Thermal effects on one-way cyclic behaviour of clay-structure interface

Soheib Maghsoodi,Olivier Cuisinier,Farimah Masrouri

doi:10.1051/e3sconf/202020505001

Abstract

In energy geostructures, which exploit the heat in soil using earth contact elements, the interface is subjected to cyclic thermo-mechanical loads. Monotonic and cyclic constant-volume equivalent-undrained (CVEU) direct shear tests were performed on clay-clay and clay-structure interface at different temperatures (22 and 60 °C). Different cyclic and average stress ratios (CSR and ASR) were applied to the kaolin clay-structure interface under 300 kPa of normal stress. The results showed that, the number of cycles to failure for the clay-structure interface test was lower than that for the clay-clay case in the same range of cyclic and average shear stress ratios. In cyclic clay-structure tests, decreasing the cyclic stress ratio, increased the number of cycles to failure; however, decreasing the average shear stress ratio decreased the number of cycles to failure. Increasing the temperature, decreased the rate of strain accumulation and the number of cycles to failure increased by 2-3 times. The rate of degradation (degradation parameter, t) decreased by 16% with heating from 22 to 60 °C for the different cyclic stress ratios tested.

Highlights

Incorporation of heat exchangers in conventional geostructures like piles can extract the heat from the soil for heating purposes and inject it to the soil for cooling purposes
The comparison of the results obtained during the monotonic tests of the clay-clay and claystructure constant-volume equivalent-undrained (CVEU) shear tests highlighted some significant differences (Fig. 4)
The peak shear stress for the clay-structure tests are around 1-1.5% of relative lateral displacement while for the clay-clay tests the peak occurs in larger relative lateral displacements (2-3%)

Summary

Introduction

Incorporation of heat exchangers in conventional geostructures like piles can extract the heat from the soil for heating purposes and inject it to the soil for cooling purposes. Research has been conducted at full and laboratory scale to investigate the effect of temperature on the geotechnical behavior of these energy geostructures as well as on the surrounding soil [2,3,4,5]. These energy geostructures can be subjected to cyclic mechanical loads and thermal variations throughout their lifetime. The current knowledge of the influencing parameters on the cyclic behavior of soil and soil-structure interface is discussed

Objectives

Results

Discussion

Conclusion