Mini-block sampler

Emdal, Arnfinn; Gylland, Anders Samstad; Amundsen, Helene; Kåsin, Kristoffer; Long, Michael

doi:10.1139/cgj-2015-0628

Cited by 21 publications

(12 citation statements)

References 20 publications

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“…The samples in this study were taken by a downsized version of the Sherbrooke block sampler (160 mm in diameter and 300 mm in height), also called the mini-block sampler, made at NTNU (Emdal et al, 2016).…”

Section: Materials and Methodologymentioning

confidence: 99%

An attempt to monitor pore pressure changes in a block sample during and after sampling

Amundsen

Jønland

Emdal

et al. 2017

Géotechnique Letters

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A soil sample goes through stress changes during and after sampling. Sensitive clays are affected by sample disturbance and stress changes have a great effect on the quality. The reduction of in-situ total stresses to zero causes the soil sample to develop a negative pore pressure, which is also referred to as residual effective stresses. In an ideal situation, a block sample shall retain its residual effective stress during sampling and storage, which prevents it from swelling. To study this, an attempt was made to monitor the pore pressure variations inside a block sample of soft, sensitive, low-plasticity clay during and after sampling. The pore pressure was measured continuously during the storage period of 3 days and the results were compared with a similar work. The findings suggest that the residual effective stress in block samples may be reduced in a matter of minutes after sampling. Testing performed on reference samples corroborate these storage effects.

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Section: Materials and Methodologymentioning

confidence: 99%

An attempt to monitor pore pressure changes in a block sample during and after sampling

Amundsen

Jønland

Emdal

et al. 2017

Géotechnique Letters

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“…This study shows that the formation and propagation of shear bands are complex in quick clays. Viggiani, G., Finno, R.J., and Harris, W.W. 1994 Tiller quick clays sampled using a 54-mm-diameter cylinder and a 160-mm-diameter mini Sherbrook block sampler developed by Emdal et al (2016). The CUC tests were done at a strain rate of 1.2%/hr, and the CRS tests were done at 6.0%/hr.…”

Section: Discussionmentioning

confidence: 99%

“…D r a f t Figure 1. Illustration of the effect of sample disturbance on the results of a consolidated undrained triaxial compression (CUC) test and a constant rate of strain (CRS) oedometer on Tiller quick clays sampled using a 54-mm-diameter cylinder and a 160-mm-diameter mini Sherbrook block sampler developed by Emdal et al (2016). The CUC tests were done at a strain rate of 1.2%/hr, and the CRS tests were done at 6.0%/hr.…”

Section: Discussionmentioning

confidence: 99%

Shear bands in undrained plane strain compression of Norwegian quick clays

et al. 2018

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This work presents the results of plane strain tests carried out at the Laboratoire 3SR Grenoble (France) on undisturbed samples of very sensitive Norwegian soft clay. Discussion of the results focuses on the observed failure mechanisms and zones of localized deformation. The tested clay is defined as quick clay because it liquefies completely upon remolding. Thus, careful handling was necessary, and original procedures were developed to place samples in the plane strain testing device with minimum disturbance. Results show that excess pore-water pressure had developed during shear loading and shear strength was lost after the peak, which is a typical phenomenon in sensitive soils. The sample was held between two glass plates to enable visual tracking of the deformations. A digital image correlation analysis revealed a complex pattern of emerging shear bands, with one or two bands dominating and providing a final failure mechanism. Two local pore-water pressure transducers were attached to the sample boundary and showed differences in local excess pore-water pressure. It is suggested that excess pore-water pressure depends on the distance from the transducers to the zones of concentrated shear strains.

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“…Mini-block samples are downsized Sherbrooke block samples with a diameter of approximately 16 cm and a height of 25-30 cm. For further description, see Emdal et al (2016). Fall-cone undrained and remolded shear strength, water content, density, Atterberg limits, triaxial and oedometer tests (not presented herein), and pore-water chemistry were determined on all samples.…”

Section: Ground Investigations and Laboratory Testsmentioning

confidence: 99%

In Situ Improvement of Highly Sensitive Clays by Potassium Chloride Migration

Helle

Aagaard

Nordal

2017

J. Geotech. Geoenviron. Eng.

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Highly sensitive, low-saline clays, termed quick clays, represent a risk for large landslides. An in-situ experiment was conducted installing salt wells filled with potassium chloride (KCl) in order to study how salt wells can be used to reduce landslide risk. The salt-plume migration and the clay volume surrounding the salt wells were investigated by resistivity cone penetration tests (RCPTU), piston samples, conductivity divers and groundwater samples. Correlating the geotechnical properties to the occurring pore-water compositions, the remolded shear strength (cur) was improved beyond 1 kPa when the ratio of the sum of potassium, magnesium and calcium over the major cations exceeded 20%. The cur was improved to about 4-8 kPa 0.5 m from the wells within 3 years, and the liquidity index decreased from more than 3.4 to less than 1.2. A diameter of minimum 1.5 m around the wells was stabilized within 3 years. Thus, it is recommended to install the salt wells with a center-to-center distance of 1.5-2.0 m. The improved post-failure properties (cur and Atterberg limits) are considered permanent in an engineering time scale due to a lasting pore-water composition inhibiting development of high sensitivity. Salt wells can be installed without substantial disturbance of the soil, and can be used as landslide mitigation in quick-clay areas.

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Mini-block sampler

Cited by 21 publications

References 20 publications

An attempt to monitor pore pressure changes in a block sample during and after sampling

An attempt to monitor pore pressure changes in a block sample during and after sampling

Shear bands in undrained plane strain compression of Norwegian quick clays

In Situ Improvement of Highly Sensitive Clays by Potassium Chloride Migration

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