Effects of Mix Proportion and Cyclic Loading on the Stress-Strain Behavior of a Flexible Thin Spray-On Liner under Uniaxial Compression

To investigate the effects of mix proportion on the compressive mechanical properties of a flexible thin spray-on liner (TSL), a series of compression tests were performed on flexible TSL specimens with different styrene-acrylic emulsion contents (ms), cement-sand ratios (mc/mq), and fiberglass contents (mF). With an increase in ms, the compressive strength of the flexible TSL first increased and then decreased, and the TSL gradually transformed from brittle to ductile. With an increase in mc/mq, the compressive strength increased. The increase of mF improved the compressive strength and elastic modulus of the TSL. Subsequently, three cyclic loading paths were selected to study the stress-strain behavior of a flexible TSL with a fixed mix proportion. The evolution characteristics of the irreversible axial strain, elastic modulus, dissipated energy, and damage variables under different cyclic loading paths were analyzed. The development of irreversible deformation accumulation reflects the characteristics of the damage evolution process under cyclic loading. Based on the experimental results, a stress-strain model is proposed to predict the stress-strain behavior of the TSL under different cyclic loading paths. The experimental results were used to calibrate and validate this model, demonstrating that the model can effectively predict the stress-strain behavior of a flexible TSL.