Abstract: The swelling process of bentonite is vital for judging the time required for completing the swelling, estimating the engineering safety, and organizing the construction plan. Many factors affect the swelling process, and the underlying mechanisms still require to be clearly explained. In this paper, the swelling process of commercial bentonite in different molar concentrations of salt solution was studied by the one-dimensional free swelling test and constant volume swelling pressure test. The curves of swelling over time were fitted using a hyperbolic model, and two parameters were extracted to reflect the swelling rate and the final swelling strain or swelling pressure quantitatively, respectively. The test results show that the final swelling strain or swelling pressure is determined by the swelling ability of the bentonite, while the swelling rate is influenced by the coupled effect of the swelling ability and permeability of soil. The mechanisms of different factors affecting the swelling process of bentonite are summarized as the effects on the permeability and swelling ability of the soil by considering the change process of pore structure during swelling. The proposed mechanism explanation can also reasonably explain the effect of initial water content in the existing literature. The influencing mechanism of the swelling process revealed in this paper from the perspective of pore structure provides a reasonable theoretical basis for analyzing the swelling process of bentonite.

Key words: swelling process, free swelling, constant volume swelling, swelling strain, swelling pressure

摘要： 膨润土的膨胀过程对于判断膨胀完成所需时间、评估工程安全和组织施工计划至关重要。影响膨胀过程的因素很多，其背后机理尚需明确解释。本文通过一维自由膨胀试验和常体积膨胀压试验，研究了商用膨润土在不同浓度盐溶液中的膨胀过程。用双曲线模型拟合了膨胀随时间变化的曲线，并提取了两个参数以定量反映膨胀速率和最终膨胀应变或膨胀压。试验结果表明：最终的膨胀应变或膨胀压是由膨润土的膨胀能力决定的，而膨胀速率则受土体膨胀能力和渗透性的耦合影响。通过考虑膨胀过程中孔隙结构的变化过程，将不同因素对膨润土膨胀过程的影响机理统一为对土体渗透性和膨胀能力的影响。所提出的机理也可以合理地解释现有文献中初始含水量的影响。本文从孔隙结构角度揭示的膨胀过程影响机理，为分析膨润土的膨胀过程提供了合理的理论依据。

关键词: 膨胀过程，自由膨胀，常体积膨胀，膨胀应变，膨胀压