Pile foundations are widely designed extending principles of saturated soil mechanics assuming drained conditions (i.e. effective stress) even in expansive soil deposits despite the fact the soil around the pile is in a state of unsaturated condition. The mechanical behavior of in-situ pile foundations are significantly influenced by suction changes associated with water infiltration. In this paper, a single model pile mechanical behavior variations associated with suction changes in an unsaturated expansive soil under a service load were investigated. Experimental results suggest pile settlement increases due to water infiltration. Such a phenomenon can be attributed to pile shaft friction reduction in the active zone associated with suction reduction due to water infiltration and volume expansion of the soil. Experimental results were also simulated and interpreted using a computation program, PEI (i.e. Pile behavior in Expansive soil upon Infiltration), which was proposed based on principles of unsaturated soil mechanics. A theoretical model was proposed for the estimation of threshold pile head load which distinguishes whether the pile would experience upward or downward movement upon water infiltration. The theoretical model and the numerical modeling approach presented in this are valuable for practicing engineers in the rational design of piles taking account of the mechanical behavior of expansive soils.

尽管桩周围的土壤处于非饱和状态，但桩基础被广泛设计，扩展了饱和土力学原理，假设排水条件（即有效应力）即使在膨胀土壤沉积中也是如此。与渗水相关的吸力变化会显着影响原位桩基础的力学行为。在本文中，研究了在使用载荷下与非饱和膨胀土中吸力变化相关的单一模型桩力学行为变化。实验结果表明，由于水渗透，桩沉降增加。这种现象可归因于活动区中桩轴摩擦力的降低以及由于水的渗透和土壤体积膨胀导致的吸力降低。P ILE行为ë在xpansive土我nfiltration），这是基于非饱和土力学的原理提出的。提出了一种用于估计桩头荷载的理论模型，该模型区分了在渗水时桩是向上移动还是向下移动。本文中提出的理论模型和数值建模方法对于实践工程师在考虑膨胀土的力学行为的情况下合理设计桩是有价值的。