This project involved designing a deep excavation test pit in soft clay for offshore equipment. The test pit featured an 8-meter-deep by 8-meter-wide excavation supported by secant concrete pile walls. Terratek is the designer and originally used 2D modeling and analysis based on estimated parameters from standard penetration tests, resulting in excessive bottom heave and horizontal displacements. To complete the design successfully, they realized that they needed a 3D technology solution to overcome these conservative results.
They selected PLAXIS 3D to perform 3D numerical modeling and analysis based on additional site investigation using cone penetration testing (CPT). Using the updated PLAXIS 3D model and CPT soil parameters yielded much smaller deformations, with the bottom heave close to zero and the maximum horizontal displacement reduced to .75 centimeters. They optimized the 2D model using Bentley’s 3D geotechnical application, enabling them to reduce the concrete secant pile wall depth and achieve a less costly design solution.