Soil Structure Interaction in Geothermal Foundations

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。美国目前正在寻求提高建筑能源效率的技术。其中一种方法是将地热热交换系统嵌入深层地基，以提高建筑热泵的能源效率，这是本研究的重点。尽管结合使用基础支撑和加热/冷却系统的设备和建筑材料可以节省潜在的成本，但这种方法并非没有风险。建筑物居住部分与其地下结构构件之间的热相互作用可能会引起岩土和建筑系统的关注。例如，从地热基础中吸收过多的热量可能导致地面冻结和潜在的地表隆起；由于热泵温度的快速波动，基础材料的循环膨胀和收缩可能导致侧摩擦的变化；随着时间的推移，不可持续的热交换模式可能导致建筑物与地面之间的热交换效率降低。一种涉及地热基础与周围土壤之间的热、水力和机械相互作用的数值模拟的研究方法被用来更好地描述这些风险。这些模拟的参数是通过新的具有温度和水力控制的真三轴试验确定的，并通过在不同温度和负载条件下的地热基础上的一系列离心机模拟实验来验证模拟结果。经过验证的模拟工具将用于为工程师提供实用的设计指导，以帮助定义适当的热交换器几何配置，基础尺寸和间距，以及建筑热泵控制条件，以获得给定土壤剖面的最佳热交换和基础性能。与行业合作伙伴（ADSC）的互动将有助于将研究成果转移给实践工程师和基础承包商。这项研究通过整合土壤力学、建筑供暖系统、物理建模和本构建模等主题，被用于加强科罗拉多大学博尔德分校的教育；这将为进入这个新领域的学生提供广泛培训的新机会。代表性不足的学生将通过与科罗拉多大学博尔德分校建立的多样性倡议合作来招募，因为这些人群在基础工程社区中尤其缺失。

This award is funded under the American Recovery and Reinvestment Act of 2009(Public Law 111-5).The U.S. is currently pursuing technologies to improve the energy efficiency of buildings. One approach, which is the focus of this research, involves embedding geothermal heat exchange systems within deep foundations to gain improved energy efficiency of building heat pumps. Despite the potential cost savings gained through the combined use of equipment and construction materials for both the foundation support and heating/cooling systems, this approach is not without risk. The thermal interaction between the inhabited part of a building and its subsurface structural components may lead to both geotechnical and building system concerns. For example, drawing excessive amounts of heat from geothermal foundations may lead to ground freezing and potential surface heave, cyclic expansion and contraction of foundation materials due to rapid fluctuations in heat pump temperatures may lead to changes in side friction, and non-sustainable heat exchange patterns can lead to a reduction in heat exchange efficiency between the building and ground over time. A research approach involving numerical simulations of the thermal, hydraulic, and mechanical interaction between geothermal foundations and surrounding soils is being used to better characterize these risks. The parameters for these simulations are being determined using novel true-triaxial tests with temperature and hydraulic control, and the results from the simulations are being validated against a series of centrifuge modeling experiments on geothermal foundations under different temperature and loading conditions. The validated simulation tool will be used to provide practical design guidance to engineers to aid in defining the appropriate heat exchanger geometric configuration, foundation size and spacing, and building heat pump control conditions to gain both optimal heat exchange and foundation performance for a given soil profile. Interaction with industry partners (ADSC) will aid in the transfer of research findings to practicing engineers and foundation contractors. This study is being used to augment education at the CU Boulder through integration of topics from soil mechanics, building heating systems, physical modeling and constitutive modeling; which will provide new opportunities for broad-based training to students entering this new field. Under-represented students will be recruited through cooperation with established diversity initiatives at CU Boulder, as these populations are particularly missing from the foundation engineering community.