【作者】 陈智杰；

【导师】 王永学；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2009， 博士

【摘要】 海洋环境条件下,大型沉管隧道管段的沉放是沉管隧道施工中的一个关键环节。海洋中的风、浪、流作用将给管段的海上沉放施工带来很大的困难,较差的海洋动力环境条件将不利于管段的沉放施工作业。研究沉管管段沉放过程中的运动特性和缆绳受力特性,有助于把握沉管的运动稳定性和施工安全性。到目前为止,对海洋环境条件下沉管管段沉放运动的研究还很少。基于此,本文开展了波浪作用下沉管管段沉放运动的试验研究和数值模拟研究。本文开展了规则波作用下沉管管段沉放的试验研究,研究了规则波作用下管段的运动响应特性和缆绳受力特性,分析了管段沉深和相关波要素对管段沉放过程中的运动响应及缆绳受力的影响;讨论了正向波作用下波浪与管段运动及缆绳张力之间的相位关系。试验结果表明,管段沉深和波浪周期对管段的运动有较大的影响,特别当管段沉深较小时,管段的运动表现出强非线性特征;管段沉深较小的情形下,波高对管段的无量纲运动位移的影响较为明显,且缆绳随时间出现周期性的松弛状态。试验还对规则波和水流联合作用下管段的运动特征和缆绳受力特征进行了研究。对于正向波流联合作用的情形,水流对管段的运动有很大的影响。在流力作用下,管段在水平、垂直方向和横摇运动方向上均产生一定的偏移,偏移量的大小与水流流速的大小有关;缆绳的张力随波高和流速的增大而增大。本文对不规则波作用下沉管管段的沉放开展了试验研究,研究了不规则波作用下管段的运动响应特性和缆绳受力特性,分析了管段沉放过程中的运动响应频谱特征及管段沉深、波浪有效波高和谱峰周期对管段运动响应和缆绳受力的影响。根据试验分析结果,不规则波作用下,管段除了产生与波浪谱峰周期对应的波频运动外还作低频运动;不同沉深的管段其横荡低频运动均大于横荡波频运动,而对于垂荡运动,随着管段沉深的增大,运动从以低频运动为主逐渐过渡到以波频运动为主;有效波高和谱峰周期越大,管段的运动响应也越大;对应于管段的运动响应,缆绳张力频谱同样存在波频谱峰和低频谱峰,并且在管段沉深较小、波浪有效波高较大和谱峰周期较大的情形下,缆绳的张力相应地大。本文分别建立了波浪作用下沉管管段运动的频域和时域数值计算模型。应用基于三维分布源方法的频域模型计算分析了波浪作用下管段处于不同沉放阶段的波浪荷载及频域响应。频域计算对于反映线性系统的管段沉放运动是一个简单而方便的方法;应用基于有限水深条件下满足自由面条件的时域格林函数建立了波浪对管段作用的时域内的积分方程,并采用边界元方法求解,应用牛顿第二定律建立了管段的时域运动方程,并采用四阶Runge-Kutta方法求解,由此建立起管段运动的时域数值计算模型。时域模型能够反映管段非线性运动和缆绳张力非线性变化的特性,并能给出管段运动响应和缆绳张力随时间变化的过程。时域计算结果与试验结果的比较验证,显示了时域计算模型的正确性和有效性。应用该时域模型研究了不同沉放深度、不同负浮力、不同波浪入射角度等影响因素条件下沉管管段的运动响应特征和缆绳的受力情况,数值计算结果进一步表明了其与试验分析结论的一致性。更多还原

【Abstract】 The immersion of large-scale tunnel elements is one of the most important procedures of immersed tunnel construction under the ocean environment conditions.The winds,waves and currents in the ocean will have an unfavorable influence on the immersion of tunnel elements. Studying the dynamic characteristics of tunnel elements in the immersion and the behaviour of cable tensions will be helpful for the immersion stability and construction safety of the tunnel elements.Up to now,there are still a very few researches about the motion dynamics of tunnel elements in the immersion under the ocean environment conditions.On the base of this consideration,the investigation on the motion characteristics of a tunnel element under wave actions during its immersion is carried out in this thesis,including the experimental and numerical study.The experimental study is conducted on the immersion of the tunnel element under regular wave actions in the finite water depth.The emphasis of the investigation is on the characteristics of the tunnel element motion responses and the cable tensions.The influences of the immersing depth and the relevant wave factors on the motion responses of the tunnel element in the immersion and the cable tensions are analyzed.The relations of phase among the waves,the motions of the tunnel element and the cable tensions are discussed under the right-angled wave condition.The experimental results indicate that the wave period and immersing depth have large effects on the motions of the tunnel element.Especially,as the immersing depth is relatively small,the motions of the tunnel element show strong nonlinearity.In the case of relatively small immersing depth,the effects of the wave height on the non-dimensional motion displacements of the tunnel element are obvious,and there occurs slack state periodically in the cables during the movement of the tunnel element.The investigations on the cable tensions and motion characteristics of the tunnel element under combined wave-current actions are also carried out.For the case of the joint actions of the right-angled waves and current,the current has large effect on the motions of the tunnel element.Under the current actions,the excursions occur to the tunnel element in the horizontal and vertical direction,as well as in the tunnel element roll motion direction.The magnitude of the excursions depends on that of the current velocity.And the cable tensions increase with the increase of wave height and current velocity.The experimental investigation on the immersion of the tunnel element under irregular wave actions is also conducted.The frequency spectrum characteristics of the motion responses of the tunnel element and the influences of the immersing depth,the significant wave height and the peak frequency period on the motion responses and cable tensions are analyzed.According to the experimental results,under the irregular wave actions the tunnel element has the wave frequency motions corresponding to the wave peak frequency period, and has the low frequency motions in addition.For the sway motion of the tunnel element,the low frequency motion is dominant in different immersing depths.But for the heave motion, that the low frequency motion is dominant gradually turns to that the wave frequency motion is dominant with the increase of the immersing depth.The larger are the significant wave height and peak frequency period,the larger are the motion responses of the tunnel element. Corresponding to the motions of the tunnel element,the frequency spectra of the cable tensions have similarly wave frequency and low frequency peak,and the cable tensions are comparatively large as the immersing depth is relatively small and the significant wave height and peak frequency period are relatively large.The frequency-domain and time-domain numerical models are developed respectively in the thesis.The frequency-domain numerical model is presented based on the 3-dimensional source distribution method,and with the model the wave loads and frequency responses of the tunnel element under wave actions in different immersing depths are calculated.The frequency analysis for the reflection to the immersion motion of the tunnel element in a linear system is a simple and convenient method.Based on the time-domain Green function that satisfies the free water surface condition in the finite water depth,the integral equation is established,and solved by the boundary element method.By adopting Newton second’s law, the time-domain motion equations of the tunnel element are proposed,and solved by the fourth order Runge-Kutta method.On the basis of the theories above,the time-domain numerical model is developed.The model can reflect the characteristics of the nonlinear motions of the tunnel element and the nonlinear variation of the cable tensions,and can give the variation information of the motion responses of the tunnel element and the cable tensions with the time.Compared with the results of the experiments,the time-domain numerical model proves to be correct and effective.By using the model,the motion responses of the tunnel element and the cable tensions are calculated under different immersing depth, different negative buoyancy and different incident wave direction conditions,etc.The computational results further show the agreement with the experimental results.更多还原