To reveal the engineering properties of Zn-contaminated soil solidified with a new cementitious material, namely phosphate rock powder-MgO-cement (PMC), several series of solidified soil characterization tests including moisture content, dry density, pH value, unconfined compressive strength, and stress-strain curve were conducted. The traditional Portland cement was selected for a comparison purpose. The effects of curing time and Zn2 + concentration on these property indexes were investigated to explore the inhibition mechanism of heavy metal Zn2+ on the stabilization process. In addition, the correlations of unconfined compressive strength with three physical property indexes were analyzed. The results indicated that the PMC stabilizer was far superior to the cement for stabilizing Zn-contaminated soil in terms of mechanical properties and environmental impacts. The normalized moisture content of PMC stabilized soil was greater than the cement stabilized soil, indicating a more complete hydration reaction. A small amount of Zn2+ can promote the hydration reaction, but when the Zn2+ concentration exceeded 0.5 %, the hydration reaction was significantly hindered. The dry density of PMC stabilized soil was about 6 % more than cement stabilized soil under the same conditions. The pH values of PMC stabilized samples were much lower than the cement stabilized soil samples and distributed in 8.0-9.5. The stress-strain characteristic of PMC stabilized soil was softening type and the heavy metal Zn2+ was solidified by adsorption, which could make the stress-strain curve of cement stabilized sample change from brittle type to ductile type.

This study presents a new experimental procedure for evaluating the durability of stabilized soils subjected to multiple wetting and drying (W-D) cycles. An integrated experimental program combining dynamic shear rheometer (DSR) testing with W-D cycles was designed and implemented to assess moisture-induced performance degradation in natural sand stabilized with two types of rapid-setting cementitious stabilizers. Small cylindrical specimens (10.5 mm in diameter and 35.0 mm in height) of stabilized sand mixes were compacted, cured, and subjected to up to seven W-D cycles. Each W-D cycle was meticulously controlled to gauge its impact on the material's durability. The mechanical properties of the stabilized samples were evaluated at different stages of the W-D cycles using the strain-sweep DSR testing based on a methodology developed from preliminary work. The proposed test method focuses on the shear properties of the material, measuring its mechanical response under the torsional loading of a cylindrical sample and providing dynamic mechanical properties and fatigue-resistance characteristics of the stabilized soils under cyclic loading. Test results demonstrate water-induced deterioration of stiffness and reduced resistance to cyclic loading with good testing repeatability, efficiency, and material-specific sensitivity. By combining dynamic mechanical characterization with durability assessment, the new testing method provides a high potential as a simple, scientific, and efficient method for assessing, engineering, and developing stabilized soils, which will enable more resilient transportation infrastructure systems.

Almost all of the existing testing methods to determine elastic modulus of the soil or aggregate for pavement design involve the application of repetitive loads applied at a single point. This approach falls short of representing the conditions that are observed when the wheel of a vehicle rolls over the surface. This study presents a new methodology, in which light weight deflectometer (LWD) is used to apply three adjacent sequential loads repetitively to replicate a multipoint loading of the surface. The elastic modulus values obtained from these multipoint LWD tests were compared against the repetitive single point LWD test results. The multipoint LWD test elastic modulus values were consistently lower than the values obtained from the single point LWD tests. The single point LWD tests showed an increase in elastic modulus with increased load repetition. The multipoint LWD results did not show an increase in the elastic modulus as a function of repetitive loading. This study showed that damping ratio values provide guidance to explain differences in the elastic modulus with an increased number of load repetitions. In repetitive single point tests, the applied load caused initial compaction, and in multipoint LWD tests, it caused disturbance in the ground. With increased load cycles, the ground reached a stabilized condition in both tests. The methodology presented in this study appeared to minimize the unintended compaction of the ground during the single point LWD tests to determine the elastic modulus.

This study demonstrates the feasibility of utilizing machine learning (ML) for routine identification of sand particles. Identifying different types of sand is necessary for various geotechnical exploration projects because understanding the specific sand type plays an important role in estimating the physical and mechanical properties of the soil. To accomplish this, dynamic image analysis was employed to generate a substantial volume of sand particle images. Individual size and shape descriptors were automatically extracted from each particle image. The analysis involved use of 40,000 binary particle images representing 20 different sand types, and a corresponding six size and four shape descriptors for each particle (400,000 parameters). Six ML models were trained and tested. The work demonstrates that using size and shape features the models efficiently identified up to 49% of individual sand particles. However, when clusters of particles were considered in conjunction with a voting algorithm, classification accuracy significantly improved to 90%. Among the ML models studied, neural networks performed the best, while decision tree exhibited the lowest accuracy. Finally, the use of size consistently outperformed shape as a classification parameter but combining size and shape parameters yielded superior results across all sands and classifiers. These findings suggest that ML holds much promise for automating sand classification using ordinary images.

This study describes the full-scale traffic evaluation of a prototype submersible matting system (SUBMAT) at a test site on the U.S. Army Engineer Research and Development Center's campus in Vicksburg, MS. The SUBMAT prototype was designed to bridge the gap between high- and low-tide at a beach interface to enable 24-h vehicle offloading operations at an expeditionary watercraft landing site. This unique system is made from common geotextile materials, is filled with indigenous sand using simple commercially available pumps, and creates a robust driving surface. The results of the study showed that the SUBMAT system was able to sustain an accumulation of 1,000 Medium Tactical Vehicle Replacement, 350 Heavy Expanded Mobility Tactical Truck, and over 150 M1A1 main battle tank passes without experiencing any significant damage. The ease of deployment, relatively low cost, and trafficability results could make the SUBMAT a suitable candidate for expedient low-volume roads in austere environments such as stream beds, low-water crossings, recently flooded or flood prone areas, and areas with weak soil.

In cold regions, the soil temperature gradient and depth of frost penetration can significantly affect roadway performance because of frost heave and thaw settlement of the subgrade soils. The severity of the damage depends on the soil index properties, temperature, and availability of water. While nominal expansion occurs with the phase change from pore water to ice, heaving is derived primarily from a continuous flow of water from the vadose zone to growing ice lenses. The temperature gradient within the soil influences water migration toward the freezing front, where ice nucleates, coalesces into lenses, and grows. This study evaluates the frost heave potential of frost-susceptible soils from Iowa (IA-PC) and North Carolina (NC-BO) under different temperature gradients. One-dimensional frost heave tests were conducted with a free water supply under three different temperature gradients of 0.26 degrees C/cm, 0.52 degrees C/cm, and 0.78 degrees C/cm. Time-dependent measurements of frost penetration, water intake, and frost heave were carried out. Results of the study suggested that frost heave and water intake are functions of the temperature gradient within the soil. A lower temperature gradient of 0.26 degrees C/cm leads to the maximum total heave of 18.28 mm (IA-PC) and 38.27 mm (NC-BO) for extended periods of freezing. The maximum frost penetration rate of 16.47 mm/hour was observed for a higher temperature gradient of 0.78 degrees C/cm and soil with higher thermal diffusivity of 0.684 mm(2)/s. The results of this study can be used to validate numerical models and develop engineered solutions that prevent frost damage.

Triaxial tests has been routinely used to measure the stress-strain relationship for geomaterials. During triaxial testing, many sources of errors that cannot be completely avoided but are often ignored or approximated using empirical equations. This paper presents a systematic investigation of soil volume change, volume strain nonuniformity, and cross-sectional calculation along the specimen during triaxial testing using a photogrammetry-based method. Consolidated drained triaxial tests were performed in which two parallel measurements were taken: (1) relative volume using the conventional triaxial testing and (2) absolute volume using the photogrammetry-based method. The difference in the observed volume and void ratio measurements between the two methods highlighted the importance of absolute soil volume over the relative volume method. The results revealed the effect of soil volume change in the interpretation of triaxial testing findings. Various preparation steps and procedures during triaxial testing have influenced the initial measured volume and thus caused deviation of the subsequent associated measurements. This method would present a quality control approach for different aspects of triaxial testing to improve the test simulations to accurately measure the soil behavior. The proposed method is important for more refined simulations and identification of setup-induced errors. Additional applications of the current research would allow correct determination of the stress path followed during triaxial testing, the critical-state soil mechanics parameters, and the stress-strain relationship, including deformation and strength parameters.

This paper presents a study of the hydraulic response of an infinite unsaturated slope exposed to a perturbation of the ordinary seasonal climatic cycle. The ground flow is modelled via a simplified one-dimensional finite difference scheme by decomposing the two-dimensional slope seepage into antisymmetric and symmetric parts. The numerical scheme incorporates two distinct hysteretic and non-hysteretic soil water retention laws, whose parameters have been selected after a preliminary sensitivity analysis. Results indicate that, in the hysteretic case, the memory of the perturbation takes a long time to fade, and the ordinary soil saturation cycle is only restored after several years of normal weather. Instead, in the non-hysteretic case, the recovery of the ordinary saturation regime is almost immediate after the perturbation. In contrast with the markedly different predictions of degree of saturation, both hysteretic and non-hysteretic slope models predict virtually identical evolutions of negative pore water pressures, with an almost immediate restoration of the ordinary cycle after the perturbation.

This paper focuses on evaluating the increase in axial pile resistance subjected to both consolidation and aging setups. Consolidation and aging setup models were first developed to estimate the setup parameters based on databases collected from literature, which include 10 instrumented piles for consolidation setup and 26 test piles for long-term aging. The eight top-performing pile cone penetration test (CPT) methods that were evaluated in a previous study were used to estimate the side resistance of soil layers at 14 days after pile driving. The developed consolidation and aging setup models were then used to extrapolate the results to evaluate the side resistance of each soil layer at the end of consolidation and for long-term aging. The estimated side and total resistances were compared with the measurements from pile load tests considering both consolidation and aging setups. The resistances estimated before and after completion of excess pore water pressure dissipation indicates that significant aging takes place after consolidation setup. The value of consolidation setup parameter (Ac) was 0.53, and, for aging, the setup parameter (Ag) was 0.23 in clay and 0.16 in sand. The results show that all pile CPT methods with/without using a consolidation setup model tend to underestimate the unit side resistance of clay soil layers. The use of pile CPT methods in combination with an aging model improved the accuracy of pile CPT methods, and this was verified using load test results for five piles subjected to aging. The Philipponnat and University of Florida (UF) methods showed the best performance on estimating the total resistance of piles subjected to aging.

Streambed scour in cohesive sediment is complex because erosion processes depend on the physical, geochemical, and biological properties of the sediment. The scouring processes can also be characterized as a slow fatigue phenomenon. Therefore, repetitive hydraulic loadings from multiple stormflow events are likely necessary for equilibrium scour depths to develop in cohesive sediment compared with non-cohesive sediment. Cumulative effective stream power, which is a surrogate measure of effective stream power duration, showed a significant relation with scour development and propagation in cohesive sediments around bridge piers, where results from this study identified a statistically significant correlation between cumulative effective stream power and the observed scour depths around different bridge piers (R-2 = 0.56, p < 0.001). However, some localized and site-specific variations were observed. It was also observed that scour depth development in cohesive soil appeared to be dependent on effective shear duration, rather than the number of flow events above erosion threshold values. In addition, the relationship between an erodibility index (K) and critical stream power showed a significant statistical correlation (R-2 = 0.61, p = 0.017). Results from this study deviated from the Annandale empirical relationship for sediments when K < 0.1. This finding supports that site-specific critical stream power should be measured using an empirical relationship for cohesive bed sediments to predict scour depths.