The water used in the grout mix came from a potable (city) water line installed along the entire over 454,000 m (120 million gallons). The project included 7 active batch plants, length of the project. This water amounted to 3 Figure 2. Operations at LPV-111 Both the TMM and the CI-CMC employed multiple sets of blades or paddles located at the bottom end of the drilling rods to enhance the cutting and mixing effect of the rotation applied to the rod string. The combination of vertical penetration/withdrawal rates, rotational speed and tool configuration, along with the injection parameters and the properties of the grout, are fundamental for the success of the soil treatment. Extensive laboratory tests and field tests established the most suitable construction parameters, which included the most effective materials, and addressed the particular subsurface conditions. The Bench Scale Test was preceded by a comprehensive soil investigation of the main underground features that provided material for soil testing and mixing. This was done in four distinct phases. Phases 1, 2 and 3 used soils from reaches 12B, 12A and 11B, respectively, progressing from west to east and then north along the project alignment. Engineers also conducted a smaller Phase 4 to supplement previous investigations of binder type. Five field validation phases were, on the other hand, accomplished at different locations along the levee, while the production was progressing in previously validated areas, once the results of the lab tests performed on soils from specific sections of the levee became available. Supply and Delivery of Materials: The material used for the project consisted of binder and water. The binder consisted approximately of 25% type I/II Portland Cement and 75% slag cement. The Bench Test determined these optimal proportions of the cement/slag. For the entire project, over 417,000 tonnes (460,000 tons) of binder was used. 14 • DEEP FOUNDATIONS • JAN/FEB 2013 Figure 3. Traffic congestion on the haul road The specifications required that 3% of the elements be cored to verify the quality of the DMM. To accomplish this, the contractor used three Soilmec coring rigs with a PQ3 or Geobore coring system. The cored samples were typically retrieved once the columns had set for at least 26 days. Subsequently, on the 28th day after element installation, the crew trimmed the samples and performed Unconfined Compressive Strength (UCS) testing (Designed UCS is 100 psi = 700 kPa) (Figure 5). spaced at approximately 500 m (1,500 ft) intervals along the protected side of the levee. The contractor mostly used Soilmec equipment at each of the grout plant locations. The contractor’s concern regarding plant placement was that, with increased pumping distance, there was a risk of compromising grout quality, especially considering the extreme high temper- atures during the summer months in New Orleans. Each batch plant could store approx- imately 225 tonnes (250 tons) of binder. The cement tankers used to feed the silos had to share the site haul road with the trucks hauling clay and other site traffic, so extra binder capacity was needed to insure an adequate supply of binder. Quality Control: Stringent contract requirements and a relatively new application for the ground improvement led to the implementation of a very thorough QC program (especially for the DMM) which, given the extent, pace and logistics of the project, resulted in a vast amount of controls, tests and records. QC results proved that the quality of the work was astonishing: ground improvement (over 30,000 DMM columns) of very soft clays and peats was completed with no remedial work necessary.
