Determining the stress state in natural soil layers is essential for accurately assessing foundation bearing capacity, predicting soil deformation and optimizing construction plans. However, few efforts have been made so far to investigate the anisotropy of horizontal earth pressure through in situ tests. In this study, both K0 stepped blade test (KSB) in different directions and pressuremeter test (PMT) are carried out at an excavated pit to explore the anisotropy of horizontal earth pressure in natural granite residual soil (GRS) deposits. Additionally, scanning electron microscopy (SEM) test is performed to analyze the orientational arrangement of soil particles of GRS. Finally, considering the excavation-induced unloading effect, the unloading response of horizontal earth pressure is conducted through a series of laboratory consolidation experiments. The results of KSB tests indicate a significant anisotropy of horizontal earth pressure, with the maximum horizontal earth pressure arising at the directions of 112.5°, as verified by conducting dilatometer test (DMT) in different directions. In addition, a tensor <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11440_2025_2698_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">${\varvec{\varPhi}}_{ij}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mi mathvariant="bold-italic">Φ</mi> </mrow> <mrow> <mi mathvariant="italic">ij</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> is introduced to quantify the anisotropy of horizontal earth pressure. From the microscopic aspect, the SEM test reveals a significant orientational arrangement of soil particles, which is coincident with the direction of maximum horizontal earth pressure measured by KSB test. According to the results of consolidation experiments, the horizontal earth pressure considering the unloading effect is more consistent with that measured in the in situ tests, which is greater than in the loading stage, indicating that the unloading effect leads to a significant rise in the horizontal earth stress in the GRS. This study could provide more insights into the horizontal earth pressure in the GRS, and a reference for determining the stress state in natural soil deposits.

Field investigation on anisotropic characteristics of horizontal earth pressure in granite residual soil and response analysis

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发表日期：

2025年6月28日

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Zhaowei Shang,
Lingwei Kong,
Fei Wang,
Zhenhua Zhou,
Junbiao Yan,
Zhiao Gao

摘要

Determining the stress state in natural soil layers is essential for accurately assessing foundation bearing capacity, predicting soil deformation and optimizing construction plans. However, few efforts have been made so far to investigate the anisotropy of horizontal earth pressure through in situ tests. In this study, both K₀ stepped blade test (KSB) in different directions and pressuremeter test (PMT) are carried out at an excavated pit to explore the anisotropy of horizontal earth pressure in natural granite residual soil (GRS) deposits. Additionally, scanning electron microscopy (SEM) test is performed to analyze the orientational arrangement of soil particles of GRS. Finally, considering the excavation-induced unloading effect, the unloading response of horizontal earth pressure is conducted through a series of laboratory consolidation experiments. The results of KSB tests indicate a significant anisotropy of horizontal earth pressure, with the maximum horizontal earth pressure arising at the directions of 112.5°, as verified by conducting dilatometer test (DMT) in different directions. In addition, a tensor ${\varvec{\varPhi}}_{ij}$ $Φ_{ij}$ is introduced to quantify the anisotropy of horizontal earth pressure. From the microscopic aspect, the SEM test reveals a significant orientational arrangement of soil particles, which is coincident with the direction of maximum horizontal earth pressure measured by KSB test. According to the results of consolidation experiments, the horizontal earth pressure considering the unloading effect is more consistent with that measured in the in situ tests, which is greater than in the loading stage, indicating that the unloading effect leads to a significant rise in the horizontal earth stress in the GRS. This study could provide more insights into the horizontal earth pressure in the GRS, and a reference for determining the stress state in natural soil deposits.