Characteristic values of geotechnical parameters in Eurocode 7

Prästings, Anders; Spross, Johan; Larsson, Stefan

doi:10.1680/jgeen.18.00057

Cited by 13 publications

(5 citation statements)

References 33 publications

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“…The coefficient of variation is a statistical indicator of the relative dispersion of data points in a data series around the mean. In a small sample size, Bayesian theory can be applied to the coefficient of variation to determine the characteristic value of geotechnical properties (Prästings et al, 2019). The split tensile strength of the specimen without fibers decreases from 217 kPa to 150 kPa by increasing the H/D from 0.5 to 2.5, while the tensile strength of the specimen with fibers increases from 284 kPa to 357 kPa.…”

Section: Resultsmentioning

confidence: 99%

Effect of the Specimen’s Height on the Split-Tensile Strength of the Fibers Reinforced Clay-Lime-Rice Husk Ask Mixture

Hartono,

Muntohar,

Diana

et al. 2024

J. civil eng. forum

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Various studies on the effect of specimen size on splitting tensile strength. However, geotechnical codes lack consensus regarding the recommended specimen diameter and height-to-diameter (H/D) ratio for the split tensile strength test. Hence, it is imperative to study the effect of the height-to-diameter ratio of the specimen on the outcomes of the split tensile strength test, especially for stabilized and fiber-reinforced soil. This research examines the effect of adding lime-rice husk ash and plastic fiber and the effect of specimen size on splitting tensile strength. The height of the specimen is varied, using a height-to-diameter ratio (H/D), namely 0.5, 1.0, 1.5, 2.0, and 2.5, in which the diameter is 70 mm. Two groups of specimens were prepared as stabilized clay without fibers and stabilized clay with 0.1% fibers. The lime required for stabilization is 10% of the dry weight of the soil. In this research, the lime and rice husk ash ratio was designed as 1:1. The splitting tensile strength test was carried out after the specimen was cured for seven days. The investigation indicates that the splitting tensile strength of the specimen without fibers reduces from 217 kPa to 150 kPa as the H/D ratio grows from 0.5 to 2.5. Conversely, the tensile strength of the specimen with fibers increases from 284 kPa to 357 kPa. The findings suggest that the fiber inclusion enhances the splitting tensile strength of the stabilized clay. The specimen size affects the splitting tensile strength, but the effect becomes less noticeable when the H/D ratio exceeds 2.5. From a fracture mechanism perspective, the specimen experiences mode II (shearing) due toa probable “flexural action” along its height. It remains challenging to conclude the dimensions of the test specimen or, at the very least, estimate the correction factor for the size-to-tensile strength ratio.

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Section: Resultsmentioning

confidence: 99%

Effect of the Specimen’s Height on the Split-Tensile Strength of the Fibers Reinforced Clay-Lime-Rice Husk Ask Mixture

Hartono,

Muntohar,

Diana

et al. 2024

J. civil eng. forum

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“…This corresponds to the statistical definition of the characteristic value (e.g. Prästings et al, 2019). If a normal distribution is assumed, the total variance ξ 2 tot related to the uncertainty in the estimation of the population mean is defined as:…”

Section: Statistical Methods For Defining the Characteristic Valuementioning

confidence: 99%

Safety margin from characteristic values in settlement calculations of embankments on clay

Ramírez

Löfman

Korkiala-Tanttu

2022

Proceedings of the Institution of Civil Engineers - Geotechnica

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Settlement calculations in serviceability limit state (SLS) design of embankments require the estimation of characteristic values of soil properties to account for different sources of uncertainty. The upcoming revised version of EN 1997-1:2004 (Eurocode 7) presents a statistically based equation to determine characteristic values of soil properties with the aim of providing a more consistent safety margin. The aim of this study is to quantify the safety margin in settlement calculations using this equation and performing probabilistic analyses. Four different cases of embankments on soft soil with different soil conditions were considered, including significant non-linear stress–strain behaviour. This allowed evaluation of the consistency of the safety margin from statistically derived characteristic values for different soil conditions. Probabilistic analyses were performed using Monte Carlo simulations to determine the statistics of total settlements. The safety margin was then defined based on the distance between the settlement from characteristic values and the mean settlement value of the simulations. The quantified safety margin was not consistent among the cases, which may be related to varying levels of non-linear compressibility and degree of consolidation. Moreover, for some cases, the safety margin might be too conservative for SLS design of embankments.

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“…In fact, a pure statistical procedure that is based on the borehole/sounding data alone would not provide the "value affecting the occurrence of the limit state" which requires a knowledge of the failure mechanism for ULS. In addition, as pointed out by Prästings, Spross, and Larsson (2019), if an engineer determines the Eurocode characteristic value statistically, does he or she actually account for all the uncertainties and other factors listed in clause 2.4.5.2 (4)P from a statistical point of view?…”

Section: Generalmentioning

confidence: 99%

What is a characteristic value for soils?

Länsivaara

Phoon

Ching

2021

Georisk: Assessment and Management of Risk for Engineered Syste

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The choice of the characteristic value of a material property is fundamental in all civil engineering design and critical in geotechnical engineering. Based on our tradition, we strive to look for a cautious value, whose evaluation includes our engineering judgement. While the definition of a characteristic value is often given with the aid of statistics as a fractile value, its determination includes considerations of mechanics because "value" refers to the relevant quantity affecting the limit state. Soils are complex, often spatially heterogeneous and our knowledge of them is typically based on sparse incomplete data. This makes the definition and determination of a characteristic value for soils more multifaceted than for structural materials. This paper discusses the choice of the characteristic value for soils from various perspectives (statistical, mechanistic and practical) and summarises some recent findings to clarify the limitations of existing practice. Overly simplified statistical approaches may lead to unsafe or overly conservative designs. The authors conclude that a balance between practicality and incorporating salient features are needed. By increasing the value of data in design decisions, engineers will be motivated to collect, share, and utilise data as much as possible and bring our practice closer to the digital economy.

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Characteristic values of geotechnical parameters in Eurocode 7

Cited by 13 publications

References 33 publications

Effect of the Specimen’s Height on the Split-Tensile Strength of the Fibers Reinforced Clay-Lime-Rice Husk Ask Mixture

Effect of the Specimen’s Height on the Split-Tensile Strength of the Fibers Reinforced Clay-Lime-Rice Husk Ask Mixture

Safety margin from characteristic values in settlement calculations of embankments on clay

What is a characteristic value for soils?

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