Preventing Borehole Instability During Drilling: Technical Adjustments for Deep Auger Piling Foundations

South American coastal regions, from the humid Atlantic seaboard of Brazil to the arid Pacific coast of Chile and Peru, present significant challenges for infrastructure development. For contractors executing PV solar pile installation or deep auger piling foundation projects, the primary adversary is high-moisture, non-cohesive soil.

Coastal profiles often consist of saturated alluvial sands and soft silts that exhibit high pore water pressure. Under these conditions, borehole instability during drilling is a constant risk. Without specific technical adjustments, the lateral pressure from the surrounding water-logged soil causes the hole to collapse (caving) or the bottom to heave (boiling), compromising the integrity of the solar foundation.

Identifying the Mechanics of Borehole Instability

In South American coastal soils, stability is lost when the hydrostatic pressure within the borehole is lower than the external soil and groundwater pressure. The vibration from the drilling process further liquefies sensitive sands, leading to structural failure.

To maintain a stable cavity for a photovoltaic solar spiral pile project, the drilling system must provide continuous lateral support while managing the extraction of saturated materials.

Technical Solutions for Stable Deep Auger Piling

Continuous Flight Auger (CFA) Integration

The most effective method for preventing collapse in saturated sands is the use of a continuous flight auger. By using a screw pipe with a diameter of up to 410 mm, the auger acts as a temporary casing. The soil trapped in the flights supports the borehole walls during the downward stroke.

For deep foundations, maintaining a consistent rotation speed (0–70 r/min) is critical. If the rotation is too fast, it creates centrifugal forces that erode the borehole wall; if too slow, the torque requirement may exceed the machine’s capacity in sticky coastal clays.

Hydraulic Mast Compensation and Ground Stability

In soft coastal soils, the weight of the rig itself can cause ground subsidence, leading to misalignment. The RC130Y addresses this through an adjustable mast compensation function.

During the drilling process, the mast is supported directly on the ground. This structural adjustment ensures that:

• Vibrations are dampened by the ground rather than the borehole wall.

• The 4360 Kg machine weight is distributed to prevent the rig from tilting.

• Borehole stability is maintained throughout the 2000 mm once promotion cycle.

Solving "Low Torque" in Saturated Clays

Coastal projects often transition from loose sand to heavy, plastic clays. This often leads to low torque ground screw installation issues, where the friction on the auger string stalls the motor.

To overcome this, a host power of 56 Kw is required to deliver the necessary rotational force. High-torque hydraulic technology allows the rig to maintain penetration rates without over-excavating the soil, which is vital for maintaining the "skin friction" necessary for a ground screw to hold its rated load.

Adaptation for Versatile Coastal Projects

Coastal South American sites are rarely uniform. A rig must be able to pivot between different drilling technologies based on the specific strata encountered:

For successful PV solar pile installation in South American coastal regions, technical parameters beat marketing promises. Stability is a result of 56 Kw of power, a 35-degree climbing ability for moving through sandy dunes, and the mechanical precision of a mast that supports itself on the ground to ensure hole integrity. By matching these specifications to the site's geological profile, contractors can eliminate the costly delays associated with borehole collapse.