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Development of pavement design over the past decades has focused on moving from empirical design equations to more powerful and adaptive design schemes. The AASHTO mechanistic–empirical pavement design guide (MEPDG) has been developed to model pavement structure and predict its service life more accurately. Although MEPDG has been widely implemented to design conventional pavement, it is not yet capable of predicting the service life of pavement reinforced with geosynthetics. Given the above concerns, seven full-scale test sections that were constructed at Louisiana Transportation Research Center-Pavement Research Facility (LTRC-PRF) were devoted to a structural experiment to investigate the performance of geosynthetic reinforced pavements. The benefits of using geosynthetics to enhance the performance of pavements constructed over soft subgrades was evaluated using cyclic plate load testing. Cyclic load at a frequency of 0.77 Hz was applied through a 305 mm diameter steel plate. The test results clearly show the benefits of geosynthetics in significantly reducing pavement rutting. The test section with double geosynthetic layers performed better than the other six sections studied. After eliminating the effect of variations in construction, the benefits of geosynthetic reinforcement are quantified within the context of the AASHTOWare Pavement ME Design Guide. The developed design procedure is capable of quantifying the contribution of geosynthetics in pavements to base reinforcement as well as subgrade stabilization. A design methodology is proposed that falls within the context of MEPDG.

The approach slab is constructed at bridge ends to serve as a smooth transition from the highway pavement to the bridge deck. However, motorists usually complain about a sudden change in elevation (bump) at the highway/approach slab (H/S) joint that causes a potential hazard for public safety, damage to vehicles, and rider discomfort. This paper develops a finite element (FE) analysis for the differential settlement at the H/S joint when supported by a strip footing that sits on compacted layers of soil embankment with uniaxial geogrid reinforcement. A parametric study was conducted to select the optimum design that consists of five geogrid layers equally spaced within a depth of 2 [Formula: see text] below the strip footing, where [Formula: see text] is the width of the footing. The inclusion of geogrid reinforcement did not only enhance the ultimate bearing stress of the strip footing but also redistributed the vertical loads over a wider region of soil embankment and thus reduced settlement. A case study is also presented for modeling the performance of a preliminary design proposed by Tennessee Department of Transportation (TDOT) for the retrofit of bridge ends. The FE analysis showed a 30%–40% improvement in the ultimate bearing stress of the strip footing when the geogrid reinforcement proposed by TDOT is extended to a depth of 1.5 [Formula: see text] below the footing.

Several approaches have been developed to estimate the ultimate capacity of piles, such as static and dynamic load tests, static analysis from soil borings, and directly utilizing in-situ test results. Recently, there has been increased interest in using in-situ cone penetration test (CPT) to estimate pile capacity. Several analytical pile-CPT methods have been developed, which involve several correlation assumptions that can affect their accuracy. In this paper, three tree-based machine learning (ML) models, namely decision tree (DT), random forest (RF), and gradient boosted tree (GBT), are developed for estimating the ultimate capacity of piles from CPT data. A database that contains 80 pile load tests and associated CPT data collected in Louisiana was used to develop these ML models. The measured ultimate pile capacity (Qm) was determined using Davisson’s interpretation method from the load–settlement curve of each pile load test. Among the developed ML models, GBT demonstrated the most accurate ML model compared with the others. The estimation of ultimate pile capacity from the GBT model is compared with those obtained from the four best-performing direct pile-CPT methods (based on a previous study): the University of Florida (UF), probabilistic, European Regional Technical Committee 3 (ERTC3), and Laboratoire Central des Ponts et Chaussées (LCPC) methods. The GBT and pile-CPT methods were evaluated and ranked based on analysis of multiple statistical criteria. The results clearly showed that the GBT model outperforms the four direct pile-CPT methods for estimating the ultimate capacity of piles.

Geosynthetic-reinforced pile-supported (GRPS) embankments are widely used in soft soil regions to support roadways. Various design methods for GRPS embankments have been developed; however, engineering experience and recent research have shown that the performance of these design methods varies case by case. This paper systematically evaluates the performance of several empirical GRPS embankment design methods, which include the BS8006 method, the Nordic method, the EBGEO method, the FHWA method, and the CUR226 method. A preliminary assessment of these methods using three field case studies confirms that their performances differ from each other and from field measurements, the differences sometimes being quite significant. To enable a more systematic evaluation of the design methods, a validated finite element model (FEM) was first used to conduct a comprehensive parametric study considering typical soft soil conditions and various geometrical parameters, the results of which served as a baseline for the evaluation of the design methods. The efficacy, stress concentration ratio, maximum differential settlement, and maximum reinforcement tension were used as indicators for the method evaluation. The results show that, overall, the CUR226 method outperforms other design methods. The percentage difference between the CUR226 method and FEM can be as small as 5%, and the maximum value is 130%. It was also found that the Nordic method does not apply to small embankment heights, and that the BS8006 method provides a large overestimation of reinforcement tension when pile spacing is large (>4 ft) for all embankment heights considered.

In geotechnical design practices, the undrained shear strength of soil is regarded as one of the engineering properties of paramount importance. Over the past years, several theoretical and empirical methods have been developed to estimate the undrained shear strength based on soil properties using in-situ tests such as cone and piezocone penetration tests (CPT and PCPT). However, most of these methods involve correlation assumptions that can result in inconsistent accuracy. In this paper, an artificial neural network (ANN) is used to devise a model with a better and more consistent prediction of the undrained shear strength of soil from CPT data. The ANN algorithm does not require such assumptions as it learns from previous cases/instances. A database was prepared of soil boring data and laboratory test data along with corresponding CPT/PCPT data from 70 test sites located in 14 different parishes in Louisiana. Presenting this data to the ANN, models were trained through trial and error using different network algorithms, such as back propagation method and quasi-Newton method. Different ANN models were trained using corrected cone tip resistance and sleeve friction input data along with some other easily measurable soil properties. The results of ANN models were then compared with a conventional empirical method of determining undrained shear strength of soil from CPT parameters. The results of this study clearly demonstrated that the ANN models outperformed the conventional empirical method, which confirms the applicability of ANN in the evaluation of the undrained shear strength of soil from CPT data.

The cone and piezocone penetration tests (CPT, PCPT) have been widely acknowledged as useful in-situ testing tools for subsurface investigation, characterization of soil type, and evaluation of different soil properties. Because of similarity between the cone and pile, the evaluation of axial pile capacity was one of initial applications of the CPT/PCPT. A previous study conducted by the authors on 80 pile load tests of precast prestressed concrete (PPC) piles demonstrated that some pile-CPT methods are able to predict the ultimate axial pile capacity with better accuracy than other methods. These methods include: Schmertmann, De Ruiter and Beringen, Laboratoire Central des Ponts et Chaussées (LCPC), European Regional Technical Committee 3 (ERTC3), University of Western Australia (UWA), probabilistic, and University of Florida (UF) methods. The results of these seven pile-CPT methods were compared and their performance was examined for different soil categories where different percentages of pile capacity contribution is because of sandy layers. The log-normal distribution of the estimated to measured pile capacity for these pile-CPT methods was adopted to develop combined pile-CPT methods that optimize the estimation accuracy of axial pile capacity in different soil categories. Reliability analysis using Monte Carlo Simulation (MCS) was used to evaluate the resistance factors ( ϕ) and efficiency ( ϕ/ λR) of the individual and combined pile-CPT methods. Results of analysis of 80 pile load tests demonstrated the advantage of using the combined pile-CPT methods over the individual methods in relation to improving the accuracy of estimating the ultimate axial pile capacity and having better resistance factors.

Cone and piezocone penetration tests (CPT, PCPT) are widely acknowledged to be useful and powerful in-situ tests for soil classification and characterization, and for evaluating different soil properties, such as strength and consolidation parameters. Due to similarity, between the cone and the pile penetration, CPT data have been used effectively for estimating ultimate pile capacity. Researchers have developed various direct CPT methods to estimate the ultimate capacity of piles ( Qp) from CPT/PCPT data (tip resistance and sleeve friction) with depth. In this study, the measured ultimate pile capacities ( Qp) obtained from static load tests on 80 square precast prestressed concrete piles in Louisiana were used to evaluate 18 direct pile-CPT methods for estimating ultimate pile capacity. Two approaches were used. In the first approach, three criteria (best fit line, arithmetic mean and standard deviation, and cumulative probability of Qp/Qm) were adopted, and the sum of ranking of all criteria was used to determine the final ranking of each method. A second approach, multidimensional unfolding, was used to display the ranking data in a two-dimensional space. This approach helps to reveal the typical ranking of the pile-CPT methods, the extent of agreement between the piles, the existence of outliers among the piles, and the similarity between the CPT methods. Based on the results of this study, Bustamante and Gianeselli (LCPC), probabilistic, UF, Philipponnat, CPT2000, UWA, De Ruiter and Beringen, and Schmertmann were found to be the best CPT methods (in order) for estimating the ultimate pile capacity of driven PPC piles.

This paper presents the results from a pile load testing program for a bridge construction project at Chalmette, Louisiana. The load testing includes three 66-in. spun-cast post-tensioned open-ended cylinder piles and one 30-in. square prestressed concrete (PSC) pile driven at four different locations along the bridge site in clayey-dominant soil. Both cone penetration tests and soil borings/laboratory testing were used to characterize the subsurface soil conditions. All test piles (TP) were instrumented with strain gauges to measure the load distribution along the length of the TPs and to measure the side and tip resistances, separately. Dynamic load tests (DLT) were performed on all TPs at different waiting periods after pile installations to quantify the amount of setup (i.e., increase in pile resistance with time). Case Pile Wave Analysis Program (CAPWAP®) analyses were performed on the DLT data to calculate the resistance distributions along the TPs. A static load test was performed only on the PSC pile and statnamic load tests (SNLT) were conducted on both pile types. Design parameters such as the total stress adhesion factor, α, and the effective stress coefficient, β, were back-calculated. The α values ranged from 0.41 to 0.86, and the β values ranged from 0.13 to 0.29. The load test results showed that SNLT overestimated the tip resistance as compared with dynamic and static load tests. Moreover, the pile tip resistance was almost constant during the testing period, and setup was mainly attributed to increase in pile side resistance with time.

Results are presented of Osterberg cell load tests (OCLTs) that were performed over a 2-year period to measure setup (increase in pile resistance with time) on a 30-in. prestressed concrete test pile at the Bayou Boeuf Bridge site in Louisiana. The test pile was instrumented with vibrating wire strain gauges to evaluate the load distribution along the pile length during the OCLTs. An Osterberg cell was installed at the tip of the pile. A series of dynamic load tests and five OCLTs was performed to measure the amount of setup from end of driving over a 2-year period. The load test results showed that setup was attributed mainly to the increase in side resistance with time, while the tip resistance remained almost constant. In this study, setup was analyzed for individual soil layers instead of total pile resistance; hence the effect of soil properties on setup behavior was evaluated. This long-duration setup study demonstrated the effect of consolidation and aging on setup behavior. The side resistance increased by 380% compared with the end-of-driving side resistance over the 2 years. The study showed that the long-term pile side resistance was 28% higher than the 14-day pile side resistance. A cost analysis was performed to determine the potential savings of including pile setup in the project. With use of long-term pile resistance, a 13% reduction in pile length for 566 piles could be made, yielding a cost savings of about $600,000.

This paper analyzes the results of 15 instrumented prestressed concrete test piles that were driven in four sites in Louisiana as part of a pile setup study. Static and dynamic load tests were conducted at specific time intervals to quantify the amount of setup after the end of driving. Laboratory and in situ soil investigations, such as the Piezocone penetration test (PCPT), were conducted at each test pile location to evaluate the subsurface soil condition. Vibrating wire strain gauges were installed in pairs in all instrumented test piles to measure the load transfer and increase in side resistance of individual soil layers over time. The load test results showed that setup followed a linear logarithmic trend. The unit side resistance, instead of the total pile resistance, was used to measure the logarithmic setup parameter A for individual soil layers along the pile lengths. Observations from the test results showed that the average A values for clayey and sandy soil layers for the four tested sites were 0.31 and 0.15, respectively. Analyses of the setup of individual soil layers showed that the parameter A decreases with increased corrected cone tip resistance measured by PCPT. A simple linear regression model is proposed to predict the side resistance setup for individual soil layers by correlating the setup parameter A with the corrected cone tip resistance.

Over time, piles driven in cohesive soils usually experience a large increase in resistance, known as setup or freeze. Dynamic load tests (DLT) and static load tests (SLT) are usually performed to verify the axial resistances of piles at specific times after end of driving (EOD) and to quantify these resistances. An extensive field testing program was performed on full-scale instrumented precast prestressed concrete piles driven in cohesive soils at the Bayou Lacassine Bridge in Louisiana, to evaluate the pile setup phenomenon. The testing program included instrumenting two full-scale test piles with a network of vibrating wire strain gauges, pressure cells, and piezometers and instrumenting the surrounding soils with multilevel piezometers. Five SLTs and three DLTs were conducted on each test pile at different times after EOD to quantify the magnitude of setup. Measurements from the load tests on both piles confirmed that the pile setup after EOD followed a logarithmic rate with time. An increase in pile...

The behavior of foundations on geosynthetic-reinforced clayey soil of low to medium plasticity using laboratory model footing tests was investigated. The model footing was made of a steel plate with dimensions of 152 mm (6 in.) × 152 mm (6 in.). The parameters investigated in this study included the top layer spacing, the number of reinforcement layers, the vertical spacing between layers, and the stiffness and type of reinforcement. The effect of reinforcement on the vertical stress distribution in the clay and the strain distribution along the reinforcement were also investigated. The test results showed that the inclusion of reinforcement could significantly improve the soil's bearing capacity and reduce the footing settlement. With three or more layers of reinforcement, the settlement could be reduced by approximately 50% at a relatively medium surface pressure. The geogrids with higher stiffness performed better than geogrids with lower stiffness. The test results also showed that the induced vertical stresses in clay under the center of footing could be appreciably reduced with the inclusion of reinforcement, which would result in reducing the consolidation settlement. Insignificant strain measured in the geogrid beyond its effective length of 6.0B (where B is the footing width) indicated that the geogrid beyond this length provided negligible reinforcement effect.

Field and laboratory testing programs were conducted to evaluate the potential use of the light falling weight deflectometer (LFWD) device for measuring the in situ elastic modulus of pavement layers and subgrades. The field tests were conducted on several highway sections selected from different projects in Louisiana. In addition, nine test sections were constructed and tested at the Pavement Research Facility site of Louisiana Transportation Research Center. All sections were tested using the Prima 100 model-LFWD in conjunction with the falling weight deflectometer (FWD), plate load test (PLT), and dynamic cone penetrometer (DCP) tests that were used as reference measurements. Linear regression analyses were carried out on the collected test data to develop models that could directly relate the LFWD stiffness modulus with moduli obtained from FWD and PLT and the DCP penetration rate. In addition, multiple nonlinear regression analyses were conducted to develop models that could predict FWD and PLT moduli on the basis of the LFWD elastic moduli and selected soil properties (moisture content and void ratio) of the tested materials. The results showed that the FWD, PLT moduli, and DCP-penetration rate could be predicted directly with LFWD at a significant confidence level. However, the prediction models were improved when the soil properties were included as variables. Laboratory tests also were conducted to determine the influence depth of the LFWD, and the results of these tests showed that the LFWD influence depth ranged from 270 to 280 mm.

The increasing use of geosynthetics to reinforce soils in many geotechnical engineering applications requires better evaluation of the soil–geosynthetic interface properties for use in the design and analysis of the different reinforced soil structures. The soil–geosynthetic interaction can be determined from direct shear tests or pullout tests. Until now, most research was focused on investigating the interface properties between geosynthetics and granular materials. Interest has increased in the use of marginal soils as backfill materials in mechanically stabilized earth (MSE) walls and embankments because of the cost-effectiveness of using the available cohesive soils. This strategy requires the evaluation of interaction parameters between geosynthetics and marginal soils. For this purpose, a series of laboratory and field pullout tests was carried out with different types of geosynthetic reinforcements in marginal silty clay soil of medium plasticity. Four types of geogrids and three types of geotextiles were used in this study. Laboratory and field pullout tests were compared. The coefficient of interaction ( Ci) between geosynthetics and cohesive backfill, the variation of pullout design parameters ( F*, α) with overburden depth, and the shear stress distribution along the reinforcement specimen also were evaluated.

The current piezocone penetration test (PCPT) interpretation methods were evaluated for their capability to estimate the vertical coefficient of consolidation (cv) of cohesive soils reasonably by using the piezocone dissipation tests. Seven PCPT methods were evaluated. Six sites in Louisiana were selected for this study. At each site, in situ PCPT tests were performed, and soundings of cone tip resistance, sleeve friction, and pore pressures at different locations were recorded. Piezocone dissipation tests also were conducted at different penetration depths. High-quality Shelby tube samples were collected close to the PCPT tests and were used to carry out a comprehensive laboratory testing program. The (cv) values predicted by the different interpretation methods were compared with the reference values determined from the oedometer laboratory tests. The results of this study showed that two methods can estimate cvbetter than the other prediction methods.

Utilization of existing recyclable materials has always been key to more efficient and economical highway construction. Use of the foamed-asphalt (FA) technique to stabilize recycled asphalt pavement (RAP) is one strategy for an efficient use of salvaged construction materials. The main objective of this study is to investigate the potential use of FA-treated RAP as a base course material in lieu of a crushed-limestone base beneath a concrete pavement layer. Test sections were constructed at US-190 near Baton Rouge, Louisiana, and used for field evaluation of the FA RAP base. The laboratory mixture design of the FA RAP, the construction of the experimental base section, and the field evaluation of the stiffness of the FA RAP base layers using different in situ testing devices are presented. Preliminary results of both laboratory and field tests showed that the FA-treated RAP mixtures are very promising and can be used as an alternative to the traditional limestone base beneath a concrete pavement layer.