CAREER: Thermo-Active Geotechnical Systems with Reinforced, Unsaturated Soils

该学院早期职业发展（CAREER）项目的研究目标是了解建筑物和工业的杂散热可用于改善涉及土工合成材料加固土壤的岩土系统性能的条件。具体而言，热诱导水流正在研究作为一种手段，保持压实的土壤回填在非饱和条件下，在这种情况下，更大的有效应力将导致增强的强度和刚度。一种在岩土系统内施加温度的新方法也正在研究中，其中热交换器管道在施工期间与土工合成材料钢筋一起沿着安装。元素规模的测试被用来衡量所获得的好处，保持土壤在非饱和条件下对潜在的负面影响，高温加固土壤。这些负面影响包括由于热体积变化、屈服面形状的热变化、土-水保持曲线的热变化以及土工合成材料增强物的蠕变变形而产生的孔隙水压力。单元尺度试验的观测结果被合成为本构关系，可用于表征非饱和土-土工合成材料复合材料的热-水-力学行为。此外，在不同的边界条件下，离心规模的热活性岩土系统的流动和变形行为被用于这些本构关系的系统级验证。 综合教育计划的目标是培养学生研究人员有效地传播研究成果，以不同层次的技术专业知识的观众，并提高学生的个人参与他们的教育的成功。这些目标将通过首先为学生研究人员开发一个交流研讨会来实现，该研讨会包括有效沟通技巧的讲座，使用书面案例陈述指导演示计划，以及电影反馈分析的演示实践。然后，学生研究人员将向丹佛东部高中的高中新生，CU BOLD中心内的各种学生组织，行业利益相关者和岩土工程公司进行演讲。教育计划的成功将通过比较观众的反馈与学生的书面案例陈述进行评估。对温度对非饱和土壤影响的进一步了解有可能使目前无法用于加固土壤系统的回填土的使用成为可能，从而节省材料和运输成本。同时，热交换过程可用于提高建筑物冷却系统的能源效率，或在不产生水蒸气的情况下消散工业过程中的杂散热量（干式冷却）。从这项研究中吸取的经验教训付诸实践，可能会形成一个新的市场领域的岩土工程和土工合成材料工程，从而带来新的经济机会。作为这一努力的一部分，土壤土工合成复合材料的本构模型将为从业者提供工具，用于对他们在这一领域的设计进行基于性能的生命周期成本评估，从而提高这项技术的可持续性和可销售性。此外，参加综合通信培训计划的学生将获得实用的策略，以有效地与具有不同技术专业知识水平的受众进行沟通，这将有助于他们在这个新市场领域开始成功的职业生涯。他们的演讲将促进研究成果传播到实践工程师，利益相关者和公众。此外，在CU和高中课堂上向不同的学生团体进行演讲将有助于招募代表性不足的学生进入STEM领域。

The research objective of this Faculty Early Career Development (CAREER) project is to understand the conditions under which spurious heat from buildings and industry can be used to improve the performance of geotechnical systems involving geosynthetic-reinforced soils. Specifically, thermally induced water flow is being investigated as a means of maintaining compacted soil backfills in unsaturated conditions, in which case greater effective stresses will result in enhanced strength and stiffness. A novel approach for imposing temperatures within geotechnical system is also being investigated, in which heat exchanger tubing is installed along with geosynthetic reinforcements during construction. Element-scale tests are being used to weigh the benefits gained by maintaining soils in unsaturated conditions against potentially negative impacts of elevated temperatures on reinforced soils. These negative impacts include pore water pressure generation due to thermal volume change, thermal changes in the yield surface shape, thermal changes in the soil-water retention curve, and creep deformation of geosynthetic reinforcements. The observations from the element-scale tests are being synthesized into constitutive relationships which can be used to characterize the thermo-hydro-mechanical behavior of unsaturated soil-geosynthetic composites. Further, the flow and deformation behavior of centrifuge-scale thermo-active geotechnical systems under different boundary conditions are being used for system-level validation of these constitutive relationships. The goals of an integrated educational program are to train student researchers to effectively disseminate research results to audiences with varying levels of technical expertise, and to improve students' personal engagement in the success of their education. These goals will be reached by first developing a communication workshop for student researchers which incorporates lectures on effective communication skills, guided presentation planning using written case statements, and presentation practice with film feedback analysis. Student researchers will then make presentations to high school freshmen from Denver East High School, diverse student organizations housed within the CU BOLD center, industry stakeholders, and geotechnical engineering firms. The education program's success will be assessed by comparing audience feedback with students' written case statements. The improved understanding of temperature effects on unsaturated soils has potential to enable the use of backfill soils currently unusable in reinforced soil systems, leading to material and transport cost savings. At the same time, the heat exchange process can be used to improve the energy efficiency of building cooling systems, or to dissipate spurious heat from industrial processes without the generation of water vapor (dry cooling). Implementation of the lessons learned from this study into practice may form a new market sector in the fields of geotechnical and geosynthetics engineering, resulting in new economic opportunities. As part of this effort, the constitutive model for soil-geosynthetic composites will provide practitioners with tools for performance-based life-cycle cost assessments of their designs in this area, enhancing the sustainability and marketability of this technology. Further, students participating in the integrated communication training program will gain practical strategies to effectively communicate with audiences with varying levels of technical expertise, which will help them start successful careers as leaders in this new market sector. Their presentations will facilitate dissemination of research results to practicing engineers, stakeholders, and the public. Further, presentations to diverse student groups at CU and high school classes will help recruit underrepresented students into STEM fields.