Unsaturated Triaxial Testing of Soil

Product Code : UNSAT

GDS Unsaturated Triaxial Testing System (UNSAT) is an extension to traditional triaxial testing, in that soils from above the water table may be tested under conditions approaching the in-situ stress state and degree of saturation or partial saturation. The Stress Dependant Soil Water Characteristic Curve (SDSWCC) may be obtained using the axis translation technique.

All GDS triaxial testing systems (as well as triaxial equipment from other manufacturers*) can be modified to allow for Unsaturated Triaxial Testing. GDS provide options for 4 methods to perform unsaturated testing, each based on alternative methods for measuring  volume change.

  • Method A:  direct volume measurement using an air pressure/volume controller
  • Method B: HKUST inner cell
  • Method C: double walled cell
  • Method D: on-sample strain transducers

White Paper & Case Study:

 

Key features Benefits to the user
Choice of different methods: To suit your testing requirements and budget, see options A, B, C & D on the product datasheet.
Hong Kong University of Science and Technology: Method B has been developed in conjunction with HKUST (Hong Kong University of Science and Technology), who are specialists in unsaturated soil testing.
Mixed and matched: Methods may be ‘mixed and matched’ to create a custom system.
GDS experience: GDS has knowledge of many different unsaturated test methods and can objectively advise customers on the best method for their test requirements. GDS are not limited to a single solution and have currently over 100 unsaturated systems in use.
Accuracy of Volume Measurement

Method A (0.25%), Method B (<0.04% or 32mm3), Method C (<0.25%), Method D (<0.8 or 0.1%).

Sample Sizes

Any size available, constraint is the cell size.

Method A: Items required for Method A UNSAT upgrade
  • Pedestal with bonded HAEPD
  • GDS 2MPa/1000cc air pressure/volume controller
  • GDSLAB 4D UNSAT software module

Optional Items required for Method A upgrade to Method D
  • Local strain (Hall Effect or LVDT)
  • Atmospheric air pressure transducer
  •  Access ring for triaxial cell

Method B: Items required for HKUST UNSAT upgrade
  • HKUST pedestal with bonded HAEPD
  • High accuracy, low range Differential pressure transducer
  • GDSLAB 4D UNSAT software module
  • Dual channel pneumatic controller (laboratory air supply or compressor required)
  • Cell access ring

Method C: Items required for Method C UNSAT upgrade
  • GDS double walled cell
  • Pedestal with bonded HAEPD
  • GDS pressure/volume controllers to suit
  • GDSLAB 4D UNSAT software module

Optional Items required for Method C UNSAT upgrade
  • Local strain (Hall Effect or LVDT)
  • Atmospheric air pressure transducer
  • Access ring for triaxial cell

Method D: On-sample strain transducers
  • Hall Effect 
  • LVDT