Which ground improvement technique to select

[ONENGINEER]

The foundation is a trapezoidal footing of 6 m length and widths of 6 m and 2 m with burial depth of 3.2 m. The subsoil is gravelly sand with about 7% fines. Measuring from the underside of foundation, soil is liquefiable between 2 and 3 m and again between 6 m and 13 m. Some loose sand may still be present below 15 m. Thank you for your response in advance.

 

[msquared48]

At that depth for liquefaction, I would seriously consider pile through and beyond the areas of liquefaction.

Mike McCann
MMC Engineering

 

[ONENGINEER]

msquared48 (Structural)

Thank you for the feedback. We think the loose sand may extend beyond the 16.5 m that was investigated. Would you still do piling if the loose sand extends even more than 20 m.

 

[BigHarvey]

With a fine content of 7%, you could achieve a good compaction with vibroflottation down to 20 m. Compaction grouting would also do the job ( economically, site mob might prove expensive if treated area is samall ).

 

[Mercycity]

If you can provide more data like SPT Data if conducted, the depth of water table,the loads expected for the structure, and ground topography. The area is within the earthquake zone or not. If you can provide these data may be members can give you more valuable infromation about which suitable method can be used for ground improvement.

 

[BigH]

Perhaps you should investigate deeper - you keep hinting that you "think" the soil below x' may be liquefiable. Thinking (pondering) and knowing are two much different concepts!

 

[ONENGINEER]

Thank you for all the comments.

Mercycity - Here are the SPT data just beside the footing of 18 ft by 12 ft. Groundwater assume 1.5 m bgl and D = 3 m.