PECASE: The Role of Specific Surface Area and Cation Exchange Capacity in Understanding and Predicting Expansive Soil Behavior

PECASE：比表面积和阳离子交换能力在理解和预测膨胀土行为中的作用

• 批准号: 0746980
• 负责人: Amy Cerato
• 金额: $ 40万
• 依托单位: University of Oklahoma Norman Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-02-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0746980&HistoricalAwards=false
• 关键词: PECASE; Role; Specific; Surface; Area

Expansive unsaturated soils cover one-fourth of the United States and undergo large amounts of heaving and shrinking due to seasonal moisture changes. These movements often lead to cracking and buckling of the infrastructure built on expansive soils, and result in billions of dollars of damage annually (e.g., Wray & Meyer 2004). Although not life-threatening or cataclysmic as compared to other natural events, expansive soils are certainly a natural hazard. Even though expansive soils have been studied for several decades, all of the idealized models presented to date to predict shrink-swell potential of expansive soils have failed to predict actual soil movement under real conditions where the presence of several cations and clay minerals can influence soil behavior (Hillel 1998). The research goal of this award is to advance the understanding of and prediction methods for macroscopic unsaturated expansive soil behavior through microscopic fundamental soil surface phenomena, such as specific surface area (SSA) and cation exchange capacity (CEC). This will be achieved by improving existing 1-D empirical models and extending the application of a physicochemical discrete element method (DEM) computer model to incorporate expansive soil movement. Understanding expansive soil behavior under various environmental conditions will allow the design of robust foundation systems using life-cycle performance as the driving factor in choice of design. This innovative unsaturated soils research program will be woven into several important high-impact educational components in order to bridge the gap between geotechnical theory and geotechnical practice. Understanding expansive soil behavior using microscopic soil surface phenomena will advance the state-of-knowledge and practice in geotechnical engineering by allowing researchers and practitioners to accurately and repeatedly predict macroscopic expansive soil behavior in a way that is not currently available. The improvement on existing empirical models for expansive soil movement prediction using microscopic soil parameters, such as SSA and CEC, is an immediate practical necessity for the geotechnical engineering profession. It is also essential to develop a physically meaningful mathematical model that utilizes a microlevel understanding of particles and interparticle forces to further advance our fundamental knowledge of expansive soil behavior. Merging physicochemical and unsaturated soil mechanics theories into a DEM will provide insight into observed laboratory and in situ behavior and speed progress toward a solution to a complex and expensive problem. The topic of expansive soils is not only compelling from a scientific perspective, but a social perspective as well. The microscopic, particle-particle understanding of expansive soil behavior will help to predict the macroscopic shrink-swell behavior that causes in the United States an estimated $15 billion dollars in annual damage to infrastructure. To initiate this improvement, students will be taught about the important role that geotechnical engineer?s play within our society to broaden their career path opportunities as well as increase, enhance and diversify our undergraduate civil engineering population. This enhanced undergraduate student population will feed a more talented and diverse graduate student population which will produce a more educated workforce. In time, this extensive network of civil engineers can dispel the poor public perception of engineers and increase their status in society. Similar to current practices and successes, the PI will focus on the recruitment and retention of women and minorities in order to enhance and diversify the engineering experience.

膨胀的非饱和土壤覆盖了美国四分之一的土地，由于季节性水分的变化，经历了大量的隆起和收缩。这些移动经常导致在膨胀土壤上建造的基础设施破裂和弯曲，每年造成数十亿美元的损失(例如，Wray&Amp；Meyer 2004)。尽管与其他自然事件相比，膨胀土不会危及生命或造成灾难性后果，但它肯定是一种自然灾害。尽管膨胀土已经被研究了几十年，但迄今为止提出的所有预测膨胀土收缩膨胀潜力的理想化模型都未能预测在真实条件下的实际土壤运动，在真实条件下，几种阳离子和粘土矿物的存在会影响土壤的行为(Hillel，1998)。该奖项的研究目标是通过微观的基本土壤表面现象，如比表面积(SSA)和阳离子交换容量(CEC)，促进对宏观非饱和膨胀土行为的理解和预测方法。这将通过改进现有的一维经验模型和扩展物理化学离散单元法(DEM)计算机模型的应用来实现，以考虑膨胀土的运动。了解膨胀土在不同环境条件下的行为将允许使用生命周期性能作为设计选择的驱动因素来设计坚固的基础系统。这一创新的非饱和土壤研究计划将被编织成几个重要的高影响教育组成部分，以弥合岩土理论和岩土实践之间的差距。利用微观的土壤表面现象来理解膨胀土的行为，将使研究人员和从业者能够以一种目前尚不存在的方式准确和重复地预测宏观膨胀土的行为，从而推动岩土工程领域的知识和实践水平的发展。改进现有的膨胀土微观参数预测的经验模型，如SSA和CEC，是岩土工程行业迫切需要的现实需要。开发一个物理上有意义的数学模型也是至关重要的，该模型利用对颗粒和颗粒间作用力的微观水平的理解来进一步推进我们对膨胀土行为的基本知识。将物理化学和非饱和土力学理论融合到DEM中，将提供对观察到的实验室和现场行为的洞察，并加快解决复杂和昂贵问题的进程。关于膨胀土的话题不仅从科学的角度来看是令人信服的，而且从社会的角度也是如此。对膨胀土行为的微观、颗粒-颗粒理解将有助于预测宏观的缩胀行为，这种行为每年给美国的基础设施造成约150亿美元的损失。为了启动这一改进，学生们将被告知岩土工程师S在我们的社会中所扮演的重要角色，以拓宽他们的职业道路机会，并增加、增强和多样化我们的土木工程本科学生。这些增加的本科生人数将养活更有才华和多样化的研究生人数，这将产生更受教育的劳动力。随着时间的推移，这个广泛的土木工程师网络可以消除公众对工程师的不良印象，提高他们在社会中的地位。与目前的做法和成功做法类似，专业人员协会将把重点放在妇女和少数群体的招聘和留用上，以加强和多样化工程经验。