【作者】 潘丽红；

【导师】 朱建荣；

【作者基本信息】 华东师范大学 ， 河口海岸学， 2011， 博士

【摘要】 随着全球气候变化的加速,所引起的极端灾害性风暴潮发生的频次在增加,强度在加大,且在北半球有路径北移的趋势;沿海地区又因城市化进程的加速和人口规模的增加面临着需要通过不断外延陆海边界以拓展活动空间的压力。建设能达到抵御高标准台风,并在超标准情况下也不会被大规模毁坏而造成人员和财产损失的城市一线海堤工程,是当前和今后一段时间像上海这样的低地势、中纬度和高密度人口的国际大都市的重要任务。本文通过对位于长江口、杭州湾的上海一线海堤进行了广泛调研,并收集了历史上发生的多次登陆上海或者在邻近省市登陆并对上海造成严重灾害的台风事件,就上海可能发生的超标准台风及由台风引起的风暴潮和台风浪进行模拟计算,结合当前海堤防御标准,分析其对海堤可能造成的破坏因素。其目的和意义在于通过此类研究,实现在不对现有海堤进行大规模加高加固的情况下,有效提高其防御能力,大幅降低可能的受灾损失,本文具体的研究内容和成果如下：(1)在对当前风-潮-浪数值模型研究进展进行了解分析的基础上,选择并建立了适用于长江河口地区的台风模型、风—潮模型和风—潮—浪耦合数学模型,以9711号台风等实测同步风、潮、和浪资料对模型进行了率定。分别编程建立了藤田—高桥(Fujita.T- Takahashi)与Jelesnianski风场模式,通过比较采用了衰减相对较小、与9711号台风和0216号台风等实际风场符合更好的Jelesnianski风场,并通过调整衰减系数和最大风速圈半径使计算风场与实际风场更为吻合。建立了风—潮数学模型,就9711号台风在登陆前对潮波过程的影响进行了分析。在外海深水区域,台风形成增水主要由低气压引起,且集中于台风中心下方局部海域,随着台风不断向岸逼近,低气压作用相对减弱,风场作用逐渐明显,近岸区发生了先增水后减水的现象,风场作用下沿岸形成的反时针方向的流动对台风中心南北两侧形成了有力的水交换。风—潮—浪耦合的台风浪模型考虑了潮位过程导致的水深变化对波浪传播的影响。波浪场能量分布与台风风场相对应,在深水中波浪强度随着风力的加强或者风圈的加大而增强,在浅水区受波浪折射、浅水、破碎及底摩阻等效应的影响,波浪强度随之变小。(2)为了构造能对上海形成最不利情况的强台风和超强台风两种超标准的气旋,模拟这种条件下海堤前沿的极端潮位和风浪,通过对9711台风的空间和时间的平移,就长江口杭州湾不同位置典型海堤,找出对其最为不利的路径和登陆时间,并以此为袭击上海最不利的强台风；在此基础上利用强台风模拟成果中的路径、登陆时间和5612超强台风低气压过程,模拟了超强台风登陆的风—潮—浪过程,并计算得到超强台风条件下海堤前沿风—潮—浪要素。(3)在调研的典型海堤中,选取临港新城新建海堤为研究对象,利用设计标准的和超标准台风条件下的风、潮、浪要素,对海堤护面结构稳定和越浪量进行复核计算,在此基础上评价海堤安全性。复核结果表明,以临港新城新建海堤为例,在设防标准情况下,现有海堤的结构稳定和越浪量基本满足安全标准；在强台风作用下,海堤堤顶越浪量不满足要求；在超强台风下,海堤防浪墙稳定和越浪量都不能满足安全要求。本文通过在不同强度台风条件下的上海海堤安全性进行了评估,就可能的受损情况进行了定量计算,提出应对措施,以达到经济有效地提高海堤整体防御能力的目标。该成果可推广应用于上海地区台风—浪—潮的预报和后报分析,建立的海堤防御能力评价体系可应用于上海沿江、沿海海堤的防御能力评价,为有关部门提高海堤防御能力制定经济有效的工程措施提供技术支持。更多还原

【Abstract】 Due to the global climate change, extremely disastrous storm surges happen more intensively and frequently, which also have the trend to go even north at the northern hemisphere. Meanwhile, the accelerated process of urbanization and population increase in the coastal areas faces the needs of the seaward extension of shoreline for more living space. Shanghai, an international metropolis in mid-latitude the low-lying area with high-density population, is vulnerable to typhoon disasters. To protect against the high-level typhoon and prevent large scale destruction, loss of lives and properties for the typhoon exceeding the design standard, first-line seawalls play an essential role in the safety of Shanghai in the current and future time periods.Through the extensive and in-depth research on first-line seawall and defense standards in Shanghai, a city at the inter-junction of Yangtze River Estuary and Hangzhou Bay, and a collection of multiple landing events at Shanghai or neighboring provinces, this study simulated the storm surge and swells in Shanghai caused by typhoons that exceed the defense standards, and analyzed the factors that probably destroy the seawall. The purpose and destination of this study is to improve the defense capabilities of the seawalls and significantly reduce the potential disaster losses by properly heightening and consolidating the existing seawalls. This specific research contents and results are as follows:(1)Based on the extensively analysis on research progress of current wind-tide-wave numerical model, the typhoon numerical model, storm surge model and typhoon-tide-wave coupling model are selected and established for the Yangtze River estuary, and these models are calculated and calibrated by synchronous wind-tide-wave observed data of Typhoon 9711 and other typhoons.In this study, Fujita.T- Takahashi formula and Jelesnianski wind model are established respectively by computer programming. Jelesnianski wind field model with relatively less decay and consistent wind verification is applied on the numerical model. By adjusting the attenuation coefficient and the radius of maximum wind speed, the calculated wind field is more consistent with the observed wind field.The wind-tide numerical model is established. The tidal wave process before landing process under the impact of Typhoon 9711 is analyzed. In the offshore deep water area, the storm surge is mainly forced by the lower air pressure under the typhoon center. With the typhoon’s approaching to the nearshore area, wind induced set-up and set-down occur successively, the impact of low pressure decreases relatively, and the anti-clockwise direction flow along the shoreline under the impact of wind field lead to the formation of a strong water exchange on the south and north sides of typhoon center.The impact of water depth fluctuation during tidal process on wave propagation has been taken into consideration by the tide-wave coupling typhoon model. The energy distribution of wave field is consistent with the typhoon wind field, and along with the movement process of typhoon, the wave intensity in deep water is enhanced with the increasement of wind strength or the radius of wind field. The maximum effective wave height is up to 9.0 m in the deep water under the impact of Typhoon 9711. Due to the impact of wave breaking and bottom friction in the shallow water, the wave intensity is reduced correspondingly.(2)To simulate the potential strong typhoon and super strong typhoons may had the worst impact on the city of Shanghai, the extreme tide level and wave in front of seawall can be simulated in these most unfavorable conditions. By the temporal and spatial transformation of Typhoon 9711, the most dangerous path and landing time can be determined for the typical sea walls at the different positions of Yangtze River and Hangzhou Bay, and take this as the most dangerous hypothetical super typhoon may attack on Shanghai. On the basis of simulation results of the path and landing time of strong typhoon, combined with the low pressure and wind field process of super strong Typhoon 5612, the wind-tide-wave process of super strong typhoon is simulated. The extreme storm surge water level and typhoon wave in front of the typical seawall under the impact of typhoon over normal standard are obtained in this study.(3)In the investigation of typical seawall, the harbor seawall is chosen as the studied seawall. By using the tide level and storm wave at designed and over normal standard criteria, the structure stability and wave overtopping discharge of seawall are tested by calculation. On this basis, the safety of the seawall is evaluated. The evaluation shows that the structure stability and wave overtopping discharge of the existing seawalls can basically satisfy the safety requirement, the wave overtopping discharge of seawall under the action of strong typhoon doesn’t meet the requirement; under the impact of super strong typhoon, the stability and wave overtopping discharge of all the studied seawalls can’t satisfy the safety requirement. Through the study on safety evaluation of seawall under the different intensity of cyclones, the reinforcement suggestions for the possible damaged seawall structure are proposed to improve the overall defense capability of seawall economically and effectively. The results of this study can be applied to typical typhoon-wave-tide model analysis in Shanghai, and the evaluation system of seawall defense capability can be applied on the seawall in the river and coastal region of Shanghai. This study can provide technical support to the related department to improve the defense capability of seawalls with economic and effective engineering applications.更多还原