Dynamic properties and microstructural mechanisms of nanoclay-modified cement-stabilized soil

To address serviceability issues of railway subgrades in Central China subjected to dynamic loading, this study investigated the dynamic behavior and microstructural mechanisms of nanoclay-modified, cement-stabilized silty clay. Specimens with var-ying nanoclay contents were prepared and tested using a dynamic triaxial apparatus, and cumulative plastic strain and dynamic elastic modulus were measured. Micro-structural and mineralogical characteristics were examined by scanning electron mi-croscopy and X-ray diffraction. The results showed that cumulative plastic strain increased with dynamic stress amplitude, whereas dynamic elastic modulus decreased. By contrast, increasing nanoclay content reduced cumulative plastic strain and increased dynamic elastic modulus, with 0.5% identified as the optimum content; beyond 0.5%, the marginal benefit diminished. Relative to cement-stabilized soil without nanoclay, cumulative plastic strain decreased by approximately 35 − 50%, while dynamic elastic modulus increased by about 75 − 82%. Microstructurally, nanoclay promoted the formation of C − (A) − S − H, reduced pore space, and densified the interfacial transition zone. These findings elucidate the governing trends in the dynamic response of nanoclay-modified silty clay and provide a basis for the design of nanoclay-modified railway subgrades in Central China.