Experimental study on the mechanical performance of tyre encased soil elements for structural wall applications

Tyre-encased-soil elements (TESEs) are segmental units made by compacting soil inside the cavity of EOL tyres. The TESEs can function similarly to bricks to build masonry walls or other load-bearing structures. Tyre walls built of TESEs have proven successful architectural and structural performance. However, the mechanical properties of TESEs have not been scientifically investigated in the past, and insufficient evidence restricted TESEs’ further application as structural components. This project attempted to fill the gap by studying the performance of TESEs subject to axial compressive loads through both laboratory experiments and analytical analysis. Soils with different properties were used in the experiments to quantify their influence on the TESEs performance. It was found that within the range of loading applied in this study, no abrupt failure was observed on the tested TESEs. The axial stress-strain relationship followed an exponential form, possibly due to the strain-hardening effect brought in by the densification of encased soil and increased confinement support from the tyre reinforcement. The encased soil’s density had a significant influence on the load-deformation behaviour of the TESEs. However, the load-carrying capacities were not highly sensitive to the soil type and its moisture content. An analytical model was proposed for capturing the axial and radial strain of TESEs under applied axial loads with a reasonable accuracy. In material characterisation, the strength of EOL tyres captured in the inflation tests were significantly larger than those obtained from direct tensile tests, which revealed the cut tyre strip could not capture the synergic effect of the embedded tyre reinforcement composites in a representative manner. The results of this study can be used by built environment professionals to design and analyse the performance of tyre encased soil and tyre walls.