The Research On Pore Water Pressure Response And Scour Around A Pile In Sloped Sandy Seabed

There are abundant energy in ocean.With the development of science and technology,the development and utilization of marine resources is increasing.In coastal and offshore engineering,pile foundations have been widely used in the supporting structures of various marine structures.In the complex ocean environment,the sea bed is subjected to the cyclic pressure under the wave action,which causes the pore water pressure of the seabed to change continuously.That makes the seabed appear to be deformed and softened,which leads to the instability of the seabed and even destroy the stability of the pile foundation.Moreover,the local scour of pile foundation is an important factor affecting the stability of marine structures.Therefore,the study on the seabed pore water pressure response and the local scour of pile under wave has important engineering value and theoretical significance.In this paper,the physical model test is carried out to study the pore water pressure response of the seabed and the local scour around the pile.In the experiment,the slope of 1:16 was used to simulate the slope seabed.The pore water pressure distribution at different positions of the seabed is analyzed by measuring the pore water pressure at different positions of the seabed without pile.By measuring the pore water pressure of seabed around pile which is arranged in the 2 different positions of seabed,the distribution of pore water pressure around pile and the influence of the position of pile on pore water pressure are studied.The influence of wave height and wave period on the pore water pressure is studied by changing the wave elements.The equilibrium scour topography around the piles in different positions under wave is measured by a topographic instrument.The influence of wave height,wave period and the maximum velocity near the bottom and KC number on the seabed morphology around the pile and maximum scour depth are analyzed.The results of physical model test show that:(1)pore water pressure of the seabed without pile decreases along with the depth and the decay rate decreases with the depth.The pore water pressure amplitude increases with the increase of wave height,and the pressure gradient does not change obviously with the wave height.The influence of wave period on the pore water pressure amplitude is related to the location of the sea bed,not all of which increases with the increase of the period.But the pressure gradient increases with the increase of the period.The pore water pressure amplitude and pressure gradient are greater close to the coast in the non-broken zone.(2)When the pile is in different positions in the seabed,decay rate of the pore water pressure in front of the pile is different.The amplitude of pore water pressure in front of the pile is much larger than that of pile side and pile rear.The amplitude of pore water pressure of pile side is only slightly smaller than that of pile rear.With the increase of wave height,the pore water pressure and pore water pressure gradient increase in the front and behind the pile.The effect of wave height on the pore pressure gradient behind the pile is greater than that in front of the pile.The influence of the period on the pore water pressure around the pile is similar to that of the seabed without pile.(3)The scouring patterns around pile under clear-water condition are similar to those of the piles under live-bed condition with small periodic incident waves.Under live-bed condition with large periodic incident waves,there is an inverted conical semi circular scour pit in the front of the pile,but it is not the biggest scour pit.The maximum scour depth increases with wave height,wave period,velocity near bottom and KC number.