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Wpływ struktury na skurczalność gruntów spoistych

Izdebska-Mucha D., Wójcik E.

Przegląd Geologiczny

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2013

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Vol. 61, nr 3

195--202

EN

This paper deals with the structural factors affecting shrinkage phenomena. Seventy eight soil samples were tested, including: Neogene (Mio-Pliocene) clays, glacial tills, clayey alluvial soils, bentonite, illitic clay and kaolinite. Destructed soils (remoulded samples) were compared with undisturbed soils (NNS). Analysis of shrinkage curves showed that the most hydrophilic clays and well-graded soils have the lowest void ratio and shrinkage limit. Shrinkage curves ofsilty and sandy soils are relatively plane with poorly differentiated shrinkage stages. For Neogene clays, shrinkage curves of remoulded samples are similar to the undisturbed ones. Both series of samples yielded similar final void ratio and shrinkage limit values. For alluvial soils and glacial tills, remoulded samples yielded a lower void ratio and higher shrinkage limit values than NNS samples. The results obtained showed that the soil fabric (natural preserved versus disturbed) does not influence shrinkage of Neogene clays while affects significantly shrinkage of alluvial soils and glacial tills. The statistical analysis revealed that there was no correlation between shrinkage limit and clay content or plastic index. A linear rela¬tionship was found between shrinkage limit and void ratio for clays as well as remoulded samples.

2

Analiza parametrów skurczalności gruntów spoistych według różnych norm

Izdebska-Mucha D., Wójcik E.

Biuletyn Państwowego Instytutu Geologicznego

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2011

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nr 446 (2)

321--327

PL

W artykule przedstawiono wyniki badań parametrów skurczalności oznaczonych wg norm polskiej PN-88/B-04481 i brytyjskiej BS1377: Part 2: 1990: 4.3 oraz wg wzoru korelacyjnego Krabbego z 1958 (Schultze, Muhs, 1967). Analizę przeprowadzono dla iłów mioplioceńskich, glin lodowcowych oraz mad z Warszawy, Mszczonowa i Płocka. Określono takie parametry skurczu, jak: granica skurczalności ws, skurcz objętościowy Vs, względny skurcz objętościowy Vp oraz przeprowadzono analizę ich zależności od parametrów wskaźnikowych gruntu. Najwyższe wartości granicy skurczalności i skurczu objętościowego (Vs i Vp) wykazały kolejno: iły mioplioceńskie > mady > gliny lodowcowe. Wartości granicy skurczalności wg normy brytyjskiej są niższe niż wg normy polskiej, a różnica wynosi ok. 1–4%. Granica skurczalności obliczona wg Krabbego znacznie odbiega i nie wykazuje jednolitej tendencji zróżnicowania w stosunku do pozostałych metod. Nie stwierdzono wiążących zależności funkcyjnych pomiędzy granicą skurczalności a zawartością frakcji iłowej oraz wskaźnikiem plastyczności. Stwierdzono zależności liniowe o wysokim współczynniku korelacji pomiędzy skurczem objętościowym (Vs i Vp) a wilgotnością gruntu w0, przedziałem skurczu, wskaźnikiem plastyczności (Ip) i zawartością frakcji iłowej. Wyznaczono wzór na względny skurcz objętościowy w zależności od parametrów łatwo i standardowo wyznaczanych w badaniach geologiczno-inżynierskich gruntów – wilgotności i wskaźnika plastyczności: Vp = 0,629w0 + 0,191Ip–1,659 ±3,166; (R = 0,968).

EN

The article presents the results of shrinkage parameters research according to Polish standard PN-88B-04481, British standard BS1377: Part 2: 1990: 6.3 and Krabbe's equation from 1958 (Schultze, Muhs, 1967). Mio-Pliocene clays, glacial tills and alluvial soils were tested, as the most typical subsoils in Poland. Shrinkage limit w/s, volumetric shrinkage Vs, relative volumetric shrinkage Vp were determined and correlated with soils properties such as moisture content, shrinkage range, plasticity index and clay content. No significant relationships between shrinkage limit and clay content or plasticity index were found. Linear regression of high correlation coefficient was found between volumetric shrinkage Vs, Vp and moisture content, shrinkage range, plasticity index, clay content . However, the most important result of the analyses was the determination of the relationship between volumetric shrinkage Vp and moisture content (w/o) and plasticity index (Ip) — parameters commonly tested in geological engineering practice: Vp = 0,629w/o + 0,191Ip-1,659 ± 3,166; (R = 0,968).

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Charakterystyka zmian deformacyjnych gruntów antropogenicznych z osadników cukrowni

Choma-Moryl K.

Przegląd Geologiczny

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2010

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Vol. 58, nr 9/2

892-897

EN

Sewer sludge that fills four wet dumps of the closed Małoszyn Sugar Factory in Malczyce near Środa Śląska, Lower Silesia constitutes a very specific anthropogenic soil. It is composed of grains and mineral particles transported in suspension after sugar beets pre-processing treatment. Presently the wet dumps are to be recultivated to meet the requirements of environmental protection. According to the recultivation project the wet dumps will be backfilled with suitable waste material and covered with sand and soil to stimulate soil forming processes. Finally grass, clover and shrubs will be introduced. The recultivation layer thickness will reach 3-6 m. Anthropogenic soil that fills the wet dumps is up to 2-3 m thick. The grain-size distribution is generally consistent with silty loam, silty clay loam and silty clay. Quartz, illite and chlorite dominate the mineral composition. The wet dump's bottom is formed by clays of the Poznań Formation, practically impermeable. Silt-dominated soils deposited in a water environment are highly susceptible to deformations caused by water and overload. Deformation behaviour was studied for the soil in a semi-solid state as well as in a soft-plastic state. Varying influence of water results, among others, in shrinkage (Ls) and swelling of the soils, characterized in the present study by swelling strain (p). Load-induced deformation of the soils is described basing on the modulus of primary compressibility. Basing on the results obtained it may be stated that the investigated anthropogenic soil undergoes moderate deformations under the influence of water. The swelling strain does not exceed 0.5-1.2% for the soil in a soft-plastic state and amount to 3.1-4.3% in a semi-solid state. The soil shrinkage limit varies between 3 and 5%. On the other hand load-induced deformations will be of remarkably higher importance. The soil in a soft-plastic state shows high shrinkage that is comparable with the one for organic soils. The modulus of primary compressibility is 282.3-925.9 kPa. The compressibility is markedly lower for a semi-solid state (MO =1 190.5-2 000 kPa). Characteristically, in both soft-plastic and semi-solid states the soil shows higher compressibility for lower load values 0-50 kPa than for the higher range 0-200 kPa. These compressibility values should be taken into account during backfilling of the wet dumps with various safe waste materials at recultivation. The load-induced pressure, initially low, will increase with adding consecutive layers. Thus highest soil deformations should be expected during the initial backfilling stages and their intensity may be estimated using the modulus of primary compressibility.