assumptions). Extensive collaboration between all parties of the design-build team and CHRPC was necessary to advance this system forward into verification testing. Site Geology The typical geology consists of fill consisting of reworked dune sand for the first 10 to 15 ft (3.0 to 4.6 m), which overlies the Hanford formation for the next 60 to 70 ft (18.3 to 21.3 m). The Hanford formation consists of sand and gravel with scattered cobbles and boulders, and is underlain by the Ringold Formation, which consists of Upper Unit E (well-rounded gravel with fine-to-medium sand) and Lower Mud Unit (silt and clay with trace sand) that extends for about 125 ft (38.1 m) and overlies the Columbia River Basalt that is part of the Ice Harbor Member. Verification Processes Due to the environmental and access challenges present, a lengthy and thorough verification process for the proposed underpinning system (micropiles and chemical/permeation grouting) was undertaken before any production work was allowed to proceed. As with any complex and sensitive project, a verification process is typically necessary to verify the design and construction assumptions made during the preliminary and design phases of this project. The verification programs were an absolute necessity to not only verify performance but also to verify worker safety and to ensure adequacy of management/ mitigation plans for unknown scenarios should they occur during installation. Due to the inherent risk of working in 324 Building, the process was even more necessary to ensure the required perfor- mance, constructability, safe construction given the site constraints and management of the various identified and latent con- taminated materials. The results from the verification programs were ultimately incorporated into the final design. As this article was being prepared, the site team was preparing the area to begin installation. Micropile Verification Program Four load tests were performed as part of the micropile verification testing program — two were performed to evaluate ultimate capacity and two were performed to evaluate performance/creep. These test piles were located strategically around 324 Building and were installed using the type D grouting method, which uses a two-step process of grouting. After the borehole was drilled and reinforcement inserted, a neat cement grout was placed under a gravity head; then, after the initial grout hardened, additional grout was injected once or multiple times using packers and tube-á-manchette (TAM) sleeve port system to target specific zone. Since the final loads were not yet determined, the design team selected this grouting method to ensure the highest capacity possible could be achieved. The micropile bond zone was designed to reside in the Hanford Formation. The general process involved the evaluation and verification of utilities prior to installation, test and reaction micropile installation, micropile grouting, micropile load testing and analysis and reporting. At Hanford, the installation process was much more involved since ground contamination dictated the means and methods of installation. During drilling, spoils were extracted through the annulus of the duplex drilling setup and passed through the drill rig’s flushing bell and hose into awai t ing barrels for containment . Radiological Control (RadCon) personnel would survey and check each barrel prior to commencing drilling. This process was repeated throughout the drilling. The micropile testing process was performed in general accordance with ASTM D1143 and the contractually specified guidelines. The predicted capacities and deflections were calculated and were compared to actual test results from cyclic and ultimate loading. The design team agreed upon a 295 kip (1,312 kN) unfactored compressive service load for each micropile. The load test frame was designed to have a maximum rated capacity of 590 kips (2,625 kN), which was the upper boundary for the ultimate load test. Load testing of test piles T-1 and T-2, south and north of 324 Building, respec- tively, was performed to attempt to achieve failure (i.e., ultimate capacity), which did not occur. The testing was stopped at applied loads of 588 kip (2,616 kN) and 583 kip (2,593 kN) for T-1 and T-2, res- pectively, with corresponding maximum permanent deflections of 0.043 in (1.1 mm) and 0.116 in (3.0 mm), respectively. For test piles T-3 and T-4, north and south of 324 Building, respectively, load testing was performed to evaluate perfor- mance and creep. The performance tests were performed to 200% of the design load and the creep tests were performed at 130% of the design load. Permanent deflections of 0.091 in (2.3 mm) and 0.034 in (0.9 mm) were measured during the performance tests and 0.000 in (0 mm) and 0.009 in (0.2 mm) were measured during the creep tests for T-3 and T-4, respectively. With these results in hand, the design team made the recommendation to proceed forward with the micropile design, as tested, due to the ability to replicate the expected design loads during installation. Chemical grout trailer setup 86 • DEEP FOUNDATIONS • NOV/DEC 2019 Grouting Verification Program The verification test and demonstration program evaluated the ability of the soil stabilization to successfully stabilize the soils using vertical and horizontal drilling and grouting methods. The testing program consisted of one horizontal and
