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2025 | Book

Proceedings of the 5th International Conference on Transportation Geotechnics (ICTG) 2024, Volume 8

Use of Rigid Inclusions, Retaining Structures, and Geosynthetics for Enhanced Stability

Editors: Cholachat Rujikiatkamjorn, Jianfeng Xue, Buddhima Indraratna

Publisher: Springer Nature Singapore

Book Series : Lecture Notes in Civil Engineering

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About this book

This book presents select proceedings of the 5th International Conference on Transportation Geotechnics (ICTG 2024). It includes papers on ground improvement methodologies, dynamics of transportation infrastructure, and geotechnical intricacies of mega projects. It covers topics such as underground transportation systems and heights of airfields and pavements. This book discusses diverse thematic landscapes, offering profound explorations into sensor technologies, data analytics, and machine learning applications. The publication highlights advanced practices, latest developments, and efforts to foster collaboration, innovation, and sustainable solutions for transportation infrastructure worldwide. The book can be a valuable reference for researchers and professionals interested in transportation geotechnics.

Table of Contents

Frontmatter
Finite Element Study of Unreinforced and Reinforced Unpaved Roads Subjected to Repetitive Vehicular Loading

An unpaved road system is frequently subjected to distresses arising especially from rutting. This phenomenon is mostly imbibed by the repeated vehicular loading acting on the aggregate layer. Traditional design undrained analysis of unpaved road design leads to overestimated aggregate thickness, which has an eventual toll on the project cost. Hence, it becomes imperative to comprehend the behaviour of the unpaved road system subjected to repetitive vehicular loading and its consequent effects on rutting. This paper reports, the detailed outcome of Finite Element (FE) based analyses of unreinforced unpaved road system comprising a soil subgrade represented by generalized shear strength parameters. The aggregate layer is subjected to repetitive vehicular loading arising from different axle loads, and their influence on the rutting behaviour is illustrated. Further, to counteract rutting originating from higher axle loading, a planar geotextile with different stiffnesses is introduced at the aggregate-subgrade interface. The study successfully shows that even a single layer of high tensile strength geotextile can completely arrest the accumulation of deformation beyond certain number of loading cycles.

Nayan Jyoti Sarma, Arindam Dey
Evaluation of Pavement Performance for Three Different Designs on the Expansive Subgrade: Three Case Studies

The expansive/reactive subgrade issue has been prevalent in pavement construction throughout Australia, with an estimated 30% of the country’s land surface covered by expansive soil. The shrink-swell problem caused by subgrade movement poses a significant challenge, damaging constructed pavements. Various approaches have been implemented to address this issue, mitigate the detrimental effects, and combat the damage caused by expansive soil. A minimum non-reactive or stabilised cover depth is recommended for low to moderately reactive subgrades. However, in the case of highly reactive subgrades, Austroads and state road agencies advise conducting a comprehensive geotechnical assessment to explore alternative solutions. This article evaluates the potential of geogrid and geotextile in resisting movement caused by reactive soil and assesses their effectiveness in minimising pavement damage. Three road sections were constructed using different configurations. One road section utilised only geogrid, another combined geogrid and geotextile, while the control section had no geogrid or geotextile. The geogrid and geotextile were placed over the expansive subgrade. The design traffic, subgrade CBR (California Bearing Ratio), and reactivity index of the subgrade were consistent across all three road sections to evaluate the performance of pavement configurations. Similar road sections were constructed on three different reactive soils in Adelaide. Over a period of time, road performance surveys were conducted following the guidelines provided by Austroads. The findings revealed that both the geogrid section and the geogrid with geotextile section outperformed the control section in all three locations. This indicates that the inclusion of geogrid and geotextile significantly improved the performance and durability of the road sections constructed on reactive soils.

Sagun Shrestha, Md Mizanur Rahman, Md Rajibul Karim, Hoang Bao Khoi Nguyen
Improved Liquefaction Resilience of Transportation Infrastructure with Geofoam Buffers

The efficacy of geofoam buffers in enhancing the seismic performance and dynamic load response of retaining walls and road embankments is well-established. However, limited research has been conducted to comprehend their role in mitigating soil liquefaction. This study investigates the shearing behavior of sands with Expanded Polystyrene (EPS) geofoam buffers, both before and after liquefaction, through a set of monotonic and cyclic simple shear tests. The investigation considers variations in layer thickness and geofoam density, employing two different thicknesses and three different densities in the tests. The results indicate that geofoam buffers reduce both pre-liquefaction and post-liquefaction shear strength of sand. However, they demonstrate a significant improvement in liquefaction resistance, with better outcomes observed at increased layer thickness and lower geofoam density. This enhancement is attributed to the exceptional energy absorption quality and compressibility of geofoam buffers. Nonetheless, this has a converse impact on the shear strength of sand. Consequently, it is imperative to carefully select the appropriate density and thickness of the geofoam layer to strike a balance between shear strength and liquefaction resistance.

Balaji Lakkimsetti, Gali Madhavi Latha
Direct Shear Testing of Recycled Construction and Demolition Waste-Geosynthetic Interfaces Under Cyclic Normal Loading

Geosynthetics have increasingly been used in geotechnical engineering applications due to their numerous benefits, including the cost-effectiveness, reliability and contribution to sustainability. When employed in transport infrastructure projects, geosynthetics may perform a variety of functions, leading to increased stability and longevity of the system. This paper describes a laboratory study carried out using a large-scale direct shear test apparatus to characterise the direct shear behaviour of the interfaces between a recycled construction and demolition (C&D) material and two geosynthetics (a geogrid and a geocomposite) subjected to cyclic normal loading. The direct shear tests were performed under a constant shear displacement rate, while the normal loading varied cyclically at predefined frequency and amplitude values. Direct shear tests under static normal loading were also performed for comparison purposes. Test results have shown that the interface shear strength and dilation behaviour tend to decrease under cyclic normal loading and are influenced by the applied frequency and amplitude. The peak and large displacement shear strengths of the interface with the geogrid exceeded those reached when the geocomposite was used, which may be attributed to more effective interlocking of the aggregates within the geogrid apertures.

Fernanda Bessa Ferreira, Pedro Valente Pereira, Castorina Silva Vieira, Maria Lurdes Lopes, Amir Shahkolahi
Experimental Investigation of Geogrid Reinforced Unpaved Sections Under Repeated Loads

Rutting has been one of the major pavement distresses that affect the performance and longevity of pavements constructed on weak or soft subgrades. Rutting is often associated with excessive deformation of the pavement layers under wheel loads, caused by layer densification and excessive vertical stress on the subgrade exceeding subgrade strength. Over the past two decades, geosynthetics have been used to reduce this excessive deformation by decreasing the vertical stresses on the subgrade. The primary objective of this study was to determine the effect of high-moduli geogrid-reinforced layers in reducing the vertical stresses on the subgrade. The current study addresses the objective by experimental investigation on reinforced pavement layers subjected to repeated loads. The experimental investigation involves conducting laboratory-based large-scale repeated load tests on geogrid-reinforced pavement sections constructed over weak subgrades. Based on the large-scale repeated load test results, it was observed that the geogrid-reinforced pavement sections reduced the vertical stress on the subgrade by 35–75% as compared to the unreinforced sections.

Krishneswar Ramineni, Nripojyoti Biswas, Anand Jagadeesh Puppala, Md. Ashrafuzzaman Khan
Performance Evaluation and Validating Design Inputs of Geogrid Reinforced Flexible Pavement Overlying Soft Subgrade: Insights from Laboratory to Field Testing

Conventional stabilization (using cement, lime, etc.) of soft subgrades incurs high project costs and raises environmental concerns. An alternative stabilization technique that can benefit the pavement without compromising design criteria and pavement performance is the foremost instigating aspect for highway industries. Thus, in this study, the on-field existing effective California Bearing Ratio (CBR) equal to 10% was first simulated in the large-scale test chamber. The prepared unstabilized and stabilized pavement base with Polyethylene terephthalate (PET) biaxial geogrid (PET80) (the ultimate tensile strength equal to 80 kN/m in the machine and cross-machine direction) sections were loaded with a static linear hydraulic actuator having a loading capacity of 100 kN for quantifying the benefit. The benefit rendered by geogrid is quantified in terms of Modulus Improvement Factor (MIF), which is used in mechanistic-empirical pavement design guidelines to assess the pavement's overall performance and reduce the use of natural aggregate. The crucial design inputs of MIF value tested at large-scale laboratory level are further validated in the field through conducting static plate load test for the initial design traffic of 150 MSA (Million Standard Axles) and CBR = 10%. The test results indicated a marginal difference in MIF values observed from laboratory and field validation. The MIF values of PET80 reinforced pavement obtained through laboratory and field were 1.96 and 1.89, respectively. Thus, the benefit indicated that the laboratory obtained MIF value was 1.04 times higher than the field. The overall reduction in asphalt and base layer was 38% and 15%, respectively, for MIF value considered in the study.

Praveen Bodhanam S, Deeraj Kumar Reddy Kambam, Ramu Baadiga
Model Test of the Influence of Cyclic Traffic Load on the Cumulative Deformations of GRS Bridge Abutment

This study investigates the deformation characteristics of geosynthetic reinforced soil (GRS) bridge abutment models under cyclic loading conditions through experimental methods. The GRS abutment models were built using well-graded sand as backfill material and biaxial geogrid for reinforcement. Settlements of the footings, displacements of the facing, and strains in the reinforcements were monitored and analyzed. The findings show that cumulative settlements increase as the cyclic load amplitude rises. Furthermore, facing displacement tends to increase with height, reaching its maximum at the top. The cyclic loading amplitude affects the strains in the upper reinforcements more significantly than those in the lower reinforcements.

Yafei Jia, Jun Zhang, Yewei Zheng
Measurement of Pressure Distribution on Roadbed Using Soil Bags During Plate Loading Tests

When constructing temporary roads for disaster recovery, it is necessary to improve the ground or replace the soil with high-quality soil when the ground conditions at the site are not good. However, it may be difficult to procure and transport a sufficient quantity of high-quality soil for replacement at some sites. In addition, when using cement to improve the ground, for example, the high strength of the ground can be maintained for a long period of time, but disadvantages are also encountered with its use. A ground improved by the addition of cement cannot be restored to its original condition. Moreover, cement is relatively expensive and has a negative impact on the environment. The use of soil bags, known as “do-nou” in Japan, is one of the effective methods for constructing temporary roads. The advantages of soil bags are that the strength of the ground can be improved more easily and quickly without the need for heavy machinery or modification by cement, and that the damaged areas can be repaired by replacing damaged soil bags with new soil bags. Thus, a roadbed can be simply removed and rapidly restored to its original condition. The loading characteristics of soil bags arranged as a stacked structure need to be understood. In the present study, in order to evaluate the loading characteristics of soil bags, cyclic plate-loading tests were conducted to investigate the pressure transfer among the soil bags and from the soil bags to the lower roadbed layer. It was found from the experiments that the earth pressure was distributed over a wider area in the structure with the staggered stacking of the soil bags than in the structure with the flat stacking of the soil bags.

Ryunosuke Kido, Natsu Nishimura, Shuuhei Mitsutani, Shigeru Maruo, Makoto Kimura
Evaluating the Reliability and Repeatability of Novel Laboratory Equipment in Investigating the Performance of Geosynthetic-Reinforced Soils

Geosynthetics have been employed as reinforcements to improve pavement behaviours. Previous attempts have been made to compare the performance of geosynthetic-reinforced soils with unreinforced soils through large-scale laboratory tests. However, large-scale testing is considered time-consuming and costly, which reduces the repeatability and reliability of such tests. Therefore, it is crucial to develop a small-scale testing apparatus, which is capable of evaluating the reinforcing effects of geosynthetics in pavements. In this study, a small-scale laboratory testing method was employed to investigate the performance of geocomposites in improving the penetration resistance of the reinforced soil system. Several tests were performed to validate the repeatability of the proposed testing apparatus. The results of this study demonstrate the capability of the developed testing method to produce consistent and repeatable results, which highlights its potential application in measuring the reinforcing effects of geosynthetics in pavements.

Jiacheng Qiu, Yue Chen, Yuekai Xie, Jianfeng Xue, Chaminda Gallage, Mark Jaksa
Effect of Granular Layer Properties on the Stabilisation of Weak Subgrade with Geosynthetics

Weak and soft subgrades present significant challenges for road pavements construction and conventional stabilization methods have become outdated due to environmental and economic concerns. The use of geosynthetics has become increasingly popular as a sustainable technique for subgrade improvement. However, limited research has been conducted focusing on the quantification of factors affecting on the stiffness improvement of weak subgrades with a granular layer and composite geogrids. This study focuses on examining the effect of gravel type on subgrade stabilization using model box tests conducted in a scaled model pavement steel box measuring length, width, and height as 1 m, 1 m and 1.2 m, respectively. The subgrade condition was kept constant for all tests and constructed to a thickness of 500 mm, maintaining CBR value as 2.5%. The gravel “Type 2.1 and Type 2.5” specified as the best and lowest quality gravel in “MRTS05- Unbound pavements” were used in 200 mm thick gravel layer for each test, respectively. Composite geogrid was placed at the gravel-subgrade interface in these tests. All the tests were subjected to a monotonic load applied on the top surface using a 200 mm diameter circular plate until reaching the point of ultimate failure obtaining parameters; vertical deformation and stress distribution to analyze the load bearing capacity and stiffness. The outcomes of the study verified the effect of granular layer properties on designing stabilized subgrades with geosynthetic reinforcement.

Shehan Mithila, Arnold Fernando, Shiran Jayakody, Yilin Gui, Chaminda Gallage, A. Shahkolahi, Raymond Chow, Nadeej Priyankara
Assessment of Geogrid Reinforcement on the Performance of Stabilized Subgrades Under Different Loading Conditions

Geogrid stabilization has gained significant attention in recent years as an effective method for enhancing the performance of subgrade soils. However, the reinforcement effect of the geogrids under different loading conditions has not been thoroughly investigated, which hinders a comprehensive understanding of subgrade stabilization. Therefore, this paper aims to investigate and compare the behavior of a stabilized subgrade with geogrids reinforcement under cyclic loading and monotonic loading conditions. The experiments were conducted within a steel model box measuring 1.0 m (length), 1.0 m (width), and 1.2 m (height). The subgrade layer was consistently maintained at a thickness of 500 mm and strength of 2.5% California Bearing Ratio (CBR). A granular layer of high-quality material with a thickness of 200 mm was applied on top of the weak subgrade and geogrid was placed at the interface between the granular layer and subgrade. The tests were conducted in a controlled laboratory setting, specifically measuring vertical displacement in response to monotonic and cyclic loading. The results were then analyzed to evaluate ultimate bearing capacity, stiffness and rutting thereby estimating the effect of geogrids on stabilization of weak subgrades. These findings are anticipated to contribute significantly to the development of design guidelines for stabilized subgrade with geogrids reinforcement. By incorporating these insights, the design, and optimization of geogrid reinforcement systems for subgrade stabilization can be enhanced, ultimately resulting in improved performance and increased longevity of transportation infrastructure.

Arnold Fernando, Shehan Mithila, Shiran Jayakody, Yilin Gui, Chaminda Gallage, Amir Shahkolahi, Nadeej Priyankara
Load-Bearing Behaviour of Geosynthetic Reinforced Soil Bridge Abutment for Railways with Waste Coal OB as Backfill Soil: Model Tests

Back-to-back MSE walls are a novel use of reinforced soil technology, and they are frequently implemented for bridge approaches and width-restricted highway and railway embankments. Urbanization has, however, led to an increase in the construction of transportation infrastructures. An investigation on model back-to-back MSE walls supporting railways has been carried out on a strong clay foundation. The foundation soil was clay with the desired shear strength. The model was conducted with a scale of 1/10th supporting railway tracks. Geogrid was used as a reinforcement, and wooden blocks were used as modular blocks for wall facings. The effects of different overlapping methods and distance between both walls on wall behavior have been evaluated. The scarcity of usable natural backfill soil for construction has been an alarming concern. Thus the recycled waste coal mine over dump was used as subballast/backfill soil. The coal mine overburden dump was used as a sustainable alternative to natural backfill/subballast. Cyclic loading simulating train loadings have been simulated in the model tests. Connected case of the model test was conducted in the laboratory. A finite element comparison of the model tests has also been conducted. A parametric study was carried out on back-to-back MSE walls subjected to heavy axle loads. Artificial intelligence-based ensemble models were used to predicted the geogrid tensile forces obtained from the parametric study.

Shilpa S. Vadavadagi, Sowmiya Chawla
How Does Multi-layer Reinforcement Affect the Performance of Geogrid Stabilised Pavement on Soft Subgrades?

Most studies and research projects in the world including past and on-going studies in Australia have been conducted on geosynthetic reinforced sections where the geosynthetic reinforcement was placed between the soft subgrade and the granular material. Very little experimental work has been conducted to document the mechanism of multiple layers of geogrid in the aggregate section. Most empirical and mechanistic-empirical design methods are also based on a single layer of geosynthetics reinforcement at the subgrade level. A critical need lies in the area of multiple layers of geogrid in the granular layer. This paper presents the mechanism of multi-layer geogrid reinforcement and its effect on the geogrid reinforced flexible pavements. Results from large-scale laboratory dynamic plate load tests as well as a full-scale field trial will be presented to compare the performance of double-layer geogrid reinforced granular pavement with single-layer reinforced and unreinforced sections.

Amir Shahkolahi, Chaminda Gallage
Subgrade Fluidization Under Cyclic Loading and Preventive Measure by Geosynthetics

The demand for increased axle loads and speeds of trains can diminish the stability of track substructure, leading to potential particle migration or slurry pumping under critical drainage conditions. This paper primarily focuses on the role of geosynthetics in mitigating the risk of soil fluidization potential under cyclic load. Laboratory experiments were conducted to evaluate the effectiveness of geosynthetics including geotextiles, geocomposites, and prefabricated vertical drains (PVDs). The laboratory study indicates that subgrade instability primarily occurs due to the migration of fines towards the subgrade surface and the substantial increase in moisture content (MC). Dynamic Filtration Tests (DFTs) reveal that geocomposite inclusion in rail tracks can reduce the fluidization potential of soft soils and the combined prefabricated vertical drains-geocomposite system can be used to mitigate the critical excess pore water pressure (EPWP) that accumulates in shallow or deeper soil layer due to activated radial drainage paths.

Joseph Arivalagan, Cholachat Rujikiatkamjorn, Buddhima Indraratna, Andy Warwick
Influence of Geosynthetic Encasement Stiffness on the Deformation Behavior of Geosynthetic Encased Stone Columns Composite Foundation Under Dynamic Loading

This paper details an experimental investigation involving shaking table tests on two composite foundations consisting of geosynthetic encased stone columns (GESC) with varying levels of geosynthetic encasement stiffness. The main objective is to examine the effect of the stiffness of geosynthetic encasement on the deformation behavior of the foundation models subjected to dynamic loading. The scaled-down foundation models were scaled in accordance with the similitude principles considering model size, stiffness of geosynthetic encasement, and input motions. The construction of the foundation models involved the use of gravel, sand, and geotextile reinforcement, and subsequently subjected to a sequence of sinusoidal excitations with rising amplitude. Results indicate the cumulative column settlements and soil settlements of the two foundation models increase notably as the input acceleration rises. The model with high stiffness of geosynthetic encasement has smaller settlements under the identical input motions in comparison to the model with low stiffness of geosynthetic encasement and has better seismic behavior in terms of settlement. In summary, with an increase in the stiffness of geosynthetic encasement, the deformation behavior of GESC composite foundation under dynamic loading is effectively improved.

Mingchang Ji, Fuxiu Li, Yewei Zheng
Effect of Geosynthetics in Asphalt Pavement Base Course on Bearing Reinforcement

It is an important issue to reduce the life cycle cost of Asphalt (As) pavement, which has a huge stock of more than 1.2 million km in Japan, in order to maintain and manage it. In this research, geosynthetics are installed in the base course to propose measures to extend the service life of As pavements by reinforcing the base course. In this paper, each material property was determined from friction property tests of geosynthetics and triaxial compression tests of silica sand. In addition, the effect of reinforcing the bearing capacity of the base course by laying geosynthetics was examined from both model experiments and analysis using loading tests in a small soil tank and FEM analysis. As a result, it was confirmed that the bearing capacity was increased by placing geosynthetics in the soil.

Kenichi Sato, Mei Akimitsu, Masaru Shimazaki, Junichi Hironaka, Yusaku Isobe
Remediation of Landslide Affected Road Using Geocell Reinforcement

Record-breaking rainfall from February to July 2022 caused widespread damage to multiple road sections within the local government area of Shoalhaven NSW, Australia. With approximately 2059 mm of rainfall in the Kangaroo Valley area alone, which was more than double the rainfall what residents would normally experience, Shoalhaven City Council experienced the wettest year on record. As a direct result of this rainfall, multiple sections along several roads have been severely affected by slope instability resulting in road damage (including 98 landslips affecting 23 roads) restricting local residents from accessing even nearby towns. Accordingly, the local Council sought feasible options that could provide temporary yet safe access to local residents. Among a number of feasible options considered, the proposed use of geocell reinforcement was selected as the preferred short-term remediation option to temporarily restore road use and facilitate safe passage. This paper presents a case study of the performance of a landslide-impacted section of Wattamolla Rd, Woodhill, NSW that was stabilised with geocell reinforcement. Limit equilibrium method and finite element analysis were undertaken to design the temporary access through the landslide affected section of the road. This study showed that geocell can effectively be used as a temporary solution and has feasibility as a permanent solution, where roads are impacted by landslide. Results showed that by confining infill material, geocell minimised axial deformations and lateral spreading and provided a semi-rigid platform that improved the stability of the road embankment.

M. M. Biabani, D. Trani, B. Tarrant
Reduction in Differential Heave of a Mechanically Stabilised Pavement on an Expansive Subgrade

Pavements, when constructed on expansive subgrades, are subjected to significant environmental loads and can fail prematurely, through the formation of longitudinal cracks. In Australia, the cover method is usually adopted to limit the adverse effects of a reactive subgrade on pavement performance. AS 2870-2011 is generally adopted as a guide for determining the cover required to limit the differential heave in pavements to tolerable limits and in doing so, it is expected that the pavements are less likely to undergo premature failure due to expansive subgrade. A recent study carried out by the authors indicates that mechanically stabilised pavements undergo less differential heave when compared to non-stabilised pavements of the same thickness and therefore are less prone to longitudinal cracking. This study aims to further the initial work undertaken by the authors, by determining the differential heave in both mechanically stabilised and non-stabilised pavements for a range of pavement thicknesses, suction depths/soil reactivities and thus quantifying the reduction in differential heave that can be achieved through mechanical stabilisation. It is expected that the outcomes of this research would give practitioners confidence in adopting mechanical stabilisation as a cost-effective way of dealing with the expansive subgrade problem rather than the conventionally adopted and more expensive cover method.

Abid Ali, Andrew Lees, John Buckley, Rajesh Bhavsar
Numerical Investigation of Geo-Naturals Effectiveness in Railway Embankments Against Mud Pumping

Railway infrastructure holds a crucial role in a nation's economic development as an affordable mode of transportation and promotes social integration. Mud pumping is one of the major challenges the railway network has faced recently in the soft and mountainous terrain within the ballast layer due to high-speed rail loads. Many researchers found that reinforcement of the ballast and sub-ballast interfaces with geosynthetics is a feasible solution to reduce mud pumping. Still, the demand for sustainable geotechnic solutions is continuously increasing, particularly in countries with abundant natural plant resources. However, studies on the natural soil reinforcement in rail embankment are scarce. In this current study, a numerical investigation was conducted to study the effectiveness of geotextiles and geogrids made from natural plants (Geo-Naturals) in railway embankments. The results showed vertical settlements drastically decreased when Geo-Naturals were included in the poor subgrade. Further, the estimated axial forces, in the lateral direction to the rail length, in single-layer geogrids were found to be the maximum in poor subgrade due to higher compressibility. Geogrids placed close to ballast and sub-ballast were effective in the reinforcement function. Geotextile placed at the subgrade and sub-ballast interface accelerated in-plane drainage and reduced excess pore water pressure, thus preventing mud pumping potential. The outcome of the current study showed the effectiveness of geo-naturals in sustainability, eco-friendliness, and cost-effectiveness in railway embankments.

Rongali Mahesh, Tadikonda Venkata Bharat, Rajan Choudhary
Development of an Empirical Correlation for Root Water Uptake and Total Leaf Area of “Alstonia Macrophylla” Using Potometer

Using vegetation for ground improvement is a sustainable, environmentally friendly, and cost-effective approach. The increase in shear strength and stiffness of soil is mainly due to the suction induced by root water uptake and the mechanical reinforcing effect provided by the tree roots. The root water uptake of the tree relies on the physiology of the tree and environmental parameters. The total leaf area, number of stomata present in a leaf, root system, spatial distribution of roots, etc. influence the root water uptake as the physiological parameters. In this study, an empirical correlation was developed between the root water uptake (Sp) and total leaf area (TLA) of Alstonia macrophylla (Attonia). A Potometer, which can be used to measure the transpiration of a small tree, was kept in a controlled environmental condition to eliminate the influence of extraneous variables. Previous studies have revealed that more than 99% of root water uptake is lost through leaf transpiration. Consequently, it was assumed that the amount of water lost through transpiration is equivalent to the amount of water taken up by the roots at any given time. This assumption leads to approximating the root water uptake rate by measuring the transpiration rate using a Potometer, which uses the traveled distance of an air bubble in a small glass tube.

Supipi Kaushalya, Muditha Pallewattha, Udeni Nawagamuwa
Influence of Ballast Fouling on Reinforced Ballasted Railway Track—A Numerical Investigation

Ballast fouling is a significant problem in railway track infrastructure, as it can lead to reduced track performance, increased maintenance costs, and even derailments. Fouling occurs when fines such as silt and clay infiltrate the ballast layer, which can reduce the ballast's drainage capacity and lead to water accumulation. Geosynthetics have been increasingly used as a solution to ballast fouling, as they can provide reinforcement and confinement to the ballast layer, which helps to prevent the infiltration of fines and the degradation of the ballast. However, the numerical studies related to reinforced ballasted railway tracks are limited. Hence, in the present study, an attempt has been made to investigate the effectiveness of geosynthetics in drainage capacity in the occurrence of ballast fouling through numerical simulation. A finite element seepage analysis was conducted using SEEP/W to assess the effect of ballast fouling on the drainage capacity of reinforced ballasted railway tracks. A parametric study is carried out, including the impact of different levels of fouling with varying depths of placing geogrids/geotextile in improving the drainage capacity of the ballast. It finds that closer placement of geosynthetic layers to the bottom of the track enhances drainage, but increased ballast contamination reduces overall drainage due to decreased strength from the geosynthetics. The study also showed that reinforcement techniques could effectively improve the drainage capacity of the ballast as it delays the ballast fouling.

M. D. Godson, Annapurna Basayya Balulmath, Bande Giridhar Rajesh
A Case Study on Lateral Ground Movements Due to Piling Driving in Soft Clay Near an Existing Elevated Roadway

As the populations of many major cities in Australia continue to grow, the availability of land to construct new road infrastructure is becoming scarce. As a consequence, existing roadways are being augmented or brownfield sites are being utilised for future development. One cost-effective way to increase the capacity of existing roadways in densely populated and congested areas is to use elevated roadways or even widen the existing ones. However, as a consequence, there is usually a need to construct new footings in close proximity to existing footings supporting other structures. This paper presents some results of field monitoring trials during the installation of precast concrete-driven piles in deep soft clay. The pile driving trials were undertaken to assess the potential effects on an existing elevated roadway founded on pile groups. Lateral ground movements in the order of 9–90 mm were observed and varied according to the ground conditions, number of piles installed, and position of the inclinometers used to measure ground movement. The field data is compared to three-dimensional finite element analysis and the shallow strain path method, and overall good agreement is observed. A discussion on how these free field movements may be used to assess the behaviour of an existing pile is also provided. It is shown that the impact on an existing pile can be readily assessed using simple published chart solutions and/or finite element analysis.

Sean Goodall, Richard Merifield
Bi-directional Load Cell Testing of 1.5-Metre Diameter Bored Concrete Piles within Surficial Deposits Near the Darling Scarp: Insights from the METRONET, Byford Rail Extension Project in Perth

This paper presents the results of bi-directional load cell testing conducted on two pre-production 1.5-meter diameter bored concrete piles as part of the METRONET Byford Rail Extension project in Perth. The testing aimed to assess the geotechnical capacity, load–displacement response, and shaft friction parameters of the piles within surficial deposits near the Darling Scarp. The information obtained from the pre-production testing has been valuable in supporting the foundation design of a 46-span rail viaduct structure, which will comprise a total of 131 1.8-meter diameter piles. Bi-directional load cell testing involves the installation of load cells within piles, allowing for the direct measurement of load distribution along the pile length and determination of its ultimate pile capacity. The load–displacement response obtained through the testing provides insights into the pile-soil interaction and facilitates the establishment of shaft friction parameters. In Perth, bi-directional load cell testing of large diameter piles is not yet common practice. Increased utilization of bi-directional load cell testing in large diameter pre-production piles may provide economic value to future projects. The insights gained from the testing enhance the accuracy of shaft friction design parameters and contribute to improved safety in design, ensuring reliable and cost-effective foundation solutions. The successful application of bi-directional load cell testing in this study emphasizes its potential as a valuable tool for geotechnical engineering practices in Perth and beyond.

Anton Hamp, Andy Websper
Investigating Passive Loading of an MSE Wall Bridge Abutment Supported on a Piled Foundation

Consolidation of embankments constructed on soft soils generates lateral loading from the moving soils. Adjacent piles subjected to the lateral loading are known as passive pile loading. Passive pile loading can be critical in design of bridge abutments supported on a piled foundation when soft soil is present. This is a complex soil-structure interaction that can be assessed using finite element modelling. This paper compares the methods available to estimate passive pile loading against finite element modelling using PLAXIS 2D. A case study is presented of an MSE wall bridge abutment supported on a piled foundation with a soft layer present. This paper investigates options to reduce bending moments in the piles. The following cases were investigated: sand in lieu of the soft layer; isolating the MSE wall from the columns supporting the bridge; replacing the MSE wall with a cantilever-reinforced concrete wall; and an innovative cantilever extended pile cap. The last solution reduced pile bending moments and pile head deflections, offering the best solution amongst the cases studied.

William Hermans, Simon Tan
Overcoming Challenges: The Construction of the Bletchley Flyover on East West Rail Phase 2

The Bletchley Flyover is a part of East West Rail Phase 2 and it allows the East West Rail lines to cross over the West Coast Main Line (WCML) and three roads in Bletchley. During the Phase 2 works, the spans over the WCML had to be reconstructed since the existing viaduct structure had failed the assessment. However, constructing a new span across the WCML was challenging due to various constraints such as the presence of adjacent properties, land boundaries, overhead electrification, and the difficulty of working around the West Coast Main Line without causing disruption. Moreover, designing the foundation for the new span bridge was also challenging since it had to accommodate the existing viaduct foundations consisting of shallow under-reamed piles within the footprint of the new linear foundation for the abutments. Assessing the existing foundation for the new loads in accordance with the current standard and designing a skewed bridge abutment foundation of approximately 90 m in length in REPUTE, which considers the pile cap to be an infinitely rigid structure were also significant design challenges. Additionally, there was little historical information available for the existing foundations, making it harder to design the foundation for the new span bridge. Cross hole seismic testing was carried out as part of the design to determine the size of existing under-reamed piles.

Anurag Kushwaha, Danielle Allum, Harshal Vaidya, Hrudya C. Sekhar, Rafael Luque Suarez
Influence of Pile Type on the Load Transfer Mechanism in Pile-Supported Low Embankments Under Cyclic Loading

This study presents two large-scale model tests to investigate the load transfer mechanism of floating pile-supported embankments subjected to cyclic loading. The soft soil and piles were prepared using Kaolin clay and reinforced concrete. Results on cumulative settlements, pile efficacy, and strain distribution were obtained and analyzed under semi-sinusoidal cyclic loading. The results show that the floating pile increased surface settlement by 7.1% compared to the end-bearing pile-supported embankment. The soil arching in floating pile-supported embankment does not degrade under cyclic loading but slowly enhances with settlement development. Floating piles result in less arching, membrane effect, and pile strain.

Chuan-Bao Xu, Jun Zhang, Jun-Jie Zheng, Yewei Zheng
Experimental Study of Pile-Supported Embankment in the Framework of the French Research Project ASIRI+

The French national project ASIRI+ (2019–2024) is the extension of the ASIRI project (2005–2012) and aims to update previous recommendations for the design of soil reinforced by rigid inclusions. This project ( https://asiriplus.fr/ ) mobilized forty-three partners (practitioners and academics) to act for a better understanding of the behavior of the composite foundation that is a soft soil reinforced with vertical rigid inclusions with a load transfer platform on top of it. This load transfer platform is a very important component of the system and the efficiency of this technique depends on the quality of this platform. Two types of platforms can be installed on rigid inclusions: granular platform reinforced or not by geosynthetics and soil treated platform. Specific studies consisting of full-scale experimentations, centrifugation tests, and numerical simulations were carried out to analyze the mechanisms developed within these platforms and propose implementation rules and design methods according to the type of loading applied (static loads, traffic loads, etc.). This paper focuses on load transfer platform under static load. This paper presents an experimental study on load transfer platforms in pile-supported embankments.

Laurent Briançon, Luc Thorel, Bruno Simon
Fire and Ice: Innovative Applications of Deep Foundations

Alternative types of deep foundations have been designed and are under construction at Denali and Yellowstone National Parks (NPs) in the United States. At Yellowstone NP, the design mitigates hot temperatures, gases, and caustic groundwater across the Yellowstone River in a valley bottom. At Denali NP, the design mitigates degrading permafrost and an advancing rock glacier on a steep mountain slope. The designs are different in almost every way except that they show the versatility and value of drilled foundation elements. The different foundation conditions that must be dealt with are the result of past decisions and they exemplify the sentiment that the good sites are already taken. Each of these is a major bridge project where the alternatives to building at these locations had severe consequences, and the avoidance of these consequences is what drove the innovation. At Yellowstone NP, large diameter drilled shafts, with innovative casings, were used to reduce the number and depth of penetrations above a hydrothermal resource and to minimize the surface area exposed to the environment. At Denali NP, micropiles and tiedown anchors were used in surprising ways to provide a reinforced rock foundation capable of supporting construction and long-term loads, including the continued evacuation by the rock glacier. Thermosiphons were added alongside these elements to keep ice in an abutment frozen for the bridge service life and to mitigate the effects of changing climate.

Scott Anderson, Brian Collins, Mark Vessely, Cole Christiansen, Seamus Millet, Heather Brooks, Evan Garich
Foundation Behaviour in Unsaturated Expansive Soils: A Review

Foundation designs typically rely on traditional soil mechanics principles, which assume the soil is either completely saturated or entirely dry. However, the impact of soil suction associated with the alternate wetting and drying conditions in the unsaturated zone (i.e. soil suction) is generally overlooked in traditional design approaches. This may lead to ground heave or differential settlement contributing to extreme distress to various infrastructures built in unsaturated expansive soils. Shallow foundations are usually built above the groundwater table, leaving much of the soil beneath them unsaturated. As a result, soil suction greatly affects the bearing capacity and settlement behaviour. Further, deep foundations extend through the active layer of unsaturated expansive soil until reaching the bedrock or rest on a high-quality soil-bearing stratum. The volume-changing behaviour of the unsaturated expansive soil typically moves upward along the pile, creating additional positive friction that can potentially uplift lightly loaded structures. This paper presents a review of foundation behaviour in unsaturated expansive soils. Particularly, this review focuses on the influence of matric suction on soil-volume expansion which contributes to the ground heave, soil-structure interface shear strength properties, bearing capacity, and load-settlement behaviour of foundations.

Shanujah Mathuranayagam, Samanthika Liyanapathirana, William Fuentes, Chin Jian Leo, Pan Hu
The Use of Micropiles in an A-Frame Arrangement to Stabilize Dalrymple Road on the Eungella Range, Mackay, Queensland Australia

This paper details the investigation, design, construction, and monitoring processes performed in the employment of a micropile solution to restore a failed section of Mackay Regional Council’s Dalrymple Road, located near the township of Eungella. The road asset was restored using micropile in an A-Frame arrangement. The restored site comprised a 140 m long section of Dalrymple Road where unstable upper soils of colluvial origin were encountered at depths of up to 7 m within the road corridor restoration extents. The road had collapsed in late January/early February of 2019 following the area experiencing a week of inclement weather with rainfalls in the order of 970 mm. Queensland Transport and Main Roads (TMR) have been historically cautious in the use of small diameter piles (micropiles) as a piled support option for managing stability issues associated with their road assets. Caution is advisable where deep seated failures are involved, as micropiles may not be well suited to mobilize the large resisting forces required to ensure stability, or where there is potential for loss of material downslope on the passive side of a micropile remediated site, in which case the effectiveness of a micropile solution is lessened due to their small diameter. Concerns regarding the use of micropiles in such situations are overcome through rigorous investigation, design, and construction processes. During construction, the site was instrumented for long-term performance monitoring purposes. Monitoring commenced in 2020 following the completion of construction works and is continuing annually. Monitoring carried out following about a 1000 mm of rainfall in the week of January 2023 indicated a total cumulative lateral displacement in the order of 10–15 mm.

Lambert E. Ezeajugh
Effects of Pile Extraction on Adjacent Bridge Structure in Soft Soil

While the effects of displacement piling on adjacent structures are well documented, limited data exist on the ground movements induced by the extraction of displacement or close-ended piles. This paper presents a case study involving significant movements observed in a newly constructed river bridge abutment, which occurred following the commencement of the extraction of adjacent temporary bridge piles. It is deemed that soil loss into the voids created by temporary pile removal is possibly the primary mechanism that caused the movements of the permanent bridge. Based on back-analysis of the survey monitoring data, the authors found that pile hole collapse mechanism may not be concentric in nature and the use of elastic cavity expansion solution could not adequately explain the preferential movements observed at the bridge abutment. Conversely, by adopting an asymmetric pile hole closure with elastic–plastic materials in the 3D finite element analysis (FEA), the authors were able to match all the measured horizontal movements at various locations of the permeant bridge abutment.

Bosco Poon, Kim Chan
Bi-Directional Static Load Testing of Large Diameters Piles in Melbourne, Australia

Bi-directional axial compression load tests using multi-level Osterberg cells (O-Cells) were undertaken on two 2.1 m diameter sacrificial test piles for the Pakenham Level Crossing Removal project in Melbourne. The purpose of the tests was to validate the design assumptions for the permanent works piles and increase the geotechnical reduction factor used for design. The target test load was 19 MN with a maximum 35 MN O-Cell loading capacity available for each pile. Both piles exceeded the design expectations from a load–displacement perspective and the maximum sustained loads were 32 MN and 24 MN for test piles TP1 and TP2, respectively. This paper presents an overview of the O-Cell test design and site setup, the test results and analysis, and the potential impact of construction methodology on pile capacity. Two CPTs were also carried out in close proximity to the test piles, prior to the load tests. The ultimate pile shaft and end bearing resistances were estimated using the CPT results and these pile capacities are compared with the load test results in this paper. The findings demonstrate that O-Cell testing can be successfully used to optimise large diameter pile lengths by adopting a higher geotechnical reduction factor in the design.

Paul Menton, Xue Le, Richard Flynn
Relaxation of Driven Pile Resistance Assessed by Dynamic Pile Load Tests

Driven piles are frequently used as deep foundations to support structures when soils at shallower depths are not suitable to provide the resistance needed. Depending on soil types at a project site and pile driving conditions, driven piles may experience setup, i.e., increase in pile resistance, or relaxation, i.e., decrease in resistance, after installation. This paper presents the investigation performed on piles experienced relaxation with time after installation. The piles were driven as foundations to support roadway bridges. Dynamic pile load tests were performed to assess the pile resistance during installation and at a later time after installation. The investigations showed that significant relaxation in pile tip resistance can occur, resulting in relaxation of pile total resistance. The properties of the piles used in the study, soil properties where the piles were driven, and pile load test results are presented. Potential correlations between the soil/pile properties and pile relaxation behavior are explored. The results show that the piles experienced relaxation were installed in predominantly coarse-grained soils, and majority of these piles had coarse-grained material at the pile tip. In addition, the steel closed-ended pipe piles, on average, experienced more relaxation compared to the H-piles.

Ömer Bilgin, Saeed Alzahrani, Chengxi Jiang
The Role of Retaining Walls in Trackbed Deflection—A Numerical Analysis of Railway Slab Tracks

Retaining walls play a critical role in railway slab tracks by significantly affecting trackbed deflection (TD), attributable to train loading. This influence, unfortunately, has been traditionally overlooked in railway retaining wall designs. This study introduces a three-dimensional numerical model that includes the slab track, a buttressed embankment, and the ground. Using the finite difference method, the model reveals insights into TD characteristics under railway loading. An artificial neural network led to the development of a metamodel to predict TD. This metamodel considered five fundamental input variables: the width, position, inclination of the retaining wall, the supported embankment's height, and the ground bearing capacity. A subsequent design strategy based on the metamodel for gravity retaining walls was proposed to control TD and prevent it from exceeding a set limit. And an explicit formula for estimating the minimum wall width required to control TD is provided. This research emphasizes the significant impact of gravity retaining wall behavior on TD, especially at the track edge close to the wall. In most cases, constraining the movement of constructed retaining walls results in less than a 10% decrease in TD.

Pengju Lyu, Qiang Luo, Tengfei Wang, Kaiwen Liu
A Perspective on Stabilizing Landslides and Slopes in Challenging Terrain Using Rigid Structural Elements

In challenging geologic and topographic conditions, traditional earthworks and drainage measures may be unfeasible, impractical, or insufficient, and rigid structural elements are used to stabilize existing landslides and to enhance the stability of slopes for transportation projects. Rigid elements commonly used for slope stabilization include drilled shafts or driven piles for passive slope support, retaining structures, and post-tensioned ground anchors for active support. A perspective is provided on these types of rigid inclusions using experiences from landslide and slope stabilization projects in the challenging, glaciated, and mountainous geography of western Canada. The perspective includes key considerations in the selection of the most effective structural support elements and integrating structural support with traditional earthworks and drainage measures for the optimal overall geotechnical approach to design. Geotechnical and structural monitoring results from completed landslide stabilization projects are described to illustrate the effectiveness of the rigid elements during and after construction. Important learnings from construction are provided, and results of geotechnical instrumentation are evaluated and interpreted. Based on experiences from several geotechnical designers and projects, the authors provide a summary of the site conditions that influence the selection of rigid inclusions and structural support for the stabilization of steep slopes.

Rod Kostaschuk, Martin Devonald, Simon Gilazghi, Cam Breckon, Jan Stirling
Concrete for Rigid Inclusions—Potential Risks and Their Mitigation Strategies

Rigid inclusions are used for ground improvement works and are usually designed as unreinforced low strength concrete columns with typical diameters ranging from 270 to 600 mm and depths up to 25 m. The installation methods of rigid inclusions often involve full-displacement drilling methods, including (but not limited to) Controlled Modulus Columns (CMC) and Controlled Stiffness Columns (CSC), or non-displacement techniques like Continuous Flight Auger (CFA) Columns. Both kinds of methods utilise pumped and pressurised in-situ concrete for the construction of rigid inclusions. Alternatively, vibro-displacement (VD) methods are also a proven technique for the installation of rigid inclusions, but VD do not use pressurized concrete. Ground improvement using cast-in-place rigid inclusions often requires the use of low to medium strength concrete to achieve project-specific design criteria. Concrete mix designs need to allow sufficient workability and stability requirements for the fresh concrete to be able to withstand external pressures from pumping and placement. This is important for minimising the risk of creating integrity issues or defective columns. Also, the workability life and the early strength development of the concrete mix need to be considered to allow for high quality rigid inclusions as well as smooth and efficient construction. This paper discusses the importance of adequate workability of the fresh concrete and, when fresh concrete performance is inadequate, outlines the effects of unsuitable concrete mix designs on the quality and integrity of rigid inclusions. The paper also highlights selected construction-related aspects—for instance, insufficient concrete placement and site traffic—that may affect the quality and integrity of rigid inclusions.

Martin D. Larisch
Design of Retaining Wall Structures in Bringelly Shale with Swelling Potential

Bringelly Shale, consisting of claystone and siltstone with occasional sandstone, is a major formation of Wianamatta group in the Sydney Basin. Due to the weak cementation and presence of swelling clay minerals, the design and construction of retaining wall structures in Bringelly Shale with swelling potential in Western Sydney present unique challenges that demand careful consideration. This paper presents a case study of an approximately 20 m-deep excavation into Bringelly Shale at the St Marys metro station site on the Sydney Metro—Western Sydney Airport, Station Boxes and Tunnelling project. The design approach to the retaining walls comprising of soldier piled wall and ground anchors is described in detail. An instrumentation and monitoring plan developed and implemented during the construction is presented and discussed. The performance of the retaining wall was monitored with inclinometers and optical survey prisms at each stage of excavation and support installation. The paper also includes a discussion on the retaining wall performance during the construction. The findings of this paper serve as a valuable resource for geotechnical engineers, designers and practitioners, who will be involved in future projects dealing with Bringelly Shale and its swelling potential.

Bo. Xu, Q. J. Yang, Eric Zhao
Safety and Sustainability in Design of Embedded Retaining Walls

Embedded retaining walls are commonly used in deep excavations for sections of retained cuts or cut and cover tunnels, in Transport Infrastructure projects. Safe, sustainable, and reliable design of retaining walls is critical, and sustainable designs can be evolved by optimisation of design approaches as well as by using alternate options and observational methods. This paper presents the challenges in the design of embedded retaining walls, following various design approaches and partial factors in accordance with the Australian Standards AS 5100, AS 1170, AS 4678, and Eurocode 7, using a live example from a station box excavation in a Transport Infrastructure project in Sydney. Results of finite element modelling using two constitutive models, demonstrate that the various design approaches and application of load and material factors based on the provisions in various Australian Standards, result in different design outcomes. The effects of action in terms of maximum bending moments and shear forces, resulting from these design approaches analysed using two constitutive models are presented, demonstrating the variation in the design outcomes which will result in different designs when the different codes are followed. The approach provided in AS 5100.3 where the analysis is conducted using unfactored loads and soil properties and then the effects of action are factored, seems more appropriate, in comparison to the other approaches. Further, design optimisation is possible using reliability-based methods to arrive at the appropriate factors in the design and achieve a more sustainable safe and reliable design.

Sujatha Manoj, Harry Poulos, Naveen Kumar Meena
Instrumentation Selection Criteria for Field Monitoring of Retaining Systems

In today’s technology era, many alternatives are available for measuring soil and structural response, and direct measurement in-situ using instruments/sensors is the best option among several alternatives. Proper selection of instrumentation for any field test is essential to obtain reliable data. The present paper discusses the instrumentation plan adopted for a field test that was conducted to assess the suitability of geofoam as a compressible inclusion material in retaining walls. The compressible inclusion is a material that is introduced between the wall and backfill which deforms in a controlled manner allowing the soil to change its stress state from at-rest to active or near-active state, causing lateral pressure reduction on the wall. The field testing aimed to measure the earth pressure on the wall, wall deflection, and compression of the geofoam. The options available for measuring each of these parameters, such as earth pressure cells and their type, inclinometer, displacement transducers, etc., are analyzed with the criterion for selecting the right instrument for measuring each parameter. Each instrument has its challenges and some of these challenges encountered during field testing are discussed in detail about earth pressure cells and inclinometers. To make sense of the data obtained by instruments, the user must have some secondary measurement tools to justify the data obtained by primary instruments.

Dinesh Bishnoi, Vikas Patil, S. M. Dasaka, A. Murali Krishna
Instrumentation Selection for Field Monitoring of Retaining Systems with Geofoam Inclusions

In today’s technology era, many alternatives are available for measuring soil and structural response, and direct measurement in-situ using instruments/sensors is the best option among several alternatives. Proper selection of instrumentation for any field test is essential to obtain reliable data. The present paper discusses the instrumentation plan adopted for a field test that was conducted to assess the suitability of geofoam as a compressible inclusion material in retaining walls. The compressible inclusion is a material that is introduced between the wall and backfill which deforms in a controlled manner allowing the soil to change its stress state from at-rest to active or near-active state, causing lateral pressure reduction on the wall. The field testing aimed to measure the earth pressure on the wall, wall deflection, and compression of the geofoam. The options available for measuring each of these parameters, such as earth pressure cells and their type, inclinometer, displacement transducers, etc., are analyzed with the criterion for selecting the right instrument for measuring each parameter. Each instrument has its challenges and some of these challenges encountered during field testing are discussed in detail about earth pressure cells and inclinometers. To make sense of the data obtained by instruments, the user must have some secondary measurement tools to justify the data obtained by primary instruments.

Dinesh Bishnoi, Vikas Patil, S. M. Dasaka, A. Murali Krishna
Metadata
Title
Proceedings of the 5th International Conference on Transportation Geotechnics (ICTG) 2024, Volume 8
Editors
Cholachat Rujikiatkamjorn
Jianfeng Xue
Buddhima Indraratna
Copyright Year
2025
Publisher
Springer Nature Singapore
Electronic ISBN
978-981-9782-41-3
Print ISBN
978-981-9782-40-6
DOI
https://doi.org/10.1007/978-981-97-8241-3