Abstract：The stress-strain relationship of soils under confining conditions is hyperbolic. In this case, secant modulus can be adopted to calculate the vertical strain of soils, which is helpful to realize the settlement calculation. The secant modulus of the soil around stone columns was determined according to the relationship between the secant modulus and the compression index and compression modulus. The column-soil stress ratio considering the nonlinear compressibility of soils was proposed based on the assumption of equal strain, and the improved stress correction method and composite modulus method for nonlinear settlement calculation of composite foundations with stone columns were further provided. The two improved methods for the settlement calculation were verified by the model test and actual project. The results show that for the laboratory model test, the differences between the measured results and the calculated results by the improved composite modulus method and modified stress correction method are less than 1.00 mm, which indicates that the improved method for settlement calculation is reliable. For the actual project, the error between the improved composite modulus method and the measured results is 8.70%, which is less than the specified error of 55.06% by the composite modulus method in the JGJ 79—2012 . The error between the improved stress correction method and the measured results is 8.73%, which is less than the specified error of 55.11% by the stress correction method in the JGJ 79—2012. The comparative analysis shows that the improved settlement calculation method is better than the composite modulus method and stress correction method in the JGJ 79—2012, and the calculated results by the improved method are closer to the measurement results, which indicates that the improved method has better reliability and applicability.
李传勋， 刘聪. 基于割线模量的散体材料桩复合地基沉降计算[J]. 江苏大学学报（自然科学版）, 2024, 45(4): 482-489.
LI Chuanxun, LIU Cong. Settlement calculation of stone columns-improved composite foundation based on secant modulus[J]. Journal of Jiangsu University(Natural Science Eidtion)
, 2024, 45(4): 482-489.
WEI R L.A new method for sorting and compressing test data[J]. Journal of Nanjing Hydraulic Research Institute，1980,11(3):90-93.（in Chinese）
［2］
杨光华. 现代地基设计理论的创新与发展[J].岩土工程学报，2021,43(1):1-18.
YANG G H. Innovation and development of modern theo-ries for foundation design[J]. Chinese Journal of Geotechnical Engineering, 2021,43(1):1-18.（in Chinese）
KONG Y, RUAN H N, HUANG X F. Method for calculating foundation settlement of compacted backfill in hilly and gully regions of loess[J]. Chinese Journal of Geotechnical Engineering, 2018,40(Sup1):218-223.（in Chinese）
YANG J, BAI X H. Nonlinear compression stress-strain relationship of compacted loess and its application to calculation of foundation settlement[J]. Rock and Soil Mechanics, 2015,36(4):1002-1008.（in Chinese）
WANG W, ZAI J M, LU T H. Analysis on hyperbolic model and exponential model for post-construction settlement of soft soil[J]. Journal of Jiangsu University (Na-tural Science Edition), 2008,29(2):173-176.（in Chinese）
LIU B J, ZHANG J L. Application and analysing method for soil compression test[J]. China Journal of Highway and Transport, 1999,12(1):37-41,100.（in Chinese）
［7］
李广信，张丙印，于玉贞. 土力学[M].3版.北京: 清华大学出版社，2022.
［8］
HOSSEINPOUR I, ALMEIDA M S S, RICCIO M. Full-scale load test and finite-element analysis of soft ground improved by geotextile-encased granular columns[J]. Geosynthetics International, 2015,22(6):428-438.
YAO B K, LIU C, LI Q J, et al. Application of vacuum well point dewatering and sand compaction pile combined with dynamic compaction method in soft foundation treatment[J].Journal of Ground Improvement, 2021,3(2):118-125.（in Chinese）
ZHANG L, ZHANG X B, XU Z Y, et al. Stress and deformation analysis of geosynthetic-encased stone columns based on symplectic system[J]. Chinese Journal of Geotechnical Engineering, 2020,42(11):2040-2049.（in Chinese）
SUN L N, GONG X N. Research on settlement calculation method of composite foundation of discrete material piles[J]. Rock and Soil Mechanics, 2008,29(3):846-848.（in Chinese）
ZHANG L, ZHAO M H. Settlement calculation of granular material pile composite foundation with consideration of lateral bulging[J]. Journal of Hunan University (Nature Science), 2016,43(5):120-124.（in Chinese）
YU Z, ZHANG Y C, ZHANG Y P. Test study on vibro replacement stone columns to improve soft soil foundation[J]. Journal of Chongqing Jianzhu University, 2007,29(6):57-61.（in Chinese）
CAO W G, LIU H T, ZHANG Y J. A new pile-soil stress ratio calculation method of composite foundation with friable material piles[J].Journal of Hunan University (Nature Science), 2009,36(7):1-5.（in Chinese）
［15］
徐龙飞. 黄土地区复合地基承载机理室内模型试验研究[D]. 西安：西北农林科技大学，2014.
［16］
HOSSEINPOUR I, RICCIO M, AIMEIDA M S S. Numerical evaluation of a granular column reinforced by geosynthetics using encasement and laminated disks[J]. Geotextiles and Geomembranes, 2014,42:363-373.
