What are micropliles? Micropiles are small diameter piles used for foundation underpinning and new construction to provide deep foundation support for a variety of structures. They are well suited to areas where space limitations exist or where soil conditions are not practical for the installation of helical piers or piles. They can be used in a variety of difficult soil and ground conditions such as clays, sands, silts, gravels and cobbles—even rocks and boulders. With their versatility and bonding capability to soils, micropiles are useful in many applications including:
- Foundation underpinning
- Stabilizing walls
- Stabilizing foundations for tall structures such as towers or wind turbines
- Seismic upgrades and retrofitting
- Foundation support in low strength or otherwise unsuitable soils
Soil Nails are usually installed on an angle to stabilize and reinforce the face of a slope or a wall, and they are often designed in a grid pattern. Similar to micropiles, they are drilled and grouted into place. Some soil nail applications also include a reinforced shotcrete surface for additional stability.
Tie-Back Anchors: Injection Bore Anchors
VersaGrade installs both helical tie-back anchors as well as injection bore (IBO) anchors. The injection bore anchors use the same process and materials used for soil nails and micropiles, but anchors are typically installed deeper into suitable soils on an angle. The grout-encased hollow bar transfers tensile loads to the surrounding soils and relies on soil resistance to prevent the tie-backs from pulling out and destabilizing the wall.
Tie-Back Anchors: Helical Tie-Back Anchors
Helical tie-back anchors are a bearing-type anchor used to transfer tensile loads to suitable load-bearing soils. Helical tie-back anchors consist of a corrosion-protected central steel shaft of varying diameters, spiral helix bearing plates (size and number of plates varies depending on design load and soil conditions), and a wall connection. Their load capacity is proportional to the rotation or torque required during installation. This relationship is in accordance with the equation Qt = TKt where Qt is the total tensile load to be resisted including a factor of safety, T = installation torque and Kt is an empirical constant which varies between 3 and 20 and is a function or geometry of the central steel shaft.
VersaGrade, Inc. utilizes a threaded, hollow bar (30 – 40 MM Diameter) that is drilled into the ground and encased by an injected cement grout body that bonds with soils. This method is also known as injection boring (IBO). The strength or carrying capacity of each micropile is determined by calculating the type of soil, the pile length and diameter, and the amount of the grout injected.
Helical Piles – Resistance Piles – Soil Retention Systems
- Helical piles are installed into the ground much like a screw into wood. They are advanced using hydraulic rotary drive motors to a depth suitable to carry the specified loads.
- Resistance Piles, or Push Piles are installed by hydraulically pressing the pile into the ground using the structure as a counter weight. Installation pressure correlates to the load capacity of the pile.
Soil Retention Systems
- Soil retention systems are mechanisms by which earth/soil is held at a vertical or sloped configuration for extended periods of time. Gravity retaining walls, MSE (Mechanically Stabilized Earth), Soil Nails / Shotcrete, & Gabbion blocks are all examples of Soil Retention Systems.
Deep Foundation Systems
A deep foundation system is a means by which the weight of a structure or object is transferred to a bearing soil strata much deeper than the existing grade. The reason for a deep foundation is to transfer the load to an area where moisture change and settlement occurs less, providing a more stable foundation. There are many types of deep foundation systems, each one designed to overcome specific soil conditions.
External Guide Sleeve
Reinforces the pile where the maximum moment is occurring. This increases the buckling and bending resistance of the pile, which increases capacity when upper soils are too soft to provide adequate lateral bracing.
It allows the pile to rifle through soft unstable soils in a straight, accurate path.