Reclaimed land constructed in seismic zones is prone to liquefaction because conventional construction practice tends to produce a loose to medium deposit. At the same time discarded tyres have become an increasingly problematic global problem whose disposal is posing dangers to the environment. This paper attempts to overcome both problems by means of mixing tyre chips with sand and using them for landfill purposes. A computer-controlled cyclic triaxial testing system has been used to determine the liquefaction strength of pure sand and sand-rubber mixtures. The results show that for 5% to 30% of tyre chips by volume, the liquefaction strength actually decreases compared to that of pure sand samples. However, when the proportion of tyre chips is increased to 40% and more, the results show a significant improvement in liquefaction resistance.
In element tests under undrained conditions a soil is considered to have liquefied when the generated pore water pressure is approximately equal to the initial effective stress. During liquefaction the soil completely loses shear strength and stiffness and behaves like a viscous fluid having the unit weight equal to a saturated soil. In such conditions, superstructures having a unit weight greater than those of the liquefied soil will sink. On the other hand, buried structures whose unit weight is smaller, will float (JGS, 1998). The probability of damage is therefore high. In geotechnical design not only is the shear strength considered, but also the settlement and deformation must be included. For liquefaction analysis, even if the ratio of pore water pressure Δu to consolidation pressure σ" 3c is still below 1.0, i.e., Δu/σ" 3c ≅ 0.6 – 0.8, the deformation due to softened soil may be sufficient to cause damage. Thus, it is customary to apply a limiting strain level in a liquefaction analysis.