Mechanical Behavior of Pile Foundations Associated with Water Infiltration in Unsaturated Collapsible Soils
Publication: International Journal of Geomechanics
Volume 24, Issue 6
Abstract
A comprehensive experimental program was performed in order to understand the mechanical behavior of model piles associated with water infiltration in collapsible loess. Real-time measurements were recorded for pile head settlement, pile shaft friction, and pile base resistance, as well as for the soil behavior, including soil settlement, volumetric water content, and soil suction. The experimental results suggest that both the pile head settlement and pile base resistance increased with water infiltration. The linear pile axial force distribution gradually changed to a “D” shape, with the maximum pile axial force occurring in the middle instead of the end stage of water infiltration. Such behavior can be attributed to a reduction in the contribution of soil suction, degradation of the pile–soil interface shear strength, and settlement of the collapsible soil. In addition, a softening model was proposed by modifying the traditional shear displacement method for interpretation of the mechanical behavior of piles in collapsible loess. There was good agreement between our experimental results and those from the literature and the results predicted using the proposed model, suggesting that the model can be used as a tool in the rational design of pile foundations in collapsible soils.
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Data Availability Statement
All data, models, or codes generated or used in this study are available from the corresponding author upon reasonable request. All data that supports all the figures and tables can be provided upon request.
Acknowledgments
The authors acknowledge funding for the research project “Study on lateral earth pressure of expansive soil considering cumulative damage effect of wet and dry cycles” (No. 42107196), received from the National Natural Science Foundation of China.
Notation
The following symbols are used in this paper:
- Ap
- cross-sectional area of pile;
- a, m, n
- parameters for fitting the SWCC;
- an
- collapsibility of the number n loess layer;
- interface effective cohesion;
- d
- pile diameter;
- Ep
- elasticity modulus of the pile;
- G
- shear modulus of the soil around the pile;
- Gs
- specific gravity;
- Gsb
- shear modulus of the soil below the pile base;
- Hn
- slope of the loess settlement;
- IP
- plastic index;
- L
- length of pile segment;
- Ln
- length of the number n pile segment;
- Pz
- axial force of the pile at depth = z;
- Pzb
- pile base axial force;
- Pzn
- head stress of the number n pile segments;
- r
- horizontal distance between the calculated point and the pile axis;
- rm
- maximum influencing radius of the pile on the soil;
- r0
- radius of the model pile;
- Sr
- degree of saturation;
- (ua − uw)f
- matric suction at failure;
- w
- vertical settlement of the soil around the pile;
- wb
- pile base settlement;
- wcr
- critical pile–soil relative displacement corresponding to the peak shear strength;
- wpz
- displacement of pile;
- wpzn
- settlement of the number n pile segment;
- z
- depth of the calculation point;
- zn
- depth of the number n loess layer;
- Δh
- collapse of soil;
- δb
- interface friction angle with respect to matric suction;
- δ′
- interface friction angle with respect to net normal stress;
- ρd
- dry density;
- (σn − ua)f
- net normal stress at failure;
- τ0
- shear strength at the corresponding position;
- τsr
- post peak shear strength;
- τsu
- peak interface shear strength;
- τunsat
- shear strength of unsaturated soil;
- υb
- Poisson’s ratio of the soil below the pile base;
- ψ
- measured suction;
- ψre
- measured residual suction;
- ω
- optimum water content;
- ωL
- liquid limit; and
- ωp
- plastic limit.
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Published In
International Journal of Geomechanics
Volume 24 • Issue 6 • June 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Jun 1, 2023
Accepted: Oct 30, 2023
Published online: Mar 21, 2024
Published in print: Jun 1, 2024
Discussion open until: Aug 21, 2024
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