Effect of Sustained Loading on the Direct Shear Behaviour of Recycled C&D Material-Geosynthetic Interfaces

Area of Science:

• Geotechnical Engineering
• Materials Science
• Sustainable Construction

Background:

• Recycled construction and demolition (C&D) waste is a potential substitute for traditional backfill in geosynthetic-reinforced structures.
• Limited understanding exists regarding the time-dependent interface behavior between recycled C&D materials and geosynthetic reinforcements.

Purpose of the Study:

• To evaluate the influence of shear creep loading on the direct shear response of interfaces between fine-grained C&D material and geosynthetic reinforcements (geotextile and geogrid).
• To compare interface shear strength parameters under sustained loading with those from conventional tests.

Main Methods:

• Conducted a series of large-scale direct shear tests using an innovative multistage method.
• Applied shear creep loading to interfaces between recycled C&D material and two types of geosynthetic reinforcements.
• Compared peak and large-displacement interface shear strength parameters from sustained loading tests with conventional tests.

Main Results:

• Shear creep deformation increased with sustained loading magnitude.
• Additional vertical contraction occurred during creep, influenced by applied normal stress.
• The C&D material-geotextile interface showed reduced apparent cohesion and a slight friction angle increase under creep.
• The C&D material-geogrid interface exhibited increased apparent cohesion with no significant change in friction angle under creep.

Conclusions:

• Time-dependent behavior under shear creep significantly alters interface shear strength parameters of recycled C&D materials with geosynthetics.
• The specific geosynthetic type influences how creep loading affects interface properties (cohesion and friction angle).
• Findings are crucial for the reliable design and application of geosynthetic-reinforced structures utilizing recycled C&D waste.