Temperature Fluctuations Weaken Concrete and Silty Clay Interfaces in Geotechnical Structures
Soil-structure interfaces exposed to thermal cycles experience measurable drops in shear strength and friction angles, according to laboratory findings published by MDPI. The study evaluates how temperature variations alter the mechanical stability of infrastructure components like energy piles and underground tunnels, showing that heating reduces load-bearing capacity across concrete and reconstituted silty clay boundaries.
Shear Stress Reductions Measured Across Constant and Cyclic Thermal Tests
Researchers tested the concrete-reconstituted silty clay interface using a custom direct shear apparatus equipped with a temperature control system. Normal stresses between 100 kPa and 400 kPa were applied while shearing occurred at a rate of 0.02 mm per minute. Across constant-temperature trials ranging from 30 °C to 60 °C, heating produced a maximum measured reduction of 12.72% in interface shear stress. Apparent interface adhesion dropped from 17.09 kPa to 9.38 kPa, marking a 45.11% decrease, while the apparent interface friction angle fell from 38.66° to 36.50°.
The investigation divided testing into three distinct series: constant temperatures at 30, 40, 50, and 60 °C; single heating-cooling paths spanning 25–30–25 °C, 25–40–25 °C, and 25–50–25 °C; and cyclic testing involving one to three thermal loops between approximately 25 °C and 50 °C. The interface displayed a strain-hardening response overall, with terminal shear stress increasing alongside normal stress but diminishing as temperatures rose.
Thermal Amplitudes and Cycling Degrade Interface Parameters
Expanding the temperature amplitude during single-cycle tests decreased the fitted apparent interface adhesion by 21.65% and lowered the friction angle by 3.05%. Additional thermal cycling from one to three cycles further eroded these values, reducing apparent adhesion by 18.45% and the friction angle by 9.07%. These outcomes demonstrate that the magnitude of heating-cooling paths and the repetition of thermal cycles directly alter interface mechanical responses.
Frequently Asked Questions About Thermal Effects on Geotechnical Interfaces
What types of structures face risks from thermal interface degradation?
Energy piles and underground structures subjected to continuous temperature fluctuations experience these interface alterations, which impact overall geotechnical design and stability.
How much did apparent adhesion drop during constant heating?
Apparent interface adhesion dropped by 45.11%, moving from 17.09 kPa down to 9.38 kPa as temperatures shifted from 30 °C to 60 °C.
What testing equipment was used to measure shear strength?
Researchers utilized a custom-designed direct shear apparatus equipped with an integrated temperature control system under normal stresses ranging from 100 kPa to 400 kPa.