Laponite has emerged as a particularly promising material for use as a soft clay surrogate in geotechnical modeling, as it provides a relevant range of transparency, plasticity, and overall geotechnical behavior. This paper presents an investigation of the significant factors affecting the transparency of laponite for its use in physical geotechnical models. Image analysis techniques and complementary optical tests were conducted to gain an understanding of the factors causing changes in optical clarity. Aging time, laponite content, and rheological additive dosage were found to be the most significant factors affecting the transparency of laponite. Specifically, the ratio between the rheological additive dosage and laponite content (additive mass ratio) was found to serve as a relevant index to define the material’s optical behavior, and its use facilitated the determination of the optimum laponite and additive contents. The presence of inclusions within the internal laponite structure, such as trapped air pockets and unhydrated laponite crystals, identified as the key factor compromising optical clarity, could be ultimately associated with the selection of insufficient dosages of rheological additive. Overall, laponite was identified as a viable surrogate of natural clays suitable for models requiring comparatively large in-depth visualization.

The use of so-called “transparent soils” as proxy geotechnical materials has allowed for the nonintrusive observation of a variety of models representing different engineered systems. Laponite is one such soft clay surrogate that has seen increased usage in recent years. However, this material has yet to be subjected to a thorough characterization and quantification of its physical and mechanical properties. The study presented herein followed a systematic approach toward the characterization of Laponite RD colloids from a geotechnical perspective across a wide range of mixes and additive dosages. Rheology tests were conducted to study the variation in apparent viscosity with time and after remixing. These tests identified two sources/types of strength gain: a reversible thixotropic strength gain and an irreversible particle aggregation strength gain. Different mixtures tested in a one-dimensional consolidation oedometer showed that mixes with laponite colloid contents as high as 21 % could be achieved from mixes with an initial colloid content of 11 % by mass. Finally, results from vane shear tests showed that the undrained shear strength increased with: (1) increasing laponite colloid content, (2) decreasing additive dosage, (3) aging time, and (4) increasing temperature. The base geotechnical characteristics and mechanical properties of the clay surrogate as provided in this study are expected to facilitate proper interpretation of the behavior of this surrogate material in geotechnical physical models involving transparent clays.

Geomaterials comprise naturally formed materials through geological processes, such as soils and rocks, or artificially processed materials, including mineral waste and geosynthetics. These materials find extensive use in geotechnical structures, such as slopes, dams, and pavements, among others. However, two issues commonly arise in earthworks: the materials available in the region do not meet the minimum engineering requirements, resulting in high transportation costs, and the exploitation of new deposits increases environmental impacts. Consequently, there is a need to develop stabilization and reinforcement techniques aimed at creating new geomaterials (NGs) to expand the range of local material applications. In this context, the present study evaluates the key success factors (KSFs) related to the application of NGs in geotechnical structures. The Delphi method was employed through a structured questionnaire developed after an extensive literature review. Brazilian experts from the public, private, and academic sectors were selected to identify the obstacles and potential pathways for the practical application of NGs. The outcomes of the study indicated that the lack of standardization, the complex behavior of geomaterials under varying conditions, as well as technical and economic limitations serve as barriers impeding the widespread adoption of NGs. Finally, a roadmap proposal was devised, encompassing a series of actions intended to facilitate the broader utilization of NGs.

This article assesses the pullout performance of ribbed metallic strips embedded in fill soils that do not conform to conventional design criteria for mechanically stabilized earth (MSE) walls. These alternative fill soils include gravelly and sandy recycled aggregates from construction and demolition waste, artificial and natural sands, and fine-grained lateritic soil. The research included soil characterization tests and large-scale pullout tests, conducted as part of this study. The results showed that the reinforcement pullout behavior was similar for recycled, artificial, and natural sands, indicating that soil particle size played a crucial role in mobilizing the interface pullout resistance. However, in the case of recycled sand, stress concentration at the reinforcement level led to particle crushing during pullout conditions, causing this material to exhibit less efficient performance compared to other sands. The fine-grained lateritic soil demonstrated inferior behavior compared to sandy soils, despite the interparticle bonding provided by the sesquioxide coating characteristic of intensely weathered tropical soils. Finally, an analytical prediction tool based on experimental results was developed, providing an alternative method to make conjectures about the performance of different soils during the pre-design stages, particularly based on particle size attributes.