Large-scale dynamic triaxial tests and dynamic characteristics of clay contaminated round gravel under subway cyclic load

Here, to reveal long-term dynamic characteristics of clay contaminated round gravel under subway cyclic load, a series of saturated undrained dynamic triaxial tests were conducted using GDS large-scale triaxial cyclic testing system. Effects of clay fouling level (VCI) on round gravel long-term dynamic characteristics under different confining pressures and dynamic stress amplitudes were analyzed. Test results showed that with increase in VCI, cumulative plastic strain of samples has a trend of firstly increasing and then decreasing, contaminated clay action changes from lubrication to filling; when confining pressure is 100 kPa, the limit VCI is 30%, and when confining pressure is 200 kPa and 300 kPa, the limit VCI is 20%; VCI for shallow buried subway tunnels (tr3 = 100 kPa) has a larger impact to treat driving safety, while VCI has a smaller impact on deep buried subway tunnels (tr3 = 200 kPa or 300 kPa), and subway operation is relatively safe; with increase in VCI, elastic strain and dynamic pore pressure ratio of samples firstly increase and then decrease, while rebound modulus firstly decreases and then increases, but change trends of the three become more obvious with decrease in confining pressure and increase in dynamic stress amplitude; the study results can provide a reference for design of subway subgrade structures and their post-construction settlement predictions. © 2024 Chinese Vibration Engineering Society. All rights reserved.