Underground Construction with Diaphragm/Slurry Walls

The diaphragm or slurry wall technique, as discussed by Dr. N. Subramanian, represents a major advancement in modern underground construction. It offers significant benefits, including excavation stabilization, effective groundwater barriers, reduced ground movement, and minimal disruption in urban areas, in addition to providing cost savings of up to 25% compared to traditional methods and exceptional durability, making it ideal for applications in metro stations, tall buildings, bridge piers, and dams. Although urban construction presents challenges, strategies have been developed to overcome these issues. This article will explore the design, construction, and applications of diaphragm walls, as well as the challenges encountered in their implementation.

Introduction

Considered one of the most significant innovations in modern underground construction, the diaphragm or slurry wall technique offers a wide range of benefits. It provides excellent barriers against horizontal groundwater seepage, minimizes ground movement during excavation, and reduces settlement of adjacent structures. These advantages lead to substantial time and cost savings, particularly by reducing the need for site dewatering and minimizing the need for underpinning nearby buildings.

In urban environments, the benefits of slurry wall construction are even more pronounced. For instance, in cut-and-cover tunneling projects—commonly used for subway construction—slurry walls can significantly reduce traffic disruption and minimize noise and vibration along the construction corridor. Furthermore, this method can lead to cost savings of up to 25% compared to traditional methods, making it a highly economical choice for deep foundation work and urban tunneling projects, especially as cities continue to grow. The pre-casting of the walls brings additional advantages.

The durability and resilience of diaphragm walls were demonstrated during the 2001 terrorist attacks at the World Trade Center site, where the underground slurry wall withstood the collapse of the towers. This incident underscored the ability of these walls to manage heavy loads, minimize construction disruptions, and ensure long-term durability, establishing their importance for modern infrastructure projects.

Types of Retaining Systems for Underground Construction

The following types of retaining systems are usually employed in underground construction.

Sheet Piling: Sheet piling involves driving interlocking steel sheets into the ground to form a retaining wall. This technique is simple and quick, making it suitable for soft and sandy soils. However, it has several drawbacks, including the following:

• Limited durability
• High noise and vibration during installation
• Significant ground movement and settlement
• Low water tightness
• Constraints on excavation depth and width.

Secant Piling: Secant piling entails drilling and concreting overlapping piles into the ground to form a robust retaining wall. This method is more durable and watertight than sheet piling, making it effective for hard and rocky soils. However, challenges include:

• High costs and longer construction times
• Difficult site access and logistics
• Complex quality control and inspection processes.

Soil Nailing

Soil nailing reinforces soil by inserting steel bars or rods into the ground to create a stable retaining wall. It is a cost-effective and straightforward method suitable for sloping or unstable soils. Nevertheless, it has limitations such as:

• Lower strength and durability compared to other systems
• Poor water tightness
• Dependence on specific soil conditions.

Diaphragm/Slurry Walls

Diaphragm walls (also known as slurry walls in the USA) are constructed by excavating a narrow trench, which is stabilized with bentonite slurry to prevent collapse. A steel reinforcing cage is then lowered into the trench, and concrete is poured to form a wall. Its advantages are:

• Highly versatile and adaptable to various soil types and site conditions
• Suitable for different loads and geometries as per project requirements
• Effective in minimizing ground movement and settlement.

Diaphragm walls are typically 0.6 to 1.5 m thick, 25 to 100 m deep, and have widths varying from 0.45 to 1.5 meters. Slurry walls are generally 0.5 to 1.2 m thick and 15 to 30 m deep.

Evolution of Diaphragm \ Slurry Walls

Before 1934, slurry walls were constructed as a series of piles in slurry-supported boreholes. Each pile was placed in contact with its neighbor, forming "tangent pile" walls. To enhance water tightness, intermediate piles were added between initial piles, using secant piling techniques. Over time, digging tools replaced boring methods to excavate the soil between the piles.

The slurry wall technique was first introduced in the 1950s during the excavations of the Red Line of the Milan Metro in Italy. Developed by the company ICOS (Impresa Costruzioni Opere Specializzate), this innovative method became a cornerstone of the top-down tunneling approach, commonly referred to as the "Milan Method" (Metodo Milano).

The technology was introduced to the rest of the EU countries and finally to the United States in the 1960s, initially for small-scale projects, before being applied to larger scale projects, for example, in the construction of the World Trade Center in 1967. This milestone project marked the technique's emergence as a crucial tool in modern urban construction. The modern approach eliminates initial piles altogether, excavating the entire wall in progressive panel lengths, resulting in an efficient interlocking panel system. This evolution highlights the diaphragm wall as a cutting-edge technique in underground construction, offering cost-efficiency and enhanced performance in various soil conditions. A valid advantage of the technology is that the execution of the structure makes very little vibration and noise. Effects of vibration in urban areas can cause great damage on surrounding buildings, thus they are especially suitable for civil engineering designs in places that are densely populated.

Interlocking Panel Slurry Walls

Interlocking panel slurry walls can be classified into two main categories:

• Cast-in-place wall panels.
• Precast wall panels assembled in the trench.

Cast-in-Place Walls: Construction Methods

Cast-in-place walls are typically constructed using one of two methods:

End Pipe System: This method involves the following steps:

• A panel trench is excavated to the desired depth
• Circular end pipes with diameters matching the trench width, are positioned at each end of the trench to act as temporary forms
• A reinforced steel cage is placed within the trench
• Tremie concrete is poured into the trench to form the wall
• Once the concrete begins to set, the end pipes are removed to facilitate the casting of the next panel.

In this method, temporary forms allow for sequential panel casting. While effective, this method presents challenges in achieving seamless panel continuity, which can be accomplished only at significant additional cost.

Steel Beam and Concrete Technique: In this alternative approach, first a trench is similarly excavated, and structural steel H-beams are installed in the trench in place of end pipes. Concrete is then poured around the H-beams. Unlike the end pipe system, the H-beams are permanently left in place within the wall, serving as shear connectors and enhancing structural integrity, simplifying construction and improving performance, particularly in shear resistance.

Plan views illustrating slurry walls constructed using the end pipe system and the steel beam method are shown in Fig. 1(a) and 1(b), respectively. Both methods have specific advantages and limitations, with the choice depending on project requirements, cost considerations, and desired structural properties.

Figure 1: Plan views of typical slurry wall cast-in-place interlocking panels (Source: FHWA-RD-80-047:1981)

Construction Procedure of Diaphragm Wall

Site Preparation

• Conduct initial excavation and install temporary support systems (if required).
• Perform soil stabilization using techniques like jet grouting to enhance bearing capacity.

Slurry Plant

Diaphragm wall installation requires sufficient work area to set up slurry plant and to assemble reinforcing cages prior to placement in wall. This work may be difficult in congested sites. To reduce area requirement of site cage, prefabrication is possible. A slurry plant includes slurry mixer, storage tanks, and descending units. Sufficient storage tanks must be used for bentonite slurry hydration.

Slurry Wall Construction Process

Slurry walls are constructed using the following systematic procedure (See Fig. 2):

Figure 2: Schematic diagram of the construction of diaphragm wall (adapted from Ref. 14)

Guide Wall Installation: Construction begins with the installation of concrete guide walls, typically 1 meter deep and 0.5 meters thick. These guide walls serve multiple purposes:

• Act as templates for the excavation panel layout
• Support the top of the trench
• Restrain end slopes
• Provide a platform for hanging reinforcement
• Establish reference elevations for inserts
• Support tremie pipes during concreting
• Hold down the reinforcing cage during concrete placement
• Provide a reaction base for jacking out specific types of end stops.

Excavation: Excavation is performed using specialized equipment, such as clamshell-shaped diggers or hydromill trench cutters, suspended from cranes. The excavation process involves digging to the design depth or bedrock for the first wall segment, and moving the excavator along the trench guided by the layout provided by the guide walls for successive cuts. Excavations are conducted in vertical segments known as panels, and the trench is continuously filled with bentonite slurry.

Slurry Functionality: Bentonite slurry serves critical roles in trench stability. It provides outward pressure to counterbalance inward hydraulic forces, prevents trench walls from collapsing, and retards water flow into the trench. The slurry's density is carefully monitored and adjusted to maintain adequate outward pressure. The fluid-filled trench allows for unrestricted movement of excavation machinery.

Reinforcement and Concreting: Once the trench reaches the required depth, a preassembled reinforcing cage is lowered into the slurry-filled trench. Concrete is poured using tremie pipes starting from the bottom of the trench. The heavier concrete displaces the bentonite slurry, which is pumped out, filtered, and stored for reuse or recycled.

Wall Continuation and Area Enclosure: Slurry walls are extended panel by panel to enclose the designated area, forming a barrier against water and softened earth. After the concrete hardens, excavation can proceed within the enclosed area.

Temporary Supports: In order to prevent the concrete wall from collapsing into the excavated area, temporary supports such as tiebacks or internal crossbeams, are installed. Once construction within the walled-off area is completed, the structure itself typically provides permanent support for the wall, allowing the removal of temporary bracing, if desired.

Endstops: Endstops are essential components for controlling concrete placement and ensuring that adjacent panels remain unaffected. As mentioned earlier, there are two main types of endstops:

• Permanent Endstops: Typically made of wide-flange sections, these remain in place after concrete placement.
• Removable Endstops: These include pipe or special keyway designs that can be removed after the concrete is set.

Different Types of Diaphragm Wall Construction

Diaphragm wall construction can be categorized into four types based on the excavation and concreting methods employed:

Grabbed Diaphragm Wall: This method involves excavating vertical panels under stabilizing slurries using mechanical or hydraulic clamshell grabs. The grabs, suspended by a crane or cable, are capable of breaking through obstructions in the soil. After excavation, a reinforcing cage is placed in the trench, which is then filled with concrete. It is commonly used for constructing basement diaphragm walls, and the cost may vary from ₹10,000 to ₹15,000 per square meter.

Hydromill Diaphragm Wall: This method utilizes a hydromill cutter to excavate vertical panels under stabilizing slurries. Hydromills are powerful tools designed to cut through hard soil and rock layers effectively. Once excavation is complete, the reinforcing cage is installed, and the trench is concreted. This method is preferred for metro diaphragm wall construction in India due to its ability to manage complex geological conditions and withstand high water pressure. The cost may be in the range of ₹15,000 to ₹20,000 per square meter.

Precast Concrete Diaphragm Wall: In this method, precast concrete panels are inserted into the trench after it has been excavated using grabs or hydromills. These panels are interlocked with one another and the surrounding soil to form a continuous wall. This method is suitable for diaphragm walls in dam construction, offering resistance to high loads and seismic forces, with their cost in the range of ₹20,000 to ₹25,000 per sqm.

Steel-Reinforced Diaphragm Wall: This method involves inserting steel tubes or beams into the trench after excavation using grabs or hydromills. The steel elements are then filled with concrete to form a composite wall. This is an alternative approach for diaphragm wall construction in India, providing enhanced strength and durability compared to conventional concrete walls. It is slightly expensive with the cost ranging from ₹25,000 to ₹30,000 per sqm.

Figure 3: Two Ways of Using Precast Panels (Source: FHWA-RD-80-047:1981)

In addition to the above classifications, the following terms are also used in connection with Diaphragm walls:

Soil-Precast-Concrete (SPTC) walls: These walls are innovative structural systems designed to provide robust and efficient solutions for deep foundations, particularly in challenging urban environments. These walls are often used in underground construction projects, such as transit stations, to address the need for stability, reduced construction time, and minimized environmental impact. The term SPTC wall can refer to either Soldier Pile Tremie Concrete walls or Soil-Precast-Concrete walls, depending on the context. Hence, a brief explanation of each is given below:

Soldier Pile Tremie Concrete (SPTC) Walls: This system involves installing soldier piles at regular intervals and then using tremie concrete (placed underwater or in a controlled, low-slump condition) between the piles to create a continuous retaining wall. They are widely used in deep excavation projects, especially in urban areas where soil stabilization and water tightness are critical. Their main characteristics are:

• They combine the strength of steel (soldier piles) with concrete infill for enhanced load bearing and stability.
• They are effective in groundwater conditions where tremie concrete can be placed without dewatering.
• They can support lateral loads and prevent soil collapse during excavation.

In this type of construction, the main focus is on cast-in-place methods with soldier piles and in-situ concrete.

Soil-Precast-Concrete (SPTC) Walls: This is a precast wall system where precast concrete panels or elements are combined with soil reinforcement or anchors to form a retaining wall. The term may also describe modular systems where precast components are directly embedded or backfilled with soil. These walls are frequently used in retaining wall construction, particularly in infrastructure projects like highways, railways, and urban foundations. These walls have the following characteristics:

• Modular and faster to install compared to cast-in-situ systems.
• Can integrate soil nailing or geotextile reinforcement for added stability.
• More sustainable and cost-effective for large-scale retaining wall applications.

In this type of construction, the main focus is to utilize precast elements for faster assembly and often involves soil-structure interaction.

Features and applications

Key Features
Precast Concrete Panels

• Fabricated off-site for consistent quality.
• Delivered and assembled on-site, minimizing construction duration and disruptions.

Integration with Soil Stabilization

• The precast panels often interact with stabilized soil to form a composite system.
• Soil improvements like grouting or jetting are typically performed to enhance the load-bearing capacity.

Durability and Longevity

• Designed to withstand significant loads and environmental factors.
• The materials and structural configuration ensure a long service life.

Ease of Construction

• Reduced on-site labor and construction footprint.
• Suitable for high-density urban areas where traditional methods may be disruptive.

Advantages of Using Precast Panels in Diaphragm Walls

• Efficiency: SPTC walls allow for rapid construction compared to cast-in-place alternatives.
• Flexibility in Design: Panels can be customized for specific architectural or structural needs.
• Durability and Longevity: As the panels are made in factories under controlled environments, they have higher resistance to environmental degradation, including corrosion, freeze-thaw cycles, and chemical exposure.
• Less wastage at site: Precast panels lead to less material wastage
• Reduced Environmental Impact: Reduced on-site activities resulting in lower on-site emissions (resulting in less air pollution) and noise, aligning with sustainable construction practices.
• High Strength and Stability: The combination of precast concrete and stabilized soil offers excellent load-bearing and deformation resistance.

Applications

Slurry wall construction was used in the USA during 1967–1968 to construct the walls surrounding the foundations of most of the buildings in New York City. In the 1980s, the Red Line Northwest Extension project in Boston was one of the first projects in the US to use the modern form of the technology with Hydromill trench cutters and the Milan method. Slurry walls were also used extensively in Boston's 1990s Big Dig tunnel project.

Underground metro construction: In underground metro construction, Diaphragm walls serve as watertight barriers, preventing groundwater from seeping into the construction site. They also act as a guiding path for launching shafts. The top down construction method used in underground metro construction ensures the safety and comfort of passengers. In the metro stations in Washington D.C. and the BART (Bay Area Rapid Transit) in San Francisco, where Diaphragm walls act as deep foundation systems capable of supporting heavy loads while ensuring stability against ground movement. The use of SPTC walls in San Francisco's downtown BART stations exemplifies their effectiveness in handling the challenges of underground construction. These walls contribute to the seamless integration of transportation infrastructure in a densely populated area, ensuring safety, durability, and environmental stewardship. Figure 4 shows how the slurry walls have helped to build the Federal Center S.W. Metro Station in a congested down-town area at Washington D.C.

Figure 4: The Sectional view and the finished Federal Center S.W. Metro Station at Washington D.C.

Load bearing walls: These are used in place of drilled piers in foundation of tall buildings, bridge piers, etc.

Cutoff walls in Dams: In hydraulic structures, Diaphragm walls help prevent water seepage, below earth dams, weirs, and levees, and act as a strong foundation to withstand earth pressure and ensure the longevity of the structure. The diaphragm wall in a dam can significantly enhance the dam’s resistance to seismic forces, especially in regions prone to earthquakes.

Basement Construction: With the growing population, the need for larger residential buildings with ample parking space has increased. Deep basement construction, with up to 5 levels, is often required. A basement diaphragm wall is used in such construction, transforming damp deep ground spaces into dry and secure areas beneath our buildings. They act as impenetrable barriers that prevent the earth from caving in, ensuring the safety of construction workers and preventing damage to nearby structures. PVC water stoppers are installed at the joints of the diaphragm wall panels to prevent water seepage, thereby ensuring a dry and secure base. They are also particularly effective in retaining soil and groundwater in deep excavation projects. Diaphragm walls are also preferred for projects in crowded urban environments due to their modular nature and reduced construction impact.

Challenges and Solutions

However, Diaphragm wall construction may also have various challenges in urban environments, as given below:

• Limited space and access: The site area and access roads may be constrained by existing buildings, traffic and pedestrians, making it difficult to transport and operate the equipment and materials.
• Existing infrastructure and utilities: The site may be surrounded by or contain underground or overhead utility lines, such as water, gas, electricity and communication, which may interfere with the excavation and installation of the diaphragm walls.
• Initial Costs: The fabrication of precast panels and soil stabilization techniques may require higher upfront investment.
• Noise and vibration control: The excavation and concreting of the diaphragm walls may generate some amount of noise and vibration, which may disturb the nearby residents and businesses and may cause damage to the adjacent structures and utilities.
• Groundwater management: The groundwater level and pressure may vary depending on the site location and season, affecting the stability of the trench and the quality of the concrete.
• Soil conditions: The soil type and properties may vary along the depth and width of the trench, affecting the excavation and concreting of the diaphragm walls.
• Design Complexity: Requires detailed geotechnical and structural analyses to ensure compatibility with site conditions.

To overcome these challenges and minimize disruptions, modern methods and technologies have been developed and applied in Diaphragm wall construction, such as (Ref. 18):

• Borehole drilling method (In this method, boreholes are drilled through the rock layers using a rotary drilling rig and then filling them with concrete; It was used in the LG06 underground station in Taipei MRT, Taiwan, where a 30 m deep diaphragm wall was constructed around the station, and hard rock layers were encountered at 15 m depth.),
• Horizontal rebar cage movement (in which the rebar cage is moved horizontally along the trench, instead of lowering it vertically),
• Grouting piles with reinforcing bars (which involves installing grouting piles with reinforcing bars around the diaphragm wall trench and then injecting grout into the piles-creating a rigid and strong support for the adjacent structures and preventing them from settling and deforming),
• Prestressing of diaphragm walls (By applying a compressive force to the diaphragm walls using tendons or cables. It can reduce the reinforcement steel and concrete required by up to 20-25% and improve the structural strength and durability of the diaphragm walls),
• Top-down construction method (which involves constructing the diaphragm wall and the basement floors simultaneously, from the top to the bottom. This method can reduce the excavation depth and duration by 50% and 40%, respectively, compared to the conventional bottom-up method, which involves excavating the entire basement depth and then constructing the floors from the bottom to the top), and
• Anchoring and water stopper systems (which involve installing anchors and water stoppers along the diaphragm walls. Anchors are steel bars or cables that are inserted into the ground and attached to the diaphragm walls, providing additional support and resistance against lateral forces. Water stoppers are rubber or metal strips that are embedded into the joints of the diaphragm walls, preventing water leakage and infiltration).

Design Principles

Geotechnical Analysis

• Soil Type and Stability:
  • A thorough study of soil properties such as cohesion, internal friction angle, and permeability is essential.
  • Soil improvement techniques like jet grouting or deep soil mixing are employed when weak or unstable soils are present.
• Groundwater Considerations:
  • Dewatering systems or impermeable membranes may be required to manage groundwater pressure effectively.

Structural Design

The design of a slurry wall (diaphragm wall) includes the design of wall thickness and reinforcements. Thickness of a slurry wall in preliminary design is generally set to about 4-8% of the excavation depth. Slurry wall design is undertaken based on bending moment and shear envelope obtained from the stress analysis. In the design of such underground walls, width of the unit is considered as one meter, and the wall is analyzed under plane strain condition. Since the length-to-width ratio of excavations is generally large, plane strain conditions can be assumed (Goh et al, 2013).

• Panel Strength: Precast concrete panels are designed to resist bending, axial, and shear forces. Reinforcement within panels is detailed per ACI or Eurocode standards for durability and strength.
• Composite Action: Interaction between stabilized soil and precast concrete can be considered for combined load resistance.

Case Study of Slurry Wall of The World Trade Center

It is remarkable that the underground slurry wall at the World Trade Center site survived the catastrophic collapse caused by the terrorist attacks on September 11, 2001, without leaking, despite being subjected to forces comparable to a small earthquake (Ref. 20). One of the primary reasons for its resilience was its robust construction, designed to withstand immense forces.

According to an official from the engineering firm that assessed the damage after the attack, as reported by Newsday in 2001, the slurry wall was firmly anchored with steel ties extending approximately 60 cm into the bedrock beneath it (Fig. 5). Initially, the slurry wall was also supported internally by the World Trade Center's six-story concrete foundation. Remarkably, even after the buildings collapsed, engineers noted in The New York Times in 2001 that the massive pile of debris continued to exert pressure against the slurry wall, effectively holding it in place.

Today, a small section of the original slurry wall, comprising three 6-meter-wide panels, has been preserved and displayed at the September 11 Museum within the World Trade Center Complex, serving as a powerful reminder of engineering resilience in the face of unprecedented destruction.

Figure 5: Slurry wall of the World Trade Center (Source: Reference 20, NY Times)

Conclusions

The diaphragm or slurry wall technique represents one of the most significant advancements in modern underground construction. Construction procedure of diaphragm walls is explained. There are various types of slurry/ diaphragm walls: Grabbed diaphragm Walls, Hydromill diaphragm Walls, Precast Concrete diaphragm Walls, Steel-Reinforced diaphragm Walls. In addition, terms like Soil-Precast-Concrete (SPTC) walls (Soldier Pile Tremie Concrete walls or Soil-Precast-Concrete walls) are also used.

The diaphragm wall construction offers numerous benefits including stabilization of excavations, providing effective barrier to groundwater seepage, reducing ground movement and settlement, protecting adjacent structures and utilities, adaptability to various soil types, site conditions, and geometries, minimizing noise, vibration, and disruption to surrounding areas (especially in urban settings), cost savings of up to 25% compared to traditional retaining wall methods, and excellent durability (provides long-term stability and resistance to seismic and load-induced stresses). Pre-casting the walls offers additional advantages. They have been used in underground metro construction, as load bearing walls in foundation of tall buildings, bridge piers, cutoff walls in dams, and in deep basement constructions.

Construction of diaphragm wall in urban environments may face various challenges, but several strategies have been developed to overcome these challenges. The survival of the underground slurry wall at the World Trade Center site when the twin towers collapsed due to the terrorist attacks on September 11, 2001, demonstrated the resilience of these structures. Their ability to manage heavy loads, minimize construction disruptions, and offer long-term durability makes them indispensable for modern infrastructure development. The following references give more information about the design and construction of diaphragm walls.

References

1. Bigonah, N., Khaksar, R.Y., Fathollahi-Fard, A.M., Gheibi, M., Wacławek , S., and Moezzi, R. (2024) "Seismic Stability and Sustainable Performance of Diaphragm Walls Adjacent to Tunnels: Insights from 2D Numerical Modeling and Key Factors”, Buildings, 14(1), 60; https://doi.org/10.3390/buildings14010060
2. Boyes, R.G.H. (1975) Structural and cut-off diaphragm walls, Applied Science Publishers Ltd, London.
3. Brown, R.E. (1974) "Excavation and Soldier Pile-Tremie Concrete (SPTC) Wall Instrumentation and Monitoring Program", in The National Materials Conservation Symposium on Resource Recovery and Utilization, National Bureau of Standards, Gaithersburg, 29 Apr.-1 May 1974.
4. Diaphragm Walls & Anchorages, Proceedings of the Conference Organized by Institution of Civil Engineers, London, 18-20, Sept. 1974
5. El-Nimr,M.T., Basha , A.M., Abo-Raya, M.M., and Zakaria., M.H. (2022)"General deformation behavior of deep excavation support systems: A review ", Global Journal of Engineering and Technology Advances, 10(01), 039–057, https://doi.org/10.30574/gjeta.2022.10.1.0181
6. EN 1538:2010 (2010). Execution of special geotechnical works. Diaphragm walls.
7. FHWA-RD-80-047 (1981) Slurry walls as an integral part of underground transportation structures-Final Report, Federal Highway Administration, U.S. Department of Transportation, 180 pp. https://ia803205.us.archive.org/10/items/slurrywallsasint00chim/slurrywallsasint00chim.pdf
8. Goh, A. T. C., Xuan, F. and Zhang, W. (2013). “Reliability Assessment of Diaphragm Wall Deflections in Soft Clays”, Geo Congress 2013, Foundation Engineering in the Face of Uncertainty, pp.487 496
9. Hsu C-F, Huang C, Li Y-F, Chen S-L. (2024) “Evaluating the Effects of Deep Excavation on Nearby Structures Through Numerical Simulation”. Applied Sciences. 2024; 14(21):10002. https://doi.org/10.3390/app142110002
10. Iffland J.S.B. (1978) “Practical Design of Concrete Diaphragm Walls”, Transportation Research Record Issue No. 684, Transportation Research Board, pp.37-43
11. IS 14344:1996 Design And Construction of Diaphragms for Under-Seepage Control - Code of Practice, Bureau of Indian Standards, New Delhi.
12. Puller, M. (1996) Deep excavations: A practical manual, Thomas Telford, New York.
13. Xanthakos, P. P. (1993) Slurry Walls as Structural Systems, Second Edition, McGraw-Hill, Incorporated, New York., 855 p.
14. https://en.wikipedia.org/wiki/Slurry_wall#
15. https://heritageconstruction.in/are-slurry-walls-and-diaphragm-walls-the-same/
16. https://heritageconstruction.in/diaphragm-wall-construction-vs-other-retaining-systems/
17. https://heritageconstruction.in/diaphragm-wall-construction-types-costs/
18. https://heritageconstruction.in/diaphragm-wall-construction-urban-areas-challenges-solutions/
19. https://resource.midasuser.com/en/blog/geotech/deep-excavation-in-diaphragm-walls
20. https://science.howstuffworks.com/engineering/structural/world-trade-center-slurry-wall.htm

About the Author

Dr. N. Subramanian, Ph.D., FNAE, an award-winning author, consultant, and mentor, living in Maryland, USA, is the former chief executive of Computer Design Consultants, India. A doctorate from IITM, he has also worked with the TU Berlin and the University of Bundeswehr, Munich for 2 years as an Alexander von Humboldt Fellow. He has 47 years of professional experience which includes consultancy, research, and teaching in India and abroad. He has authored 25 books and 325 technical papers and served as a past vice president of ICI and the ACCE (I). He is a recipient of several awards including the Edmund Friedman Professional Recognition Award by the American Society of Civil Engineers (2024), Gourav Award of the ACCE(I) (2021), ICI - L&T Life-Time Achievement award of the ICI (2013), ACCE(I)-Nagadi best book award for three of his books (2000,2011,2013), and the Tamil Nadu scientist award (2001). He has also been in the Editorial Board/Review committee of several Indian and international journals.