开孔双壁圆形钢吊箱围堰消波效果影响因素分析

Analysis on the influence factors of wave attenuation effect of double-wall circular steel cofferdam with trepanning on outer wall

跨海大桥桥墩基础施工若采用双壁钢围堰,则在其外壁进行开孔可有效减小波浪力,有利于降低钢围堰的制作造价和提高基础施工的安全性。以某跨海大桥基础施工采用的双壁圆形钢吊箱围堰为研究对象,引入波浪力折减系数K_(d)对消波效果进行评价,采用数值方法着重分析波浪参数和围堰自身结构设计参数对消波效果的影响规律。结果表明:K_(d)随波陡增大呈先快后缓的增大趋势,波陡超过0.032后,消波效果基本不再变化;随着相对水深的增大,K_(d)呈先减小后增大并趋缓的规律,在相对水深d/L约为0.455时取得最小值;K_(d)随开孔率的增大呈线性减小,开孔率越大,消波效果越好。随着双壁间距s的增大,K_(d)总体上呈减小趋势,且减小速率先快后慢;双壁间距较小时,开孔的消波作用较弱。开孔率和双壁间距两种因素间存在耦合作用,两者越大,其耦合作用也越强。围堰设计中可适当增大开孔率并选取合适的双壁间距以得到最佳消波效果。

If double-wall steel cofferdam is used in pier foundation construction of sea crossing bridge,trepanning on outer wall can effectively reduce the wave force,which is beneficial to reducing the production cost of steel cofferdam and improving the safety of foundation construction.In this research,the double-wall circular steel hanging box cofferdam used in the foundation construction of a sea-crossing bridge was taken as the research object.The wave force reduction coefficient K_(d) was introduced to evaluate the wave elimination effect,and the finite element numerical simulation was used to analyse the impact of wave parameters and structural design parameters.The main conclusions are as follows:K_(d) increases rapidly and then slowly with the wave steepness,and the attenuation effect is basically no longer changed after the wave steepness exceeds 0.032.With the increase of relative water depth,K_(d) firstly decreases,then increases and slows down,and the minimum value is obtained at about d/L=0.455.The K_(d) decreases linearly with the increase of the trepanning ratio,and the higher the trepanning ratio,the better the attenuation effect.With the increase of the spacing s between two walls,K_(d) tends to decrease in general,and the decreasing rate is fast at first and then slows down.When the distance s is small,the attenuation effect of trepanning is weak.There is a coupling effect between the trepanning ratio and the distance s,and the larger the two factors are,the stronger the coupling effect is.In the design of cofferdam,the best wave elimination effect can be obtained by increasing the opening rate and choosing the proper distance between two walls.