61 State Street

Charleston, SC


Mashburn Construction




Rigid Inclusions and Earthquake Drains


The project consisted of a 4-story boutique hotel in the historic French Quarter of Charleston.

The Problem

The geotechnical investigation found loose sands and layers of soft sandy clay in the upper forty feet of the soil profile.  The sands could liquify under seismic loads and the soft sandy clay would experience settlement detrimental to the structure.  To complicate matters, there was a historic building within one foot of the proposed hotel.

Earth Tech Solution

Earth Tech proposed a ground improvement program consisting of Earthquake Drains and Rigid Inclusions in lieu of a costly deep pile foundation system. The Earth Quake Drains were installed on a grid pattern beneath the slab and foundations to mitigate liquefaction. Rigid inclusions were installed to the top of the underlying dense sand layer around fifty feet below grade to transfer structural loads and reduce settlements to within tolerable limits. The Rigid Inclusions were used in conjunction with a load transfer platform.