DEEP AND SHALLOW SOIL MIXING FOR THE SR-83/US-331 CHOCTAWHATCHEE BAY BRIDGE PROJECT IN SANTA ROSA BEACH, FLORIDA

摘要

The SR 83/US 331 highway is located in the Florida panhandle, where it connects the Walton Countybeaches to the I-10 corridor. The roadway is of vital importance to the economy of the area as well as itssafety since it represents the primary hurricane evacuation route from southern Walton County. The FloridaDepartment of Transportation (FDOT) decided to increase the number of traffic lanes from two to four andimprove the geotechnical properties of the moderately deep, very loose foundation soils, that had affectedthe highway rideability for years. The soil mixing was selected as the method to meet the unique deepground improvement challenges of the project. The design required that Shallow Mixing Method (SMM)be used to build a 10-foot thick platform that transferred axial load to the bottom soil layers through a seriesof Deep Mixing Method (DMM) columns. Upon completion over 8,300 SMM columns and 1,500 DMMcolumns had been installed, with no remedial work required. Also, only 1% of the almost 1,500 specimenstested did not meet the specification requirements. This paper will describe the challenges encountered andprovide valuable information that may be useful for other future projects, including details not previouslypublished.