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1

Assessment and verification of correlations in CPTu testing on the example of soil from the Wroclaw surroundings (Poland)

Tankiewicz Matylda, Bagińska Irena

Archives of Mining Sciences

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2021

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Vol. 66, no. 2

313--327

EN

The paper presents the results of a series of Cone Penetration Test CPTu performed near the city of Wroclaw (Poland). The tests were carried out in 13 testing points located in close distance to each other. To verify the results of the penetration tests, fine-grained soil samples from selected depths were taken for laboratory tests. The study focuses on the evaluation of soil type, unit weight, and undrained shear strength cu, and compression index Cc. The grain size distribution of the soil and its mechanical parameters on the basis of a uniaxial compression and an oedometer tests were estimated. A comparison of laboratory and CPTu for selected values is presented. Determination of soil type was carried out on the basis of ISBT and IC values and good agreement with the granulometric composition was found. For undrained shear strength, commonly used correlations based on Nk, Nkt and Nke were adopted. However, the values obtained from the CPT are significantly lower than the results from laboratory tests. Therefore, values of cone factors suitable for investigated soil type and reference test were proposed. In the case of the compression index, the coefficient values βc and αm obtained agreed with those available in the literature. The findings presented in the paper indicate that laboratory tests remain necessary to identify soil properties from CPTu. The presented results are also a contribution to the knowledge of local soil conditions in the Lower Silesia area (Poland).

2

One-dimensional consolidation parameters of cemented paste backfills

Yilmaz E., Belem T., Benzaazoua M.

Gospodarka Surowcami Mineralnymi

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2012

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T. 28, z. 4

29-45

EN

Each year, mine and mill operations generate enormous amounts of two waste types - fine-grained tailings and coarse-grained waste rocks. Fine-grained tailings are either discharged in slurry form to surface tailings dams or delivered in cementitious form to underground mine stopes as backfilling, while coarse-grained rocks are typically stored by depositing as a dry material in large dumps. The engineering design of surface tailings dams or underground mine stopes is often controlled by the high compressibility and low shear strength characteristics of fine-grained tailings. Cemented paste backfill CPB indicating saturated, fine-grained backfills can undergo major consolidation settlement during early curing stages. Thus, a better understanding of the rate and magnitude of both differential and total settlement of CPB cured under stress is essential for a proper backfill geotechnical design. The consolidation parameters of CPB can be determined from an improved lab setup called CUAPS (curing under applied pressure system). This setup is capable of simulating the CPB placement and curing conditions, and measuring the consolidation parameters of CPB cured under effective stresses ranging between 0.5 and 400 kPa. In this study, a series of one-dimensional consolidation tests were conducted on CPB samples allowing for examination of the effects of binder type and rate as well as curing time on the compression properties (e.g., coefficient of consolidation cv, compression index Cc, and recompression index Cr) and the final geotechnical index properties (e.g., void ratio ef, water content wf, and degree of saturation Sf). Results showed that as the binder content increases, the initial resistance to consolidation increases. The cv value decreases over the course of time due to evolution of the CPB microstructure generated by the hydration process.

PL

W procesach pozyskania i przeróbki węgla powstają duże ilości odpadów dwóch rodzajów: drobnoziarniste odpady (muły) i gruboziarniste - odpady skały płonnej. Odpady drobnoziarniste (muły) są odprowadzane jako zawiesina na stawy osadowe lub kierowane są do wypełnienia zrobów w podziemiach kopalń, natomiast odpady gruboziarniste zazwyczaj są składowane w postaci suchego materiału na hałdach. Składowiska tych odpadów, zarówno powierzchniowe jak i podziemne, wymagają częstych kontroli ze względu na dużą kompresję (ściśliwość) oraz płynięcie (ścinanie). Drobnoziarniste odpady nasycone cementem CPB (Cement Paste Backfill) mogą we wczesnych stadiach utwardzania ulegać konsolidacji w procesie osiadania w zrobach. Aby przygotować odpowiednią mieszaninę do wypełnienia zrobów konieczna jest dobra znajomość całkowitej wielkości i różnic w osiadaniu CPB utwardzanych w warunkach ciśnienia. Parametry konsolidacji CPB mogą być badane w warunkach laboratoryjnych z wykorzystaniem ulepszonego zestawu aparaturowego o nazwie CUAPS (Curing Under Applied Pressure System) - utwardzanie pod ciśnieniem. Taka konfiguracja jest w stanie symulować warunki utwardzania CPB, a więc pomiar parametrów konsolidacji przy efektywnych naprężeniach w zakresie od 0,5 do 400 kPa. W tym przypadku, seria jednowymiarowych prób konsolidacji prowadzona była na próbkach PCB, umożliwiających zbadanie wpływu rodzaju spoiwa i czasu utwardzania na właściwości kompresji (np. współczynnik konsolidacji Cv, wskaźnik kompresji Cc i wskaźnik dekompresji Cr) oraz końcowe właściwości geotechniczne (np. wskaźnik porowatości ef, zawartość wody wf i stopień nasycenia Sf). Wyniki pokazują, że ze wzrostem zawartości spoiwa, wzrasta odporność na konsolidację. Wartość współczynnika konsolidacji cv maleje w miarę upływu czasu w wyniku zmiany mikrostruktury CPB wywołanej hydratacją.

3

Compressibility of Organic Soils Polluted with Diesel Oil

Olchawa A., Kumor M.

Archives of Hydro-Engineering and Environmental Mechanics

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2007

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Vol. 54, nr 4

299-307

EN

The paper presents results of experimental study on the compressibility of soils contaminated by diesel oil from Żuławy region. The investigation results show that compressibility of the soils increases with increasing diesel oil content. A significant increasing in compression was found when diesel oil content in soil exceeded 3%. The compression index Cc changes inversely to changes in the dielectrical constant of a porous medium. The index Cc for contaminated organic soil can be estimated from the established compression index of "clean" soil and dielectric constant of the porous medium of polluted soil.