Time-Dependent Response of a Recycled C&D Material-Geotextile Interface under Direct Shear Mode

Abstract

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate.

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

“…Although some studies have recently suggested that recycled C&D waste may be used in the construction of geosynthetic-reinforced structures as a sustainable replacement for natural soils or aggregates, the interface behaviour between this alternative backfill and the reinforcement deserves further investigation. The short-term recycled C&D material and geosynthetic interface response under direct shear [ 9 , 21 , 23 , 27 ] and pullout loading conditions [ 9 , 18 ] has been examined in recent studies with satisfactory results. These studies showed that the mechanical behaviour of the interfaces between properly compacted recycled C&D materials and geosynthetics is generally comparable to that of the interfaces with conventional backfills.…”

“…However, during the service life of permanent geosynthetic-reinforced soil systems, time-dependent phenomena (i.e., creep and stress relaxation) are likely to occur, which is why the understanding of the time-dependent response of the geosynthetic and confining material interface is of the utmost importance. Nevertheless, there have been very limited studies on this topic, irrespective of the backfill material type [ 19 , 27 , 28 , 29 , 30 ].…”

“…In a previous related paper, the direct shear response of the interface between a recycled C&D material and a high-strength geotextile during and after a period of shear stress relaxation was evaluated and discussed. It was found that, for the conditions investigated, the effect of stress relaxation on the interface peak and residual shear strength was almost negligible [ 27 ]. The main purpose of this current study is to investigate the shear creep and post-creep behaviour of the interfaces between a recycled C&D material and two different geosynthetic reinforcements (a high-strength geotextile and a geogrid) and to determine whether the application of sustained loading can affect their peak and residual shear strength parameters, which are essential for the design and stability analysis of geosynthetic-reinforced structures.…”

Long-Term Tensile Behavior of a High-Strength Geotextile after Exposure to Recycled Construction and Demolition Materials

“…ORCID: https://orcid.org/0000-0001-6328-4504. Email: cvieira@fe.up.pt the performance of the reinforced structures where they are installed, which is why the assessment of the long-term mechanical properties of geosynthetics is of primary interest when these materials are used in permanent reinforcement applications (Lopes et al 1994;Leshchinsky et al 1997;Li and Rowe 2001;Kongkitkul et al 2007;Bathurst et al 2012;Miyata et al 2014;Ferreira et al 2021). If the durability and long-term behavior of geosynthetics are important factors when conventional backfill materials are used, their assessment becomes even more relevant when alternative (i.e., nonconventional) materials, such as recycled wastes, are considered.…”

Substitute Building Materials in Geogrid-Reinforced Soil Structures

“…The authors found that the geotechnical properties of the CDW met the requirements of an ideal backfill material for RSS. Ferreira et al [13] reported on the results of time-dependent shear tests on CDW materials in connection with an underlying geotextile material. A stress relaxation was discovered in the tests.…”