Edyta Malinowska

Estimation of Flow Characteristics in Peat

This paper presents the behavior of the soft subsoil under structures such as embankment dams, particularly tailing dams which are nowadays usually placed in swampy areas often dominated by organic soils, such as peat. Structures construction on soft organic soils makes it necessary to calculate subsoil deformations with special consideration of the water flow. Constructions of embankments on soft organic soils cause many problems because of their specific properties. The organic soils, such as peat, are characterized by high porosity and low shear strength as well as high initial permeability which decreases during consolidation. In the deformation process of soil skeleton under loading the porosity decreases and causes changes of flow characteristics. Therefore, the water flow characteristics are very important to be considered in predicting and calculating the subsoil deformation under load. The specific behavior of soft subsoil demands estimation reliability of the flow characteristics. Therefore in the statistical analysis suitable statistical methods and proper measures in laboratory tests should be used. Several statistical functions have been applied to analyze the flow-pump test data in order to provide a correct estimation of flow characteristics in soft soils. In this paper, the results of water flow characteristics obtained in laboratory tests and the estimation of flow characteristics in soft organic soils are presented.

Determination of the coefficient of consolidation in soft organic soils using ACONS

Abstract Determination of the coefficient of consolidationin soft organic soils using ACONS. To determine the coefficient of consolidation using oedometer laboratory tests usually two common methods are used, Casagrande and Taylor. In the paper, the ACONS apparatus and ClispStudio program is characterized. The methodology and the test results of determination coefficient of consolidation in soft organic soils are presented. In the paper, the laboratory test results obtained from Automatic CONsolidation System are analyzed and the relationships between coefficient of consolidation, void ratio, and vertical stress are also presented. Streszczenie Wyznaczanie współczynnika konsolidacjiw słabonośnych gruntach organicznychz wykorzystaniem zestawu ACONS. W celu wyznaczenia współczynnika konsolidacji w słabonośnych gruntach organicznych w laboratoryjnych badaniach edometrycznych zwykle stosowane są dwie podstawowe metody, Casagrande’a i Taylora. W artykule przedstawiono ACONS (zestaw automatycznych edometrów) wraz z oprogramowaniem ClispStudio. Podano charakterystykę zestawu i metodykę wyznaczania współczynnika konsolidacji w słabonośnych gruntach organicznych. W artykule zostały przedstawione i przeanalizowane wyniki badań uzyskane z ACONS. Zaproponowano także funkcję opisującą zależność współczynnika konsolidacji od wskaźnika porowatości i pionowego naprężenia

Vertical and horizontal permeability measurements in organic soils

Abstract The paper is referring to vertical and horizontal laboratory permeability measurements in soft organic soils. The estimation of anisotropic permeability in soft organic soils, as peats, requires to use a special apparatus and the knowledge of proper analysis of the test results. During loading the void ratio decreases substantially that causes the changeability of the permeability. The change of permeability during the compression is very important because of the influence of the consolidation co-efficient. Initial strain in soft organic soils appears very quickly, just after loading, and brings immediately the decrease of permeability. In most of the estimations, it is assumed that during the consolidation process the water flows just in the vertical direction. In soft organic soils, like peats, the consolidation theory should consider the changes of mechanical and physical properties in consolidation period, in both directions. The direct measurement of vertical and horizontal permeability of organic soil and the non-Darcian flow theory may be of considerable importance in estimating pore water pressure dissipation, and settlement rates in the consolidation model. In the paper, the method of investigation and the test results of the vertical and horizontal permeability are presented. The Modified Rowe Cell Set for obtaining consolidation and flow characteristics in different directions is used.

Derivation of consolidation partial differential equations with non-linear fl ow characteristics on organic soil example

Abstract Derivation of consolidation partial differential equations with non-linear flow characteristics on organic soil example. Derivation of consolidation partial differential equation with non-linear flow characteristics is proposed. The non-linear flow characteristics are obtained from flow-pump test on organic soil and described with empirical relationship. Several reasons were crucial to perform tests on organic soil. Firstly organic soils are very compressible, so that results in high permeability changes. Even with small stresses organic soil deforms a lot. Secondly road embankments, flood control levees, dykes and dams are very often located on organic soil, so it is important to model deformations under these constructions. Thus to model consolidation process in soft organic soil one should consider as follows: physical and mechanical properties, non-linear stress-strain relationship, non-linear flow characteristics, and creep strains. This paper is focused mainly on non-linear flow characteristics that change with porosity and hydraulic gradient variations. Streszczenie Wyprowadzenie równania różniczkowego cząstkowego konsolidacji z uwzględnieniem nieliniowości przepływu na przykładzie gruntów organicznych. W artykule zaproponowano wyprowadzenie równania różniczkowego cząstkowego konsolidacji z uwzględnieniem nieliniowości przepływu. Nieliniowe charakterystyki przepływu wyznaczono na podstawie badań flow-pump na gruntach organicznych. Zależność pomiędzy prędkością przepływu wskaźnikiem porowatości i gradientem została zapisana za pomocą równań empirycznych. Analiza wyników badań laboratoryjnych potwierdziła dużą zmienność przepływu wraz ze zmianą porowatości. Wiele budowli, takich jak: nasypy drogowe, obwałowania, zapory i wykopy budowlane, jest bardzo często posadowionych na ściśliwych gruntach organicznych, dlatego właściwe zamodelowanie przebiegu konsolidacji jest bardzo istotne. W tym celu należy wziąć pod uwagę czynniki, takie jak: fi zyczne i mechaniczne właściwości gruntu, nieliniową zależność naprężenia i odkształcenia, nieliniową charakterystykę przepływu i pełzanie. W artykule skupiono się na nieliniowych charakterystykach przepływu zmiennych z porowatością i gradientem hydraulicznym. Zaproponowano równanie różniczkowe cząstkowe konsolidacji uwzględniające nieliniowość przepływu w gruntach organicznych.

Analysis of yield stress ratio and overconsolidation ratio as parameter determination preconsolidation in eemian gyttja

Abstract The preconsolidation stress is an important phenomenon that determines the value of stress history exerted in the past on the subsoil in the geotechnical engineering. Overconsolidation ratio (OCR) is one of the main criteria conditioning soil behaviour and its characteristics. Here thought, the yield stress ratio (YSR) is used to determine the value of preconsolidation stress resulting from mechanical overburden than can be changed by many post depositional processes like secondary and tertiary compressibility, cementation, aging, temperature change and others. The yield stress ratio (YSR) is defined as the relationship between vertical yield stress (σ’vy) to the effective vertical stress (σ’v0). The eemian gyttja was used as a foundation in the engineering construction. In practical geotechnical engineering, evaluation of stress history is usually based on the overconsolidation ratio (OCR). The yield stress ratio (YSR) was used in the laboratory as one of the basic parameters for the geotechnical design of the structure. To know the relation between geological background, history and mechanical behaviour in long-time process of the soil aims a knowledge that can help engineers who often have to predict soil behaviour based upon the soil geological history and a few geotechnical data. In order to evaluate the yield stress ratio of eemian gyttja it is necessary to restore this soft, organic soil as much as possible to the in situ conditions. The laboratory tests were used to determinate the vertical yield stress and then the yield stress ratio. The laboratory tests were made in the automatic oedometer and the in situ tests were carried out on the dilatometer test (DMT). The comparison between the determination the yield stress ratio of eemian gyttja from the laboratory and the overconsolidation ratio from in situ test has been done. The studies have shown that the values of the overconsolidation ratio determinate from the laboratory tests are a little higher than determinate from the in situ tests.

The overconsolidation ratio of eemian gyttja determination

Abstract The overconsolidation ratio of eemian gyttja determination. The overconsolidation ratio is an important parameter that determines the value of stress history exerted in the past on the subsoil in the geotechnical engineering. Overconsolidation ratio (OCR) is one of the main criteria conditioning soil behavior and characteristics. To know the relation between geological background, history and mechanical behavior of the soil, aims a knowledge that can help engineers who often have to predict soil behavior based upon the soil geological history and a geotechnical data. In order to evaluate the overconsolidation ratio of eemian gyttja, it is necessary to restore this soft soil as much as possible to the in situ conditions. The eemian gyttja is an organic soft soil from the “Zoliborz channel” located in Warsaw. These soils are used as a base construction in the foundation engineering. In practical geotechnical engineering, evaluation of stress history is based on the overconsolidation ratio. The overconsolidation ratio is one of the basic parameters for the geotechnical design of the structure. Determination of this parameter using for example dilatometer tests, is usually based on empirical formulas which were established in different countries. Therefore, regional geotechnical conditions could have substantially affected on the empirical relationships. The laboratory tests are used to determinate the preconsolidation pressure and then the overconsolidation ratio. The laboratory tests were made in the automatic oedometer and the in situ tests were carried out on the dilatometer test (DMT). The paper presents results of determination the overconsolidation ratio of eemian gyttja from the laboratory and in situ tests. The studies have shown that the values of the overconsolidation ratio determination from the laboratory tests are a little higher than determination from the in situ tests.