Vacuum consolidation effect on the hydromechanical properties of the unusual soft clays of the former Texcoco Lake

The area of the former Texcoco Lake in Mexico is characterized by soft lacustrine clay strata with high water content and high compressibility. The construction of a new airport was planned in this area, which requires soil stabilization. One soil improvement option is the use of vacuum preloading systems that apply a vacuum to the soil through vertical drains. This study evaluates the improvement on hydromechanical properties resulting from the implementation of two vacuum techniques. In 2016, two test embankments with surcharge preloading and vertical drains were constructed to apply a vacuum using the drain-to-drain technique in one embankment and the airtight membrane technique in the other. The average vacuum pressures applied for six months in the test embankments were −58 kPa and −63 kPa with the drain-to-drain and airtight membrane techniques, respectively. The improvement on the properties varied between the two techniques. The airtight membrane technique reduced the water content and the void ratio up to 50 % and 46 %, respectively. While the drain-to-drain technique reduced the water content and the void ratio up to 15 % and 13 %, respectively. The degree of consolidation estimated using different observational methods at the center of both test embankments ranged from 86 % to 88 %.