Laboratory Investigation and Modelling of the Thermal-Mechanical Properties of Soil in Shallow Mineralized Groundwater Area

• Published in: Geofluids Vol. 2019; no. 2019; pp. 1 - 21
• Main Authors: Xia, Zhao, Gu, Jiali, Liu, Xiao-ming
• Format: Journal Article
• Language: English
• Published: Cairo, Egypt Hindawi Publishing Corporation 2019; Hindawi; John Wiley & Sons, Inc; Hindawi Limited; Wiley
• Subjects: Analysis; Calcium; Calcium chloride; Clay; Conductivity; Construction; Dry density; Earth; Electric properties; Energy research; Equipment and supplies; Experiments; Feasibility studies; Geothermal energy; Geothermal power; Groundwater; Heat conductivity; Heat exchangers; Heat pumps; Heat transfer; Heating; Investigations; Laboratories; Mechanical analysis; Mechanical properties; Mineralization; Modulus of elasticity; Moisture content; Outdoor air quality; Quartz; S waves; Saline soils; Salinization; Salt; Salts; Shear modulus; Shear strength; Shear wave velocities; Sodium; Sodium chloride; Soil; Soil investigations; Soil layers; Soil mechanics; Soil moisture; Soil properties; Soil sciences; Soil strength; Soil stresses; Soil treatment; Soils, Salts in; Studies; Thermal conductivity; Tunnels; Velocity; Water content; Water, Underground; Wave propagation; Wave velocity; China
• ISSN: 1468-8115; 1468-8123
• DOI: 10.1155/2019/5121740

The capillary rise of shallow mineralized groundwater can contribute to the salinization of the soil layers. The excessive salt amounts adversely affect soil physical and mechanical properties, as well as the heat transfer performance, all of which are key factors with regard to the design of geothermal-related earth structures such as geothermal energy piles (GEP), ground source heat pumps (GSHP), and earth-air tunnel heat exchangers (EATHE). Therefore, in this study, the thermal-mechanical properties of saline soils are systematically investigated. A series of thermal and mechanical response tests were carried out under different salinity conditions, and the shear wave velocity-stress behavior of saline soil was measured using a modified oedometric cell coupled with an anchored bender element pair. Experimental results showed that saline soils generally have higher dry density and lower optimum moisture content at higher salt contents. The shear strength of saline soil increased about 5% while the salt concentrations of bulk solution increased from 0 mol/kg to 6 mol/kg, and the shear wave velocity increased by 50% to 83% when the normal load increased from 12.5 kPa to 250 kPa for sodium chloride- (NaCl-) treated soil and 39% to 52% for calcium chloride- (CaCl2-) treated soil. In addition, the thermal conductivity decreased by 0.121 W m-1 K-1 for NaCl-treated soil and 0.129 W m-1 K-1 for CaCl2-treated soil on average when the salt concentration increased from 0 mol/kg to 6 mol/kg. Finally, an elastic shear modulus (G0) model and a thermal conductivity (K) model were formulated for saline soil for the first time, and the effectiveness and feasibility of the proposed models were validated by comparisons of the model predicted values and experimental data.