Subgrade Conditions Research Articles

A Life Cycle Cost Comparison of Flexible Versus Rigidpavements in Nigeria: Case Study of Papalanto - Sagamu Road

The condition of roads in Nigeria, most of which are made from asphalt, is generally considered unsatisfactory. This has led to calls for a blanket switch from asphalt pavements to concrete pavements for new road construction. This study examines the characteristics and relative advantages of the two pavement types; and carried out the design and life cycle cost comparison of a case study road with heavy traffic and poor subgrade conditions. The results indicate that, the initial cost of construction is actually less for the concrete pavement by 12% when compared with the asphalt alternative, while the life cycle cost analysis further yielded an advantage of 36% for the concrete pavement. The paper therefore recommends that major roads, particularly those on the national and international transit corridor, being of heavy traffic, should be reconstructed as the need arises, as concrete pavements. The paper however further recommends that, axle load control should be enforced through the introduction of weigh bridges and that routine maintenance should mandatorily be carried out, as even the best constructed concrete pavements have failed due to lack of routine maintenance like clearing the road verges of weed and road sand and desilting of drainage structures

Road Damage Analysis using Surface Distress Index (SDI) and Its Handling on Provincial Road Babat - Jombang (STA 7+000 - 12+500)

The Babat - Jombang road is often traveled by highly loaded vehicles because there are large industries along this section. In addition, the road is damaged by weather and poor subgrade conditions. Thus, resulting in road damage that can interfere with user comfort. Therefore, road damage analysis research was conducted on Babat - Jombang Road (STA 7+000 - 12+500). Road damage analysis in this study using the SDI method. The SDI (Surface Distress Index) method is a road performance scale obtained from visual observations of road damage that occurs in the field. The SDI method is a method that produces an SDI value obtained from the percentage of crack area, crack width, number of holes per 100 m, and the depth of the ruts. From this research, the types of damage on Babat - Jombang Road (STA 7+000 - 12+500) are the hole damage area of 0.11%, longitudinal cracks of 12.05%, transverse cracks of 0.17%, edge cracks of 0.29%, crocodile skin cracks of 79, 66%, shoulder joint cracking by 0.0015%, ruts by 1.48%, bleeding by 1.1%, ravelling by 2.61%, surface layer flaking by 0.13%, patches by 0.26%, upheavel by 0.51%, shoving by 1.6%. Road condition assessment using SDI method shows 87.27% in good condition and 12.73% in moderate condition. Handling carried out is leveling, sealing, hot aggregate sprinkle, and patching holes.

A Review on Experimental Study of Design of Rigid Pavement by using Recycled Coarse Aggregate with M30 Mix Design

Concrete, a fundamental construction material, boasts attributes like durability, versatility, and cost- effectiveness. However, the depletion of natural resources and the escalating concrete waste production necessitate innovative solutions. In this rapidly industrializing world, recycling construction materials plays a pivotal role in preserving our finite resources. Concrete pavements, widely practiced in developed countries, are relatively new in India. Selecting the right pavement type is crucial, but equally important is determining the optimal pavement thickness based on traffic levels, subgrade conditions, and environmental factors. Unfortunately, many existing methodologies overlook critical factors (such as vehicle loads, support loss, thermal gradients, and environmental stress), leading to inaccurate thickness calculations. In this context, rigid pavement construction using recycled coarse aggregate (RCA) emerges as an eco-friendly and cost- effective solution. In a recent research endeavour, Recycled Coarse Aggregates (RCAs) sourced from demolished material took center stage. These demolished materials are meticulously crushed to a suitable size and repurposed as recycled coarse aggregate. Meanwhile, natural sand continues to serve as the fine aggregate. Notably, the concrete industry consumes a staggering 12.6 billion tons of raw materials annually, making it the world’s largest natural resource consumer. The environmental impact of concrete production—especially the extraction of raw ingredients such as cement, coarse aggregates, and fine aggregates—is considerable. To address this, the study employed a trial-and-error approach for mix design, adhering to relevant standards (such as IS code and IRC: 44-2008). For M30 grade cement concrete, varying percentages (0%, 25%, 50%, 75%, and 100%) of recycled coarse aggregates replaced conventional coarse aggregates. Casting used cube and beam models to obtain laboratory test results for rigid pavement to determine how much optimal percentage of RCA can be substituted in place of NCA. By integrating RCAs, we not only mitigate environmental impact but also contribute to sustainable rigid pavement structures. Key Words: Rigid Pavement Design, Recycled Coarse Aggregate, RCA Concrete, Natural Coarse Aggregate, NCA Concrete, Mix Proportion, Pavement Thickness, Life Cycle Cost, And Environmental Benefits etc.

Effect of Soil Stabilization on Structural Design of Flexible Pavement

Inadequate subgrade conditions often diminish the lifespan of pavements built on these soils. However, this challenge can be addressed through various methods, including soil stabilization, which enhances soil strength. This research focuses on soil stabilization using two types of waste materials (rubber and plastic) as additives in concentrations of 5%, 10%, and 15%, along with a consistent cement inclusion of 3% across all samples. Different tests, such as Sieve analysis, Atterberg Limits, Specific Gravity, Standard proctor Test and California Bearing Ratio, were performed for both the soil and the additive materials. As a result, this stabilization approach improved the California Bearing Ratio (CBR), leading to thinner pavement layers, which potentially lowers construction costs. Notably, the highest CBR observed was 49.95% with 10% plastic, while the top result for rubber was a 28.01% CBR at 5% inclusion. These enhancements in CBR values contributed to reducing the total thickness of the pavement layers by (435 mm) for both materials.

Investigation of the mechanical response of recovered geogrids under repeated loading

This study investigates the mechanical response and performance of biaxial polypropylene geogrid specimens cyclic loading. This work assesses the influence of embedment depths and subgrade strengths on the of geogrids. The experimental program involved subjecting the geogrid specimens to 100 repeated tensile loading cycles at four distinct load targets: 20%, 40%, 60%, and 80% of the geogrid ultimate tensile strength. The analysis focused evaluating the effects of preloading factors such as California Bearing Ratio (CBR) values, embedment depth, and the response to cyclic testing. Results show trends in stiffness reduction and changes in damping ratio with increased number of cycles. A comparative analysis was conducted with a control specimen from the same batch, highlighting the difference in mechanical response attributed to precycling variables. The findings indicate that the overall mechanical behavior of recovered geogrids is comparably consistent with new geogrids. However, variations in strain and stiffness reduction were observed among the recovered specimens, suggesting a pattern of yielding before failure. The findings suggest a minimal effect of embedment depth on the damping ratio at lower CBR. Overall, it was found that precycling and subgrade conditions have minimal effect on the mechanical response of the recovered specimens when tested in isolation.

Subgrade Strength Recovery of Fine-Grained-Soil-Containing Roads in Western Oregon Forest

Forest roads are composed of surface and subsurface layers. Determining the seasonal strength and associated moisture changes in these roads is required to understand their capacity. This study looks at changes in the subgrade layer. Laboratory and field studies were conducted to determine the changes in subgrade conditions by measuring moisture content and subgrade strength for fine-grained, non-plastic soils in Western Oregon. One field and one laboratory experiment were conducted. Drying in the field experiment occurred during the summer months in the absence of rainfall, while the laboratory study allowed drying for 48 h under controlled suction. In both cases, there was a slight reduction in the subgrade’s moisture content and no significant improvement in subgrade strength. These findings are supported by the soil physics theory that shows that limited water content reduction is expected for these fine-grained soils, as the numerous tiny soil pores can hold water at high capillary tensions. Adding rock layers adds an insulation effect for the subgrade, further reducing evaporation. Consequently, the moisture content remains high, and there will be little change in subgrade strength during the measurement periods.

Pavement maintenance strategy for Provincial roads in Tarakan City, North Kalimantan

Tarakan City has several road segments on provincial roads that have experienced significant damage in the form of sinkholes and substantial potholes on the road surface. These deteriorations are primarily attributed to the impact of traffic, excessive traffic loads, subgrade soil conditions that fall short of requirements, and the use of pavement materials that do not meet the specified standards. To devise effective road repair plans, the collection of field data is crucial. Two distinct methods are employed for data collection to assess pavement conditions: the International Roughness Index (IRI) and the Surface Distress Index (SDI). The IRI method measures road roughness using the Rough meter III instrument, while the SDI method focuses on parameters like crack area, crack width, pothole count, and wheel path rut depth. The surveyed road sections encompass Amal Lama, Gunung Selatan, Aji Iskandar, Bhayangkara, Aki Pingka, and the Ring Road of Tarakan City. Research findings reveal the surface damage level of roads in Tarakan City using the SDI and IRI methods, with the following breakdown: roads in good condition account for 42.86%, those in moderate condition make up 51.90%, slightly damaged roads constitute 4.8%, and heavily damaged roads represent 0.44%. Additionally, the study has determined the percentage of each type of maintenance required: Routine Maintenance at 94.77%, Periodic Maintenance at 4.8%, and Reconstruction at 0.44%.

EVALUASI TEBAL PERKERASAN PADA RUNWAY BANDARA SYUKURAN AMINUDDIN AMIR LUWUK BERDASARKAN CUMULATIVE DAMAGE FAILURE

Air transportation is a mode of transportation still quite in demand, although recently there has been a decline in passengers. Syukur Aminuddin Amir Luwuk Airport belongs to the category of Class II Domestic Airport with airside facilities, a Runway with a size of 2,250 m x 45 m, a Taxiway 60 m x 18 m, and an Apron with a size of 315 x 15 m. The operation of several types of aircraft with a larger capacity occurs due to the increase in the number of passengers every year. An increase in the number of passengers will certainly have an impact on the number of aircraft movements, it is necessary to analyze how to determine the thickness of the runway pavement which is influenced by the type of aircraft that will operate based on the subgrade conditions that are there using the FAARFIELD method. The results of the evaluation on the thickness of the runway pavement which has a CBR value of 15%, with a pavement thickness of 215 mm for HMA Surface, 152 mm for Crushed Aggregate, and 200 mm for Uncrushed Aggregate with a service life of 20 years in 2040 it was found that the Subgrade CDF value was 0.00 and the HMA CDF of 0.86. The test results with FAARFIELD software change the pavement thickness for the base layer to 152 mm (minimum value) from the value of 100 mm. So planning the thickness of the pavement requires an additional layer of 52 mm.

Laboratory Model Test on The Sand Column for Reinforcement System of Flexible Pavement

Flexible pavement failures in Indonesia are primarily attributed to weak subgrade conditions, necessitating soil reinforcement measures. This study aimed to enhance soil-bearing capacity through soil reinforcement experiments utilizing a mixture of sand columns, rice husk ash, and cement. A prototype was constructed, including a 1×1×1 m steel box, an IWF steel frame, a dial gauge, a steel plate, and a proving ring, to apply a load to soil arranged within the iron box using a 3-ton hydraulic jack. The study focused on a clay soil type (following the AASHTO method) and conducted soil reinforcement in four scenarios. The result shows that in all scenarios involving a sand column, Scenario 1: 3% sand, 3% rice husk ash, and 6% cement obtained a qult is 0.23 kg/cm2 and BCR 114.94%; Scenario 2: 3% sand, 6% rice husk ash, and 3% cement obtained a qult is 0.12 kg/cm2 and BCR 11.49%; Scenario 3: 6% sand, 3% rice husk ash, and 3% cement obtained a qult is 0.14 kg/cm2 and BCR 26.44%; Scenario 4: 6% sand, 6% rice husk ash, and 0% cement obtained a qult is 0.24 kg/cm2 and a BCR of 116.09%. Notably, scenario 4, featuring a column composition of 6% sand, 6% rice husk ash, and 0% cement, achieved a significant increase in bearing capacity (qult) with a value of 0.24 kg/cm2 and a high Bearing Capacity Ratio (BCR) of 116.09%. Scenario 1 was the most effective in reducing moisture content by 4% relative to the original soil moisture content, with a mixture comprising 3% sand column, 3% rice husk ash, and 6% cement. The findings suggest that applying soil columns can enhance the performance of flexible pavements.

Investigation of subgrade conditions on the Airbara – Toboali road section to improve road quality

The Airbara - Toboali Road Section is a national road located in South Bangka Regency, Bangka Belitung Islands Province. Some segments of this road often experience road damage, although road repairs have been carried out several times to overcome the damage. The subgrade layer is the most important layer in the pavement structure because it functions to withstand all the loads above it. CBR (California Bearing Ratio) is penetration test used to evaluate the subgrade strength of roads and pavement. Therefore, this study aims to investigate the subgrade conditions on the Air Bara – Toboali road section in order to improve road quality. This study uses hand boring testing with 4 sampling points and field CBR testing with the DCP tool. Field CBR samples were taken as many as 30 points every 50 meters from STA 0+000 – STA 1+450. The average CBR value obtained shows that the CBR of this subgrade is in the good category (10.77%). Subgrade conditions per layer, namely at a depth of 0-2 meters the roads have almost the same soil characteristics. However, the soil depth of more than 2 meters in several locations on the road segment has a different character. The results of this investigation are expected to assist road planning so that road quality can improve.

Effect of material hydraulic properties on temporal moisture variations and performance of unbound pavements with sprayed seals

Moisture is widely recognised as a primary factor responsible for road failures. In particular, unbound pavements with sprayed seals, a common type of flexible pavement used in Australia and New Zealand are highly susceptible to moisture-related performance losses. The wearing course of these pavements, i.e. the sprayed seals, is moderately permeable, which allows for moisture exchange between the environment and the pavement structure throughout its service life. As a result, the moisture content of pavement layers varies according to the prevailing climate, which could cause noticeable performance reductions.This study extensively investigates the moisture variations in pavement layers of unbound pavements with sprayed seals during the service life due to the variations of ambient climatic conditions. The moisture variations in 18 different typical sprayed sealed pavements were numerically simulated for 10-year climates of Melbourne and Adelaide. Both the degree of saturation (Sr) and suction (s) variations were simulated for a number of practical scenarios. The results indicated that the pavement layers reach an equilibrium condition within less than 6 months under the climates considered. A series of sensitivity analyses were performed to evaluate the effect of hydraulic properties of seal, unbound granular material (UGM), subgrade and effect of water table depth on the moisture variations of pavement layers. The parametric analysis revealed that relatively permeable seals facilitate significant wetting of the UGM layer and substantial drying due to variations in prevailing climatic conditions. Moreover, this study identified primary influencing factors that determine the equilibrium state and the temporal moisture variations of the pavement layers. The effect of water table depth is evaluated for different subgrade conditions. A pavement performance evaluation conducted following the effective stress concept, the factor Sr.s is presented in this study. Overall, the results highlight the importance of considering temporal moisture variations in the design stage to improve pavement performance.

ANALISIS STABILITAS TIMBUNAN DENGAN PLAXIS MEMBANDINGKAN 2 METODE AKIBAT KETERBATASAN LAHAN

In the Cibitung - Cilincing Ramp 3-1 Toll Road development project, where the road alignment is an embankment construction with subgrade conditions that have dominant soil layers with sand and limited land. Then the implementation of subgrade improvement is carried out by comparing 2 methods, namely the first Replace 1.5 m (50 cm Limestone + Geomembrane + 50 cm Granular backfill + Geotextile Non Woven) + Sheet Pile with a length of 15 meters + Retaining Wall and the second Replace 1.5 m (50 cm Limestone + Geomembrane + 50 cm Granular backfill + Geotextile Non Woven) + Retaining Wall with Bore Pile D60 Int. 2 meters + Retaining Wall.The analysis of the two treatments used Plaxis with the results for the 1 year and 10 year consolidation of the two treatments meeting the requirements. The safety factor for the embankment slopes also meets the requirements. The results of the Horizontal Displacement in the first treatment are still very large, namely 6.73 cm, not in accordance with the AASTHO criteria of 3.8 cm and it can be seen from the profile bending moment on the Sheet Pile that the Sheet Pile is not pinched so that for this case the handling suitable is to use the second treatment, namely Replace 1.5 m (50 cm Limestone + Geomembrane + 50 cm Granular backfill + Geotextile Non Woven) + Retaining Wall with Bore Pile D60 Int. 2 meters + Retaining Walls

Evaluation of pavement design input parameters of biaxial and triaxial geogrid stabilized flexible pavements overlying soft subgrades

Stabilization of flexible pavement layers using geogrids to improve the mechanical response of pavement layers is gaining importance over conventional stabilization techniques due to their low cost and superior performance. However, the lack of experimental data on quantifying the design input parameters of stabilized subgrades or granular layers limits the extensive use of geogrids in the field. Evaluation of design input parameters such as modulus improvement factor (MIF) or layer coefficient ratio (LCR) would promote the use of geogrids in the pavement, reducing the consumption of natural aggregates and the overall project cost. This study attempts to evaluate MIF and LCR due to geogrid stabilized soft subgrades considering different scenarios. All possible combinations of stabilization of pavement layers using biaxial and triaxial geogrids were considered. This involved stabilization of (a) the subgrade layer alone, (b) base layer alone, and (c) subgrade, subbase, and base layers. Accordingly, an extensive, systematic experimental program consisting of eighteen large-scale model pavement experiments (LSMPE) were conducted in five categories (designated as Series I through V). The stabilization of subgrade and granular layers was carried out using commercially available biaxial (BX1 and BX2) and triaxial (TX1) geogrids overlying soft and moderate subgrades with California bearing ratio (CBR) equal to 2.5 and 4%. Test results showed that stabilized subgrade prepared with existing and prepared subgrade material in conjunction with geogrid improved the effective CBR to as high as 10.9% from effective CBR = 7% corresponding to existing and prepared subgrade material without geogrid. The design inputs of geogrids (BX1/BX2/TX1) stabilized granular layers resulted in the MIF and LCR values ranging from 1.9 to 2.8 and 1.31 to 1.63, respectively, for the tested configuration considered in the study. Based on the findings of the study, inputs on resilient modulus of pavement layers were recommended for similar reinforcement and subgrade conditions considered.

Combined CNN and RNN Neural Networks for GPR Detection of Railway Subgrade Diseases.

Vehicle-mounted ground-penetrating radar (GPR) has been used to non-destructively inspect and evaluate railway subgrade conditions. However, existing GPR data processing and interpretation methods mostly rely on time-consuming manual interpretation, and limited studies have applied machine learning methods. GPR data are complex, high-dimensional, and redundant, in particular with non-negligible noises, for which traditional machine learning methods are not effective when applied to GPR data processing and interpretation. To solve this problem, deep learning is more suitable to process large amounts of training data, as well as to perform better data interpretation. In this study, we proposed a novel deep learning method to process GPR data, the CRNN network, which combines convolutional neural networks (CNN) and recurrent neural networks (RNN). The CNN processes raw GPR waveform data from signal channels, and the RNN processes features from multiple channels. The results show that the CRNN network achieves a higher precision at 83.4%, with a recall of 77.3%. Compared to the traditional machine learning method, the CRNN is 5.2 times faster and has a smaller size of 2.6 MB (traditional machine learning method: 104.0 MB). Our research output has demonstrated that the developed deep learning method improves the efficiency and accuracy of railway subgrade condition evaluation.

Punching shear capacity of GFRP bar-reinforced concrete slabs-on-ground

This work investigated the punching shear capacity of slabs-on-ground reinforced with GFRP bars subjected to concentrated loads. A total of 12 slabs measuring 1.5 × 1.5 × 0.15 m3 were fabricated with a single-layer of reinforcement grid and placed on a 100 mm-thick extruded polystyrene foam with a modulus of subgrade reaction of 124 MPa/m, simulating dense sand subgrade conditions. The variables of the study were the rebar type (two types of GFRP bars and conventional steel), spacing of bars (200 mm and 300 mm), reinforcement grid location in the slab (top-third, middle-depth, and bottom-third), location of concentrated load (center, edge, and corner), and type of loading (monotonic and repeated). The study found that the load-carrying capacities of GFRP bar-reinforced slabs were approximately 79.0 % and 91.0 % of the steel-reinforced slabs at 200 mm and 300 mm spacings, respectively. Crack patterns, failure modes, load–deflection response, punching shear capacities, deflection profiles, and strains in GFRP bars in the slabs are presented. An empirical equation is proposed to predict the punching shear capacity of GFRP bar-reinforced slabs-on-ground. The proposed equation was validated with the experimental results and the limited data reported in the literature for slabs-on-ground. GFRP bars in slabs-on-ground are a potential and sustainable alternative to conventional steel as reinforcements.

Construction and Performance Evaluation of Polyurethane-Bound Porous Rubber Pavement (PRP) Trial Section in the Cold Climate

Porous pavements are designed and used in current construction practices to address environmental and safety issues related to wet weather. Porous rubber pavement (PRP) is a novel porous pavement material consisting of recycled crumb tire rubbers, stone aggregates, and polyurethane binders. The higher permeability (up to 45% of air voids) of PRP and its composition offers excellent benefits to the urban hydrological system and environment. Due to its recent outset in the Canadian climate, its properties and performance are not yet investigated. This research investigates PRP’s properties and performance as pavement material through the construction of two trial sections incorporating three newly developed PRP mixes along with a Control Mix. Samples were obtained from the field and tested in the laboratory to determine the mechanical and durability properties, including indirect tensile strength, moisture-induced damage due to freeze-thaw cycles and permanent deformation. A field evaluation was also performed three times: right after construction, three weeks later and after seven months to determine stiffness, frictional properties, roughness and permeability. The results revealed that all PRP mixes exhibited excellent permeability and retained more than 68% of tensile strength after five freeze-thaw cycles. Although PRP showed significantly lower initial elastic modulus than conventional pavement material, ranging between 28 MPa to 59 MPa, in the springtime none of them went below 23 MPa. Material composition, site geometry and subgrade conditions were found to be the main factors influencing the field performance of PRP pavement.

Design of Tunnel Initial Support in Silty Clay Stratum Based on the Convergence-Confinement Method

The stress release ratio of the surrounding rock in tunnel excavation is one of the most important indicators that affect the stress distribution and displacement of the surrounding rock. To determine the variation law of the stress release ratio of the surrounding rock during excavation in silty clay stratum, the stress release law is determined based on the convergence–confinement method (CCM) and field test data. The stress release law of the surrounding rock under support is determined based on the displacement back analysis method. The permitted displacement safety factor of silty clay under different subgrade conditions and the optimal supporting time of the initial supporting structure are determined by comparing the stress release ratio with surrounding rock displacement. The results indicated that the stress release ratio of surrounding rock in the silty clay stratum is approximately 78–90% when the coordinate displacement of the supporting structure and surrounding rock is stable under the current excavation and support conditions. For the surrounding rock of subgrade V in the silty clay stratum, the safety factor of the permitted displacement in the tunnel vault is approximately 2.91, and the initial support should be carried out within 1 m behind the face advancing. For the surrounding rock of subgrade VI1, the safety factor of the permitted displacement is 1.40, and the initial support must be carried out 1 m ahead of the tunnel face. For the surrounding rock of grade VI2, the initial support must be carried out 4 m ahead of the tunnel face.

Evaluation and Improvement of the Current CRCP Pavement Design Method

Continuously reinforced concrete pavement (CRCP) is a representative type of concrete pavement constructed with continuous steel bars without intermediate transverse expansions. With reference to pavement conditions, CRCP is an exceptional type of concrete pavement according to the Highway Pavement Condition Index (HPCI) and International Roughness Index (IRI). The two main design methods for CRCP are AASHTO 86/93 and the Mechanistic-Empirical Pavement Design Guide (MEPDG). Because of limitations of the AASHTO 86/93 design method, the MEPDG method is more reliable. While incorporating the interactions among geometrics, pavement structure layers, material properties, subgrade, traffic, and environmental conditions, and the prediction values according to the MEPDG method, it matched the measured results of crack spacing and crack width. The MEPDG punchout, crack width and spacing, and load transfer efficiency (LTE) models were evaluated, and results were compared with the test sections in three European countries consisting of different construction details, which were investigated and recorded between 2019 and 2021. In this sense, a calculation tool was developed to consider the influence of different parameters in design process. In addition, sensitivity analyses were executed for the development of punchout, considering various input parameters. The track surveying and the evaluation of the results indicated that the design process can be improved with consideration of some criteria such as crack formation time or adjustment of the correlation between crack width and crack spacing. Due to the very important function of erosion and resulting pumping in the deterioration of CRCP, it is advisable to include the influence of the base layer and the influence of different shoulder type and heavy traffic volume or effect of deflection in the calculations.

Dynamic Response Characteristics of Railway Subgrade Using a Newly-Developed Prestressed Reinforcement Structure: Case Study of a Model Test.

Poor subgrade conditions usually induce various subgrade diseases in railways, leading to some adverse influences. An innovative technology that involves installing a prestressed reinforcement structure (PRS) that consists of steel bars and lateral pressure plates (LPP) for subgrade was introduced to improve its stress field and provide compulsive lateral deformation constraints for slope. In this study, an investigation into the dynamic acceleration responses of railway subgrade strengthened according to different PRS schemes was presented using a 1:5 scale model test, aiming to explore the effects of the axle load, the reinforcement pressure, and the loading cycles on the acceleration characteristics of the subgrade. The experimental results showed that (1) after pretension of the steel bar, prestress loss occurred due to the soil creep behavior and group anchor effect, so a moderate amount of over-tension in practices would be necessary; (2) a distinctive periodical behavior of subgrade subjected to the cyclic loads was observed, the horizontal accelerations were generally less than the vertical accelerations at the same measurement heights, and the vibration energy attenuated gradually from the shoulder to the toe along the slope; (3) in the short-term tests, the peak accelerations at all measurement points had a linear correlation with the axle load, and oppositely, it showed an approximately linear decrease with the increasing reinforcement pressure; And (4) in the long-term tests, to simulate the heavy haul wagon with a 35 t axle load, the variation in the effective acceleration with loading cycles under reinforcement pressure 100 kPa initially exhibited a decrease and subsequently tended to be stable, which is apparently less than that without reinforcement pressure. Consequently, it was demonstrated that the PRS itself and increasing reinforcement pressure can effectively mitigate the subgrade vibration, and provide an appropriate alternative to improve the dynamic performance of railway subgrade under the moving train loads.

Behavior of Geogrid- and Geocell-Stabilized Unpaved Pavements Overlying Different Subgrade Conditions Under Monotonic Loading

Behavior of Geogrid- and Geocell-Stabilized Unpaved Pavements Overlying Different Subgrade Conditions Under Monotonic Loading