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Triple-Axis Mixing Piles: A Comprehensive Guide for Foundation Support and Soil Stabilization

Introduction

Triple-axis mixing piles are widely used in foundation pit support and ground improvement projects due to their high construction efficiency, broad applicability across soil types, uniform pile quality, and excellent strength. This technique involves using a triple-axis mixing pile machine to forcibly mix cement with soil at depth (two shafts rotate in the same direction to inject slurry and mix with soil, while the central shaft rotates reversely to inject high-pressure air, ensuring thorough blending). The physicochemical reactions between soil and cement hydration products form a solidified cement-soil composite, enhancing strength, permeability, and bearing capacity.

Key Features

1. Equipment Specifications

  • Common diameters in domestic projects: 650mm, 850mm, 1000mm

2. Applications

  • Waterproof curtains

  • Ground improvement

  • Passive zone soil stabilization

3. Suitable Soil Types

  • Normally consolidated soft clay & silty clay

  • Silt

  • Saturated loess

  • Plain fill

  • Cohesive soil

  • Peat soil

  • Organic soil

4. Pile Depth

  • Generally ≤30m

Construction Process

1. Workflow Overview

(Refer to Construction Flowchart 1 & 2)

2. Construction Sequences

Triple-axis cement-soil mixing piles adopt overlapping hole construction, with three primary methods:

  • Skip-and-build (jump construction)

  • Unilateral compaction method

  • Pre-drilling skip method

Equipment

1. Triple-Axis Mixing Pile Machine

Comprises a drilling rig and a pile driver frame:

A. Drilling Rig Components:

  • Power unit: Lifting/guiding mechanism with motor (multiple power options)

  • Drill rod: Available in auger-type or spiral blade-type

  • Support frame: Ensures vertical alignment

B. Pile Driver Frame Types:

  • Crawler-mounted

  • Hydraulic walking-type

2. Auxiliary Equipment

  • Slurry mixing station

  • Air compressor

  • Pumping unit

(See Reference Table for Common Domestic Equipment)

Quality Control

1. Material Requirements

  • All materials must meet specifications and undergo pre-construction testing

2. Construction Monitoring

A. Pile Positioning

  • Clear and level the site before equipment setup

  • Reinforce soft ground with backfill if needed

  • Maintain baseplate levelness and frame verticality

B. Pile Diameter

  • Regularly measure drill bit diameter; replace if worn beyond tolerance

C. Water-Cement Ratio

  • Adjust based on soil type:

    • Cohesive/sandy soils: Ratio 1.5–2.0 with 20% cement content

D. Mixing Speed

  • Descent rate: 0.5–1.0 m/min

  • Lift rate: 1–2 m/min

  • Optimize parameters via trial piles and environmental assessments

3. Post-Construction Testing

Verify:

  • Pile strength

  • Diameter accuracy

  • Position deviation

  • Length compliance

  • Impermeability performance

Conclusion

Triple-axis mixing piles offer a robust solution for modern geotechnical challenges. By adhering to strict quality protocols and selecting appropriate equipment/parameters, contractors can achieve durable, high-performance foundations tailored to diverse soil conditions.

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