Risk Analysis Of Wave Overtopping At Inclined Seawall

Along the18000kilometers coastline of China, tens of thousands of kilometersof sea dikes are constructed to protect the safetay of their backlands. Each year, thestorm surge induced by typhoon may make seawall suffered different degrees ofdamage, which caused heavy loss of lives and properties. Extreme wave overtoppingmay caused serious disruption on seawall. It is significant to rationally calculate thecrestelevation of seawall and study the overtopping for disaster prevention andmitigation.Construction of the seawalls are mainly aimed to resist typhoon, and to protectthe property security after the breakwater, general requirements of strong strength andstability, and not damaged by big waves. At present, there is no national code for thedesign of seawalls in our country. However, there exist different design criteria incoastal provinces.In these criteria, the seawall crest elevation is the sum of the designhigh tide level, wave run-up and the safety free-board, that is not allow overtoppingstandard. The design high tide level is estimated by annual maxima frequency analysismethod recommended by Code for Sea Port Hydrology in China. In allow partialovertopping design, both make the seawall crest elevation have the certain standardand height to achieve moisture standard, and properly reduce the crest elevation ofallowed partial overtopping in order to achieve the purpose of saving investment.Therefore, the wave overtopping as the standard, make the wave overtopping underthe control of the maximum allowable. Also need to solve the influence about waveovertopping water on levee revetment, dike road surface, the back slope and so on, aswell as the overtopping water how to eliminate in time so as not to affect the fair landuse and other issues. In this procedure, a proper wave run-up equation andovertopping equation are selected and related variables in generalized random spacechecking point method are applied to determine the crest elevation. In the specificcalculation, different extreme value distributions, for example Pearson-III distrbutions,log-normal distribution, Gumbel distribution and Weibull distribution, are adopted to fit random variables. At the same time, considering the random variable correlation,build the crest elevation of calculation of the limit state equation, considering thewave runup and overtopping two factors to estimate the crest elevation of returnvalue.The main work of this paper includes the following contents:(1) To summarize and analyze the domestic and foreign wave run-up andovertopping formula, such as Owen formula, VDM method, method in Code for SeaPort Hydrology and the method in Code for Hydraulic Dike Design. The calculationof wave run-up is used method in Code for Sea Port Hydrology, and applicatedsmoothed particle hydrodynamics (SPH) method to simulate and verificate, and usedOwen formula to calculate wave overtopping.(2) To summarize and analyze frequently applied reliability methods, such as thefirst-order second-moment method, correlated random variables in the reliabilityanalysis method, and Monte-Carlo method. The corresponding program about relatedvariables in generalized random space checking point method is compiled withMATLAB software.(3) The crest elevations of typical seawall cross section are separately calculatedby the local criteria method and the reliability method. Results show that thepresented method is feasible and rationality.(4) Combined with the mean wave overtopping, re-estimating the failureprobability of seawall, and analysis other different damage forms and failuremechanism of seawall caused by overtopping.