Stress Relief Disturbance and Residual Pore Pressure in Cohesive Soils

Carrubba, Paolo

doi:10.3208/sandf.40.57

Cited by 10 publications

(4 citation statements)

References 15 publications

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“…Similar observations are also reported in the literature (Table 2), where the relation between I p and the OCR is illustrated (e.g. Gens, 1982;Hight & Burland, 1990;Carrubba, 2000).…”

Section: Theoretical Background For Pore Pressure Variation During Sasupporting

confidence: 78%

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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“…Similar observations are also reported in the literature (Table 2), where the relation between I p and the OCR is illustrated (e.g. Gens, 1982;Hight & Burland, 1990;Carrubba, 2000).…”

Section: Theoretical Background For Pore Pressure Variation During Sasupporting

confidence: 78%

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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“…Calculation of σ' ps is, however, not straightforward and requires knowledge of Skempton's pore pressure parameter, A u (consequent to the release of deviatoric stress), and K 0 (coefficient of earth pressure at rest). Authors such as Tanaka et al (1996) and Carrubba (2000) have recently used u r normalised by the in-situ vertical effective stress (σ' v0 ) to evaluate disturbance. Tanaka et al (1996) suggested that for high quality samples of normally to lightly overconsolidated clay, u r is approximately 1/5 σ' v0 to 1/6 σ' v0 .…”

Section: Introductionmentioning

confidence: 99%

Assessment of sample quality in soft clay using shear wave velocity and suction measurements

Donohue¹,

Long²

2010

Géotechnique

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Publication informationGéotechnique, 60 (11) (Kleven et al., 1986), and the normalised change in void ratio, Δe/e 0 (Lunne et al., 1997). Most of these approaches, however, require reconsolidation back to in-situ stresses, a process that may require a number of days of testing. This is a particular problem for offshore sampling, where rapid assessment of sample quality could significantly improve efficiency.A number of studies in recent years have observed that laboratory determined shear wave velocities (V s ), and corresponding small strain shear modulus, G max :are generally lower than the in-situ equivalent, and have attributed this difference to sampling disturbance (Shiwakoti et al. 2000; Porcino & Ghionna 2004). These studies involved reconsolidation of laboratory specimens back to their in-situ stress, before measurement of V s . For a quick assessment of sample quality, Hight & Leroueil (2003), Nash (2003) and Landon & DeGroot (2007) used portable bender element kits to measure V s , immediately after removal from the subsurface on unconfined samples. Hight & Leroueil (2003) also suggested simultaneous soil suction (u r ) measurements, enabling differences between unconfined and in-situ stress state to be taken into account.The use of suction measurements for sample quality evaluation was introduced by Ladd & Lambe (1963), who proposed using the ratio u r /σ' ps to evaluate disturbance, where σ' ps is the effective stress for a "perfect" sample. Calculation of σ' ps is, however, not straightforward and requires knowledge of Skempton's pore pressure parameter, A u 3 (consequent to the release of deviatoric stress), and K 0 (coefficient of earth pressure at rest). Authors such as Tanaka et al. (1996) DESCRIPTION OF SITES AND TECHNIQUESThe soft soils investigated during this study were located at Onsøy in Norway and at Ballinasloe and Bogganfin in Ireland (Table 1). A number of samplers of varying quality were used, the dimensions and features of which are given in Table 2. Onsøy, NorwayThe Onsøy test site is the main soft clay research site used by the Norwegian Geotechnical Institute (NGI). Onsøy is underlain by an extensive deposit of uniform marine clay, as described by Lunne et al. (2003). 4In this paper comparisons are made between Sherbrooke block, 76mm steel and 54mm composite piston samples at two depths (approximately 10m and 13m). The Scandinavian displacement approach was adopted for the piston sampling, wherein the sampler (with the piston in front of the sampling tube) was pushed down to the desired depth without preboring. Ballinasloe and Bogganfin, IrelandThe Ballinasloe and Bogganfin test sites (Donohue, 2005), located in the midlands of Ireland, are both underlain by post glacial lacustrine clay. Although generally uniform, the soils contain some thin silt laminations (1mm to 2mm). Testing TechniquesIn-situ V s measurements were obtained from the seismic cone (SCPT -Eidsmoen et al., 1985) Measurements of V s and u r were performed on all samples either immediately after extrusion...

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“…The extraction of soil samples from the ground under "perfect conditions" (Class 4 sampling) generates negative pore water pressure (Carrubba, 2000;Hight et al, 2003: Donohue et al, 2009Donohue et al, 2010;Delage et al, 2016). Whether or not the negative pore water pressure makes air get into the voids and causes the sample to become de-saturated (i.e.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Skempton's pore water pressure parameters B and A using a high-capacity tensiometer

Sanlon

Sivakumar

Solan³

et al. 2021

Géotechnique

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Stress Relief Disturbance and Residual Pore Pressure in Cohesive Soils

Cited by 10 publications

References 15 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

Assessment of sample quality in soft clay using shear wave velocity and suction measurements

Assessment of Skempton's pore water pressure parameters B and A using a high-capacity tensiometer

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