Centrifuge modelling of cone penetration tests in layered soils

Mo, Pin‐Qiang; Marshall, Alec M.; Yu, Hai‐Sui

doi:10.1680/geot.14.p.176

Cited by 40 publications

(18 citation statements)

References 25 publications

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“…This is followed by a detailed illustration of the effect of soil layering on soil deformation patterns. The paper supplements the work presented in Mo et al (2015Mo et al ( , 2017 in several ways: (1) additional results are presented that relate to the effects of stress condition; (2) the method for interpreting layered effects on soil displacements is elaborated; (3) profiles of displacements after penetration are presented which indicate different mechanisms for a loose-over-dense compared to a dense-over-loose configuration of soil layers; and (4) transition parameters of both horizontal and vertical displacements are introduced to quantitatively evaluate the layered effects on soil displacements, which are also related to the transitions based on penetration resistance.…”

Section: Introductionsupporting

confidence: 60%

“…The penetrometer had a diameter of and was pushed into the sand at a speed of . Soil models were prepared by the multiple-sieving air pluviation method (Mo et al, 2015) A half-cylindrical model container with a Perspex window was used to enable the observation of penetration-induced sub-surface soil deformations, as shown in Figure 1(a). Digital cameras were used to obtain a series of images of the penetrometer and soil throughout the tests.…”

Section: Centrifuge Tests and Soil Deformation Measurementmentioning

confidence: 99%

“…The evolution of soil element deformation was illustrated and the reduction of stresses above the pile tip was related to cavity contraction caused by the densification of soil around the shaft. Mo (2014) reported results from axisymmetric elevated-g tests using a geotechnical centrifuge in which a half-cylindrical probe with a conical tip was pushed along a Perspex wall into both uniform and layered soil profiles.…”

Section: Introductionmentioning

confidence: 99%

“…Thus the transition zone around the soil layer interface can be separated into two parts: (1) the transition zone above the interface in which the probe begins to sense the underlining soil layer, and (2) the transition zone below the interface which extends to the depth where the probe is no longer influenced by the upper soil layer. Transition zones around soil layer interfaces have been shown to depend on the properties and thickness of soil layers (Meyerhof and Sastry, 1978a,b;Youd and Idriss, 2001;Mo et al, 2015). Analytical methods (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…The experimental equipment is the same as that presented in Mo et al (2015); the penetrometer consisted of a half-cylindrical probe with a conical tip which was pushed into the soil at a Perspex wall in an axisymmetric container, thereby enabling the measurement of subsurface soil movements using digital image analysis. The paper first discusses the effect of soil density and stress level effect on deformation patterns.…”

Section: Introductionmentioning

confidence: 99%

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Layered effects on soil displacement around a penetrometer

Marshall

2017

Soils and Foundations

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The interpretation of cone penetration test (CPT) data is important for the in-situ characterisation of soils. Interpretation of CPT data remains a predominately empirical process due to the lack of a rigorous model that can relate soil properties to penetrometer readings.Interpretation is especially difficult in layered soils, where penetrometer response can be affected by several horizons of soil with different properties. This paper aims to provide some insight into the mechanisms of soil displacement that occur as a penetrometer is pushed into layered soils. Data is presented from centrifuge modelling of probe penetration in layered soils in an axisymmetric container where soil deformation patterns around the probe can be measured.Results obtained from uniform soil tests are also presented to illustrate the effects of soil density and stress level (i.e. centrifuge acceleration). A large influence zone is found to relate to the higher penetration resistance obtained in a denser soil. Differing soil displacement patterns at low and high stresses are related to the tendency of the soil to dilate, with the well-known consequence of a non-linear increase of penetration resistance with stress level. Layered soil tests show a clear difference of soil deformation patterns compared to uniform tests, especially for vertical displacements. The peak value of vertical displacement of the soil occurs at denseover-loose interfaces, while a local minima occurs at loose-over-dense interfaces. Parameters are proposed to quantitatively evaluate the layered effects on soil deformations and a deformation mechanism is described for penetration in layered soils based on the transition of displacement profiles.

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Section: Introductionsupporting

confidence: 60%

Section: Centrifuge Tests and Soil Deformation Measurementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Layered effects on soil displacement around a penetrometer

Marshall

2017

Soils and Foundations

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A cavity expansion–based solution for interpretation of CPTu data in soils under partially drained conditions

Gao

Yang

et al. 2020

Num Anal Meth Geomechanics

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Summary A cavity expansion–based solution is proposed in this paper for the interpretation of CPTu data under a partially drained condition. Variations of the normalized cone tip resistance, cone factor, and undrained‐drained resistance ratio are examined with different initial specific volume and overconsolidation ratio, based on the exact solutions of both undrained and drained cavity expansion in CASM, which is a unified state parameter model for clay and sand. A drainage index is proposed to represent the partially drained condition, and the critical state after expansion and stress paths of cavity expansion are therefore predicted by estimating a virtual plastic region and assuming a drainage‐index–based mapping technique. The stress paths and distributions of stresses and specific volume are investigated for different values of drainage index, which are also related to the penetration velocity with comparisons of experimental data and numerical results. The subsequent consolidation after penetration is thus predicted with the assumption of constant deviatoric stress during dissipation of the excess pore pressure. Both spherical and cylindrical consolidations are compared for dissipation around the cone tip and the probe shaft, respectively. The effects of overconsolidation ratio on the stress paths and the distributions of excess pore pressure and specific volume are then thoroughly investigated. The proposed solution and the findings would contribute to the interpretation of CPTu tests under a random drained condition, as well as the analysis of pile installation and the subsequent consolidation.

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Large‐strain analysis for cylindrical cavity contraction in strain‐softening geomaterials

Wang

Sheng

2022

Num Anal Meth Geomechanics

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This study presents a large‐strain analysis for cylindrical cavity unloading–contraction problem in strain‐softening geomaterials. Based on the unified strength theory (UST) and non‐associated flow rule, the process of cavity contraction in cohesive‐frictional geomaterials is regarded as a large‐strain problem by introducing the UST parameters and the volumetric force of seepage into the conventional cylindrical cavity contraction analysis, the effects of strain‐softening characteristic, intermediate principal stress, large‐strain, and seepage are considered. Finally, according to the comparison of the results of the radius ratio with those in the published literature, the correctness and reliability of the theoretical method are proved. The results show that it is necessary to consider the effect of volume force of seepage in the stability of excavation problem in geomaterial, the larger the volume force of seepage, the smaller the plastic radius. The traditional two‐dimensional cavity contraction solution overestimates the plastic radius. The results provide a theoretical basis for the elasto‐plastic analysis of excavation in rich water geomaterial and have a certain reference value for engineering design.

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Centrifuge modelling of cone penetration tests in layered soils

Cited by 40 publications

References 25 publications

Layered effects on soil displacement around a penetrometer

Layered effects on soil displacement around a penetrometer

A cavity expansion–based solution for interpretation of CPTu data in soils under partially drained conditions

Large‐strain analysis for cylindrical cavity contraction in strain‐softening geomaterials

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