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Influence of Soft Soil Samples Quality on the Compressibility and Undrained Shear Strength – Seven Lessons Learned From the Vistula Marshlands

Konkol Jakub

Studia Geotechnica et Mechanica

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2023

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Vol. 45, nr s1

262--281

EN

This technical article presents the influence of sample quality on the compressibility parameters and undrained shear strength (cu) of soft soils from the Vistula Marshlands. The analysis covers: (1) quality of soft soil according to three criteria: void ratio (Δe/e0 index), volumetric strain (Δɛv) and Cr/Cc ratio; (2) influence of storage time on quality; (3) influence of sample quality on undrained shear strength (cu), and (4) reliability of compression and undrained shear strength parameters estimation. The sample quality of three different soft soils (peat, organic clays, and organic silts) was investigated using dataset of geotechnical investigations from the Vistula Marshlands. The reliability of oedometer tests and compressibility parameters determination was shown. Different undrained shear strength estimates (from lab and field tests) were juxtaposed with sample quality. In situ estimates of undrained shear strength were compared with results of triaxial tests and direct simple shear test on reconstituted samples as well as SHANSEP estimates. The results of research are grouped in seven lessons. The most important outcomes are: (1) the quality of samples is at best moderate or poor and there is no significant influence of storage time on sample quality, (2) regardless of testing method, the undrained shear strength natural variability of the Vistula Marshlands soft soils is between 20% and 50% depending on deposit depth and soil type, (3) the most accurate estimation of undrained shear strength can be obtained from field vane test (FVT) while unconsolidated, undrained compression (UUC) triaxial tests should be avoided, (4) SHANSEP approach can be considered as a valuable estimate of cu (next to the FVTs), which additionally allows in relatively easy way to establish lower and upper bounds of cu.

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Assessment of deformation properties of coal measure sandstones through regression analyses and artificial neural networks

Köken Ekin

Archives of Mining Sciences

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2021

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Vol. 66, no. 4

523--542

EN

The deformation properties of rocks play a crucial role in handling most geomechanical problems. However, the determination of these properties in laboratory is costly and necessitates special equipment. Therefore, many attempts were made to estimate these properties using different techniques. In this study, various statistical and soft computing methods were employed to predict the tangential Young Modulus (Eti, GPa) and tangential Poisson’s Ratio (vti) of coal measure sandstones located in Zonguldak Hardcoal Basin (ZHB), NW Turkey. Predictive models were established based on various regression and artificial neural network (ANN) analyses, including physicomechanical, mineralogical, and textural properties of rocks. The analysis results showed that the mineralogical features such as the contents of quartz (Q, %) and lithic fragment (LF, %) and the textural features (i.e., average grain size, d50, and sorting coefficient, Sc) have remarkable impacts on deformation properties of the investigated sandstones. By comparison with these features, the mineralogical effects seem to be more effective in predicting the Eti and vti. The performance of the established models was assessed using several statistical indicators. The predicted results from the proposed models were compared to one another. It was concluded that the empirical models based on the ANN were found to be the most convenient tools for evaluating the deformational properties of the investigated sandstones.

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Skład mineralny gruntów spoistych a ich właściwości deformacyjne

Gawriuczenkow Ireneusz

Geologos

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2007

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Vol. 11

455--462

PL

W artykule przedstawiono wpływ zawartości minerałów ilastych na niektóre właściwości deformacyjne gruntów spoistych, takie jak pęcznienie, ciśnienie pęcznienia, odkształcenie. Badania przeprowadzono na próbkach o strukturze naruszonej i modelowanym składzie mineralnym. Zbadano wpływ najczęściej występujących minerałów ilastych w gruntach spoistych (beidellitu i kaolinitu) na właściwości deformacyjne.

EN

The paper presents influence of clay mineral composition on selected clay soils deformation properties, namely: free swell, swelling pressure, strain. The examined samples had disturbed structure and modeled mineral composition. The influence of the most occurring clay minerals (beidellite and kaolinite) on the deformation properties of soils were tested.