Vacuum Preloading with Drain to Drain Method for the New International Airport of Mexico City-Paper

Paper

Pdf Summary

The study evaluates vacuum-assisted preloading using the “drain-to-drain” method to improve the extremely soft, compressible clays beneath the planned New International Airport of Mexico City, in the Texcoco Lake area. A 76-by-56-m trial embankment was built from 2 m of lightweight volcanic fill, applying about 24.4 kPa of surcharge. Star Drains, installed to 28 m depth at 1.2 m spacing, were individually connected to vacuum lines. Vacuum was applied for 180 days, with an average pressure of approximately 60 kPa at drain connections. The site was extensively instrumented to monitor settlement, pore pressure, groundwater, and lateral ground movements.<br /><br />Settlement at the embankment centre reached 1.97 m, corresponding to an estimated 70% consolidation. Settlements largely ceased soon after vacuum application ended. The results indicate that vacuum combined with a relatively light surcharge accelerated consolidation substantially: a conventional surcharge trial in the same area required more than a year to achieve a similar settlement.<br /><br />Ground movements extended beyond the embankment. Near its edges, maximum measured horizontal displacements were 170–270 mm, with appreciable movement still observed 20 m away; localized tension cracks also formed. Settlement patterns and pore-pressure measurements were broadly consistent with the predicted consolidation response.<br /><br />Numerical analyses reproduced measured surface and deep settlements satisfactorily, supporting use of the trial results in designing larger ground-improvement works. Overall, the trial demonstrated that drain-to-drain vacuum preloading can effectively and reliably improve Mexico City’s exceptionally weak clay deposits, while requiring monitoring and consideration of lateral effects beyond the treated area.

Keywords

vacuum-assisted preloading

drain-to-drain method

soft clay consolidation

Mexico City airport

Texcoco Lake

trial embankment

Star Drains

pore pressure monitoring

lateral ground movement

ground improvement