Overview
What Are Solid Bar Micropiles?
Solid bar micropiles are installed using a two-step process: first, a borehole is drilled using casing or open-hole methods, then a solid steel reinforcing bar is inserted into the hole and the annular space is filled with neat cement grout. The casing is extracted (if used) and the grout cures to form the completed pile.
The key advantage of solid bar systems is maximum structural steel capacity. Solid bars are available in larger cross-sectional areas than hollow bars — meaning higher yield strengths and ultimate capacities per pile. When the project demands the highest possible loads per pile, solid bar is the system of choice.
Rocky Mountain Micropiles installs solid bar micropiles using Grade 75 and Grade 150 (all-thread) reinforcing bars in diameters from #8 (1″) to #20 (2.5″) and larger, with cased drill holes from 5″ to 12″+ depending on design requirements. Post-grouting techniques are available to further enhance bond capacity in the bearing zone.
Technical Data
Solid Bar Specifications
Key parameters for our solid bar micropile systems. Actual design values are project-specific based on geotechnical conditions and structural requirements.
Solid reinforcing bars from #8 (1″ diameter) through #20 (2.5″) and larger. Bar size is selected to provide the required structural steel capacity for design compression, tension, and shear loads.
Borehole drilled with temporary casing or open-hole methods depending on ground stability. Larger casing diameters provide greater grout body and increased bond surface area.
Solid bar systems achieve the highest micropile capacities — exceeding 1,000 kips when designed with large-diameter bars, adequate bond zones, and competent bearing material.
Grade 75 ksi deformed reinforcing bars for standard applications, or Grade 150 ksi all-thread bars (Williams, Dywidag) for the highest-capacity piles requiring maximum steel contribution.
Every production pile is proof-tested to 200% of design load. Verification and performance tests on designated test piles provide additional data for the engineer’s acceptance criteria.
Post-grouting (pressure grouting through a tube-a-manchette after initial grout sets) available to significantly increase grout-to-ground bond capacity in the bearing zone — often doubling unit bond values.
Applications
When to Use Solid Bar Micropiles
Solid bar is the preferred system when the design demands maximum capacity per pile, when the ground is stable enough to hold an open or cased borehole, or when specific corrosion protection or post-grouting requirements apply.
Discuss Your ProjectHigh-Capacity Foundations
Commercial and industrial structures with column loads exceeding 500 kips per pile. Solid bar’s larger steel cross-sections deliver the structural capacity needed for the heaviest applications.
Rock-Socketed Piles
When the bearing stratum is competent rock, the borehole stays open during drilling — allowing solid bar insertion and tremie grouting without the need for simultaneous grouting. Rock sockets provide extremely high unit bond values.
Seismic Retrofit
Adding foundation capacity to existing structures for seismic upgrade. Solid bar micropiles provide reliable compression, tension, and lateral resistance under dynamic seismic loading conditions.
Structural Underpinning
Stabilizing settling foundations or adding capacity for building additions and renovations. Solid bar micropiles can be installed through existing footings and pile caps with cored access holes.
Bridge & Infrastructure Foundations
Bridge abutments, retaining wall foundations, and transportation infrastructure where design loads are high and long-term corrosion protection is critical for 75+ year design life.
Tension & Uplift Resistance
Structures subject to uplift forces — wind, buoyancy, or overturning moments. Solid bar with threaded connections provides a continuous tension element from the bearing zone to the pile cap.
Installation
Solid Bar Installation Process
A controlled, two-step process — drill the hole, then place the bar and grout — for maximum quality control at every stage.
Drill Borehole
Advance temporary casing or drill an open hole to the design depth using rotary, percussion, or duplex drilling methods. In unstable soils, casing maintains hole integrity during drilling.
Insert Bar
Lower the solid reinforcing bar with centralizers into the borehole. Centralizers ensure the bar is centered within the casing for uniform grout cover and consistent structural performance.
Tremie Grout
Pump neat cement grout from the bottom of the hole upward via tremie pipe, displacing any water and filling the entire annulus. Extract casing simultaneously as grout rises to maintain grout pressure in the bond zone.
Post-Grout (Optional)
For maximum capacity, pressure-grout through a tube-a-manchette after the primary grout sets. This fractures the initial grout body and forces additional grout into the surrounding soil — significantly increasing bond values.
Proof Test
Load-test to 200% of design load per IBC and project specifications. Record load vs. displacement at each increment. Verification tests on designated piles to 300% available for critical structures.
Comparison
Solid Bar vs. Other Foundation Systems
Solid bar micropiles compete with driven piles, drilled shafts, and other deep foundation systems. Here’s how they compare.
vs. Driven Piles
No vibration, no impact noise, no heave risk. Micropiles can be installed immediately adjacent to existing structures and sensitive utilities without damage — impossible with driven piles in most urban and commercial settings.
vs. Drilled Shafts
Micropiles require much smaller equipment, less site disturbance, and can be installed in low-headroom and limited-access conditions where full-size drill rigs can’t operate. Multiple smaller piles can replace a single large shaft with equivalent capacity.
vs. Hollow Bar Micropiles
Solid bar achieves higher ultimate capacities per pile due to larger steel cross-sections. Better corrosion protection options and post-grouting capability. Choose solid bar when loads exceed ~400 kips per pile or when the hole can be maintained during drilling.
vs. Helical Piles
Micropiles achieve significantly higher capacities per pile. Helical piles are typically limited to lighter loads (under 100 kips) and can’t penetrate dense or rocky soils. For commercial and infrastructure applications, micropiles are the more capable system.
Featured Project
Commercial Foundation, Salt Lake Valley
Rocky Mountain Micropiles installed solid bar micropiles with permanent casing to support a new commercial structure on variable clay soils over bedrock. Piles were drilled through soft upper soils and socketed into competent rock to develop high-capacity end bearing. Every pile was proof-tested to 200% of design load with zero failures. The micropile system eliminated the need for over-excavation and soil improvement, keeping the project on schedule and within budget.