Experiment on triaxial shear strength of soft soil in Poyang Lake area
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Abstract:
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.