Hot-mix Asphalt Layer Research Articles

Effects of existing concrete pavement condition on performance of unbonded jointed plain concrete overlay

Abstract Unbonded concrete overlay (UBCO) is the most used pavement rehabilitation technique across United States with an overall usage of 47% amongst all the rehabilitation methods. It is aimed to improve the performance of any deteriorated/cracked jointed plain concrete pavement (JPCP). Unbonded JPCP overlay involves placement of a separation layer of hot mix asphalt (HMA), which acts as a stress relief layer between the existing concrete pavement and the overlay. There are numerous factors that affect the design and performance of UBCOs and out of these, existing pavement condition or the severity of damage of existing pavement is a prime factor. The severity of damage is described by the distressed elastic modulus thus, accurate determination of the distressed elastic modulus of the existing concrete pavement is essential for predicting the accurate performance of the unbonded overlay. This study focuses on analyzing the impact of distressed modulus by conducting simulations in the AASHTOWare pavement ME design software version 2.3 and evaluating the predicted performance of JPCP overlay for two different climatic regions. The results indicated that the distressed modulus of existing concrete pavement affects the performance of the overlay with regards to transverse cracking, joint faulting and pavement roughness. Transverse cracking is the most affected performance parameter with a change of 0.27%–2.31% with a unit change in distressed modulus. The impact of climatic conditions on the performance of unbonded overlay was also observed. The adverse effects of distressed modulus can be minimized by reducing the joint spacing or increasing the overlay slab thickness.

Field Performance of Chip Seals for Pavement Preservation

Over time, new pavements deteriorate due to the effect of traffic loads and the environment. If appropriate treatments are applied during the early stages of deterioration, it is possible to extend the service life of the pavement without incurring in costly rehabilitation or reconstruction activities. Chip seals are preservation treatments that can help protect the pavement structure, reduce the rate of pavement deterioration, improve skid resistance, and address minor surface problems. As part of the National Center for Asphalt Technology Pavement Preservation Study, chip seal test sections were placed in a low traffic volume road (Lee County Road 159) in Auburn, Alabama. The location consists of a two-lane county road that provides dead end access to a quarry and an asphalt plant, resulting in a high percentage of heavy loads. At the time of treatment, the existing pavement was 14 years old and consisted of a 5.5 in. hot-mix asphalt layer over a 6.0 in. granular base. Treatments were applied in the summer of 2012 and have been in service for approximately 4.5 years. During this time, cracking, roughness, rutting, and macrotexture data were collected weekly to evaluate pavement performance. The results determined that the performance of the treated sections is highly dependent on the initial condition of the pavement, particularly the percentage of area cracked. Pavements that are treated while still in good condition tend to remain in that category for a longer time. Macrotexture may also be used to evaluate the functional performance of the chip seals.

Effect of Pavement Structure on the Mechanical Response and Performance of Perpetual Pavements at the National Airport Pavement Test Facility

Construction Cycle 7 (CC7) conducted at the FAA National Airport Pavement Test Facility (NAPTF) was aimed to study the effect of hot mix asphalt (HMA) layer thickness and develop perpetual pavement design criterion for airfield flexible pavements. Four fully instrumented perpetual test pavements were designed, constructed, and tested, with all test items trafficked under heavy aircraft loads using a three duals in tandem configuration. Pavement condition was monitored using heavy weight deflectometer tests, distress surveys, and surface profiles. Comprehensive response data analysis revealed that increasing HMA layer thickness significantly reduced the tensile strain at the bottom of the HMA layer, permanent deformation in the unbound layer, and vertical stress at top of the subgrade. Thicker HMA test items exhibited better rutting performance, as evidenced in both multiple depth deflectometer and surface profile data. The interaction between HMA layer temperature and thickness was captured in the pressure cell responses. More tests are planned to determine the threshold HMA strain to prevent fatigue cracking.

Flexural properties of chemically stabilised subgrade in designing semi-rigid pavements

Although flexural fatigue cracking of chemically-stabilised subgrade (CSS) layers is a major distress in semi-rigid pavements, the fatigue model of the CSS layer in the Mechanistic-Empirical Pavement Design Guide (M-EPDG) has not been calibrated. Design of semi-rigid pavements with regard to flexural fatigue life of the CSS layer was conducted using the M-EPDG method. Cylindrical and beam specimens of a lean clay, mixed with different types (cement kiln dust (CKD) and lime) and amounts of additives were prepared in the laboratory. Resilient modulus, modulus of rupture (MoR), flexural modulus and four-point flexural fatigue (FPFF) beam tests were conducted. Also, finite element (FE) models of different pavement sections having different thicknesses of hot mix asphalt (HMA) and different materials and thicknesses of CSS layer under traffic load were developed. The minimum required thickness of the HMA layer to avoid fatigue failure in the CSS layer was determined for different sections using the laboratory test results and the FE analyses. Finally, the effect of considering the flexural properties and fatigue life of the CSS layer on the designed HMA layer thickness was evaluated. The results showed that for the CSS materials with relatively low laboratory fatigue lives, the fatigue cracking of the CSS layer contained the most critical distress to be considered in designing the pavement structure. It was also found that by substituting the CSS resilient modulus with the properly-determined flexural modulus in the mechanistic-empirical design procedure, the designed HMA thickness, and, consequently, the construction cost could decrease significantly.

Performance evaluation of modified asphalt based trackless tack coat materials

In this study, a modified asphalt based trackless tack coat material (TTCM) was prepared by adding styrene–butadiene–styrene, uintaite mastic asphalt, anti-rut asphalt master batch and Sasobit wax to 50# base asphalt (penetration grade). Mehcnaimcal properties like track resistance, shear strength, pull-off strength, and rheological as well as temperature performance of TTCM were studied. Results showed that the adhesive bond strength of TTCM was greater than cohesive forces within hot mix asphalt layer, track-free time was less than 1 min and it did not deteriorate upon contact with tyres at 60 °C. Furthermore, bonding mechanism of TTCM was proposed. Surface morphology and functional group characterization were achieved using SEM and FTIR, respectively. The present approach utilizing routine raw materials and ease of operation for the synthesis of novel modified asphalt based TTCM with enhanced performance can be effectively applied on industrial level production for practical applications.

Full-waveform inversion using a stepped-frequency GPR to characterize the tack coat in hot-mix asphalt (HMA) layers of flexible pavements

The use of tack coats in the construction of road structures is a technique that ensures pavement layer bonding. Unfortunately, existing techniques commonly used in France to estimate tack coat conditions require coring structures for ad hoc characterization in the laboratory. This paper investigates a non-destructive approach to characterize changes in geometric and dielectric properties of the tack coats present inside the hot-mix asphalt (HMA) layers of flexible pavements, with the use of a stepped-frequency radar combined with a mono-static, off-ground, ultra-wideband Vivaldi antenna. The principle of this method is to consider the flexible pavement as a multi-layered medium with changing properties (thicknesses, dielectric susceptibilities and dispersion parameters). Then a full-waveform inversion is applied, which allows for the extraction of the dielectric and geometric parameters of each layer composing the structure. Following numerical validations, the multi-layered forward model, namely, a Green's function model integrating the 2-parameter variant of Jonscher's model, combined with Lambot's et al. radar full-wave method was experimentally validated using calibrating media (up to three layered media). Then, the link between both the dielectric and the geometric parameters of the tack coats and the emulsion quantity (bonding) was analyzed. The results showed good agreement between measured and modeled radar data. Radar data inversions showed in particular that the dielectric susceptibility and thickness of the transition zone increase with the emulsion quantity. Future research will focus on the establishment of a reference database of calibration curves linking dielectric susceptibility and tack coat characteristics.

Field Measurement and Modeling of Vertical and Longitudinal Strains from Falling Weight Deflectometer Testing

AbstractThis study investigates longitudinal tensile and vertical compressive strains at the bottom of the hot mix asphalt (HMA) layer subjected to a falling weight deflectometer during different s...

Impact of high recycled mixed on HMA overlay crack development rate

Illinois has many years of experience using various reclaimed materials in highway construction; and in recent years, recycled asphalt shingles (RAS) have been adopted for use in hot-mix asphalt (HMA), along with much higher amounts of reclaimed asphalt pavement (RAP). These reclaimed asphalt materials usually contain aged asphalt binders, which may increase the mix brittleness and hence, a challenge for maintaining a flexible pavement and ensuring good performance. To counter these hard asphalt binders, softer asphalts are incorporated into the HMA. The goal is for the final mix to provide acceptable mix properties for the life of the pavement. To determine the impact of recycled materials on pavement performance, this study monitored nine field projects in terms of the testing, construction, and performance of surface mixes that have a variety of asphalt binder replacement levels from RAP and RAS which used different virgin asphalt binder grades. Simple performance tests (Hamburg wheel tracking test and the Illinois flexibility index test [I-FIT]) were used to evaluate the mix designs. Flexibility index (FI) from the I-FIT showed good correlation with field crack development, especially after first year performance of the mix. Early-age field performance showed that placing the HMA overlay directly over existing bare concrete pavement or milling off all the HMA and placing new overlay on concrete pavement results in higher extents of cracking in early age than the sections that left an HMA layer in place. Regardless of which mix type is designed and what material sources are used, the performance of mix should be evaluated to ensure it has sufficient flexibility to resist cracking before the mix is used in road construction. This allows owners and contractors to use low-cost reclaimed and recycled materials to the extent possible without negatively impacting pavement performance.

Laboratory observation of cracks in road pavements with GPR

Cracks are one of the main distress mechanisms that affects the structural performance, comfort and durability of Hot Mix Asphalt (HMA) layers in road pavements. These cracks are generally of small size and can occur superficially, from top to bottom, from bottom to top, or they can run across the entire HMA layer thickness. Pavement rehabilitation is planned according to the bearing capacity of the pavement that is related to the number of cracks but also to its width (opening) and depth. Visible surface cracks can be manifested as superficial cracks or as cracks that already crossed the entire layer, and, both situations need different rehabilitation strategies. Therefore, there is an urgent need of accurate assessment of cracks characteristics to plan rehabilitation accordingly.Due to its characteristics useful for road inspection and high resolution, Ground Penetrating Radar (GPR) was used to assess its capability on detecting cracks of different widths. A laboratory experiment was setup to analyze the detectability of a crack in an asphalt slab (across the entire thickness) before and after a new slab was placed over the cracked one. The results showed that the possibility of the crack detection depends essentially on the contrast of the layers surrounding that crack. A numerical simulation was also performed and confirmed the experimental findings. It was also found that the amplitude of the reflected signal grows with crack width, contrarily to their shape, which remains fairly constant.

The Effect of Dustler on Reducing Stripping Failure in Hot Mix Asphalt Mixture

Hot mix asphalt (HMA) is one type of premix widely used in road construction worldwide. Aggregates for HMA are usually classified by size as coarse aggregates, fine aggregates, or mineral fillers. Moisture damage or stripping is one of the major concerns in HMA industry. The existence of water in asphalt pavement is often one of the major factors affecting the durability of HMA. The water- induced damage in HMA layers may be associated with two mechanisms a loss of adhesion and loss of cohesion. The main focus of this study based on these two objectives which is to develop HMA that involves used of dustler in asphalt mixture and to investigate the performance of dustler against stripping failure. The asphalt mixture of combination virgin aggregate and this waste material was studied. The percentages of dustler used in this study were 0.5%, 1.0% and 2.0% respectively. The method used in this study was Superpave mix design method. From the laboratory test, the indirect tensile strength (ITS) test was conducted to show the stripping performance. The result from that test showed that the value of ITS for dry sample is higher compared to wet sample for all percentages. The moisture sensitivity was determined through tensile strength ratio (TSR) test. From the results, it showed that the percentages of dustler were fulfilled the minimum requirement of AASHTO T283 which is 80% minimum requirement of moisture susceptibility. The highest value of TSR is 0.5% of dustler sample which is 98.55% compared to 1.0% of dustler sample, control sample and 2.0% of dustler sample. So, it can be concluded that dustler inhibits great potential on reducing stripping failure in hot mix asphalt.

Design and Properties of Thin Surfacing Hot Mix Asphalt Containing Crumb Rubber as Partial Aggregate Replacement

Road damage caused as a result of the traffic load and environment. One method to improve the road condition is from an overlay. But the new layer on the top of the pavement structure is thick enough and elevate the surface of the pavement, so it will cause some impact on the user safety and engineering. The use of a thin layer of hot mix asphalt is an alternative to anticipate the thickness problem. Crumb rubber is a waste material that has a flexible nature, these materials are used as an aggregate replacement in the hot mix asphalt thin layer. The research was conducted to find the optimum bitumen content and optimum crumb rubber content on asphalt mixtures by the Marshall procedure. Finally, it was concluded that the addition of crumb rubber in a thin layer of hot mix asphalt indicates the better the interlocking between aggregates so that gave the better Marshall stability, the higher the flow rate, the lower the marshall quotient, reduce the void ratio. The results show that the addition of crumb rubber content as an aggregate replacement leads to the use of less optimum bitumen content.

Effects of tire inclination (turning traffic) and dynamic loading on the pavement stress–strain responses using 3-D finite element modeling

In this study, ABAQUS finite element (FE) modeling in three-dimensional (3-D) loading mode was utilized to analytically investigate and quantify the effects of tire inclination and dynamic loading on the stress–strain responses of a pavement structure under varying loading and environmental conditions. The input variables for modeling consisted of actual laboratory and field data obtained from an in-service highway US 59 and included the in-situ pavement structure, material properties (i.e., modulus and shear strength), traffic, and climatic (i.e., temperature) data. Computational modeling and sensitivity analyses were conducted through variation of the following two input variables with a focus on the top surfacing hot-mix asphalt (HMA) layer: a) tire inclination angle to simulate turning traffic, and, b) dynamic loading to simulate accelerating, steady rolling, and decelerating (braking) traffic. The generated maximum shear stress and vertical strain responses were then analyzed and correlated to the HMA material strength and the actual measured/observed field rutting performance data. The corresponding results indicated that inclined tires (simulating turning traffic) and decelerating (braking) vehicles induced the most severe shear stresses and vertical strains on the pavement structure in terms of magnitude (i.e., increased); exceeding the HMA material strength in some cases. Thus, for pavement design and structural analysis purposes, the following critical highway areas that may be subjected to extreme stresses and strains due to turning and stopping (braking) traffic, particularly in high temperature environments, should be given more attention with respect to material strength characterization to mitigate potential shear/rutting failures: intersections, junctions; urban stop–go sections, and curves.

Effects of Short-Term Aging on Asphalt Binders and Hot Mix Asphalt at Elevated Temperatures and Extended Aging Time

The production process of Hot Mix Asphalt (HMA) causes a short term aging (STA) to asphalt binder due to the heating of both asphalt binder and aggregates before mixing together. Laboratory protocols are followed to simulate the STA conditions for both asphalt binders and asphalt mixtures. STA protocols expose asphalt binders or asphalt mixtures to specific aging temperature for a specific period of time to produce stiffening that is similar to that of actual production conditions. Successful construction of HMA in cold season/regions may require elevating the production temperature of HAM to achieve proper compaction of HMA layers. Producing HMA mixtures at elevated temperatures may cause further increase in the binder stiffness and negatively affect the future field performance of asphalt pavements. This negative affect can be even worse especially if it is coupled with extended exposer time increase. This study aims to investigate effect of elevated production (mixing and STA) temperatures and exposure time on the stiffening of binders and asphalt mixtures. The binder experiment involved aging of two Performance Graded (PG) binders (PG 76-16 and PG 64-22) at two different temperatures and aging durations. The asphalt mixture experiment involved the STA of asphalt mixtures produced in the laboratory at mixing and STA temperatures 25°F above standard practice and aging time 2 and 4 hours longer than standard practices. The effect of different aging times and temperatures was investigated by running viscosity tests on binders and dynamic modulus |E*| and Indirect Diametrical Strength (IDT) tests on asphalt mixtures. The results showed that increasing the mixing and STA temperatures by 25°F seems to have no significant effect on the asphalt mixture properties while doubling the standard STA time seems to have a significant effect on binder and asphalt mixture properties.

Combined Model Framework for Asphalt Pavement Condition Determination After Flooding

Flooding of pavements often causes damage that is invisible on the surface. A way to predict the condition of a pavement after flooding will be useful for agencies to make rational decisions about the need for closing a road to traffic or opening it up for cleaning and recovery work. In this study, the problem of flooded pavement assessment was formulated as a combination of hydraulic and structural analyses. A model was developed; it consisted of results from unsaturated hydraulic and layered elastic structural analyses. An interactive simulation was developed from the model and was made available on the web to users in the public domain. Simulations with the model showed significant impacts when subgrade layer moduli were below 50 MPa and layer thickness was less than 200 mm for the hot-mix asphalt (HMA) and less than 600 mm for the base. Axle loads exceeding 80 kN exacerbated damages and hazardous conditions. The time to reach conditions that will not lead to damage or failure within a short period of time depends on both the pavement conditions and the load magnitude. On the basis of thickness of surface HMA layer and soil subgrade moduli, restrictions of traffic could be placed on flooded pavements.

An Assessment of Concrete Over Asphalt Pavement Using Both the Ultrasonic Surface Wave and Impact Echo Techniques

A portable seismic property analyzer (PSPA) was used to simultaneously acquire both ultrasonic surface wave (PSPA-USW) and impact-echo (PSPA-IE) data at predetermined locations along a section of multi-layered pavement. The pavement consisted of a basal concrete layer (∼220 mm), an intervening layer of hot-mix asphalt (∼60 mm), and a concrete overlay (∼220 mm). The section of multi-layered pavement was cored at multiple PSPA test locations for verification purposes. The conditions of the extracted cores were assessed visually, and the static elastic modulus, as well as the compressional wave velocity of each concrete overlay core, were measured in the laboratory. Results from this study demonstrated that the PSPA-USW tool can be used to evaluate the conditions of concrete overlay, the interlayer (hot-mix asphalt), and their bonding conditions from a qualitative perspective. A good correlation between the static and laboratory dynamic modulus from core specimens of concrete overlay were confirmed based on laboratory testing results. However, the field dynamic modulus of core specimens, based on PSPA-USW tests, was lower than both the static modulus and laboratory dynamic modulus. Furthermore, the PSPA-IE tool was not able to estimate the depth of the entire pavement and to various pavement layer interfaces due to the interference of flexural mode vibration. Fortunately, the difference between intact and deteriorated pavement can be qualitatively identified from the amplitude spectrum. More core specimens are needed for further studies in order to verify the performance of both PSPA-USW and PSPA-IE techniques for multi-layered pavement condition assessment.

Field investigation on the lateral resistance of railway tracks including hot mix asphalt layer

One of the most important problems in the ballasted railway tracks is the inappropriate distribution of stress through the ballast over the subgrade layer, which causes damage to the super/substructure layers. Application of hot mix asphalt (HMA) layer in the forms of underlayment or full depth has been proposed in order to decline the stress concentration over the subgrade. Lack of sufficient track lateral resistance, especially in curved routes, is regarded as a concern when using this layer in ballasted railway tracks. Since there is not enough knowledge about the influence of the HMA layer on the lateral resistance of ballasted tracks, the present study was allocated to investigate the mentioned issue by a series of field tests. For this purpose, a test track (including different sections on asphalt layers, as underlayment HMA (with thickness of 100 and 150 mm) and full-depth HMA (with thickness of 100, 150 and 200 mm)) was constructed in Qom-Jamkaran railway line. Afterwards, a series of single tie push tests and track panel displacement tests were performed to measure the lateral resistance of all the test track sections. The results show that the lateral resistance of the common ballasted track is about 75–100% and 55–80% more than that of the ballasted track with underlayment HMA and full-depth HMA, respectively. Hence, on average, the lateral resistance of full-depth HMA track is about 15% more than that of underlayment HMA track.

Density profile of hot mix asphalt layer during compaction with various types of rollers and lift thickness

The effects of different compactors and lift thickness on hot mix asphalt (HMA) have been persistently discussed among asphalt experts. In many cases, pavements paved with the high-in-place air voids permit water to penetrate the permeable pavement causing an increased tendency for pavement deformation. The thin lifts have had problems achieving high density, which leads to high-in-place air voids. The present paper is aimed at evaluating the effects of different compactors, an 11-ton steel drum compactor and a 15-ton pneumatic tyre roller, on the HMA mat with different ratios of thickness to nominal maximum aggregate size (t/NMAS). In order to achieve this aim, seven field sections with a total 36 locations with distinct HMA mixes, thicknesses and rolling patterns were built. Each of the sections was approximately 40m long and 3.5m wide. The section was constructed with t/NMAS ratio varying from 2.0 at the beginning to 5.0 at the end of the section. The air temperature during construction varied from 26°C to 35°C. More so, for comparison purposes, the simulated HMA mat temperatures using MultiCool 3.0 software and their respective measured temperature were also taken. The results indicate that the optimum number of passes to achieve maximum density is four passes. This could be achieved by merely using the steel roller with vibratory mode. However, the introduction of rubber tyre roller during the intermediate rolling initially reduced the density by one to two percent but started to increase after several passes.

Influence of chemical additives on mixing procedures and performance properties of asphalt emulsion recycled mixture with reclaimed cement-stabilized macadam

During rehabilitation of pavement structure with cement-stabilized macadam (CSM) base course and hot mix asphalt (HMA) surface course, it is expected to recycle severe cracked CSM layer using the same method as HMA layer. In this study, asphalt emulsion and chemical additives were adopted to stabilize reclaimed CSM aggregates. Considering the surface characteristic of the CSM aggregate, the addition procedures of chemical additives were investigated by volumetric parameters and strength tests. The moisture susceptibility and rutting resistance test were conducted to evaluate effect of different chemical additives on performance properties of the recycled mixture. To understand the mixing procedures and performance characteristic, the microstructure images of the recycled mixture were observed by environmental scanning electron microscope (ESEM). The results of volumetric parameters and strength tests indicate the addition procedures of chemical additives affect the optimum composition and mechanical strength of the recycled mixture. It is recommended to add cementitious additives prior to asphalt emulsion during mixing process. Furthermore, the optimum composition and performance properties of the recycled mixture depend on types and content of chemical additives. Some suggestions are provided for the selection of chemical additives. The interface bonding mechanism between the recycled aggregates and cementitious materials is proposed to explain the mixing procedures and performance characteristic of the recycled mixture.

Estimating fatigue endurance limits of flexible airfield pavements

In perpetual pavements, damage from bottom-up cracking can be limited to the top surface lift through using a very thick surface layer or a binder-rich intermediate layer. This can be attained by maintaining tensile strains at the bottom of the hot-mix asphalt (HMA) layer below a certain value known as the fatigue endurance limit (FEL). This paper presents a method for estimating a strain-based FEL for flexible airfield pavements. The proposed method is based on the concept that a 50% reduction in HMA layer modulus would indicate initiation of fatigue cracking. Falling weight deflectometer (FWD) testing results, collected from National Airport Pavement Test Facility (NAPTF) flexible pavement sections, were analyzed to determine at which loading pass each section had a 50% reduction in HMA layer modulus (Nf50). NAPTF tensile strain data were also used to determine the tensile strain at Nf50 for each pavement section by averaging the peak tensile strains. The proposed approach was validated by comparing its results to those obtained using a common FEL estimation model known as the rate of dissipated energy change (RDEC) model. To further verify the results of the proposed approach, peak tensile strain was plotted vs. number of loading cycles for all sensors. Using these plots, the peak tensile strain at which the variability in the strain gauge data increased was used as an estimate of a possible FEL. The Nf50 tensile strains estimated using the proposed method were comparable to the values determined from RDEC and variability approaches.

Performance of Geotextile-Reinforced Bases for Paved Roads

Geotextiles have been widely promoted for pavement structure, but only a few full-scale experiments have investigated the effects of geotextile reinforcement on pavement design. In this study, full-scale accelerated pavement testing (APT) was conducted on six pavement test sections with granular bases reinforced with various types of woven geotextiles. The control section had a granular base without any reinforcement. All sections were paved with Superpave® hot-mix asphalt (HMA). Base and subgrade materials were the same, but the test sections had varying thicknesses of base and asphalt layers. Each section was instrumented with two pressure cells at the top of the subgrade, six strain gauges on the geotextile, six H-bar strain gauges at the bottom of the asphalt layer, and two thermocouples. The sections were loaded to 250,000 to 400,000 repetitions of an 80-kN single-axle load of the APT machine. Mechanistic responses of the test sections were periodically monitored and analyzed. Rutting profile, pressure on the subgrade, strains in the geotextiles, and strains at the bottom of the HMA layer were measured. Falling weight deflectometer (FWD) tests were performed before and after loading. Reinforced-base sections with similar cross sections outperformed the control section in terms of rutting, and the reinforced-base layer reduced pressure on the subgrade. Backcalculated moduli from FWD tests demonstrated that the base layer in reinforced sections was significantly stronger than the control section base layer after loading. Strain measurements at the bottom of the HMA layer indicated that fatigue life of test sections did not improve with geotextile reinforcement.