Jet Grouting creates in-situ columns of grouted soil using high-pressure grout injection. Grouting is performed by pumping high-velocity jets of grout (or sometimes grout and air or grout, water, and air) through the side of a grout monitor, attached at the end of the drill string. The jets erode and mix the soil as the drill string and the monitor is rotated and withdrawn.
The jet grouting process constructs jet grout panels, full or partial columns with designed strength and permeability. Jet Grout column size is dependent on soil type, soil density, injection pressures and flow rates of the various fluids employed, rotation speed, lift rate and type of system used. This process can also be used to construct seepage barriers or can find its application in ground treatment/modification.
It is the best practice to perform a pre-construction test program to calibrate, adjust and verify jet grout parameters and the design.
Single fluid jet grouting (cement only)
The single fluid system is the simplest. This simplicity is due to exclusive reliance on the high velocity of the jetstream to cut, remove and mix the in-situ soil.
Double fluid jet grouting (cement with air)
The double fluid system simultaneously injects a high-velocity grout stream within a cone of compressed air. The double-fluid system is capable of creating a larger column compared to the single-fluid system.
Triple fluid jet grouting (cement with air and water)
The triple fluid system is the most complicated jet grouting system due to the simultaneous injection of three different fluids, air, water, and grout. The triple fluid system can create the largest diameter of the column among the three types.
Jet-grouting technology is an easy and safe installation process without unwanted disruption to other operations. This often results in reduced construction time and eliminates ground vibration often associated with other soil improvement technologies when compared to alternate and competing systems. This benefit is of particular importance in dense urban environments where unwanted vibration during construction may damage the surrounding facilities.
Jet grouting can be advantageous in the following applications:
- cut-off wall
- shoring (temporary and permanent) & vertical shaft;
- underpinning of existing structures
- tunnel liners.
- Construction of horizontal barriers
- Control of groundwater
- Support for excavation
- difficult logistic conditions
- confined spaces & presence of obstacles to cross
- high-depth treatment with crossing of voids
ROCK & SOIL ANCHORS
Rock and soil anchors are structural elements used in civil engineering to provide stability and support to various structures, especially those located on slopes or in areas with challenging soil or rock conditions. These anchors are employed to resist forces such as tension, compression, or lateral loads and prevent movement or failure of structures.
- Purpose: Rock anchors are used in situations where a structure needs support in rock formations. They are commonly employed in slope stabilization, rock slope protection, tunnelling, and foundation support.
- Installation: Typically, rock anchors are installed by drilling into the rock and then grouting the borehole to enhance the bond between the anchor and the surrounding rock. The anchor is then tensioned to provide the necessary support.
- Components: A typical rock anchor consists of a steel tendon or cable, an anchor head or plate that transfers the load to the rock, and grout that fills the drilled hole to enhance the bond.
- Purpose: Soil anchors, also known as ground anchors or earth anchors, are used to provide stability to structures in soil conditions where conventional foundations may be insufficient. They are often used in retaining walls, slope stabilization, and deep excavations.
- Installation: Soil anchors are installed by drilling into the soil and placing a tendon or cable within the drilled hole. Grouting may also be used to enhance the bond between the anchor and the soil. The anchor is then tensioned to provide the necessary support.
- Components: Similar to rock anchors, soil anchors consist of a tendon or cable, an anchor head or plate to transfer loads, and grout to improve the bond with the surrounding soil.
Application of Soil/Rock Anchors
- Stabilization of Unprotected Slopes or manmade cuts
- Securing Structures below Groundwater level against Buoyancy
- Inclined rock/rod anchor for slope stabilisation
- Inclined anchor for basement excavation
- Vertical anchor for uplift pressure in foundation
- Increase the stability of Hydro Electric Structures and Dams
- Mining and Refinery
Benefits of Soil/Rock Anchors
- Provides a high load capacity even in poor ground conditions,
- Does not involve large area excavation
- attractive option when space is limited
- low impact on the environment
- Quick Installation
Both rock and soil anchors play a crucial role in ensuring the stability and safety of civil engineering structures, particularly in challenging geological conditions. The selection of the appropriate type of anchor depends on factors such as the type of soil or rock, the magnitude of loads, and the specific requirements of the project.
Sheet piles are long, thin, interlocking steel or concrete sections that are driven or vibrated into the ground to create a continuous barrier for earth or water retention. They are commonly used in construction, especially in projects involving excavation, foundation support, and waterfront structures. The primary purpose of sheet piles is to provide lateral support to soil or water, preventing the collapse of excavations and offering stability to structures.
Here are key aspects of sheet piles and their utility in civil engineering:
Types of Sheet Piles:
- Steel Sheet Piles: These are the most common type and are made of steel for strength and durability. They come in various shapes, including U-shaped, Z-shaped, or straight plates with interlocking edges.
- Concrete Sheet Piles: Made of precast concrete, these piles are used when a more massive and rigid structure is required. They are often used in marine environments due to their resistance to corrosion.
- Sheet piles are installed by driving them into the ground using vibratory hammers, impact hammers, or other specialized equipment.
- Interlocking edges allow the sheets to form a continuous barrier, creating a wall that resists lateral pressures from soil or water.
Applications and Uses:
- Retaining Walls: Sheet piles are commonly used to create retaining walls, providing support to excavated slopes and preventing soil erosion or collapse.
- Deep Foundations: They are used to form cofferdams or to support deep excavations for construction projects like basements, underground parking structures, or foundations of buildings.
- Waterfront Structures: Sheet piles are used in the construction of seawalls, bulkheads, and other waterfront structures to protect against erosion and provide stability.
- Flood Control: In flood-prone areas, sheet piles are used to create barriers that prevent water from inundating specific areas.
- Rapid Installation: Sheet piles can be installed quickly, making them suitable for projects with tight timelines.
- Versatility: They can be used in various soil conditions and are effective in both temporary and permanent applications.
- Cost-Effective: Compared to some alternative methods, sheet pile walls can be a cost-effective solution for providing lateral support.
- Corrosion Protection: For steel sheet piles, corrosion protection measures such as coatings or cathodic protection may be necessary, especially in marine environments.
- Driving Conditions: The method of installation and the conditions of the soil or rock at the site influence the choice of sheet pile type.
In summary, sheet piles are valuable in civil engineering for their ability to provide efficient and cost-effective lateral support in a variety of construction scenarios, ranging from deep foundations to waterfront protection.
A diaphragm wall is a reinforced concrete wall that is cast in situ (on-site) using a trench excavation technique. It is typically used as a structural element in underground construction projects, providing support and stability to deep excavations. Diaphragm walls are commonly employed in projects such as deep basements, underground structures, tunnels, and as retaining walls in areas with challenging soil or water conditions.
Here are key features and uses of diaphragm walls:
- Trench Excavation: A trench is excavated to the desired depth and width using special equipment such as grabs or clamshells.
- Reinforcement Installation: Steel reinforcement cages are lowered into the trench. The reinforcement is usually in the form of vertical bars and sometimes includes horizontal reinforcement to enhance the structural integrity of the wall.
- Concrete Placement: High-strength concrete is poured into the trench, displacing the slurry (usually bentonite or polymer-based) that stabilizes the trench during excavation.
- Slurry Wall Technique: The use of a slurry during excavation helps support the walls of the trench, preventing collapses. The slurry is usually maintained until the concrete has set.
Key Components and Design:
- Thickness: The thickness of diaphragm walls can vary based on design requirements but is typically in the range of 0.6 to 1.5 meters.
- Reinforcement: Diaphragm walls incorporate reinforcement to provide additional strength and ductility. Reinforcement cages are designed based on the specific structural requirements of the wall.
Advantages and Uses:
- Deep Excavations: Diaphragm walls are particularly suitable for deep excavations where the lateral support of the soil is critical to prevent collapse.
- Waterproofing: Due to the construction process involving a slurry wall, diaphragm walls can be relatively impermeable, providing effective waterproofing for underground structures.
- Stability: Diaphragm walls offer high structural stability, making them suitable for retaining large volumes of soil or resisting lateral earth pressures.
- Adjacent Structures: They are used in urban areas where the proximity of existing structures makes traditional excavation methods challenging.
- Basement Construction: Diaphragm walls are commonly used in the construction of deep basements for buildings.
- Tunneling: In tunnel construction, diaphragm walls may be used to provide structural support and control groundwater ingress.
- Underground Structures: They are used for the construction of underground structures such as subway stations, parking garages, and utility tunnels.
In summary, diaphragm walls are a versatile and effective solution for providing structural support in deep excavations, especially in urban areas where space constraints and the need for waterproofing make them a preferred choice. Their ability to resist lateral soil pressures and provide stability makes them a valuable element in various civil engineering and construction projects.
Secant piles are a type of deep foundation element used in civil engineering and construction. They are formed by constructing overlapping reinforced concrete piles, creating a continuous wall. The term “secant” refers to the fact that each pile is constructed to intersect with or partially overlap its neighboring piles. This design creates a continuous barrier that is particularly useful in deep excavation projects, providing structural support and preventing soil or water ingress.
Here are key features and uses of secant piles:
- Alternate Construction: In a secant pile wall, the primary piles (female piles) are constructed first, leaving gaps or voids. Subsequently, secondary piles (male piles) are constructed in the voids, overlapping with the primary piles.
- Reinforcement: Both primary and secondary piles are typically reinforced with steel to enhance their structural strength and integrity.
- Grout or Concrete Filling: After construction, the voids between the primary and secondary piles may be filled with grout or concrete to increase the wall’s overall impermeability.
Key Components and Design:
- Overlap: The degree of overlap between adjacent piles can be adjusted based on design requirements and subsurface conditions. The overlap is chosen to ensure sufficient structural integrity and to control soil or water infiltration.
- Diameter and Spacing: The diameter and spacing of the piles are also design considerations and depend on factors such as soil conditions, the depth of excavation, and the structural requirements of the wall.
Advantages and Uses:
- Excavation Support: Secant pile walls are commonly used for deep excavations in urban areas, providing lateral support to prevent soil collapse.
- Waterproofing: The construction of secant piles with grout or concrete filling between the overlapping piles enhances the wall’s impermeability, making it suitable for preventing water ingress in below-grade structures.
- Adjacent Structures: Secant piles are often used in close proximity to existing structures where minimal ground movement is critical.
- Tunneling: They can be employed in tunneling projects to provide structural support and control ground movement.
- Basement Construction: Secant pile walls are commonly used in the construction of deep basements for buildings.
- Deep Excavations: They are employed in projects where deep excavations are necessary, such as for underground parking structures or subway stations.
- Retaining Walls: Secant pile walls can act as retaining walls in situations where the terrain requires additional structural support.
In summary, secant piles are a versatile solution for providing structural support and stability in deep excavation projects. Their ability to create continuous walls with controlled overlap makes them effective in preventing soil or water ingress, and their use is often favored in urban environments with limited space and proximity to existing structures.
CONTIGUOUS / CFA PILES
Contiguous piles, also known as contiguous bored piles or CFA (Continuous Flight Auger) piles, are a type of foundation element used in civil engineering and construction. These piles are constructed using a continuous auger, and the construction process involves drilling a borehole using the auger while simultaneously filling it with concrete or grout. Contiguous piles are commonly used in various applications, including building foundations and deep excavation support.
Here are key features and uses of contiguous piles:
- Continuous Auger Drilling: The process begins with drilling a borehole into the ground using a continuous flight auger. The auger is equipped with a hollow stem, allowing the soil to be removed as it drills.
- Concrete or Grout Injection: While the auger is withdrawn, concrete or grout is pumped through the hollow stem, filling the void left by the auger.
- Reinforcement: In some cases, reinforcement, such as steel bars, may be inserted into the fresh concrete to enhance the structural strength of the pile.
Key Components and Design:
- Diameter and Depth: The diameter and depth of contiguous piles can vary based on project specifications, soil conditions, and structural requirements.
- Spacing: The spacing between contiguous piles is typically determined by the structural engineer based on the load-bearing capacity of the soil and the anticipated loads on the foundation.
Advantages and Uses:
- Deep Foundations: Contiguous piles are suitable for creating deep foundations in various soil conditions, providing support for structures.
- Retaining Walls: They are often used in the construction of retaining walls, especially in situations where a continuous barrier is needed to resist lateral soil pressure.
- Reduced Noise and Vibration: The construction process of contiguous piles tends to generate less noise and vibration compared to other piling methods, making them suitable for projects in urban or sensitive areas.
- Suitable for Limited Access Sites: CFA piles can be constructed in areas with limited access because the drilling equipment can be adapted to fit into confined spaces.
- Building Foundations: Contiguous piles are commonly used to support the foundations of buildings, especially in areas with challenging soil conditions.
- Deep Excavations: They can be employed to provide support for deep excavations, preventing soil collapse and ensuring stability during construction.
- Infrastructure Projects: Contiguous piles are utilized in various infrastructure projects, including bridges, highways, and other structures.
In summary, contiguous piles are a versatile and efficient solution for creating deep foundations and providing support in challenging soil conditions. Their construction process, which involves continuous auger drilling and simultaneous concrete or grout injection, makes them suitable for various applications, including building foundations and retaining walls. The reduced noise and vibration associated with their construction process make them advantageous in urban or sensitive environments.
Soldier piles, also known as soldier beam walls, are a type of retaining wall system used in civil engineering and construction to provide temporary or permanent support for excavations. Soldier piles are typically steel H-sections, wide-flange beams, or other steel shapes that are installed at regular intervals along the excavation perimeter. The spaces between the soldier piles are then filled with lagging material, such as timber, concrete panels, or steel sheet piles, to create a continuous retaining structure.
Here are key features and uses of soldier piles:
- Installation of Piles: The soldier piles are driven, drilled, or vibrated into the ground at predetermined intervals along the excavation perimeter.
- Lagging Installation: Lagging materials are installed horizontally between the soldier piles. Lagging provides lateral support to the soil and prevents it from collapsing into the excavation.
- Tiebacks (Optional): In some cases, horizontal elements called tiebacks or ground anchors may be installed to provide additional lateral support and enhance the stability of the soldier pile wall.
Key Components and Design:
- Lagging: Lagging materials, which fill the spaces between the soldier piles, contribute to the overall stability of the wall.
- Tiebacks (Optional): Tiebacks are used to anchor the soldier piles and provide additional resistance against lateral soil pressure.
Advantages and Uses:
- Versatility: Soldier pile walls are versatile and can be used in a variety of soil conditions, making them suitable for temporary and permanent applications.
- Rapid Installation: The installation of soldier piles is generally faster compared to other deep excavation support methods, making them a cost-effective solution.
- Adaptability: The system can be adapted to different site conditions and can accommodate changes in excavation depth or configuration.
- Minimized Vibration: Soldier pile walls can be a preferred choice in urban areas where minimizing ground vibration is important.
- Deep Excavations: Soldier piles are commonly used to support deep excavations for basements, foundations, or other underground structures.
- Retaining Walls: They are employed as retaining walls for earth retention in areas with sloping terrain.
- Trench Shoring: Soldier piles can be used for shoring trenches during construction activities.
In summary, soldier piles are a reliable and versatile method for providing temporary or permanent support in deep excavations. Their use is widespread due to their adaptability to various soil conditions, relatively rapid installation, and effectiveness in providing stability during construction. The flexibility of soldier pile walls makes them a popular choice in both urban and rural construction projects.
SOIL NAIL WALLS
A soil nail wall is a type of earth retention system used in geotechnical engineering and construction to stabilize slopes and retain soil. It involves installing passive reinforcing elements, called soil nails, into the slope or excavation face. These soil nails are then anchored into the ground, creating a reinforced zone that improves the stability of the soil mass. Soil nail walls are commonly used in areas with steep slopes, landslides, or where traditional retaining walls may not be feasible or cost-effective.
Here are key features and uses of soil nail walls:
- Drilling: Holes are drilled into the slope or excavation face at a predetermined spacing and angle.
- Insertion of Soil Nails: Reinforcing elements, typically threaded steel bars or grouted reinforcing bars, are inserted into the drilled holes.
- Grouting (Optional): The drilled holes may be filled with grout to improve the bond between the soil and the reinforcing elements.
- Installation of Facing: A facing, such as shotcrete or other facing materials, may be applied to the slope face to prevent erosion and provide a finished appearance.
Key Components and Design:
- Soil Nails: The soil nails are the primary reinforcing elements. They are installed at a specific angle and spacing to optimize the stability of the slope or excavation.
- Facing Material: The facing material provides protection to the soil nail wall, prevents erosion, and gives the structure a finished appearance.
- Grout (Optional): Grout is used to improve the bond between the soil and the reinforcing elements, enhancing the stability of the soil nail wall.
Advantages and Uses:
- Flexibility: Soil nail walls are flexible and adaptable to various soil conditions and slope geometries.
- Rapid Installation: The construction process is generally faster compared to traditional retaining wall systems.
- Cost-Effective: Soil nail walls can be a cost-effective solution, especially in projects where traditional retaining walls may be impractical.
- Minimal Disruption: The construction process typically involves minimal disruption to the surrounding area, making it suitable for urban or environmentally sensitive locations.
- Slope Stabilization: Soil nail walls are used to stabilize natural or man-made slopes to prevent landslides and erosion.
- Excavation Support: They are employed in excavations to provide temporary or permanent support to prevent slope failure.
- Retaining Walls: Soil nail walls can act as retaining structures in situations where conventional retaining walls may not be feasible.
In summary, soil nail walls are a geotechnical solution for stabilizing slopes and retaining soil in a flexible and cost-effective manner. Their adaptability to various site conditions and relatively rapid installation make them a popular choice in geotechnical engineering, particularly in projects where slope stability is a critical consideration.