Development of Thermal-Insulating Soilcrete using Laboratory Jet Grouting Setup

• Author / Creator

  Nikbakhtan, Babak

• One of the most effective ways to lower the energy used to heat or cool residential and commercial buildings is Underground Thermal Energy Storage (UTES) systems. These systems store thermal energy in underground enclosures (borefield) where it can be used when it is needed. UTES systems significantly improve energy efficiency. This results in decreasing usage of fossil fuels and fewer greenhouse gas emissions into the atmosphere. In most UTES systems, the top portion of the borefield is insulated to prevent heat from escaping. However, most of the time, there is no insulation on the sides and bottom of the borefield area. This can reduce the UTES systems’ performance when the surrounding ground does not have desirable thermal properties and underground water flow conditions. The current research focuses on the Southwood UTES project in Edmonton, Alberta, Canada. A 67-meters core logging was confirmed a coal layer at 30 to 50 meters beneath the borefield. That layer prevents heat from escaping from the borefield underneath. However, there is no insulating element around the perimeter. Hence, a proposal was made to develop new insulating material to create thermal-insulating elements for underground enclosures that will keep the heat inside the enclosure from escaping and will increase the efficiency of the UTES systems. In order to inject the thermal-insulating material into the soil structure, an appropriate ground modification method is required. During past two decades, jet grouting has been introduced as one of the most effective methods for ground modification. Developments during the past decade have progressed to where jet grouting is now a suitable substitution for common grouting methods in cohesive soils. Therefore, the jet grouting technique was chosen to inject the thermal-insulating grout into the soil and modify its thermal properties. The understanding of jet grouting process is very limited because of its complex operations. It is difficult to predict or precisely control the quality of the jet grouting product, soilcrete. In most cases, to evaluate the performance of the jet grouting operation on a particular soil type, it is necessary to conduct trial jet grouting in the field. Trial jet grouting takes place at a temporary location that has the same geotechnical properties as the main jobsite. It involves grouting more than one column using different operational parameters. After jet grouting, test columns are dug out for visual inspections and desired tests. In the trial jet grouting method, finding a location that is similar to the jobsite is not always possible. It can be time-consuming and expensive, and not even lead to desired results. Thus, it was proposed to design and manufacture a laboratory jet grouting setup with almost the same performance ability as the field equipment but with a reduced footprint and cost. To verify and validate the success of the proposed design, thermal-insulating grout was developed in the laboratory. Then, based on the theoretical definition of the jet grouting process, soilcrete specimens were hand-mixed and cast in the laboratory. Physical, mechanical, and thermal properties of the specimens were calculated using laboratory tests. The results were verified based on the literature values. After the a suitable thermal-insulating grout mixture was developed and the manufacturing laboratory jet grouting setup was completed, an actual jet grouting test was performed on the reconstructed in-situ soil formation in the jet grouting tank. This test was performed to validate the laboratory results obtained from hand-mixed specimens. Also, the capability of the manufactured jet grouting setup and actual laboratory jet grouting experiment results were verified with well-documented literature about jet grouting projects. The results revealed tremendous improvements in thermal and strength properties of the soilcrete compared to the in-situ soil, as well as a successful performance of the laboratory jet grouting setup.

• Subjects / Keywords

  • Physical Modeling
  • Thermal Insulating
  • Underground Thermal Storage System
  • Soilcrete
  • Jet Grouting

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3QR4NW4X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.