为研究复杂应力条件下湖相软土的力学性质及破坏规律, 对鄱阳湖区典型软土进行等加载速率( 0.01 mm/ min) 下, 基质吸力分别为 0.50、100、200 kPa, 净围压为 100、200、300 kPa 的标准应力途径 GDS 三轴剪切试验, 得到湖相软土的三轴剪切应力-应变曲线、基质吸力与偏应力的关系、围压与偏应力的关系, 并根据Fredlund 双应力变量强度理论分析鄱阳湖区软土在不同基质吸力、不同围压下的土体抗剪强度变化规律。结果表明: 在相同基质吸力条件 下, 鄱阳湖区软土非饱和强度在低应变范围内( < 8% ) , 抗剪强度随着应变的快速增加, 在高应变范围内, 强度增速放缓; 在相同围压条件下, 强度与吸力基本呈正相关线性关系, 其基质吸力相关角为 6.6°, 处于低吸力范围内; 在 4 种基质吸力条件下, 其内摩擦角的范围为 21. 8°~ 26. 2°, 总黏聚力范围为 16. 7~ 44. 4 kPa。结合双应力变量强度理论, 提出鄱阳湖区湖相土的抗强度理论公式。

In order to study the mechanical properties and failure laws of lacustrine soft soil under complex stress conditions, constant loading rate ( 0.01 mm/ min) GDS triaxial shear tests were carried out for typical soft soil in Poyang lake area at four matrix suctions ( 0, 50, 100 and 200 kPa) and three net confining pressures ( 100, 200 and 300 kPa) . Triaxial shear stress and stra in curves of lacustrine soft soil, the relationship between matrix suction and deviatoric stress, and the relationship between co nfining pressure and deviatoric stress were obtained. The shear strength of Poyang lake soft soil under different matrix suction and confining pressure was analyzed based on Fredlund’s two-stress variable strength theory of unsaturated soil. The results show that under the same mat rix suction condition, the shear strength increased rapidly with the strain when the unsaturated strength of Poyang lake soft soil was in the low strain range( < 8% ) , but the strength growth slow down in the high strain range. Under the same confining pressure condition, the intensity was positively related with to the suction basic linear r elationship, and the related matrix suction angle was 6.6° which was within the low suction range. Under the condition of four kinds of matrix suction, the scope of its internal friction angle was a range from 21.8° to 26.2°. The total cohesive force range was 16. 7~ 44. 4 kPa. Combined with the strength theory of the double stress variable, the strength theory formula of lacustrine soil in the Poy-ang lake area was proposed.

江西省水利科技项目( KT 201635) ; 江西省科技厅第一批科技计划项目( 20161BBG70051 ) ; 江西省教育厅科技研究项目 (GJJ151124) ; 国家自然科学基金项目( 4164102)