Chemical Grouting for Water Control in Nearshore Poorly Cemented Sands

The construction of a new beach resort along the southern shoreline of the city of Beirut comprised a 29m deep excavation, which extended about 6m below sea level. The size of the lot (16.000m2), its direct proximity to the sea and the nature of the subsurface materials presented an unusual and extremely challenging water control context. Further constraints regarding local materials, expertise, and practically and economically pumpable water quantities, compounded the difficulties. This paper presents the results of the subsurface investigation campaigns and the solutions adopted which included secant pile cutoff walls and a 2m thick chemically grouted base plug. The problems faced, given the nature and variability of subsurface materials, and lessons learned in relation to grouting strategies and solutions, are presented along with actual trial and production pumping test results.