Application of a Suction Control System in the Method of Specimen Saturation in Triaxial Tests

A new soil suction control system was developed to saturate soils in triaxial tests. The suction control system was used to reduce the void ratio change during the saturation stage in triaxial tests and to preserve their small-strain behavior. A series of CK₀UAC triaxial tests (K₀ consolidation and undrained axial compression) on Taipei silty clay, saturated with and without suction control, are presented. The results are presented in terms of the stress-strain behavior during consolidation and undrained shearing. Bender element tests were also performed during the K₀-consolidation stage. Results show that the new saturation method with suction control resulted in a better quality soil specimen than conventional saturation. Both the measured Young’s modulus and the shear modulus of the specimens saturated conventionally were underestimated by 20 % and 14 % compared with those saturated with suction control for the reconstituted soil. It is expected that such a difference would be much larger for soils sampled at greater depths. However, the proposed suction control system is not applicable to soil specimens with suctions greater than 100 kPa. The proposed approach would only be applicable for high air-entry value soils so that the suction does not cause desaturation in the soil specimen. Finally, two empirical equations are proposed to estimate the shear modulus of in-situ soils.