Advances and Innovations in Pavement Technologies and Geomechanics

The special collection on Advances and Innovations in Pavement Technologies and Geomechanics is available in the ASCE Library (https://ascelibrary.org/page/ijgnai/advances_innovations_pavement_technologies).

This special collection contains thirteen technical articles, seven of which address pavement materials and technologies and six of which cover geomaterials and geomechanics.

Among the seven articles dealing with pavement materials and technologies, four articles (Liu et al. 2019; Peng and Bao 2018; Dormohammadi et al. 2019; Yang et al. 2018) focused on numerical analyses, two papers (Cao et al. 2018; Sun et al. 2020) proposed analytical procedures, and one paper (Wang et al. 2019) presented an experimental study. In these numerical analysis articles, three articles (Liu et al. 2019; Peng and Bao 2018; Yang et al. 2018) used discrete-element models, while one article used finite-element models (Dormohammadi et al. 2019).

In the research done by Liu et al. (2019), the authors used discrete-element models to study the virtual sieving analysis of aggregates. The sieve was modeled with three vibration patterns (vertical, horizontal, and hybrid vibrations) to simulate the actual sieving analysis. The authors employed both ideal and realistic aggregate shapes in the simulation and found that the aggregate shapes had a major influence on the simulation results.

Peng and Bao (2018) adopted two-dimensional (2D) and three-dimensional (3D) micromechanical discrete-element models to simulate an indirect tensile test (IDT) of compacted asphalt mixture. They compared the predicted strengths and stresses of the compacted asphalt mixtures using these two models and found that the 3D discrete-element model was better to simulate the behavior of an IDT sample than the 2D model.

Dormohammadi et al. (2019) evaluated the influence of overlay thickness and interface bonding on overlay service life using 3D finite-element models in the software package Abaqus. The authors verified the impact of interface bonding strength on the changes of the overlay durability and structural characteristics of pavements drastically by changing the overlay thickness.

The research work by Yang et al. (2018) aimed to develop and validate a modeling technique to analyze and quantify the aggregate morphology and internal structures of computer-generated microstructural models of asphalt concrete. The researchers used both discrete-element models and finite-element models on the reconstructed microstructure. The potential application of this work is in the modeling of stone-based models.

Cao et al. (2018) evaluated the fatigue resistance of asphalt binders in relation to their composition and established the correlation of the fatigue behavior of asphalt binders with the property of mixtures using the viscoelastic continuum damage (VECD) approach. The authors used recycled asphalt materials and recycled asphalt shingles as well as warm mix asphalt in this study. The data indicated that a reasonable correlation could be identified between the fatigue resistance of asphalt binders and mixtures. The authors proposed a constant depending on the linear viscoelastic and damage properties of a binder and the fatigue-simulation condition as a valid indicator for the fatigue resistance of asphalt binders.

Wang et al. (2019) presented an experimental study on the influence of epoxy grouting reinforcement on the fatigue behavior of cracked cement mortar under different stress ratios and stress levels. The authors studied the fatigue life with the variation of stress level and stress ratio and proposed a damage evolution equation with the data from the lab work.

To accurately separate and obtain the actual irrecoverable and recoverable responses of asphalt binders from the multiple stress creep recovery (MSCR) test, Sun et al. (2020) proposed a procedure of using the full Schapery nonlinear viscoelastic (NLVE) model and the linear viscoelastic properties from the frequency sweep test. Their test results and analysis showed that the proposed procedure could accurately characterize the NLVE and irrecoverable behavior of the neat and polymer-modified binders.

Among six articles on geomaterials and geomechanics, five articles (Han et al. 2017; Hu et al. 2017; Li et al. 2017; Song et al. 2019; Zheng et al. 2018) addressed the problems related to soil–structure interaction and one (Niu et al. 2017) studied the properties of weathered granite soils.

Specifically, Han et al. (2017), Li et al. (2017), and Zheng et al. (2018) investigated different aspects of pile-supported embankments, including soil arching, differential settlement, and serviceability reliability. All these aspects are related to the settlement of the foundation containing piles. Han et al. (2017) examined the two-dimensional trapdoor test data obtained by the authors and available in the literature and found that the soil arching ratio (defined as the ratio of the vertical stress on the trapdoor to the overburden stress) decreased and then increased with the displacement of the trapdoor simulating a soft foundation. In this study, the supports next to the trapdoor were considered rigid to simulate rigid piles. Han et al. (2017) proposed a simplified ground reaction curve to describe the soil arching behavior progressively changing with the displacement of the trapdoor. Han et al. (2017) also found that the soil arching ratio at the normalized displacement (defined as the ratio of trapdoor displacement to trapdoor width) of 10% was approximately equal to that predicted by the Terzaghi (1943) soil arching formula when the lateral earth-pressure coefficient (K) of 1.0 was used. Li et al. (2017) presented a field study to compare the performance of a pile–slab system (referred to as sheet piles in their paper) and Cement Fly-Ash Gravel (CFG) piles for roadway widening. Based on the measurements of settlement plates and horizontal inclinometer tubes, they found that the pile–slab system was more effective at reducing the settlement of the roadway than the CFG piles. Zheng et al. (2018) investigated the load–settlement response of a multicolumn composite foundation (MCF) consisting of soil–cement columns, stone columns, and soil and proposed a formula for estimating the equivalent modulus of the MCF under elastic and/or plastic condition. Based on the spatial variability in the material properties of natural soils and soil–cement columns, Zheng et al. (2018) proposed a reliability-based design for estimating the settlement of the composite foundation under the serviceability limit state. They found that the reliability index of the composite foundation mainly depended on the variability of the soil–cement columns rather than that of the natural soil.

Instead of the pile-supported embankments, Song et al. (2019) adopted a three-dimensional coupled discrete-element method–finite-element method (DEM-FEM) to investigate the ballast–sleeper interaction and the effect of different sleeper types (timber and steel sleepers) on pressure distributions under the sleeper subjected to dynamic loading. In their study, the ballast was modeled as spherical particles using the DEM, while the sleeper was modeled as a continuum medium using the FEM. They compared the numerical results with the experimental data and found similar pressure distribution patterns under both timber and steel sleepers at the large loading level but different distribution patterns at the small loading level. Song et al. (2019) attributed the difference in the pressure distribution pattern to the possible differences in the compaction state and the particle shape between the experimental test and the numerical model. Both the experimental and the numerical results showed the stresses under the sleeper concentrated at the center of the sleeper. Song et al. (2019) also found that the porosity of the ballast under the steel sleeper was lower than that under the timber sleeper at the same location and loading condition.

Hu et al. (2017) presented a 3D finite-element analysis of horizontal ground freezing for shield-driven tunneling. This study examined the feasibility of the use of the horizontal ground-freezing method for large-diameter shield-driven tunneling and the heat transfer within the cup-shaped frozen soil wall formed by different types of soil. They found that ground freezing is most effective in the cement-stabilized sandy soil and least effective in the soft clay. The influence distance of each freezing pipe was approximately 1 m based on typical coolant parameters used in the practice. They concluded that the closure time for the cup-shaped frozen soil wall depended on the thermal physical properties and the in situ water content of the soil.

Niu et al. (2017) conducted a series of laboratory tests including X-ray diffraction, sieving, expansion potential, compaction, California bearing ratio (CBR), and large-scale triaxial tests to evaluate the physical and mechanical properties of weathered granite soils. They found that the weathered granite soil had the largest maximum dry density at approximately 8% clay content, while the maximum CBR value existed at approximately 4% clay content.