What Is Micropile?
- Micro-piles/ mini-piles/ pin-piles/ root-piles are high-strength, durable, small-diameter generally 6-12”(150-300mm) steel casing pile or rib or bar and stuffed with a high strength cement grout used to bore hole.
- The bearing stratum is logged throughout installation drilling to assure that bearing capability is adequate.
- Since small piles are smaller in diameter they will be advanced through the bottom at a better speed and may break through materials with larger ease than a caisson casing or a driven pile.
- The micropiles will penetrate any obstructions which will typically cause premature refusal whereas putting in mistreatment typical spile strategies.
- Grouting is achieved by tremie grouting, pressure grouting throughout casing retraction, and tremie-grouting with post-grouting. Post-grouting among the bond length will increase resistance forces with close soils, so achieving larger capability.
- Micropile capacities in way over four hundred kips (1,780 KN).
- Micropiles to depths surpassing two hundred feet (60 m).
Also, Read: Pile Cap Design | Pile Cap Construction | Piles Structure | Pile Cap Foundations | Square Piling Caps | Pile Cap Reinforcement
Common Reasons to Use This Micropile
- To give structural support
- To underpin your foundation
- To transfer hundreds
- To enhance mass stability
Common Uses of Micropile
- Provide structural support
- Underpin foundations
- Enhance mass stability
- Transfer loads
Advantages of Micropiles:
- The main advantage of a micropile is its ability to figure in terribly engorged and low height areas and on any soil surface regardless of its sort.
- Fast ballroom dancing installation even in environmentally-challenging conditions. They’re little and comparatively lightweight. they’re comparatively cheap.
- Simultaneous drilling and grouting allow low overhead, restricted access installation. Micropiles are typically preferred to “H” piles attributable to overhead physical constraints.
- Improves the bottom (densification)
- Offers higher skin friction
- Total single corrosion protection intentionally
- The restricted vibration and noise cause very little disturbance.
- Piling rigs may be low-emission or perhaps electrically driven.
- They can be put in on the point of existing walls with restricted headroom and engorged website conditions.
- They have a high load capability and a capability to resist compressive, tensile, and lateral masses.
- Micro-piles can penetrate any surface.
Also, Read: Piling for Foundation | Use of Pile Foundation | Characteristics of Pile Foundation
Disadvantages of Micropiles:
- If there aren’t any obstacles they’re longer overwhelming than a driven pile
- Water infill is often a problem
Micropile Vs Typical Pile:
- Micropiles are engaged in any difficult conditions involving soil and rock.
- Micropiles are custom and applied for tough terrains and applications.
- Micropiles are used for rehabilitation.
- Micropiles penetrate any surface and might be put in even though an existing foundation creating it one of the simplest doable solutions for foundation rehabilitation and strengthening works.
- Small piles are used for slope stabilization, hill stabilization, and different soil improvement and any kind of ground improvement works.
- Micro piles are employed in areas wherever geological formation is high, urban backfills, areas having floating boulders or different tough terrains that can’t even be accessed with a traditional pile.
- Used extensively within the rehabilitation of monuments, recent structures, sinking structures, etc altogether components of the globe.
Also, Read: What Is Mat Foundation | Mat Building | Advantage and Disadvantage of Mat Slab Foundation | Types of Mat Foundation | Where Mat Foundation Is Used
Micropiles for Foundation Stabilization:
Certain soil conditions will obstruct installation and even thwart the advancement of conventional underpinning solutions. When such conditions exist, trained and grouted micropiles provide an economical, deep foundation possibility capable of penetrating obstructions connected among competent bedrock.
- In compression applications, capability is achieved through finish bearing and conjointly skin friction on the interface of the grout column and therefore the bedrock.
- In tension applications, solely the skin friction contributes to the micropile capability.
Also, Read: What Is Pier and Beam Foundation | Advantages & Disadvantage of Pier and Beam Foundations | Pier and Beam Foundation Design | How to Build a Post and Pier Foundation
Drilling Ways Adopted for Small Piles:
The foremost common ways adopted for drilling are:
- Percussive Drilling used with a driving point/drill at an all-time low of the permanent casing is outlined as displacement technique whereas once the air is employed as a flushing medium. It is outlined as a non-displacement technique.
- Rotary drilling uses air or water as a flushing medium for removing the trained materials from the excavation. The air jet or water pumped up through the drilling system exit at the drilling bit finish flushing out the cuttings.
Also, Read: Functions of Foundation | Requirements of Good Foundation | Types of Foundation | Types of Shallow Foundations | Types of Deep Foundations
What Are the Everyday Applications for a Micropile?
- Micro-pile systems are most popular to support and stabilize buildings, bridges, highways, towers and alternative unreal structures, either as new foundations or remedial construction.
- Morever, they are used for underpinning and shoring applications because of their high load capability and versatile installation techniques.
Also, Read: What Are Weep Holes | Need for Weep Holes | Foundation Weep Holes | Types of Weep Holes | Weep Holes In Retaining Wall | Window Weep Holes
How Will the Micropile Installation Method Work?
- The first and foremost affair anyone would like to attempt, is to dig a cavernous hole with a tiny diameter.
- Once, house has been secured for the pile, lower that into the outlet and apply force to secure the pile.
- Then fill the outlet with a concrete grout concoction to keep everything in situ.
How Are Micropiles Installed?
- Drilled into bedrock, micro-piles are bond to the rock socket wall for conveying a load.
- The casings of the minipiles are advanced as piles are trained into bedrock.
- Drill rod is withdrawn and the steel casing remains. On reaching the saturation level the drilling bit is withdrawn with casing left within the bore-hole.
- A reinforcement load bar is lowered into the casing. Assign reinforcement with centralizer within the borehole, along with tremie grout & cement water blend.
- Cementitious grout along with pressure is fed into the minipile casing and rock socket. After Tremie grouting, perform a pressure grouting through preinstalled grouting tubes.
- The casings for the mini piles are heaved up to a high of bedrock, which permits bonding to the bar.
- Excess steel is cut from the superior of minipiles.
Also, Read: Grillage Foundation | Types of Grillage Foundation | Features of Grillage Foundation
Types of Micropile:
Piles are generally categorized into 2 types:-
- Displacement Piles
- Replacement Piles
#1. Displacement Piles
- Displacement piles are driven or vibrated into the bottom, there by displacing the adjacent soil sideways during the inauguration.
#2. Replacement Piles
- Replacement piles are constructed within a formerly drilled borehole, thus restoring the excavated ground.
Micropiles as Per Based on Design:
Based on Design Application mini piles are categorized into 2 cases:-
- Micro-pile elements, which are stuffed directly & where the pile reinforcement withstands the bulk of the applied load.
- Micro-pile elements circumscribe and internally reinforce the soil to create a reinforced soil composite that withstands the applied load.
Also, Read: What Is Pad Foundation | Failure of Pad Foundation | Pad Foundation Detail | Types of Pad Foundation | Design of the Pad Footing Depends on Several Factors
Grouting Methods Adopted in Micro Piles:
Grouts utilized for micro-piling comprise a blend of sand, cement, and water. The micro piles are categorized into 4 types based on the stratagem of grouting.
Type A Micropiles: Gravity Grout:
- They use tremie grouting and through gravity head.
- The grouting is started from the substratum and follows an identical tremie grouting procedure followed in conventional piles.
Type B Micropiles: Pressure Through Casing:
- After performing the initial tremie grouting, a pressure grouting is finished concomitantly with the lifting of the casing from the bond zone through a pre-installed tube.
- 2nd stage of grouting serves in amplifying grout soil bonding.
- Neat cement grout is placed in to the cavity as the provisional steel casing is withdrawn.
- Injection pressures range from 0.5 to 1.0 MPa.
Type C Micropiles: Single Global Post Grout:
- Pressure grouting is followed by tremie grouting.
- Then, a global injection grouting is performed through a pre-installed sleeve port pipe.
- Before hardening of the primary grout, similar grout is injected once via a sleeve grout pipe at a pressure of a nadir of 1.0MPa.
Type D Micropiles: Multiple Repeatable Post Grout:
- This method is a twin of Type C.
- Primary grout is done under pressure and after coagulation, secondary grout is finished through installed sleeve ports.
Also, Read: What Is the Best Foundation for a House | Types of House Foundations | How to Build a House Foundation | What Is the Strongest Foundation for a House
|F/R/P Pile Caps||$39,039.56|
|F/R/P Grade Beams and Piers||$75,354.92|
|F/R/P Foundation Walls||$18,583.76|
|Concrete ‐ 3000 psi||$81,456|
Micro Piles cost about $120 per linear foot, which is more expensive than the original H-piles. Changing the foundation system to Micro Piles will cost an additional $120,435. However, the Micro Piles also reduce the schedule by 24 days and allows the building to be rented sooner.
What Is Micropile
Micropiles, also known as minipiles, pin piles, needle piles, and root pile, is a deep foundation element constructed using high-strength, small-diameter steel casing and/or threaded bars.
Also, Read: What is Floating Foundation | Suitability of the Floating Foundation | Advantages & Disadvantage of Floating Foundation | How to Build a Floating House Foundation
Common Uses of Micropiles
Micropiles are generally used when there are difficult ground conditions, such as natural or man-made obstructions, sensitive ground with adjacent structures, limited access/low headroom and/or karstic geology.
Advantages of Micropiles
- High load capacity in both tension and compression.
- Easily socketed into hard rock and can penetrate through subsurface obstructions and/or boulders encountered during installation.
- Minimal vibration and disturbance to adjacent structures in close proximity during installation.
Disadvantages of Micropiles
The only disadvantage of micropiles is the relatively high cost as compared to other piling systems except for the case of shallow pile termination depth. Micropiles are generally classified firstly according to design application and grouting method.
Also, Read: What Is Grade Beam | What Is Grade Beam Foundation | Grade Beam Construction Process |Advantages & Disadvantage of Grade Beam
Micropile Vs Typical Pile
A foundation is described as piled when its depth is more than three times its breadth. Micropiles are piles that have a relatively small diameter, typically in the range of 100-250 mm. They can also be described as Minipiles (generally mini piles are smaller than micro piles)
How Are Micropiles Installed
The micropile casing generally has a diameter in the range of 3 to 10 inches. Typically, the casing is advanced to the design depth using a drilling technique. Reinforcing steel, typically an all-thread bar is inserted into the micropile casing. High-strength cement grout is then pumped into the casing.
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