu Wang Bo Feng Haipeng Yu Taiping Guo Guangyun Yang Junwu Tang 《Environmental Earth Sciences》2013,69(3):863-872
During foundation pit excavation, groundwater is often the most important factor that affects pit stability. Dewatering is widely used in pit excavation to avoid uplift of excavation floors due to high water pressure. The characteristics of seepage in small-scale deep foundation pits of high-rise buildings or in the long narrow foundation pits of subway stations have been extensively investigated. However, the characteristics of seepage in large-scale deep excavations have not been studied. This paper investigates the large deep excavation of the buildings in Oriental Fisherman’s Wharf. The total area of the construction site is 33,917 m2. Single-well and group-well field pumping tests were performed and a numerical simulation by 3D finite difference method (FDM) was carried out. The simulation used results from the field pumping tests. The permeability parameters of the confined aquifer were then revised, based upon comparisons of simulation and observation results. Subsequently, dewatering schemes were simulated by FDM forward analysis. The simulation results show that dewatering schemes can minimize seepage and uplift in large excavation pits, though settlement outside the pit may need treatment measures. 相似文献
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正Objective Symphyta,as an ancestral and paraphyletic group,are mainly phytophagous lineages.In order to truly elucidate their natural history and the development trends,we need to cover more species,including the extinct and extant species.In general,fossils sometimes appear to be necessary since extinct species usually have the so-called transitional states,which play important roles in their early evolution.It is well known that the Early Cretaceous 相似文献
63.
岩体型斜长岩为由90%以上斜长石组成的岩浆岩,具变压结晶的特点,仅形成于元古宙(2.1~0.9Ga),常赋存有Fe-Ti-P矿床。Fe-Ti-P矿体既呈整合层状也呈透镜状和席状等不规则形式产出;矿石类型有块状和侵染状,前者矿石矿物含量>70%,后者矿石矿物含量为20%~70%;矿物组成上,不同矿床稍有差别:部分矿床的Fe-Ti氧化物以钛磁铁矿为主、钛铁矿次之,而其他矿床则以赤钛铁矿为主、磁铁矿次之。一些矿床磷灰石含量较高,出现仅由Fe-Ti氧化物和磷灰石组成的铁钛磷灰岩。研究表明,Fe-Ti-P矿床由富Fe、Ti的岩浆演化形成,其母岩浆是在深部岩浆房中大量结晶斜长石后的残余岩浆。部分学者认为不同矿石经正常的结晶分异作用并堆晶形成,但该机制很难解释呈不规则状产出的矿石;其他学者则认为不混熔作用对矿石的富集(尤其是脉状、席状的铁钛磷灰岩)有重要作用,但该机制缺乏岩相学和地球化学方面的证据。河北大庙Fe-Ti-P矿体呈透镜状、席状等不连续地分布于斜长岩中,矿体不发育明显岩浆分层,但仍出现不同矿石的相带。依据详细的岩相学、矿体中矿物含量和成分的变化规律以及全岩地球化学特征,我们判断大庙矿床中不同矿石为堆晶矿物和晶隙流体的混合产物,它们由铁闪长质岩浆经结晶分异和堆晶作用形成,与不混熔作用关系不大。矿体不规则状产出的特点可能与岩浆动力分异作用有关,并伴随有小范围的亚固相迁移。 相似文献
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通过对过马营-同仁一带侵位于晚三叠世陆相火山岩中的印支期花岗岩类杂岩体的岩石学、岩石化学、地球化学、稀土元素定量模拟、Sr 同位素资料的初步研究,结合大地构造背景分析认为该杂岩体属壳型或S 型花岗岩类,由于岩浆成分受陆壳源岩成分的控制,又具有过渡型或同熔型花岗岩的某些特点。 相似文献
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A modeling study of coastal inundation induced by storm surge,sea-level rise,and subsidence in the Gulf of Mexico 总被引:2,自引:2,他引:0
Zhaoqing Yang Taiping Wang Ruby Leung Kathy Hibbard Tony Janetos Ian Kraucunas Jennie Rice Benjamin Preston Tom Wilbanks 《Natural Hazards》2014,71(3):1771-1794
The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of climate change, such as hurricane-induced storm surge, and such risks are exacerbated by land subsidence and global sea-level rise. This paper presents an application of a coastal storm surge model to study the coastal inundation process induced by tide and storm surge, and its response to the effects of land subsidence and sea-level rise in the northern Gulf coast. The unstructured-grid finite-volume coastal ocean model was used to simulate tides and hurricane-induced storm surges in the GoM. Simulated distributions of co-amplitude and co-phase lines for semi-diurnal and diurnal tides are in good agreement with previous modeling studies. The storm surges induced by four historical hurricanes (Rita, Katrina, Ivan, and Dolly) were simulated and compared to observed water levels at National Oceanic and Atmospheric Administration tide stations. Effects of coastal subsidence and future global sea-level rise on coastal inundation in the Louisiana coast were evaluated using a “change of inundation depth” parameter through sensitivity simulations that were based on a projected future subsidence scenario and 1-m global sea-level rise by the end of the century. Model results suggested that hurricane-induced storm surge height and coastal inundation could be exacerbated by future global sea-level rise and subsidence, and that responses of storm surge and coastal inundation to the effects of sea-level rise and subsidence are highly nonlinear and vary on temporal and spatial scales. 相似文献
70.