Mini Pile Construction Method
This method defines the selection of machinery, equipment, materials, and the preparation, application, and quality-control procedures required for mini pile construction. Production will follow the DIN 4128 Small Diameter Injection Piles standard.
1. Site Preparation
The construction area must be level, stable, and kept dry to ensure efficient machine and personnel operation. Heavy machinery (drilling rigs, cranes, mixers, pumps) must operate without sinking more than 10 cm. Proper drainage must be provided, and drilling materials and groundwater must be continuously removed.
2. Soil Information
Execution methods shall be based on site-specific geotechnical reports.
3. Environmental Conditions
Underground or surface obstacles (concrete, steel, utilities) must be identified officially and removed by the employer.
4. Pile Layout & Tolerances
Pile locations are marked individually by survey teams. Verticality and inclination must remain within project tolerances. Adjacent piles must not be drilled within a 3-diameter radius for at least 24 hours.
5. Drilling Works
Mini piles of Ø15–35 cm are drilled using high-torque hydraulic rigs with telescopic masts.
Drilling tools vary depending on soil/rock:
• Auger
• Rock bit
• Top hammer
• Down-the-hole hammer
• ODEX
• Casing systems
Deviation must not exceed 2% of the pile length. Water is avoided unless necessary.
In weak soil or groundwater conditions, pre-grouting or casing may be required.
6. Reinforcement Cage Installation
Rebars must have production certificates. Cages are assembled cleanly, extended via tie-wire or welding, equipped with spacers, and lowered carefully into boreholes. Required anchorage length must remain above ground.
7. Concreting
Concrete must come from certified suppliers. Concreting begins the same day as drilling.
Slump: 16–18 cm, initial set ≥ 3 hours.
Concrete is poured continuously at ≥15 m³/hour with vibration. Finishing is done at the pile head.
8. Injection Method (Alternative Construction)
If standard concreting is not possible (deep boreholes, groundwater, collapse risk), piles may be constructed by grout injection:
• Materials: Cement + clean water + crushed stone
• Mix ratio: Water/Cement ≈ 0.50
• Pressure: ~5 bar
• Injection continues until clean grout exits at the top.
• Secondary injection may be needed.
9. Materials
• Cement: Minimum 28-day strength 325 kg/cm²
• Water: Clean, particle-free
• Crushed stone: Clean, 5–15 mm
10. Machinery
• Drilling rig suitable for required depth
• Injection set (mixer + pump + hoses)
11. Reporting
Daily reports include pile location, diameter, depth, soil layers, reinforcement, water/cement ratio, and injection details in accordance with DIN 4128.
12. Quality Control
All works comply with project QC procedures and material acceptance criteria.