The project involved replacement of an existing 161 kV line with a double-circuit 345/161 kV line, and existing 69 kV line with a double circuit 345/69 kV line. It also included a new single-circuit 345 kV line. Wood H-Frame structures were replaced with steel monopoles.
MJE Drilling provided drilled shaft installation at 163 structures and performed Thermal Integrity Profiling (TIP) to confirm structural integrity of the foundations. TIP analysis revealed potential fluctuation in select shafts, requiring MJE Drilling to conduct further testing and confirm the integrity of the shafts had not been affected.
QS Scope & Solution
Quanta Subsurface (QS) analyzed the reports to confirm foundation integrity. When potential anomalies were detected, the shafts were further analyzed for specific conditions that may have existed based on the TIP report. Analysis was completed at the point of maximum moment and at the point of the first anomaly to identify any structural concerns.
Drilled shafts are generally installed with uniform reinforcing and cross-sections from top to bottom, as opposed to tapered cross-sections. As such, they inherently have a tremendous amount of reserve capacity at locations above and below the point of maximum stress. This reserve capacity was confirmed in all QS analyses, leading to the determination that all shafts were structurally sound.
Alternatives to TIP report evaluation, including coring the shaft to identify areas of weakness, can be costly and time-consuming, and require additional evaluation. Estimated repair costs could exceed $35,000 per shaft, and full replacement costs could be as high as $250,000 per shaft. QS’s expertise and experience in drilled shaft design and evaluation resulted in all shafts being validated, and no remediation measures required.