The ball penetrometer is widely performed in-situ and laboratory tests to interpret the strength characteristics of clayey soils. The penetration of ball penetrometer is a large deformation process. Therefore, large deformation finite element (LDFE) method has to be employed. However, the accuracy of the interpreted intact undrained shear strength in the strain-softening and rate-dependent nonhomogeneous soil is hampered by the penetrometer-soil interaction and soil heterogeneity. In the present study, a sliding contact model, which allows for the simulation of strain-softening effect, rate-dependent effect, and relative sliding at the interface, is proposed to simulate the penetrometer-soil interaction. The ball penetration into the seabed from the mudline is simulated using large deformation finite element analysis with the proposed interface model. The effects of dimensionless strength parameters <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11440_2025_2571_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="151" /> </InlineMediaObject> <EquationSource Format="TEX">$\left[ {s_{\text{um}} /\left( {\gamma^{\prime } D} \right){\text{and}}\;k/\gamma^{\prime } } \right]$</EquationSource> <EquationSource Format="MATHML"><math> <mfenced close="]" open="["> <mrow> <msub> <mi>s</mi> <mtext>um</mtext> </msub> <mo stretchy="false">/</mo> <mfenced close=")" open="("> <mrow> <msup> <mi>γ</mi> <mo>′</mo> </msup> <mi>D</mi> </mrow> </mfenced> <mtext>and</mtext> <mspace width="0.277778em" /> <mi>k</mi> <mo stretchy="false">/</mo> <msup> <mi>γ</mi> <mo>′</mo> </msup> </mrow> </mfenced> </math></EquationSource> </InlineEquation>, degree of soil strength heterogeneity (kD/sum), and interface friction coefficient (α) on the bearing capacity factor (N) of the ball penetrometer in strain-softening and rate-dependent soil are quantified. Finally, a back-analysis framework is proposed to interpret the intact undrained shear strength profile and the strain-softening and rate-dependent parameters of soil based on the penetration resistance of the ball penetrometer. The accuracy and robustness of the back-analysis framework are validated by comparing its results with those of numerical analysis, laboratory test and field test.

Interpreting intact undrained shear strength of nonhomogeneous clay using ball penetrometer

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发表日期：

2025年2月25日

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Zhixuan Li,
Ping Yi,
Jun Liu

摘要

The ball penetrometer is widely performed in-situ and laboratory tests to interpret the strength characteristics of clayey soils. The penetration of ball penetrometer is a large deformation process. Therefore, large deformation finite element (LDFE) method has to be employed. However, the accuracy of the interpreted intact undrained shear strength in the strain-softening and rate-dependent nonhomogeneous soil is hampered by the penetrometer-soil interaction and soil heterogeneity. In the present study, a sliding contact model, which allows for the simulation of strain-softening effect, rate-dependent effect, and relative sliding at the interface, is proposed to simulate the penetrometer-soil interaction. The ball penetration into the seabed from the mudline is simulated using large deformation finite element analysis with the proposed interface model. The effects of dimensionless strength parameters $\left[ {s_{\text{um}} /\left( {\gamma^{\prime } D} \right){\text{and}}\;k/\gamma^{\prime } } \right]$ $[s_{um} / (γ^{'} D) and k / γ^{'}]$ , degree of soil strength heterogeneity (kD/s_um), and interface friction coefficient (α) on the bearing capacity factor (N) of the ball penetrometer in strain-softening and rate-dependent soil are quantified. Finally, a back-analysis framework is proposed to interpret the intact undrained shear strength profile and the strain-softening and rate-dependent parameters of soil based on the penetration resistance of the ball penetrometer. The accuracy and robustness of the back-analysis framework are validated by comparing its results with those of numerical analysis, laboratory test and field test.