A geotechnical investigation is essential because it provides the foundational data required to design a safe and reliable helical pier system. Soil properties vary significantly, and understanding the specific conditions at your site—such as soil stratigraphy, groundwater levels, and the presence of expansive clay—directly influences foundation stability.

Key reasons for this investigation include:

• Identifying Competent Strata: Helical piers must transfer structural loads past weak surface soils to deeper, load-bearing layers. We use borings and tests like the Standard Penetration Test (SPT) to identify exactly where these competent layers begin.
• Determining Soil Parameters: Engineers require specific values, including cohesion (c) for clays and internal friction angles (φ) for sands, to calculate theoretical bearing capacity. Without this data, we cannot accurately determine the necessary pier depth or helix configuration.
• Calibrating Torque Correlations: While we monitor torque in real-time during installation, the relationship between torque and capacity (the Kt factor) is site-specific. A geotechnical report allows us to calibrate these readings to ensure field results are accurate within 15% to 30% of actual capacity.
• Safety and Compliance: To ensure building code compliance and account for variables like construction tolerances, we apply a safety factor (typically 2 to 3) to the ultimate bearing capacity to find the allowable working load. Detailed soil data ensures this safety margin is correctly calculated for your specific project.

Estimates are preliminary and subject to change after site inspection and a full scope review. Please consult a licensed contractor for definitive advice and verify licensure with the Colorado Department of Regulatory Agencies (DORA).

• Soil Bearing Capacity for Helical Piers: A Guide for Centennial