tone columns are widely used to improve soft ground, and their mechanical behavior is commonly represented by homogenized composite assumptions at the unit-cell level. However, such assumptions are often adopted without sufficient large-scale experimental validation and may not adequately capture the nonuniform load transfer, confinement-dependent friction mobilization, and drainage-sensitive nonlinear response caused by the interaction between a granular column and the surrounding soft clay. To address this issue, a series of large-scale triaxial tests was conducted on stone column-reinforced composite unit cells under static loading. The effects of area replacement ratio, confining pressure, and drainage condition on the stress-strain behavior, peak deviatoric stress, and equivalent shear strength parameters were systematically examined. Based on the test results, a modified Duncan- Chang hyperbolic model was developed, in which the area replacement ratio was explicitly incorporated into the constitutive parameters through experimental calibration. The results show that both the soft soil and the composite unit exhibit strain-hardening behavior, while the reinforced composite develops higher stiffness and strength. The peak deviatoric stress increases approximately linearly with confining pressure and replacement ratio. In addition, the equivalent cohesion changes only slightly after reinforcement, whereas the equivalent friction angle increases significantly, indicating that the strengthening effect is governed mainly by frictional enhancement. The modified model reproduces the measured stress-strain curves with good accuracy, with coefficients of determination generally above 0.90 and relative errors in peak deviatoric stress within about 10% for the tested cases. The proposed framework provides a practical constitutive description for stone column composite unit cells and a useful basis for geotechnical analysis and design.
Key Words
Duncan-Chang model; equivalent shear strength; large-scale triaxial test; stone column; unit cell
Address
Bicheng Du, Yuqi Li, Xu Deng, Xiangrong Li — School of Civil Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
Binhui Ma, Qiunan Chen — School of Civil Engineering, Hunan University of Science and Technology, Xiangtan 411201, China; Hunan Provincial Key Laboratory of Geotechnical Engineering Stability Control and Health Monitoring, Xiangtan 411201, China
Tian Lan — School of Civil Engineering, Hunan University of Science and Technology, Xiangtan 411201, China; National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment, Changsha 410114, China
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