Injections

Low-pressure injections are a soil consolidation and cavity filling technique that involves introducing a low-pressure liquid mixture into porous, cracked soils or cavities to enhance their strength and stability. This technique is widely used for soil stabilization, void filling, and water infiltration control.

Injectable Mixtures:

• Cement Grout: Composed of cement, water, bentonite, and sometimes additives for workability or mechanical properties.
• Chemical/Silicate Mixtures: Polyurethane resins or other synthetic materials that react and solidify in the soil.

Injection Equipment:

• Low-Pressure Pumps: Generate pressures typically below 10 bar for gentle injection.
• Injection Tubes: Flexible or rigid conduits for introducing the mixture into the soil.
• Injection Packers: Terminals that regulate mixture distribution.

Monitoring Systems:

• Pressure Sensors: Monitor injection pressure to prevent exceeding desired levels.
• Flow Meters: Measure the amount of injected mixture for precise volume control.

Functioning:

1. Drilling: Create holes in the soil to the desired depth.
2. Positioning Injection Tubes: Insert tubes into the prepared holes.
3. Preparing and Injecting the Mixture: Pump the mixture through the tubes at low pressure to fill pores or cavities.
4. Solidification and Monitoring: The mixture solidifies, enhancing soil cohesion and strength.

Applications:

• Soil Consolidation: Improve load-bearing capacity and stability under buildings and infrastructures.
• Cavity Filling: Fill underground voids or cavities.
• Waterproofing: Reduce soil permeability to prevent water infiltration.
• Foundation Reinforcement: Stabilize and reinforce existing foundations.
• Crack and Fracture Repair: Fill cracks or fractures in soil or structures like dams and levees.

Advantages:

• Low Impact: Reduced risk of damaging adjacent soil or structures.
• Versatility: Suitable for various applications, from small consolidation jobs to large waterproofing operations.
• Simple Installation: Generally less complex equipment and easier management compared to high-pressure techniques.

Limits:

• Limited Penetration Depth: Low pressure limits the mixture’s penetration depth.
• Effectiveness Dependent on Soil Permeability:** More effective in permeable soils or with cavities, less efficient in compact or clayey soils.
• Consolidation Time: The mixture’s solidification can take longer, affecting intervention speed.

Main References:

• Metropolitana Milanese Spa: Line 1, Line 5, Line 4

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