Spatial Distribution of Excess Pore-Water Pressure due to Piezocone Penetration in Overconsolidated Clay

Kim, Taijun; Kim, Nak Kyung; Tumay, Mehmet T.; Lee, Woojin

doi:10.1061/(asce)1090-0241(2007)133:6(674)

Cited by 15 publications

(5 citation statements)

References 13 publications

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“…In clay deposits, there are quite a number of cases reported in the literature that the value of ∆u is larger than the yield vertical effective stress of the soil. For example, Kim et al (2007) reported some laboratory model test results that for OCR = 1.0, ∆u was about 1.6 times of the yield vertical effective stress.…”

Section: Soil Samples Cases Tested and Test Resultsmentioning

confidence: 99%

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A modified method for estimating permeability of clayey soils based on piezocone sounding results

Chai

Chanmee

2018

Can. Geotech. J.

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A modified method for estimating permeability of clayey deposits in the horizontal direction (kh) based on piezocone sounding (uCPT) results is proposed. Most of the currently available methods relate the value of kh with the Δu/[Formula: see text] ratio (Δu is the measured excess pore pressure from uCPT at the shoulder of the cone and [Formula: see text] is the initial vertical effective stress at the measurement location). However, it has been understood that the effect of the overconsolidation ratio (OCR) on the Δu/[Formula: see text] ratio is more significant than that on the value of kh. As a result, for an overconsolidated deposit, there is no suitable method for estimating the value of kh based on uCPT results. Based on the results of laboratory model uCPT, an empirical equation for considering the effect of the OCR on Δu/[Formula: see text] and then kh corresponding to the yield vertical effective stress ([Formula: see text]) and initial vertical effective stress ([Formula: see text]) for OCR > 1.0 is established. The modified method for kh corresponding to [Formula: see text] requires two parameters: OCR and a model parameter (α). In addition, for kh corresponding to [Formula: see text], two more soil parameters are needed: the swelling index (Cs) and the initial void ratio (e0). The methods for estimating these parameters are also proposed. Finally, the modified method is applied to three field case histories to show its usefulness.

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Section: Soil Samples Cases Tested and Test Resultsmentioning

confidence: 99%

“…7). Kim et al (2007) conducted a series of large scale (diameter of the model 1.2 m) laboratory model test with OCR of 1 to 20. The soil tested was a mixture of pure kaolinite and a sand with a mixing ratio of 1:1.…”

Section: Obtaining K H0mentioning

confidence: 99%

A modified method for estimating permeability of clayey soils based on piezocone sounding results

Chai

Chanmee

2018

Can. Geotech. J.

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“…where Λ = 1-κ/λ, λ = slope of consolidation line in an e-lnp' plot (e is voids ratio and p′ is effective mean stress); κ = slope of rebound line in an e-lnp' plot; Μ = strength parameter for the Cam-clay model, which is the stress ratio, q/p′, at failure, (q is deviator stress); e 0 = initial void ratio. Assuming Λ = 0.9, for OCR = 8, the predicted value of I r is about 48% of the value for OCR = 1 However, Kim et al (2007) reported the results of some large-scale model test (diameter of the mold used was 1.2 m) involving piezocone penetration. The measured excess pore water pressure (u) distribution indicated that the diameter of the zone with an increase in u (assumed to be the plastic zone) is almost the same for cases of OCR from 1 to 20.…”

Section: Materials Used and Cases Testedmentioning

confidence: 99%

“…One displays monotonic reduction of the measured values of u 2 with time (e.g., Teh and Houlsby 1991), i.e., the so called "standard" dissipation curve; and the other is a "non-standard" curve, for which the measured value of u 2 increases initially and then reduces with time (Burns and Mayne 1998;Sully et al 1999;Chai et al 2012a;Ha et al 2015). Some results of numerical simulation (e.g., Chai et al 2012a) and laboratory testing (Kim et al 2007;Chai et al 2014) have suggested that the reason for a non-standard dissipation curve is that at the beginning of the dissipation the pore water pressure at the filter element induced by cone penetration is lower than the pore pressures generated in the soil nearby. The causes of this kind of initial pore water pressure distribution are thought to be: (1) the shear-induced dilatancy effect (e.g., Burns and Mayne 1998) and (2) the partial unloading effect when a soil element moves from the face to the shoulder of the cone during cone penetration (Chai et All laboratory test results published to date regarding the distribution of u around the cone only address the variation of u in the horizontal (radial) direction at the elevation of the shoulder of a cone.…”

Section: Introductionmentioning

confidence: 99%

Pore pressures induced by piezocone penetration

Chai

Hossain

Yuan³

et al. 2016

Can. Geotech. J.

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The excess pore-water pressures (u) induced by piezocone penetration and their dissipation around the cone have been investigated by laboratory model tests and theoretical–numerical analyses. Based on the test results, a method for predicting cone penetration–induced distribution of u has been proposed. By numerical analysis using the predicted initial distribution of u it has been demonstrated that dissipation of the pore-water pressure measured at the shoulder of the cone (u2-type cone) is a two-dimensional (horizontal radial and vertical) process. A back-fitted coefficient of consolidation in the horizontal direction (ch) can be obtained by comparing the simulated and laboratory-measured two-dimensional dissipation curves. It has also been shown that a published method for estimating ch from measured nonstandard dissipation curves (in which u2 increases initially and then decreases) results in values of ch that agree well with values of ch deduced from the two-dimensional analysis.

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“…The estimated rigidity index in OC soils from measured cone indices is converted to a rigidity index of the equivalent NC soils. Making use of the condition that the failure shear stress is the same for both the equivalent NC and OC soils [25] and, taking the shear modulus corresponding to 50% of the failure shear stress [26], the equivalent NC and the exiting OC soils rigidity indices were related in terms of the OCR, as follows:…”

Section: Expressing C Und In Terms Of Piezocone Parametersmentioning

confidence: 99%

Estimating Hydraulic Conductivity of Overconsolidated Soils Based on Piezocone Penetration Test (PCPT)

Bekele

Song

Jin³

et al. 2021

Infrastructures

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Overconsolidated (OC) soils may develop a low or negative pore pressure during PCPT. Thus, it is challenging to develop an “on-the-fly” estimation of hydraulic conductivity from PCPT results. This study presents a method to estimate the hydraulic conductivity of OC soils from PCPT results based on a previously developed method for normally consolidated (NC) soils. To apply the existing method, PCPT pore pressure in OC soils is adjusted by using a correction factor. An equation for the correction factor is derived based on the concepts of critical state soil mechanics, cavity expansion, and consolidation theories. Then, it was reformulated so that traditional cone indices could be used as input parameters. It is shown that the correction factor is mainly influenced by the cone tip resistance, pore pressure, and the rigidity index. The comparison of predicted, which is based on corrected pore pressure and measured hydraulic conductivity showed a good match for four well documented data sets. With the findings of the study, it is expected that an “on-the-fly” estimation of hydraulic conductivity of overconsolidated soils is possible.

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Spatial Distribution of Excess Pore-Water Pressure due to Piezocone Penetration in Overconsolidated Clay

Cited by 15 publications

References 13 publications

A modified method for estimating permeability of clayey soils based on piezocone sounding results

A modified method for estimating permeability of clayey soils based on piezocone sounding results

Pore pressures induced by piezocone penetration

Estimating Hydraulic Conductivity of Overconsolidated Soils Based on Piezocone Penetration Test (PCPT)

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