Dynamic behaviour of oyster shell powder-modified expansive soil under cyclic loading

This paper systematically studies the dynamic mechanical properties of oyster shell powder (OSP)-modified expansive soil under simulated train loads. A GDS dynamic triaxial test system was used in the study. The axial cumulative strain development and hysteresis curve characteristics of expansive soil with different oyster shell powder particle sizes (dosp=0-0.075 mm, 0.075-0.15 mm, 0.15-0.25 mm, 0.25-0.5 mm, 0.5-1.0 mm, 1.0-2.0 mm), dosages (Fosp=0 %, 3 %, 6 %, 9 %) and cyclic stress ratios (CSR=0.1, 0.15, 0.2, 0.25, 0.275, 0.3) were studied. The results show that when dosp< 0.5 mm, the axial cumulative strain, damping ratio and dynamic resilient modulus of the modified soil are significantly improved with increasing oyster shell powder content; when Fosp= 9 % and dosp< 0.5 mm, the dynamic performance of the modified soil is similar. When Fosp= 9% and dosp= 0.25-0.5 mm, compared with plain soil, the axial cumulative strain decreases by 37.3 %, the damping ratio decreases by 39 %, and the dynamic elastic modulus increases by 29.9 % after 200,000 cycles. When dosp> 0.5 mm, the performance of each dynamic performance index of the modified soil deteriorates compared with that of the plain soil, and the deterioration effect is more significant with increasing oyster shell powder content and particle size. When oyster shell powder-modified soil is used as a subgrade filler for a ballasted track railway with a design speed below 200 km/h, it is recommended to control the content of oyster shell powder as Fosp= 9 % and the particle size of oyster shell powder as dosp= 0.25-0.5 mm. At this time, from the perspective of controlling the postconstruction settlement of the railway subgrade, the cyclic stress ratio CSR should be controlled below 0.2.