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EAGER: Solar Thermal Soil Improvement over Different Depths

EAGER：不同深度的太阳能热土壤改良

基本信息

批准号：
1941571
负责人：
John McCartney
金额：
$ 24.41万
依托单位：
University of California-San Diego
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-09-01 至 2022-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1941571&HistoricalAwards=false
关键词：
EAGER Solar Thermal Soil Improvement

项目摘要

This EArly-concept Grant for Exploratory Research (EAGER) project addresses the geotechnical engineering research needed to assess the feasibility of using solar thermal energy to improve the mechanical properties of soft soil deposits over different depth ranges. Specifically, heated fluid collected from solar thermal panels circulated through closed-loop geothermal heat exchangers in the subsurface is used to induce thermal volumetric contraction and a corresponding increase in shear strength of a targeted zone of soil. Arrays of geothermal heat exchangers in vertical and horizontal configurations will be investigated to improve soil over different depth ranges and areal distributions. Advantages of this approach are that soil improvement can be gained in a targeted manner using renewable energy, after which the geothermal heat exchangers can be used for long-term underground thermal energy storage, yielding cost savings when compared to available soft soil improvement technologies. The research plan seeks to better understand fundamental processes governing the thermal volume change of soft soils over different depth ranges and to improve constitutive models for soft soils needed in advanced computer simulations, addressing the NSF mission "to promote the progress of science." If feasible, solar thermal energy and geothermal heat exchangers will be important tools for the cost-effective improvement of challenging soft soil deposits encountered in civil infrastructure projects, offshore or river sediments, mine tailings dams, and coal ash impoundments. This project will introduce undergraduate students from diverse backgrounds to research through established summer programs at UCSD like STARS and ENLACE. A fundamental issue investigated in this study that will impact the feasibility of solar thermal soil improvement is the possible impact of the initial mean effective stress (or initial void ratio) on the magnitude of drained thermal volume change of normally consolidated soils for a given temperature increment. Although existing thermo-elasto-plastic models indicate that all normally consolidated soils should have the same thermal volume change due to thermal hardening, limited data available for heating of normally consolidated soils indicate that soils lower in initial mean effective stress and higherin initial void ratio may experience greater thermal volume changes and greater increases in undrained shear strength after improvement. If these limited data are valid, this would indicate that shallower soils may experience greater improvement for a given temperature increment. The objective of this project is to better understand the thermal volume change of normally consolidated clay through a comprehensive experimental testing program in a thermal triaxial cell and to use the experimental results to enhance existing drained thermo-elasto-plastic models and undrained thermal pressurization models. Along these lines, this project seeks to investigate potential impacts of temperature and mean effective stress on key material properties including the thermal hardening parameter, the coefficient of thermal expansion of the soil skeleton and the coefficient of compressibility of the soil. Using the knowledge gained from this investigation, this project seeks to unify predictions from the transient coupled heat transfer and water flow process associated with solar thermal soil improvement with the observed trends in drained thermal volume change. The unified model will be used to simulate solar thermal soil improvement process to understand the roles of heat exchanger geometry and solar thermal boundary conditions in reaching different degrees of soil improvement.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

EARLY概念探索性研究资助（EAGER）项目致力于岩土工程研究，以评估利用太阳热能改善不同深度范围内软土沉积物力学性能的可行性。具体地，从太阳能热板收集的加热流体通过地下的闭环地热热交换器循环，用于引起热体积收缩和土壤目标区域的剪切强度的相应增加。将研究垂直和水平配置的地热换热器阵列，以改善不同深度范围和区域分布的土壤。这种方法的优点是可以使用可再生能源以有针对性的方式进行土壤改良，之后地热换热器可以用于长期的地下热能储存，与现有的软土改良技术相比，可以节省成本。该研究计划旨在更好地了解不同深度范围内软土热体积变化的基本过程，并改进先进计算机模拟所需的软土本构模型，实现NSF的使命“促进科学进步”。“如果可行，太阳能和地热换热器将成为具有成本效益的重要工具，用于改善民用基础设施项目中遇到的具有挑战性的软土沉积物，海上或河流沉积物，尾矿坝和煤灰蓄水池。该项目将介绍来自不同背景的本科生，通过在UCSD像明星和ENLACE既定的暑期课程进行研究。在这项研究中，将影响太阳能热土壤改良的可行性的一个基本问题是初始平均有效应力（或初始孔隙比）的排水正常固结土壤的热体积变化的大小为一个给定的温度增量的可能影响。虽然现有的热弹塑性模型表明，所有正常固结的土壤应该有相同的热体积变化，由于热硬化，有限的数据可用于正常固结的土壤加热表明，土壤在初始平均有效应力较低和较高的初始孔隙比可能会经历更大的热体积变化和更大的增加后，不排水剪切强度的改进。如果这些有限的数据是有效的，这将表明，较浅的土壤可能会经历更大的改善，为给定的温度增量。本项目的目的是更好地了解正常固结粘土的热体积变化，通过一个全面的实验测试程序，在一个热三轴单元，并使用实验结果，以加强现有的排水热弹塑性模型和不排水热压模型。沿着这些路线，该项目旨在调查温度和平均有效应力对关键材料特性的潜在影响，包括热硬化参数，土壤骨架的热膨胀系数和土壤的压缩系数。利用从这项调查中获得的知识，该项目旨在统一预测从瞬态耦合传热和水流过程与太阳能热土壤改善与所观察到的趋势，在排水热体积变化。统一模型将用于模拟太阳能热土壤改良过程，以了解热交换器几何形状和太阳能热边界条件在达到不同程度的土壤改良中的作用。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

期刊论文数量（5）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Effect of Drained Heating and Cooling on the Preconsolidation Stress of Saturated Normally Consolidated Clays

排水加热和冷却对饱和常固结粘土预固结应力的影响

DOI：
10.1061/9780784482780.061
发表时间：
2020
期刊：
GeoCongress 2020
影响因子：
0
作者：
Samarakoon, Radhavi A.;McCartney, John S.
通讯作者：
McCartney, John S.

C7.(2021). Performance of prefabricated thermal drains in soft clay. Geosynthetics 2021. Kansas City. Feb. 21-23. IFAI, Roseville, MI. 1-12.

C7.（2021）。

DOI：
发表时间：
2021
期刊：
Proceedings of Geosynthetics 2021
影响因子：
0
作者：
Samarakoon, R.;McCartney, J.S.
通讯作者：
McCartney, J.S.

Role of initial effective stress on the thermal volume change of normally consolidated clay

初始有效应力对正常固结粘土热体积变化的影响

DOI：
10.1051/e3sconf/202020509001
发表时间：
2020
期刊：
E3S Web of Conferences
影响因子：
0
作者：
Samarakoon, Radhavi;McCartney, John S.
通讯作者：
McCartney, John S.

Analysis of thermal drains in soft clays

软粘土热排水分析

DOI：
发表时间：
2020
期刊：
GeoAmericas 2020
影响因子：
0
作者：
Samarakoon, R.;McCartney, J.S.
通讯作者：
McCartney, J.S.

Temperature-Dependent Model for Small-Strain Shear Modulus of Unsaturated Soils

非饱和土小应变剪切模量的温度相关模型

DOI：
10.1061/(asce)gt.1943-5606.0002406
发表时间：
2020
期刊：
Journal of Geotechnical and Geoenvironmental Engineering
影响因子：
3.9
作者：
Vahedifard, Farshid;Thota, Sannith Kumar;Cao, Toan Duc;Samarakoon, Radhavi Abeysiridara;McCartney, John S.
通讯作者：
McCartney, John S.