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41.
Bacterial concentration (Escherichia coli) is used as the key indicator for marine beach water quality in Hong Kong. For beaches receiving streamflow from unsewered catchments, water quality is mainly affected by local nonpoint source pollution and is highly dependent on the bacterial load contributed from the catchment. As most of these catchments are ungauged, the bacterial load is generally unknown. In this study, streamflow and the associated bacterial load contributed from an unsewered catchment to a marine beach, Big Wave Bay, are simulated using a modelling approach. The physically based distributed hydrological model, MIKE‐SHE, and the empirical watershed water quality model (Hydrological Simulation Program – Fortran) are used to simulate streamflow and daily‐averaged E. coli concentration/load, respectively. The total daily derived loads predicted by the model during calibration (June–July 2007) and validation (July–October 2008) periods agree well with empirical validation data, with a percentage difference of 3 and 2%, respectively. The simulation results show a nonlinear relationship between E. coli load and rainfall/streamflow and reveal a source limiting nature of nonpoint source pollution. The derived load is further used as an independent variable in a multiple linear regression (MLR) model to predict daily beach water quality. When compared with the MLR models based solely on hydrometeorological input variables (e.g. rainfall and salinity), the new model based on bacterial load predicts much more realistic E. coli concentrations during rainstorms. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
42.
Pile foundations that support transmission towers or offshore structures are dominantly subjected to cyclic lateral load induced by wind and waves. For a successful design, it is crucial to investigate the effect of cyclic lateral loads on the pile behavior that is loaded laterally. Although the p–y curve method is generally utilized to design the cyclic laterally loaded pile foundations, the effect of cyclic lateral loads on the pile has not been properly implemented with the p–y curve. This reflects a lack of consideration of the overall stiffness change in soil–pile interaction. To address this, a series of model pile tests were conducted in this study on a preinstalled aluminum flexible pile under various sandy soil conditions. The test results were used to investigate the effect of cyclic lateral loads on the p–y behavior. The cyclic p–y curve, which properly takes into account this effect, was developed as a hyperbolic function. Pseudo-static analysis was also conducted with the proposed cyclic p–y curve, which showed that it was able to properly simulate cyclic laterally loaded pile behavior in sandy soil. 相似文献
43.
Werasak Raongjant 《地震工程与工程振动(英文版)》2011,10(3):417-422
This paper describes a quasi-static test program featuring lateral cyclic loading on single piles in sandy soil. The tests were conducted on 18 aluminum model piles with different cross sections and lateral load eccentricity ratios, e/d, (e is the lateral load eccentricity and d is the diameter of pile) of 0, 4 and 8, embedded in sand with a relative density of 30% and 70%. The experimental results include lateral load-displacement hysteresis loops, skeleton curves and energy dissipation curves. Lateral capacity, ductility and energy dissipation capacity of single piles under seismic load were evaluated in detail. The lateral capacities and the energy dissipation capacity of piles in dense sand were much higher than in loose sand. When embedded in loose sand, the maximum lateral load and the maximum lateral displacement of piles increased as e/d increased. On the contrary, when embedded in dense sand, the maximum lateral load of piles decreased as e/d increased. Piles with a higher load eccentricity ratio experienced higher energy dissipation capacity than piles with e/d of 0 in both dense and loose sand. At a given level of displacement, piles with circular cross sections provided the best energy dissipation capacity in both loose and dense sand. 相似文献
44.
Levent Yilmaz 《洁净——土壤、空气、水》2011,39(2):121-127
Employing bed load formulae hydraulic geometry relations were derived for stream width, sediment transport velocity, and bed slope. The relations were examined in terms of friction factor, bed load discharge, bed load diameter, and water discharge. Two fundamental approaches to the prediction of hydraulic geometry have been developed. The first and most widely adopted approach is based on empirical equations whereas the second is based on solution of the governing equations of flow. The applied bed load formulae belong to different authors. Here, the comparison with the other derived relations is presented. 相似文献
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低阻覆盖层对高频大地电磁测深的影响 总被引:3,自引:0,他引:3
低阻覆盖层对电磁波具有屏蔽效应,会降低高频大地电磁测深的探测能力。通过一维正演模拟,对无低阻覆盖层时探测能力和有低阻覆盖层时探测能力的变化进行对比研究,表明有低阻覆盖时,探测能力普遍下降;在相同探测能力条件下,高频大地电磁测深可探测异常体上覆围岩厚度与异常体厚度的比值,和围岩与异常体电阻率比值呈线性关系。通过綦江县某铁... 相似文献
47.
长期动荷载作用下冻结粉土的变形和强度特征 总被引:6,自引:2,他引:4
根据长期动荷载作用下的蠕变试验结果,研究了冻结粉土的变形和动强度特征.试验分3组,第一、二组是小振幅动荷载试验,且第二组的动荷载幅值为第一组的两倍;第三组是大振幅动荷载试验,荷载最小值取接近于零的值,最大值与第一组对应.试验结果表明:各种振幅的动荷载作用下,冻土的累积应变随荷载振动次数的变化规律相同(都包括初始蠕变阶段、稳定蠕变阶段、渐进流阶段)但数值上有差异.在初始和稳定蠕变阶段,第三组试验的累积应变小于第一、二组的,但是第三组试验稳定蠕变阶段的应变速率很大,蠕变曲线迅速进入渐进流阶段,此后其累积应变值大于小振幅动荷载试验的;第一、二组试验的应变幅值随振次的变化规律相似,但与第三组的有明显不同,而且,第三组试验的应变幅值明显大于第一、二组试验的.各种振幅动荷载作用下冻土的残余应变随振次的变化规律相同,且偏移荷载载越大或动荷载振动幅值越大,残余应变越大;冻土的动强度随荷载振动次数的增加而衰减,直至趋于极限动强度,大振幅动荷载试验的极限动强度明显小于小振幅动荷载试验的. 相似文献
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49.
四川盆地蜀南地区下二叠统茅口组缝洞型储层具有强烈的非均质性特征,而且埋藏相对较深,信噪比和分辨率较低,地震预测的难度大。这里通过模型正演,分析不同道距二维地震资料对茅口组单缝洞体储层的分辨能力,并且在资料处理中,研究了高密度地震资料对抑制空间假频,以及提高横向分辨率的影响,最后通过实际资料对比和速度反演,进一步分析证实了高密度采集地震资料,能够有效提高缝洞型储层的预测精度。 相似文献
50.
珠江口盆地番禺天然气区PY 气田位于坡折带上,特殊的沉积环境导致该气田已钻探的各井 T50 储层泊松比关系异常,含油气性特征非常复杂。为更好的判断储层的含油气性,利用Biot-Gassmann 方程对坡折带储层的流体性质进行了替换,考查不同流体性质下储层的含油气响应特征。研究结果表明: Biot-Gassmann 方程能有效的用于坡折带储层的流体替换研究; 坡折带T50 储层含水和含气时的AVO 响应特征相近,但两者响应的幅值不同,含水砂岩的幅值更小。 相似文献