海洋环境中结构基础冲刷防护措施及预警模型研究

发布时间：2018-05-22 10:18

本文选题：海洋环境 + 冲刷防护　；参考：《清华大学》2014年博士论文

【摘要】：海洋结构物基础周围会在波浪以及海流的作用下会发生冲刷现象,过深的冲刷坑会使其承载力下降,从而对结构安全造成威胁。台风灾害到来时,在台风引发的洪水以及风暴潮的双重威胁下,结构基础面临的安全挑战更为严峻。为此,一方面需要有合适的基础冲刷预警模型对日常和极端天气条件下的水动力过程和冲刷过程进行准确可靠的预报,使得可以及时采取防护加固、撤离物资、限制交通等措施减小损失;另一方面需要应对海洋环境中波流共存的特点,选择适合海洋环境的基础冲刷防护措施,有效削减结构物基础的冲刷量,保证结构的安全性。本文结合天气预报模型、风暴潮水动力学模型以及结构基础局部冲刷模型,首次建立了海洋结构基础冲刷的预警数值模型。分析了不同分辨率气象数据对风暴潮模拟的影响。该预警模型所模拟的多场台风路径、强度和降水均有较好的精度;两场台风作用下预报的潮位变化、增水分布都具有较好精度,模型1-2天的潮位预报误差在0.2m左右。然后把验证过的预警模型应用于嘉绍大桥工程中,所预报的潮位、潮流均有较高精度,预报的最大桥墩冲刷深度亦与实测值接近。利用此预警模型可以预报海上结构基础在未来几天的最大可能冲刷深度,提前预知风险,及时采取防护措施。为缓解海洋环境中冲刷对结构的不利效应,本文采用物理模型试验方法,在波流水槽中研究了在恒定流以及波流联合作用下不同冲刷防护措施保护下桩柱周围基础冲刷的变化规律和防护效果。研究的冲刷防护措施包括抛石防护、水平隔板、扩展基础、减冲桩、拦沙坎、套筒、四面体框架群、柱身开槽、抛石防护与四面体框架群的组合措施共9种。其中对拦沙坎、套筒、四面体框架群、柱身开槽、组合措施等防护措施在波流环境中的冲刷防护效果研究尚属首次。各种防护措施均能削减冲刷深度,但效能相差很大。多种防护措施在波流环境中会导致较恒定流环境中更深的冲刷坑,其行为与单独圆柱在不同水流环境中的冲刷深度变化情况有显著的区别。防护措施在波流联合作用的环境下表现出许多新特点,波浪的参与对冲刷深度、冲刷削减能力、达到冲刷平衡所需时间均有明显的影响。提出的组合措施融合了四面体框架群和抛石防护措施的优点,对海洋环境有较强的适应性。
[Abstract]:The scour around the foundation of ocean structures will occur under the action of waves and currents, and a deep scour pit will reduce its bearing capacity, which will threaten the safety of the structure. When the typhoon disaster comes, the security challenge of the structure foundation is more severe under the double threat of the flood caused by the typhoon and the storm surge. Therefore, on the one hand, it is necessary to have an appropriate scour warning model for accurate and reliable prediction of hydrodynamic processes and scour processes under daily and extreme weather conditions, so that timely protection and reinforcement can be taken, and materials can be evacuated. On the other hand, it is necessary to deal with the characteristics of the coexistence of waves and currents in the marine environment, to select the appropriate basic scour protection measures, to effectively reduce the scour amount of the structure foundation, and to ensure the safety of the structure. Combined with weather forecast model, storm tide dynamics model and local scour model of structural foundation, the early warning numerical model of ocean structure foundation scour is established for the first time in this paper. The influence of different resolution meteorological data on storm surge simulation is analyzed. Both the intensity and precipitation of typhoon track simulated by the model have good accuracy, and the tidal level variation and water increase distribution predicted under the action of two typhoons have good accuracy, and the prediction error of tidal level in 1-2 days of the model is about 0.2 m. Then, the verified early warning model is applied to Jiashao Bridge project. The predicted tidal level and tidal current have higher accuracy, and the predicted maximum pier scour depth is close to the measured value. By using this early warning model, the maximum possible erosion depth of offshore structural foundation in the next few days can be predicted, the risk can be predicted in advance, and protective measures can be taken in time. In order to mitigate the adverse effects of scour on structures in marine environment, the physical model test method is used in this paper. The variation law and protective effect of foundation scour around pile column under the protection of different scour protection measures under the action of constant current and combined wave and current are studied in the wave-current flume. The scour protection measures studied include: riprap protection, horizontal partition, extended foundation, anti-impact pile, sand bar, sleeve, tetrahedral frame group, slotted column body, and combined measures of riprap protection and tetrahedron frame group. It is the first time to study the scour protection effect of sand bar, sleeve, tetrahedron frame group, column slotted and combined measures in wave and current environment. All kinds of protective measures can reduce the scour depth, but the efficiency is very different. A variety of protective measures can lead to deeper scour pits in the wave-current environment than in the constant flow environment, and their behavior is significantly different from the variation of the scour depth of a single cylinder in different flow environments. The protective measures show many new characteristics under the combined action of wave and current. The participation of wave has obvious influence on the depth of scour, the ability of erosion reduction and the time required to achieve the balance of scour. The proposed combined measures combine the advantages of the tetrahedron frame group and the riprap protection measures, and have a strong adaptability to the marine environment.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U447;U442.32

【参考文献】