Bentonite Grouting

Bentonite grouting involves the injection of bentonite slurry into the ground to improve soil or rock stability and control water flow.

Definition:

Bentonite grouting involves the injection of bentonite slurry into the ground to improve soil or rock stability and control water flow. The bentonite slurry fills voids, displaces water, and forms a low-permeability barrier to prevent water ingress and improve the overall integrity of the tunnel or underground structure.

Uses/benefits:

Bentonite grouting is commonly used in tunneling and underground structures for the following purposes:

Groundwater Control: Bentonite grouting helps to control and mitigate groundwater inflow into tunnels and underground structures, reducing the risk of water-induced problems such as erosion, flooding, and structural damage.
Soil Stabilization: The injected bentonite slurry stabilizes loose or unstable soils, improving their load-bearing capacity and reducing settlement or ground movement.
Leak Prevention: Bentonite grouting forms an impermeable barrier that seals cracks, joints, and voids in the surrounding ground, preventing water or soil particles from infiltrating the tunnel or underground structure.
Trenchless Excavation: In tunneling or underground construction using trenchless methods, such as pipe jacking or micro-tunneling, bentonite grouting is used to lubricate the soil and reduce friction, facilitating the smooth advancement of the tunneling equipment.
Backfilling and Ground Improvement: Bentonite grouting can be used as a backfill material or for ground improvement purposes, enhancing the strength and stability of the surrounding ground.

Specifications:

Specifications for bentonite grouting in tunneling and underground structures can vary depending on the specific project requirements, geotechnical conditions, and desired outcomes. Some common specifications include:

Bentonite Slurry Concentration: The concentration of bentonite in the grout mixture is determined based on the desired properties, such as viscosity, gel strength, and permeability reduction, which should be suitable for the project's objectives.
Injection Pressure and Flow Rate: The injection pressure and flow rate of the bentonite slurry are controlled to ensure effective grout penetration, complete filling of voids, and proper distribution within the target area.
Grouting Depth and Spacing: The grouting depth and spacing of injection points are determined based on the specific geotechnical conditions and the desired coverage of the grout within the ground.
Setting Time: The setting time of the bentonite grout should be considered to allow sufficient time for injection, expansion, and proper sealing of voids or fractures.
Quality Control: Quality control measures, such as monitoring slurry properties, testing permeability reduction, and conducting grout volume checks, should be implemented to ensure the effectiveness and consistency of the grouting process.

Types:

Different types of bentonite grouting can be used in tunneling and underground structures, including:

Sodium Bentonite: Sodium bentonite is the most commonly used type of bentonite for grouting applications. It swells upon contact with water, forming a gel-like barrier that seals voids and controls water flow.
Calcium Bentonite: Calcium bentonite, also known as non-swelling bentonite, is typically used in situations where low permeability is required without significant swelling properties. It is often used in combination with other materials in grout mixtures.
Polymer-Modified Bentonite: Polymer-modified bentonite grouts combine bentonite with polymers to enhance certain properties such as viscosity, thixotropy, and long-term stability. This type of grout is often used in challenging ground conditions or when specialized performance requirements are needed.

Bentonite for Grouting in Civil Engineering Works, according to IS 12584-1989, conforms the Requirements of Bentonite for use as Grouting Material.

The selection and application of bentonite grouting in tunneling and underground structures depend on factors such as the geological conditions, groundwater flow, structural requirements, and project specifications.