<p><p><figure id='attachment_3579' style='max-width:400px' class='caption aligncenter'><img class="wp-image-3579 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Aerial photograph showing the Kansai International Airport." width="400" height="311" /><figcaption class='caption-text'> Kansai International Airport. (Photograph courtesy of Fudo Construction, Inc.)</figcaption></figure></p><p><div></div><div><h2>Project Summary/Scope:</h2>The Kansai International Airport is the first large-scale off-shore airport in the world. The site is underlain by soft soils at a depth 16.5 to 19 meters below sea level. Sand compaction piles were used to provide foundation improvement for the surrounding seawall.</p><p>Subsurface Conditions: 20-meter thick soft clay layer at the offshore side of the seawall and a 16-meter thick soft clay layer at the shore side of the seawall. Layers of gravel and diluvial clay were found below the alluvial clays described above. The unconfined compressive strength of the clay is described by the function q=0.04z (kgf/cm²), where z is the depth in meters. The unit weight of the clay is 1.4 to 1.6 gf/cm³. Water contents ranged from 120 to 150%, and liquid limits ranged from 30 to 120%. The coefficient of consolidation (c­_v) ranged from 60 to 140 cm²/day.</p><p>Large diameter sand compaction piles were installed in the soft clay layer on a 2.1‑meter square grid. The diameter of most installed piles was 2.0 meters; smaller, 1.25‑meter piles were also installed at certain locations. The construction of large diameter piles was advantageous compared to other methods since it does not require soil disposal and minimizes pollution to the seawater. The average pile length was 25.7 meters. About 18,000 sand compaction piles were installed.</p><p>Five ships were equipped to install the sand compaction piles. Two of these ships contained conventional SCP equipment, while the remaining three contained a Mechatronic Consolidation System. The Mechatronic Consolidation System allows for automatic operation and adjustment of pile diameter and strength based on specified target values.</p><p><strong>Complementary Technologies Used:</strong></p><p><strong> </strong>Sand Drains</p><p><figure id='attachment_3580' style='max-width:389px' class='caption aligncenter'><img class="wp-image-3580 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Schematic cross section of the soil conditions at the Kansai International Airport showing locations improved using sand drains." width="389" height="102" /><figcaption class='caption-text'> Cross section of Kansai International Airport. (Courtesy of Fudo Construction, Inc.)</figcaption></figure><h2> Performance Monitoring:</h2>A light wave surveying apparatus was used to set the sand compaction piles at their accurate location on the sea floor. Use of the Mechatronic Consolidation System allowed for real-time feedback of pile strength and size. A digital method of measuring the rate of pile penetration was used to verify that the SCPs were driven into the bearing layer. A check boring was used to verify design values. Satisfactory performance was achieved.<br><h2>Project Technical Paper:</h2>Fukute, T., Nakamura, M., and Nishikawa, K. (1988). “Foundation Improvement Work by Sand Compaction Pile Method for Seawall Construction at Kansai International Airport Island.” The Kozai Club 1988 Seminar on Engineering for Coastal Development, Hong Kong, Bangkok, 4, pp. 127-151.<br><h2>Date Case History Prepared:</h2>November 2012</p><p></div></p></p>