Micropile works require proper planning, controlled drilling, correct reinforcement placement, reliable grouting procedures, and clear quality control records. This page provides an overview of Shinei Geotechnique’s typical method statement for micropile installation works.
Our method statement is commonly prepared for submission to consultants, main contractors, developers, and project engineers who require a clear understanding of how micropile works will be carried out on site.
The purpose of this micropile method statement is to describe the general construction procedure, equipment, materials, and quality control steps required for the installation of micropiles.
The actual procedure may be adjusted according to site conditions, ground conditions, consultant requirements, access limitations, and approved construction drawings.
Where changes are required, the proposed modifications may be submitted to the Engineer or Consultant for review and approval before implementation.
Unlike standard building materials, micropile costs are not fixed. They depend heavily on subsurface conditions and construction realities that are often unknown at the early stage.
The typical scope includes:
Typical plant and machinery used for micropile works include:
The final equipment selection depends on access, pile depth, ground condition, working platform, borehole diameter, and site constraints.
Grout Material
The grout is typically mixed using Ordinary Portland Cement and clean water. The water used for grout mixing must be clean and free from harmful or deleterious materials.
A common grout mix requirement includes:
The grout should be free from segregation, excessive bleeding, or slumping during and after placement.
Typically, six grout cubes are prepared for each grouting day. Three cubes may be tested at 7 days and the remaining cubes tested at 28 days by an independent testing laboratory.
For this typical micropile method, the reinforcement may consist of API pipe, such as 88.9mm outer diameter with 6.45mm thickness, Grade N80, subject to project design and consultant approval.
Before drilling begins, survey control points such as TBMs should be established by the Main Contractor’s licensed surveyor.
Based on the approved piling layout plan, individual micropile positions are set out on site. These pile positions should be protected from disturbance before drilling starts.
Accurate setting out is important because micropiles are often used in constrained sites, near existing buildings, or within tight structural layouts.
1. Drilling of Micropile Borehole
A typical micropile borehole may be drilled to approximately 200mm diameter or as specified in the approved design.
The drilling method depends heavily on ground condition.
Dry hole drilling may be used where the ground is stable with little or no groundwater seepage. Air flushing is commonly used to remove drill cuttings.
For hard rock or hard formations, a rotary percussive down-the-hole hammer may be used to advance the borehole.
Wet hole drilling may be required where soil conditions are unstable due to weak soil, high groundwater table, or granular formations.
In these conditions, temporary casing, water, mud flushing, or soil stabilising agents may be used to reduce the risk of borehole collapse.
Micropile Drilling Depth Check
Micropile Drilling Depth Check
Micropile Drilling Depth Check
After drilling is completed, the steel reinforcement or API pipe is lowered into the drilled borehole before grouting.
The reinforcement must be installed carefully to ensure correct positioning, continuity, and alignment according to the approved drawings and site requirements.
Cement grout is mixed using a high-speed mixer and discharged into an agitation tank before pumping.
A grout hose is inserted to the base of the borehole. Grout is then pumped from the bottom upward using the tremie method.
The tremie grouting process helps displace loose cuttings and unstable materials from the borehole.
During grouting, the grout hose should remain below the grout level to avoid contamination or discontinuity. Grouting continues until clean grout is discharged from the borehole.
4. Debonding of Pile Body
Where required by the design, debonding may be carried out after grouting works. A smooth PVC pipe may be inserted to the required depth to create the debonded length.
This is project-specific and should follow the approved construction drawings and consultant’s requirements.
Micropile grouting
Micropile grouting
Micropile grouting
Quality control is a key part of micropile installation.
Typical QAQC items include:
These records help consultants and main contractors verify that the micropile works are carried out according to the approved method and design intent.
Can the micropile method be changed on site?
Yes, but changes should be reviewed and approved by the Engineer or Consultant before implementation.
Temporary casing, wet drilling, mud flushing, or soil stabilising measures may be used depending on the actual ground condition.
Grout quality is controlled through water/cement ratio, proper mixing, visual inspection, cube sampling, and laboratory testing.
Yes. Micropiles are often suitable for restricted access, low headroom, slope, renovation, and strengthening projects, subject to proper planning and equipment selection.
For consultants, main contractors, engineers, and project owners who require a formal reference document, you may download our typical Micropile Method Statement PDF.
Need help reviewing a micropile method statement for your project?
Contact Shinei Geotechnique for technical support.
Ir Tan Chin Shu is a Geotechnical Engineer with over 40 years’ experience in the foundation and geotechnical engineering industry. He is the founding Director of Shinei Geotechnique, a specialist contractor in Malaysia.
