Soil Suction Surrogates for Advancing Complete-Stress-State Solutions to Expansive Soils

世界上约有3.2亿公顷的土地被膨胀的粘土覆盖，这些粘土会因土壤水分条件的变化而收缩和膨胀。膨胀的粘土对美国公共基础设施造成的损失估计为每年150亿美元。非保守的设计每造成10亿美元的损失，或许就有100亿美元的损失来自过于保守的设计。膨胀粘土是非饱和土壤，因为粘土颗粒之间的空隙部分被空气填充，部分被水填充。然而，处理膨胀土的常见方法没有充分考虑导致基础设施破坏的非饱和土壤方面。该奖项支持开发一种创新的方法，将非饱和土力学理论广泛应用于处理膨胀粘土剖面上的基础设施开发。由于膨胀土问题的严重性，以及数以万计的从业者参与解决这些问题，这项研究将通过每年在美国基础设施上节省数十亿美元来提供社会效益。该项目有许多扩展部分，包括研究人员和执业工程师之间的交叉培训，这将改善工程教育。代表不足的学生和返乡退伍军人的参与将通过发展更多样化和训练有素的劳动力来扩大这项研究的影响。将采用双重方法估计膨胀土的胀缩运动，其中基于基本原理的土壤吸力和净法向应力方法将与基于替代的方法相关联。该方法将包含非饱和土壤理论的原理，但通过有充分依据但通常测量的土壤吸力替代参数来扩展适用性。气候效应(包括特定地点的‘小气候’)将被纳入替代参数确定，这与最近关于土壤表面-大气相互作用的研究一致。这项研究填补了理论和大量可用现场数据之间的空白。一个根本性的土壤吸力替代物将促进过去膨胀土调查中可用的土壤参数的巨大数据库的使用。将使用含水率和指数性质的简单函数来代替土壤吸力来评估膨胀土在田间净正常应力条件下的部分湿化或干燥的运动。主要目标是开发一种土壤吸力替代方法，产生与完全基于应力状态的吸力方法完全相同或基本上相同的膨胀土运动结果，并允许岩土工程师从更根本的角度利用他们丰富的经验。

Approximately 320 million hectares of the world's land is covered with expansive clays that are subject to shrinkage and swelling in response to changes in soil moisture conditions. Damage to U.S. public infrastructure from expansive clays is estimated to be $15 B/yr. For every billion dollars in damage from unconservative design, perhaps $10B is lost from overly conservative design. Expansive clays are unsaturated soils in that the void space between clay particles is filled partly with air and partly with water. However, common approaches to dealing with expansive soils do not fully consider the unsaturated soil aspects that drive infrastructure damage. This award supports the development of an innovative approach to bringing unsaturated soil mechanics theory into wide use in dealing with infrastructure development on expansive clay profiles. Due to the magnitude of expansive soils problems, and the involvement of 10s of thousands of practitioners addressing these problems, this study will provide societal benefit through saving billions of dollars annually on U.S. infrastructure. The project has numerous outreach components, including cross-training between researchers and practicing engineers that will improve engineering education. Participation of underrepresented students and returning-veteran students will broaden the impact of this study through development of more diverse and well-trained work force. A dual approach will be taken for estimation of expansive soil swell-shrinkage movements, wherein a fundamentals-based soil suction and net normal stress approach will be linked to a surrogate-based approach. The method will embrace principles of unsaturated soils theory, yet expand applicability through well-founded yet commonly-measured soil suction surrogate parameters. Climatic effects (including site-specific 'microclimate') will be incorporated into surrogate parameter determination, consistent with recent research on soil surface-atmosphere interactions. This research fills a gap between theory and the vast amount of available field data. A fundamentally-based soil suction surrogate will facilitate use of the huge database of soil parameters available from past expansive soil investigations. Simple functions of water content and index properties will be used - in lieu of soil suction - to evaluate expansive soil movements for partial wetting or drying under field net normal stress conditions. The primary goal is to develop a soil suction surrogate approach that yields exactly the same, or essentially the same, expansive soil movement results as the complete-stress-state based suction approach, and which allows geotechnical engineers to take advantage of their vast experience from a more fundamental perspective.