西北太平洋上层海洋对台风响应的个例研究     

张志伟 《海洋通报》2019,38(5):562-568

基于数字台风网、欧洲中心ERA-Interim、美国国家海洋与大气局以及中国Argo实时资料中心的资料研究了西北太平洋上层海洋对台风"奥鹿"的响应。研究结果表明,当"奥鹿"移动速度在2 m/s以下时,强风应力产生的Ekman泵是上层海洋响应的主要机制,移动速度越慢,Ekman抽吸速率(EPV)越大,海表温度(SST)降温持续时间短,冷尾迹出现在台风中心位置处。当"奥鹿"移动速度达到6 m/s以上时,持续风应力驱动的惯性泵是主导机制,SST降温持续时间长,冷尾迹出现在台风路径的右侧。惯性泵比Ekman泵持续的时间长,但Ekman泵影响深度比惯性泵大得多。在"奥鹿"经过西北太平洋时,混合层深度(MLD)变浅并伴随着"冷抽吸"作用的出现。上层海洋中"冷抽吸"现象较"热泵"现象影响深度深,持续时间长,在"奥鹿"过境后可持续20天以上。  相似文献   

工程养护海滩对"803"风暴潮的响应过程研究     

朱磊  杨燕雄  杨雯  房克照 《海洋通报》2019,38(1):102-14

研究养护海滩对风暴潮的响应过程在人工养滩工程设计与施工中具有重要意义。老龙头养护海滩在竣工半个月后遭遇“803”风暴潮，导致岸滩滩肩最大蚀退 6.5 m，沙坝坝顶最大下蚀 1.2 m。在现场测量的基础上，利用 XBeach 建立风暴潮过程 的老龙头海滩海床演变模型，研究结果表明： （1） XBeach 模拟结果与实际地形变化侵淤趋势一致，风暴潮期间人工沙坝均向岸移动，但模拟结果的侵蚀程度更大，海滩响应更加剧烈； （2） 强浪条件下人工沙坝的透射系数为 0.29~0.42，常浪条件下透射系数为 0.45~0.95，因而人工沙坝在大浪条件下掩护作用更佳； （3） 风暴潮期间人工沙坝附近破波显著，坝顶流速明显增大，最大可达 1.21 m/s，是无人工沙坝情况下的 2.3 倍，而在人工沙坝向岸侧，因波能提前耗散，流速减为 0.28 m/s，是无人工沙坝时的 0.4 倍，且没有产生离岸流。老龙头养护工程整体泥沙损失较少，易于恢复.  相似文献   

Dynamic analysis of a cylindrical casing–cement structure in a poroelastic stratum          下载免费PDF全文

Yang Xia  Yan Jin  Mian Chen  Yunhu Lu 《国际地质力学数值与分析法杂志》2017,41(12):1362-1389

The transient response of a cylindrical casing–cement structure in a poroelastic stratum under dynamic radial tractions is one of the significant issues during the analysis of downhole operations and the selection of safe material. Based on the Biot theory and general elastic mechanics, this paper gives a set of exact solutions for radial displacement, stresses for the casing–cement system and the pore pressure of the infinite surrounding poroelastic stratum in the Laplace transform space. Solutions are presented for three different types of transient radial loadings acting on the surface of casing, i.e., suddenly applied constant load, gradually applied step load and triangular pulse load. Time domain solutions are obtained using a reliable numerical method of inverse Laplace transforms. A detailed parametric study about the transient response is presented both at the casing–cement interface and the cement–stratum interface, and the distributions of the pore pressure and the effective stresses in the stratum are also examined. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

The droughts of 1996–1997 and 2004–2005 in Amazonia: hydrological response in the river main‐stem     

Javier Tomasella  Laura S. Borma  José A. Marengo  Daniel A. Rodriguez  Luz A. Cuartas  Carlos A. Nobre  Maria C. R. Prado 《水文研究》2011,25(8):1228-1242

Severe hydrological droughts in the Amazon have generally been associated with strong El Niño events. More than 100 years of stage record at Manaus harbour confirms that minimum water levels generally coincide with intense warming in the tropical Pacific sea waters. During 2005, however, the Amazon experienced a severe drought which was not associated with an El Niño event. Unless what usually occurs during strong El Niño events, when negative rainfall anomalies usually affect central and eastern Amazon drainage basin; rainfall deficiencies in the drought of 2005 were spatially constrained to the west and southwest of the basin. In spite of this, discharge stations at the main‐stem recorded minimum water levels as low as those observed during the basin‐wide 1996–1997 El Niño‐related drought. The analysis of river discharges along the main‐stem and major tributaries during the drought of 2004–2005 revealed that the recession on major tributaries began almost simultaneously. This was not the case in the 1996–1997 drought, when above‐normal contribution of some tributaries for a short period during high water was crucial to partially counterbalance high discharge deficits of the other tributaries. Since time‐lagged contributions of major tributaries are fundamental to damp the extremes in the main‐stem, an almost coincident recession in almost all tributaries caused a rapid decrease in water discharges during the 2005 event. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

A new numerical approach to the hyperstatic reaction method for segmental tunnel linings     

Ngoc Anh Do  Daniel Dias  Pierpaolo Oreste  Irini Djeran‐Maigre 《国际地质力学数值与分析法杂志》2014,38(15):1617-1632

This paper proposes a numerical approach to the hyperstatic reaction method (HRM) for the analysis of segmental tunnel linings. The influence of segmental joints has been considered directly using a fixity ratio that is determined on the basis of the rotational stiffness. The parameters necessary for the calculation are presented. A specific implementation has been developed using a FEM framework. This code is able to consider the three‐dimensional (3D) effect of segment joints in successive rings on the tunnel lining behaviour. The present HRM allows one to take an arbitrary distribution of segment joints along the tunnel boundary into consideration. In addition, the rotational stiffness of segment joints has been simulated using nonlinear behaviour, as it is closer to the true behaviour of a joint than linear or bilinear behaviour. The numerical results of three hypotheses on ring interaction, which allow the 3D effect of a segmental tunnel lining to be taken into account, have been compared with data obtained from the shield‐driven tunnel of the Bologna–Florence high‐speed railway line project. The numerical results presented in the paper show that the proposed HRM can be used to effectively estimate the behaviour of a segmental tunnel lining. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Torsional dynamic response of a large‐diameter pipe pile in viscoelastic saturated soil     

Changjie Zheng  Hanlong Liu  Xuanming Ding  Yaru Lv 《国际地质力学数值与分析法杂志》2014,38(16):1724-1743

An analytical solution is developed in this paper to investigate the dynamic response of a large‐diameter end‐bearing pipe pile subjected to torsional loading in viscoelastic saturated soil. The wave propagation in saturated soil and pile are simulated by Biot's two‐phased linear theory and one‐dimensional elastic theory, respectively. The dynamic equilibrium equations of the outer soil, inner soil, and pile are established. The solutions for the outer and inner soils in frequency domain are obtained by Laplace transform technique and the separation of variables method. Then, the dynamic response of the pile is obtained on the basis of the perfect contacts between the pile and the outer soil as well as the inner soil. The results in this paper are compared with that of a solid pile in elastic saturated soil to verify the validity of the solution. Furthermore, the solution in this paper is compared with the classic plane strain solution to verify the solution further and check the accuracy of the plane strain solution. Numerical results are presented to analyze the vibration characteristics and illustrate the effect of the soil parameters and the geometry size of the pile on the complex impedance and velocity admittance of the pile head. Finally, the displacement of the soil at different depth and frequency is analyzed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Hydrologic responses to land cover change: the case of Jedeb mesoscale catchment,Abay/Upper Blue Nile basin,Ethiopia          下载免费PDF全文

S. Tekleab  Y. Mohamed  S. Uhlenbrook  J. Wenninger 《水文研究》2014,28(20):5149-5161

The objective of this study was to quantify the impacts of land use/land cover (LULC) change on the hydrology of the Jedeb, an agricultural dominated mesoscale catchment, in the Abay/Upper Blue Nile basin, Ethiopia. Two methods have been used. First, the trends of certain daily flow variability parameters were evaluated to detect statistical significance of the change of the hydrologic response. Second, a conceptual monthly hydrological model was used to detect changes in the model parameters over different periods to infer LULC change. The results from the statistical analysis of the daily flows between 1973 and 2010 reveal a significant change in the response of the catchment. Peak flow is enhanced, i.e. response appears to be flashier. There is a significant increase in the rise and fall rates of the flow hydrograph, as well as the number of low‐flow pulses below a threshold level. The discharge pulses show a declining duration with time. The model result depicts a change in model parameters over different periods, which could be attributed to an LULC change. The model parameters representing soil moisture conditions indicated a gradual decreasing trend, implying limited storage capacity likely attributed to increasing agricultural farming practices in the catchment. This resulted in more surface runoff and less infiltration into the soil layers. The results of the monthly flow duration curve analysis indicated large changes of the flow regime. The high flow has increased by 45% between the 1990s and 2000s, whereas the reduction in low flows was larger: a 15% decrease between 1970s and 1980s, 39% between 1980s and 1990s and up to 71% between 1990s and 2000s. These results, could guide informed catchment management practices to reduce surface runoff and augment soil moisture level in the Jedeb catchment. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

鄂西岩溶槽谷区洼地的水位响应特征及产流阈值估算   总被引：1，自引：0，他引：1  

廖春来  罗明明  周宏 《中国岩溶》2020,39(6):802-809

以湖北省兴山县黄粮镇刘家坝和龙湾两处岩溶洼地作为研究对象，利用其降雨、水文和土壤水等监测数据，探讨灌入式补给条件下洼地汇流的水位响应特征和产流特点，并基于降雨量和洼地内明渠流量的关系，采用数学拟合方程，估算两处洼地的降雨产流阈值，进而分析了影响产流阈值的因素。结果表明:降雨强度增大，产流阈值减小；土壤前期含水率越大，越有利于坡面产流；落水洞和岩溶泉水位与降雨有较好的同步响应关系，水位变化曲线随雨强大小分别表现出“陡升陡降”和“缓升缓降”的特点；刘家坝和龙湾洼地的产流阈值分别为7.4 mm和10.6 mm。   相似文献   

高烈度区双洞隧道洞口段地震响应分析与振动台模型试验          下载免费PDF全文

皇民  苑俊杰  赵玉如  毕洁同  王松 《中国地质灾害与防治学报》2020,31(1):113-119

强震作用下,隧道地下结构损伤严重,其中洞口段更是抗震的薄弱环节,但其影响规律和特点目前尚缺乏系统的计算分析和研究。以强震区扯羊隧道为例,首先采用FLAC3D对双洞隧道洞口段地震响应进行分析,再用模型试验的方法进行洞口段模型试验,测量其地震响应应变规律,观测其震害发展情况,并与数值分析结果相互验证。结果表明:地震作用下,隧道仰拱横向位移较大;随着隧道埋深增加,内力逐步增加,其中墙角部位内力较大;洞口处隧道围岩在强震作用下会产生贯通性裂缝,影响隧道洞口稳定;地震作用下的明洞与暗洞交接处内力较大;地震作用下的双洞隧道之间存在较强的动力相互作用。  相似文献   

1980 - 2015年南迦巴瓦峰地区冰川变化及其对气候变化的响应   总被引：6，自引：5，他引：1  

吴坤鹏  刘时银  郭万钦 《冰川冻土》2020,42(4):1115-1125

基于地形图和Landsat TM/OLI遥感影像等数据， 利用目视解译和波段比值法提取1980年、 2000年和2015年南迦巴瓦峰地区冰川空间分布数据， 分析研究区近35年冰川变化， 探讨冰川对气候变化的响应。结果表明： 1980 - 2015年， 南迦巴瓦峰地区冰川面积持续减小并呈加速退缩的趋势， 近35年共减少了（75.23±4.67） km²， 占1980年冰川总面积的（25.2±1.6）%， 年平均面积减小率为（0.73±0.05）%。研究区东南坡冰川面积变化速率大于西北坡， 在不同流域、 海拔及朝向上， 冰川变化差异较大。南迦巴瓦峰地区冰川表碛十分发育， 表碛覆盖冰川面积变化率小于裸露冰川， 表碛覆盖对冰川消融具有抑制作用。南迦巴瓦峰地区在气温显著升高的背景下， 虽然降水量有所增加， 但冰川对气温更加敏感， 因气温升高引起冰川消融所带来的物质损失超过降水增加对冰川的补给， 导致南迦巴瓦峰地区冰川普遍萎缩。  相似文献