Earthquake Retrofit Study (Voids in block walls)

A large ongoing earthquake retrofit project is underway at a large medical college hospital. During the upgrades, it was found that many of the concrete block walls in the basement were not adequately filled with grout. The project was delayed since it was necessary to install the earthquake retrofit supports in only grout filled blocks. To support the ongoing upgrades, we were called upon to provide geophysical services in marking which blocks in the basement walls were grout filled and which were empty.

The survey area had many obstacles (beams, pipe chases, air ducts, electrical conduits, and hanging ceilings). GPR traversing was performed at each of the proposed support installation sites in an attempt to identify filled blocks or blocks with voids. Following the delineation of grouted blocks and voids, drill holes were conducted at several locations and were successful in validating the GPR results.

900 MHz Antenna in use at the site

Grouted Cell       Empty Cell       Grouted Cell