Pore Water Pressure in Sand Bed under Oscillating Water Pressure

In this paper the theoretical method to analyse the pore water pressures in the sand bed under the oscillating water pressure is developed. In the former researchs the validity of the theoretical treatment for the one-dimensional problem has been verified. However, the one-dimensional treatment is not sufficient to obtain the precise informations concerning the many practical problems. From this point of view, in this study, we derive the fundamental equations for the general three-dimensional sand layer under the oscillating water pressure. The validity of this theoretical method is verified by experiments for the twodimensional problems

Dynamic Behavior of Sand Bed under Oscillating Water Pressure

Under the attack of storm waves, there are many destructions of coastal structures in the forms of sinking and sliding. These types of destructions will be in close relation to the dynamic behavior of sand bed around the structures. From this point of view, in this paper, we investigate the characteristics of the pore water pressure and effective stresses in the highly saturated sand bed under oscillating water pressure theoretically. The results indicate that the oscillating water pressure induce the notable drop of strength of sand bed around the structure under certain condition

Floatation of Buried Submarine Pipeline under Cyclic Loading of Water Pressure -Numerical and Experimental Studies-

A dynamic response of a submarine pipeline buried in sandy seabed sediments to water loading generated by harmonically oscillating water-table vertical movements is examined in the present report experimentally and numerically. The aim of small-scale laboratory experiments was: (1) to record time-histories of pipeline vertical displacements, and (2) to observe a shape of slip surface of an overburden sand body involved in breakout together with the pipeline. A parametric study was carried out in order to investigate the influence of two meaningful factors, that is the depth of burial and the specific gravity of pipeline, on a gradual upward displacement of the pipeline. Based on a numerical finite-element 2D-analysis of the hydrodynamic pore pressure and effective stresses oscillations in the pipeline vicinity, an analysis of the pipeline stability potential is presented, in which all the experimental cases tested are verified. All important component forces (e.g., hydrodynamic uplift force) associated with floatation phenomenon of the buried submarine pipeline are considered and quantified

Movement of Sand around Revetment under Water Pressure Variation

Many hydraulic structures are damaged by under flood flow and storm waves year after year. Many cases of dike and breakwater failure are caused by the suck out of sand from behind the revetment. This type of failure will be in close relation to the dynamic behavior of sand bed around the revetment. In this paper, from this point of view, we investigated the basic characteristics of such sand movement by small model tests and tried to explain the hydro- and soil-mechanical mechanism of this phenomenon theoretically

Effect of Displacement Method on Sand Bed Liquefaction under Oscillating Water Pressure

In this paper the liquefaction of sand bed under oscillating water pressure are treated as a basic study of the prevention works against the scouring around the hydraulic structures. The results of the former resurch show that the occurrence of the liquefaction depends on both properties of the oscillating water pressure and of the sand layer. Considering the latter properties, that is, the resistivity against the liquefaction increases with the increase of the permeability of the sand bed, we propose the displcement method as one of the prevention works, which is a method to displace the upper layer of the sand bed by the sand with large permeability. The effects of this method are investigated theoretically and experimentally. By the experimental study, it is shown that the proposed displacement method has the apparent effect to prevent the liquefaction. The experimental results are explained fairly well by the theoretical analysis based on the theory of the flow through the elastic porous media

Dynamic Behavior of Sand Bed around Structure under Wave Motion

Under the attack of storm waves, there are many destructions of coastal structures due to scouring, sinking and sliding. These types of destructions are considered to be in close relation to the dynamic behavior of sand bed around the structures. In this study the characteristics of pore water pressure and stresses in the sand bed around a breakwater under the attack of superposed waves are treated theoretically. The results show that during the crest or the trough being in front of the structure the strength of sand bed around the structure decreases notably and the unstable zone will occur

Destruction Prediction of a Rubble Mound Weir Using VOF-DEM Coupled Model

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Wave-Induced Pore-Pressure Response on a Submarine Pipeline Buried in Seabed Sediments - Experiment and Numerical Verification -

The response on sandy seabed sediments to a harmonically oscillating water-table, with a special consideration of the wave-induced pore-pressure oscillations around a pipeline buried in seabed sediments, is studied in the present work experimentally and numerically. The aim of the analysis was: (1) to observe a true distribution pattern of the wave-induced pore-pressure oscillations acting on the pipeline outer surface, and (2) to verify small-scale test results using numerical computations performed for a wide range of saturation conditions of seabed sediments, under the assumption of a compressible two-phase medium compound of the pore-fluid and soil skeleton, as well as a finite thickness of a permeable seabed layer

Numerical Analysis of Dynamic Behavior of Highly Saturated Sand Bed around Cylindrical Block under Cyclic Loading of Water Pressure

In this paper the theoretical procedure to analyze the dynamic behavior of highly saturated sand bed around a cylindrical block under the cyclic loading of water pressure is developed. The fundamental equations were derived for the axially symmetric coordinates. Then, the finite element equations were developed to solve these fundamental equations numerically. Finally, the numerical method was verified by experiments