Monopiles vs. Group Piles in Marine Bridge Construction: A Comparative Case Study of the Mumbai Coastal Road Project

Abstract

The Mumbai Coastal Road Project (South) Package-1 includes major infrastructure such as a navigational bridge, interchanges, sea walls, and reclamation works, with one of the most complex components being foundation construction in the intertidal zone. This thesis examines the use of monopile foundations for bridge structures in this marine environment, comparing them to traditional group pile systems. Through a case study of the Mumbai Coastal Road Project, it evaluates structural performance, construction methods, environmental impact, and cost-efficiency. Results show monopiles offer advantages in reduced construction time, simpler logistics, and lower material use, particularly in moderate water depths with uniform soils. However, group piles remain preferable in complex loading and variable ground conditions. The study emphasizes the importance of site-specific analysis and contributes to the advancement of sustainable and efficient marine foundation systems.

Introduction

Marine bridge construction poses unique challenges, including complex geotechnical conditions, dynamic hydrodynamic forces, and environmental sensitivity. Monopile foundations, widely used in offshore wind farms, are emerging as a viable alternative to conventional systems (like pile groups and well foundations) due to:

• Structural simplicity

• Faster installation

• Lower environmental footprint

2. Mumbai Coastal Road Project (MCRP)

Mumbai’s MCRP is a large-scale infrastructure initiative aimed at easing traffic congestion by creating an 8-lane, 29.2 km expressway along the western coastline. A critical component involves marine bridges and viaducts, particularly in Package 1 (Marine Drive to Lotus Jetty), where monopile foundations are being used.

3. Rationale for Monopile Use

Monopiles were adopted in MCRP for their:

• Quicker installation and reduced underwater work

• Better performance under lateral and seismic loads

• Smaller marine footprint

However, their application in Indian marine bridge infrastructure is new and under-researched, prompting this study.

4. Objectives of the Study

• Understand design and construction of monopile foundations.

• Compare costs, time, environmental impact, and maintenance with traditional methods.

• Assess their suitability for future Indian marine infrastructure.

5. Monopile Overview

• Structure: A single large-diameter vertical pile (2–4 m), designed to resist axial, lateral, and dynamic loads.

• Construction Methods: Driven, bored, or drilled, depending on site conditions.

• Behavior: Requires detailed analysis of soil–structure interaction, especially in soft or layered marine soils.

6. Evolution of Monopile Technology

• 1950s–90s: Initially used in shallow coastal structures and oil platforms.

• 2000–Present: Offshore wind industry drove rapid advancement—larger sizes, advanced modeling (e.g., FEM, p–y), and real-time monitoring.

• Now used in major bridge projects like Hong Kong–Zhuhai–Macau Bridge.

7. Comparative Performance

Adapted from Bhattacharya (2014), IRC 78:2014, IS 2911

8. Challenges with Monopiles in India

• Soil variability, such as soft marine clay over basalt.

• Corrosion risks in saline waters.

• Vibration/noise during installation near urban areas.

• Lack of Indian design codes and local data.

Despite these, engineering studies suggest long-term benefits in cost and constructability when well designed.

9. Study Limitations

• Focuses only on structural and cost performance.

• Limited to Package 1 of the MCRP.

• Excludes hydrological modeling and detailed procurement data.

Conclusion

Structural and Geotechnical Performance • Monopiles demonstrated excellent structural efficiency, particularly in resisting lateral loads, which are predominant in marine environments. • Their performance in soft marine clay overlying rock strata, as encountered in MCRP, was found to be favourable, especially with drilled installation techniques and appropriate scour protection. • Design methodologies adopted from international standards (API, Eurocode, DNV) provided a reliable framework in the absence of detailed Indian codes. Construction and Time Efficiency • Monopile installation was significantly faster than conventional pile group foundations, reducing the total foundation construction time by up to 70% per pier. • The requirement for less staging and underwater construction simplified logistics and minimized risks, especially in high-traffic marine zones. Cost Effectiveness • Despite higher per-unit material costs, the overall foundation cost per pier using monopiles was observed to be 20–30% lower due to savings in construction time, formwork, and material quantities. • Lifecycle costs were also lower, with reduced maintenance requirements and better durability under marine exposure. Environmental Impact • Monopiles resulted in lower seabed disturbance, reduced construction noise (in drilled systems), and minimal disruption to the marine ecosystem. • These factors contributed to easier environmental clearances and compliance with Coastal Regulation Zone (CRZ) conditions in sensitive areas like Haji Ali Bay. Practical Challenges • The lack of Indian design codes and contractor familiarity posed initial challenges, often necessitating reliance on foreign consultants or hybrid design approaches. • Availability of large-diameter drilling rigs and skilled manpower was limited but gradually improving through capacity building during MCRP. Key Conclusions Based on the comparative analysis and field data from the Mumbai Coastal Road Project: • Monopile foundations offer a structurally sound, cost-efficient, and environmentally sustainable alternative to conventional pile group systems in marine bridge construction. • Time savings and reduction in complexity make monopiles particularly suited for urban coastal projects where rapid execution and minimal disruption are critical. • Monopiles can be successfully designed for Indian geotechnical conditions using internationally validated tools, pending future updates to domestic standards. • The successful implementation in MCRP suggests scalability for use in future coastal infrastructure across India. The Mumbai Coastal Road Project has served as a pioneering case in the Indian context for monopile use in bridge foundations. Its success opens up opportunities to rethink traditional marine construction methods and embrace smarter, faster, and more resilient foundation technologies. With appropriate regulatory, technical, and educational support, monopiles can redefine the future of India’s coastal infrastructure.

References

Standards and Design Codes [1] American Petroleum Institute (API). (2014). API RP 2A-WSD: Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms- Working Stress Design. [2] Bureau of Indian Standards (BIS). (2015). IS 2911 (Part 1/Sec 2): Design and Construction of Pile Foundations – Bored Cast-In-Situ Concrete Piles. [3] Eurocode 7. (2004). EN 1997-1: Geotechnical Design – General Rules. [4] DNV GL. (2016). DNVGL-RP-C212: Offshore Substations – Foundations. [5] Indian Roads Congress (IRC). (2011). IRC: 78 – Road Bridges: Foundations and Substructures. [6] Ministry of Road Transport and Highways (MoRTH). (2020). Specification for Road and Bridge Works (5th Revision). Books and Academic References [1] Poulos, H. G., & Davis, E. H. (1980). Pile Foundation Analysis and Design. Wiley. [2] Das, B. M. (2015). Principles of Foundation Engineering (8th ed.). Cengage Learning. [3] Tomlinson, M., & Woodward, J. (2014). Pile Design and Construction Practice (6th ed.). CRC Press. [4] Bowles, J. E. (1997). Foundation Analysis and Design (5th ed.). McGraw-Hill. Journals and Conference Papers [1] Doherty, James & Lehane, Barry. (2017). “An Automated Approach for Designing Monopiles Subjected to Lateral Loads.” V009T10A013. 10.1115/OMAE2017-61603 [2] Mu, Linlong & Xingyu, Kang & Feng, Kai & Huang, Maosong & Cao, Jie. (2017). “Influence of vertical loads on lateral behaviour of monopiles in sand.” European Journal of Environmental and Civil Engineering. 22. 1-16. 10.1080/19648189.2017.1359112. [3] George Gazetas, Seismic response of end-bearing single piles, International Journal of Soil Dynamics and Earthquake Engineering, Volume 3, Issue 2, 1984, Pages 82-93, ISSN 0261-7277, https://doi.org/10.1016/0261-7277(84)90003-2 [4] Basack, S., & Dey, A. (2020). “Assessment of Monopile Foundations in Coastal Structures: Design and Performance,” Indian Geotechnical Journal, 50(3), pp. 412– 425. [5] Liu, Y., & Randolph, M. (2010). “Monopile foundations for offshore wind farms: Comparison of design methods,” Journal of Geotechnical and Geoenvironmental Engineering, ASCE. [6] Sharma, R. K., & Goyal, M. (2022). “Innovations in Coastal Infrastructure in India: Case Study of Mumbai Coastal Road,” Proceedings of the National Conference on Urban Coastal Engineering. Project Reports and Government Publications [1] Municipal Corporation of Greater Mumbai (MCGM). (2021). Mumbai Coastal Road Project – Environmental Impact Assessment Report, Coastal Road Division. [2] L&T Infrastructure Engineering. (2020). Geotechnical Investigation Report for Marine Sections – Mumbai Coastal Road Project, Package 1. [3] National Institute of Ocean Technology (NIOT). (2019). Marine Environmental Baseline Report for Mumbai Coastal Areas. Web and Online Resources [1] Mumbai Coastal Road Project Official Website – https://coastalroad.mcgm.gov.in [2] Ministry of Environment, Forest and Climate Change (MoEFCC), India – https://moef.gov.in [3] Offshore Wind Design Manual (2021), DNV – https://www.dnv.com

Copyright

Copyright © 2025 Irshad Khan, Shubham Singh. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.