Reconciling soil-water retention properties and shear strength parameters of compacted clayey soils via suction-controlled ring shear testing

Laureano R Hoyos,Jairo E Yepes,Anand J Puppala,P Delage,A.-M Tang,S Ghabezloo,J.-M Pereira,Y.-J Cui

doi:10.1051/e3sconf/20160909013

Abstract

A preliminary experimental program has been undertaken to assess suction-controlled peak and residual shear strength properties of a statically compacted, moderate plasticity clayey soil. The experimental program was accomplished in a fully servo/suction-controlled ring shear apparatus, suitable for testing unsaturated soils under large deformations via the axis-translation technique. The test results highlight the important role played by matric suction on residual shear strength behaviour of compacted clayey soils. For the range of net normal stresses and suction states investigated, the increase in peak shear strength with increasing suction was found to be significantly nonlinear for the clayey soil. A distinct correspondence was also observed between the nonlinear nature of peak shear strength envelope, with respect to increasing matric suction, and the soil-water retention curve. The residual failure envelope, however, remains reasonably linear for the range of suction values induced in the present work via axis-translation.

Highlights

Background and importanceA vast majority of geotechnical infrastructure made of compacted soil, or resting on unsaturated ground, involves a wide range of deformations
Assessment of residual shear strength parameters at relatively low net normal stresses and suction states, as reflected by the range of experimental variables considered in this work, is of critical importance in slope stability analyses involving potentially shallow failures triggered by rainfall at relatively high degrees of saturation
It is in this context that a suctioncontrolled ring shear (RS) apparatus plays a fundamental role in a thorough characterization of this type of materials

Summary

Background and importance

A vast majority of geotechnical infrastructure made of compacted soil, or resting on unsaturated ground, involves a wide range of deformations. Embankments, and soil bearing capacity, on the other hand, requires good estimations of shear strength from peak to residual. Research efforts have been deterred in the past by the lack of suitable testing tools and techniques. It is in this context that a suctioncontrolled ring shear (RS) apparatus plays a fundamental role in a thorough characterization of this type of materials. 3. A 15-mm (0.59-in) thick specimen is statically compacted directly into a bottom annular platen: Figure 1(b). 4. The vertical load shaft is brought up via a servo controller and the upper annular platen affixed to the top of the piston shaft: Figure 1(c).

Test soil and procedures

Shear strength parameters