|RETAINING WALL REPAIR, STABILIZATION OF WALL BACKFILLL AND BEACH EROSION PROTECTION|
|Gorian and Associates, Inc., provided geotechnical consulting services for beach erosion protection and the strengthening of a 25-foot high, unreinforced rock retaining wall. The wall also had no foundation and was backfilled with rubble uncertified fill. The wall and backfill supported a newly constructed residence and a cantilevered infinity pool on the oceanfront in Puerto Vallarta, Mexico.|
|Problems began during the El Nino winter of 1998 when storm waves eroded sand from the beach front residence exposing the base of the rock wall and removing sand from both under and behind the wall. Settlement of the wall and backfill occurred resulting in settlement and cracking of the patio decks above.|
|If left unrepaired, it was expected that the settlement would progress toward the residence. Of additional concern was the potential for strong seismic ground motion in the area and its effect on the wall, backfill, residence and pool. The beachfront is exposed to strong waves that during high tide often reached the wall. Rock filled wire baskets (gabbions) were placed as emergency forms in front of the damaged wall.|
|Concrete was pumped behind the gabbions and under the exposed wall to provide emergency temporary support. Construction of repairs and improvements were further complicated by access problems to the beach. No vehicle access was possible and all equipment and supplies had to be transported to the beach by hand. This involved breaking equipment down, hand carrying to the beach and reassembling. Constant wave activity prevented a sea approach by barge.|
Permanent repairs involved constructing beach erosion protection on a sand cobble beach. Bedrock was too deep to provide erosion protection by anchoring to bedrock. Large concrete armor units were constructed on the beach and were spaced to provide a means to absorb the wave energy rather than reflect the energy. No cranes were accessible to the beach to move the units so the units had to be built in place. The absorption of wave energy created the additional benefit of allowing more sand to be deposited on the beach during periods of moderate to low wave energy.
Once wave protection was in place, repairs could then safely begin on the wall. A grid of reinforced concrete columns and beams with tiebacks were installed on the face of the existing wall to support the unreinforced rock wall. The uncertified wall backfill was then grouted from the bottom up to stabilize the backfill that supported the residence and pool. A sand beach was then constructed over the concrete armor units using gravel, cobbles and filter fabric to improve the aesthetic look of the protection.