破碎波作用下砂质海床孔隙水压力响应试验研究
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摘要
波浪传播到近岸水深较浅处会发生破碎,海床破坏与破碎波浪冲击作用下孔隙水压力的分布有着密切的关系。本文采用理论分析、模型试验相结合的方法,揭示了波浪破碎、海床变形及孔隙水压力分布之间的关系,为海洋工程设计提供可参考的依据。
本文基于1:30的斜坡床面上的波浪水槽试验,研究砂质海床上破碎波作用时海床孔隙水压力响应规律,观察波浪破碎区的地形变化并分析其形成原因。试验使用影像处理技术,观察底床受破碎波浪作用后的变形情况。由此找出扰动与未扰动砂层交界剖面,从中了解波浪对底床掏刷程度。试验将传感器埋设于破碎带区域,获得底床内部压力变化并进行分析。
试验结果表明,在波浪破碎前后孔隙水压力变化不同。波浪破碎处地形变化剧烈,破碎带处孔隙水压力竖向衰减幅度均比破碎前、后大。孔隙水压力在沙床顶部的变化比底部变化明显。不同碎波形态的孔隙水压力横向沿程变化没有明显区别,但不同碎波形态对砂层作用的表现方式不同,波浪发生卷破时,主要表现为对砂层大幅度的掏刷与堆积;波浪发生崩破时,主要表现为对已破坏的砂层有一定程度的整平作用。
破碎带内砂层掏刷,孔隙水压振幅变大;砂层堆积,振幅变小。若砂层处于掏刷作用后又堆积的情形,新堆积的砂层不如初始状态紧密,仍有较大的振幅,在波浪的持续作用下,振幅才明显减小。若初始孔隙水压力振幅大于该深度理论静土压力,波浪对底床有着较大的影响深度与砂层移动能力。
破碎带内若传感器均处于未扰动砂层之中,上下两传感器间的压力梯度差值较小。而若上层传感器由于砂层在波浪的持续作用下开始松动,上下两传感器间有着最大的压力梯度差值。波浪的持续作用,上下两传感器间的覆土均被扰动,此时压力梯度差值较小。若波浪对底床的侵蚀作用持续,上述现象会发生于更深层的传感器之间。
The breaking wave will occur when the wave propagates to the area of near-shore and shallow water. It has a close relationship between the seabed destruction and the distribution of pore water pressure under the action of breaking wave. The relationship between the breaking waves, seabed deformation and pore water pressure distribution are presented combined with theoretical analysis, model test method, and this may provide assistance for coastal engineering design.
Based on the wave flume experiments, response pattern of pore water pressure is studied on a 1:30 slope sandy seabed under breaking wave action. The topographic change is observed and its causes are analyzed. It used the image processing technique, and the actual situation of movable seabed change could be calculated. It sets braces near surf zone, obtain the change of the pore pressure under the movable bed and analysis the relationship between moved sand and pore pressure.
The results show that the pore pressure changes significantly differently before and after the wave breaking. The pore pressure reaches the maximum on the area away from the nearest bed surface of the breaking point in the whole process, and the vertical decay rate of pore pressure is larger than the before and after wave breaking in the breaking section. The pore water pressure increases significantly at the breaking point. The topographic change is greatly on the wave breaking section. Pore water pressure changing at the top is significantly higher than it is at the bottom. The changing of the pore water pressure has no relationship with the wave breaking pattern. The pore water pressure attenuates slowly before the wave breaking and attenuates rapidly after the wave breaking. The different patterns of the breaking wave have different performance on the sand. It mainly presented the substantial undercutting and accumulation on the sand when the breaking wave is plunging breaker, and it mainly presented that it has a certain degree of leveling effect on the destructed sand.
When the sand scours, the amplitude of the pore water pressure increases; and when the sand accumulates, the amplitude of the pore water pressure decreases. When the amplitude of the initial pore water pressure is greater than static earth pressure theory, the wave has a greater impact on bed depth and sand mobility.
When the pressure gauges are all in the sand, the upper and lower gauges have a low pressure gradient. And when the gauge in the sand continued to start loosening up and down under the wave action, the two gauges have the greatest pressure gradient. With the continuing action of the wave, the casing on the two pressure gauge is to be disturbed, the two gauges have the low pressure gradient. If the wave action continues eroding the bed, this phenomenon will occur in the deeper sand.
本文基于1:30的斜坡床面上的波浪水槽试验,研究砂质海床上破碎波作用时海床孔隙水压力响应规律,观察波浪破碎区的地形变化并分析其形成原因。试验使用影像处理技术,观察底床受破碎波浪作用后的变形情况。由此找出扰动与未扰动砂层交界剖面,从中了解波浪对底床掏刷程度。试验将传感器埋设于破碎带区域,获得底床内部压力变化并进行分析。
试验结果表明,在波浪破碎前后孔隙水压力变化不同。波浪破碎处地形变化剧烈,破碎带处孔隙水压力竖向衰减幅度均比破碎前、后大。孔隙水压力在沙床顶部的变化比底部变化明显。不同碎波形态的孔隙水压力横向沿程变化没有明显区别,但不同碎波形态对砂层作用的表现方式不同,波浪发生卷破时,主要表现为对砂层大幅度的掏刷与堆积;波浪发生崩破时,主要表现为对已破坏的砂层有一定程度的整平作用。
破碎带内砂层掏刷,孔隙水压振幅变大;砂层堆积,振幅变小。若砂层处于掏刷作用后又堆积的情形,新堆积的砂层不如初始状态紧密,仍有较大的振幅,在波浪的持续作用下,振幅才明显减小。若初始孔隙水压力振幅大于该深度理论静土压力,波浪对底床有着较大的影响深度与砂层移动能力。
破碎带内若传感器均处于未扰动砂层之中,上下两传感器间的压力梯度差值较小。而若上层传感器由于砂层在波浪的持续作用下开始松动,上下两传感器间有着最大的压力梯度差值。波浪的持续作用,上下两传感器间的覆土均被扰动,此时压力梯度差值较小。若波浪对底床的侵蚀作用持续,上述现象会发生于更深层的传感器之间。
The breaking wave will occur when the wave propagates to the area of near-shore and shallow water. It has a close relationship between the seabed destruction and the distribution of pore water pressure under the action of breaking wave. The relationship between the breaking waves, seabed deformation and pore water pressure distribution are presented combined with theoretical analysis, model test method, and this may provide assistance for coastal engineering design.
Based on the wave flume experiments, response pattern of pore water pressure is studied on a 1:30 slope sandy seabed under breaking wave action. The topographic change is observed and its causes are analyzed. It used the image processing technique, and the actual situation of movable seabed change could be calculated. It sets braces near surf zone, obtain the change of the pore pressure under the movable bed and analysis the relationship between moved sand and pore pressure.
The results show that the pore pressure changes significantly differently before and after the wave breaking. The pore pressure reaches the maximum on the area away from the nearest bed surface of the breaking point in the whole process, and the vertical decay rate of pore pressure is larger than the before and after wave breaking in the breaking section. The pore water pressure increases significantly at the breaking point. The topographic change is greatly on the wave breaking section. Pore water pressure changing at the top is significantly higher than it is at the bottom. The changing of the pore water pressure has no relationship with the wave breaking pattern. The pore water pressure attenuates slowly before the wave breaking and attenuates rapidly after the wave breaking. The different patterns of the breaking wave have different performance on the sand. It mainly presented the substantial undercutting and accumulation on the sand when the breaking wave is plunging breaker, and it mainly presented that it has a certain degree of leveling effect on the destructed sand.
When the sand scours, the amplitude of the pore water pressure increases; and when the sand accumulates, the amplitude of the pore water pressure decreases. When the amplitude of the initial pore water pressure is greater than static earth pressure theory, the wave has a greater impact on bed depth and sand mobility.
When the pressure gauges are all in the sand, the upper and lower gauges have a low pressure gradient. And when the gauge in the sand continued to start loosening up and down under the wave action, the two gauges have the greatest pressure gradient. With the continuing action of the wave, the casing on the two pressure gauge is to be disturbed, the two gauges have the low pressure gradient. If the wave action continues eroding the bed, this phenomenon will occur in the deeper sand.
引文
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[2] Oumeraci H. Review and analysis of vertical breakwater failure-lessons learned. Coastal Engineering, 1994,22: 3-29
[3]李炎保,蒋学炼,刘任.防波堤损坏特点与其成因的关系.海洋工程, 2006, 24(2):130-138
[4] Pumam J A.Loss of wave energy due to percolation in a permeable sea bottom. Transactions, American Geophysical Union,1949,30(3):349-356
[5] Massel S R.Gravity waves propagated over permeable bottom. Journal of Waterways, Harbors and Coastal Engineering,ASCE,1976,102(2):111-121
[6] Yamamoto T, Sellmeiher H L , Hijum E V. On the response of a porous-elastic bed to water waves. Journal of Fluid Mechanics, 1978 , 87 (1) : 193 - 206
[7] Madsen O S. Wave induced pore pressures and effective stresses in a porous bed Geotechnique,1978,28(4):377-393
[8] Okusa S. Wave-induced stresses in unsaturated submarine sediments.Geotechnique, 1985, 35(4):517-532
[9] Hsu J R C,Jeng D S,Tsai C P.Short-crested wave-induced soil response in a porous seabed of infinite thickness. International Journal for Numerical and Analytical Methods in Geomechanics,1993,17(8):553-576
[10] Hsu J R C,Jeng D S.Wave-induced soil response in an unsaturated anisotropic seabed of finite thickness.International.Journal for Numerical and Analytical Methods in Geomechanics,1994,18(2):785-807
[11] Seymour B R,Jeng D S Hsu J R C.Transient soil response in a porous seabed with variable permeability.Ocean Engineering,1996,23(1):27-46
[12]范庆来.软土地基上深埋式大圆筒结构稳定性研究:[大连理工大学博士论文],岩土工程,2007
[13]章根德,顾小芸.有限厚度砂床对波浪载荷的响应.力学学报.1993.25(1):56-68
[14]沈瑞福,王洪瑾,周克骥等.动主应力旋转下砂土孔隙水压力发展及海床稳定性判断.岩土工程学报,1994,16(3):70-78
[15]陈仲颐,李向维.波浪引起的饱和土体残余孔隙水压力计算.第五届全国土力学及基础工程会议论文集,北京,1990
[16]盛虞,卢盛松,姜朴.土工建筑物动力固结的耦合振动方程.水利学报,1989,(12):1-42
[17]杨少丽,沈渭铨,杨作升.波浪作用下海底粉砂液化的机理分析.岩土工程学报,1995,17(4):28-37
[18]王栋.波浪作用下海床动力响应与液化的数值分析:[大连理工大学博士论文].大连:大连理工大学水工结构工程,2002
[19]张晨明.波浪作用下海床动力响应与液化分析:[大连理工大学博士学位论文].大连:大连理工大学水工结构工程,2002
[20]吴梦喜,楼志刚.波浪作用下海床的稳定性与液化分析.工程力学,2002,19(5):97-102
[21]马时冬.平台地基在波浪荷载下的循环位移和固结沉降计算.岩土力学,1991,12(4):1-10
[22]吴梦喜,楼志刚.立波作用下海床的有效应力与液化分析.水利学报,2002,(1):56-61
[23] Clukey,E C ,F H Kulhawy, P L F liu. Laboratory and field investigation of wave sediment interaction. Joseph H.De Free Hydraulics Laboratory Rep,1983,83,201-290
[24] Tsui Y T, Helfrich S C. Wave induced pore pressure in submerged sand layer. Journal of the Geotechnical Engineering Division,ASCE,1983,109(4):603-618
[25] Maeno Y H, Hasegawa T. In situ measurements of wave induced pore pressure for predicting properties of seabed deposits. Coastal Engineering in Japan,1987,30(1):99-115
[26] Demars K R, Vanover E A. Measurement of wave induced pressures and stresses in a sand bed. Marine Geotechnology,1985,6(1):29-59
[27] Zen K, Yamazaki H. Mechanism of wave induced liquefaction and densification inseedbed. Soils and Foundations,1990,30(4):90-104
[28] Tsai C P, Lee T L. Standing wave induced soil response in a porous seabed. Proceedings 24th International Conference on Coastal Engineering,ASCE,1995:3369-3377
[29] Huang C M. A fluidization model for cross-shore sediment transport. Ph.D.Dissertation, University of California, Berkeley,U.S.A.
[30]陈佳兴.不规则波作用下直立式防波堤动态行为试验研究:[国立台湾海洋大学硕士论文].台湾:国立台湾海洋大学水工结构工程,1993
[31]王立忠,潘冬子,潘存鸿等.波浪对海床作用的实验研究.土木工程学报,2007,40(9):101-109
[32]程永舟,周援衡,王永学.波浪作用下抛石基床直立堤砂质底床中孔隙水压力响应.大连理工大学学报,2005,2(4):28-33
[33]王忠涛,栾茂田,刘占阁,王栋.浅水区波浪非线性效应对砂质海床动力响应的影响.海洋工程,2005,23(1):41-46
[34] Battjes J A. Surf similarity. Proc 14th Int Conf Coastal Eng,1974:466-480
[35]吴宗仁.海岸动力学.北京:人民交通出版社,2000
[36]俞聿修.随机波浪及其工程应用.大连理工大学出版社,2000
[37] Weggel J R. Maximum breaker height for design.Proc13th on Coastal Eng.,1972:419-432
[38] Dalrymple R A, Eubanks R A, Birkemeier W A. Wave-induced circulation in shallow basins.J. Waterway, Port, Coastal and ocean Division,1977,103:122-134
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