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1

Theoretical analysis of model seabed behavior under water wave excitation

Sawicki A., Mierczyński J., Smyczyński M.

Studia Geotechnica et Mechanica

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2015

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Vol. 37, nr 2

33--37

EN

Theoretical analysis of the behavior of a model seabed subjected to water wave excitation is presented. The experiments were performed in the wave flume at the Danish Technological University in Lyngby. Such experiments are unique in engineering sciences and therefore provide unique empirical data for testing various models of the seabed. A controversial explanation of the experiments is presented in the literature. The goal of this research was to study pore pressure changes caused by water waves and the subsequent liquefaction of the seabed. The authors of the present contribution offer their own theoretical explanation of the wave flume experiments and discuss errors found in the literature cited. The analysis is based on the classical soil mechanics, including the Biot type approach.

2

Liquefaction of saturated soil and the diffusion equation

Sawicki A., Sławińska J.

Studia Geotechnica et Mechanica

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2015

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Vol. 37, nr 2

39--44

EN

The paper deals with the diffusion equation for pore water pressures with the source term, which is widely promoted in the marine engineering literature. It is shown that such an equation cannot be derived in a consistent way from the mass balance and the Darcy law. The shortcomings of the artificial source term are pointed out, including inconsistencies with experimental data. It is concluded that liquefaction and the preceding process of pore pressure generation and the weakening of the soil skeleton should be described by constitutive equations within the well-known framework of applied mechanics. Relevant references are provided.

3

Uni-axial liquefaction wave in saturated sands

Sawicki A.

Journal of Theoretical and Applied Mechanics

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1998

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nr 3

681-701

EN

A compaction theory is applied to description of stress wave propagation through saturated sands, including such associated phenomena as pore pressure generation and liquefaction. Numerical examples show that liquefaction is possible during either loading or unloading, depending on the magnitude of applied stress and mechanical properties of saturated sand. It is shown that the stress wave propagates without change of shapes but produces regrouping of the intrinsic stresses in matrix and fluid, i.e. generating excess pore pressure and reducing mean effective pressure, which leads to liquefaction. Those effects are caused by permanent porosity changes due to rearrangement of the granular structure of the sand, and pore water compressibility.

PL

Przedstawiono zastosowanie teorii zagęszczania do opisu propagacji jednowymiarowej fali upłynnienia w nawodnionych piaskach. Wykazano, że upłynnienie jest możliwe zarówno podczas procesu obciążenia jak i odciążenia w zależności od wielkości naprężeń oraz od właściwości mechanicznych materiału. Pokazano, że fala globalnego naprężenia propaguje się bez zmiany kształtu. Procesowi temu towarzyszy przegrupowanie naprężeń parcjalnych w składnikach mieszaniny, tj. generowane jest ciśnienie porowe, któremu towarzyszy redukcja naprężeń efektywnych w szkielecie gruntowym. Zjawisko to prowadzi do upłynnienia nawodnionego gruntu.