Behavior-oriented calculation of the annual coastal bathymetry evolution caused by a reclamation work

A behavior-oriented formula is improved to calculate the annual coastal bathymetry evolution caused by a reclamation work. This formula is based on a simple hypothesis that, on the time scale of years, the bathymetry evolution is closely related to the change of tidal current field due to the reclamation work. A new coefficient,named the erosion reduction coefficient, is introduced to extend the original formula for applications in calculating bed erosion. A simplified relationship between the annual variation of the siltation/erosion rate and the water depth is introduced to more realistically represent the long-term process of the bathymetry evolution.The improved formula is applied to calculate the bathymetry evolution in 3 a following a reclamation project in the Xiaomiaohong Tidal Channel in Jiangsu coast in China. The results compare well with measurements and those obtained from a process-based numerical model, demonstrating the capability of the improved behaviororiented formula in reproducing the impact of the reclamation project on the local bathymetry evolution.

Contributors to tidal duration asymmetry with varied coastline configurations on western shelf of Yellow Sea

Coastal management in China is confronted with an urgent choice between natural restoration and maintenance of existing seawalls and reclaimed land for economic development.A key criterion for making this decision is the resilience to coastal flooding,which depends on the ability to predict tidal level.Tidal duration asymmetry(TDA)is a key parameter in determination of the arrival and duration of flood tides.This study selected the western inner shelf of the Yellow Sea(WYS)as the study area and investigated the responses of TDA to different shoreline configurations and relative sea level rise.The responses of TDA to shoreline reconstruction yielded spatial variability locally and remotely.In the nearshore area,the responses of TDA to the complex ocean environment mainly originated from the combined functions of reflection,bottom friction,and advection,which controlled the energy transfer from M2 or S2 constituents to their overtides or compound tides.The sensitivity of TDA to coastline typologies was not limited to coastal waters but could stretch over the entire inner shelf.The vulnerability of tidal responses was due to the displacement of the M2 amphidrome of the Kelvin wave on the WYS,which in turn changed tidal energy fluxes over the regime.The relative sea level rise could intensify the feedback of TDA to seawalls and land reclamation.

Experimental Investigation of the Response of Monopiles in Silty Seabed to Regular Wave Action

Excessive displacement responses of monopiles affect the serviceability of offshore structures.Related to complicated pile−seabed−wave interactions,the actual behavior of monopiles in silty seabed under periodic wave action remains unclear,and relevant studies in the literature are limited.A series of experiments were conducted in a wave flume containing single piles in silty seabed with relative density of 0.77 subjected to regular waves.Two stages of wave loading were applied successively,accompanied by data recording which included pore water pressure,water surface elevation,pile head displacement,and pile strain.Development of pile-head displacement and pore pressure in silty seabed was the main focus,but the effects of pile diameter,pile type,and pile stiffness were also investigated.The experimental results indicate that,in silty seabed,piles of large diameter or with fins accelerate soil liquefaction,resulting in strengthened soil which allows a higher upper boundary of pore pressure.Using fins at deeper locations led to a quick failure of the piles,but the opposite result was observed with an increase in fin dimensions.Once pile-head displacement entered its rapid development period,the wave load calculated via the pile moment was an overestimation,especially for the piles of large diameter.

Regional Frequency Analysis of Significant Wave Heights Based onL-moments

L-moments are defined as linear combinations of probability-weighted moments, They are, virtually unbiased for small samples, and perform well in parameter estimation, choice of the distribution type and regional analysis. The traditional methods of determining the design wave heights for planning marine structures use data only from the site of interest. Regional frequency analysis gives a new approach to estimate quantile by use of the homogeneous neighborhood informatian. A regional frequency analysis based on L-moments with a case study of the California coast is presented. The significant wave height data for the California coast is offered by NDBC. A 6-site region without 46023 is considered to be a homogeneous region, whose optimal regional distribution is Pearson Ⅲ. The test is conducted by a simulation process. The regional quantile is compared with the at-site quantile, and it is shown that efficient neighborhood information can be used via regional frequency analysis to give a reasonable estimation of the site without enough historical data.

Centrifuge modeling of tunneling-induced ground surface settlement in sand

Stress changes in the soil induced by tunnel excavation may cause excessive ground settlement.However,high-quality experimental data on ground settlement due to tunnel excavation are limited.In this study,centrifuge tests are conducted to investigate the threedimensional ground surface settlement,considering different intersection angles and cover-to-tunnel diameter ratios.The results indicate that the major influence zone along the longitudinal direction on the ground surface settlement is±1.25D,where D is the tunnel diameter.When the monitoring section is perpendicular to the tunneling direction,the transverse ground settlement due to the tunnel excavation is symmetrical with respect to the tunnel centerline.In contrast,an asymmetric ground settlement profile is observed when the monitoring section intersects the tunneling direction at an angle of 60.Applying a Gaussian curve to fit the ground surface settlement curve,the width parameter,K(i.e.,the distance between the tunnel centerline and the inflection point of the settlement trough to the tunnel burial depth),varies from 0.33 to 0.39.The ground surface settlement induced by twin tunnel excavation can be captured reasonably by superimposing two identical Gaussian curves.When the cover to tunnel diameter ratios(C/D)are 1.5 and 2.7,the maximum ground surface settlements are 0.67%of D and 0.35%of D,respectively.It is clear that the maximum ground surface settlement decreases with an increase in the C/D ratio.