Technical Manual: Conduits through Embankment Dams (FEMA 484)

Chapter 4—Structural Design of Conduitsengaged to the fully extended condition of the joint when the adjoining pipe sectionsare in parallel, concentric alignment while maintaining full confinement of the gasket.The joint limiting angle of the joint is defined as the maximum deflection anglebetween adjoining pipe sections that the joint will permit before the outer surface ofthe spigot comes into direct contact with inside of the mating bell or sleeve. Part ofthe elongation and rotational capacity of the joint to accommodate expectedsettlement and movement along the conduit is lost due to installation tolerances anddesigned conduit camber. Standard and deep joints are usually available from mostmanufacturers. Where joint capacity is inadequate, shorter lengths of pipe can beused to decrease the movement of each individual joint. Figures 66, 67, 68, and 69illustrate the joint details of AWWA C300, C301, and C302, as RCCP, PCCP, andRCP respectively.4.3.1.3 PlasticMethods used to join plastic pipe are discussed in section 12.1.1.4.3.1.4 MetalMethods used to join metal pipe are discussed in section 12.1.2.4.3.2 Barrier within jointsChapter 2 discussed materials used for the construction of conduits, such asreinforced cast-in-place concrete, precast concrete, plastic, and metal. The followingsections provide guidance pertaining to the barrier within joints used with thesetypes of materials.4.3.2.1 Reinforced cast-in-place concreteWaterstops are used to prevent the movement of water through joints of reinforcedcast-in-place concrete conduits. Figure 75 illustrates how a waterstop is typicallyplaced across the joint of a reinforced cast-in-place conduit. Waterstops are availablein a variety of materials and shapes. The most common waterstops used in conduitconstruction are typically made of preformed flexible materials, the basic resin ofwhich is virgin PVC. The waterstop is fabricated, such that the cross section isdense, homogeneous, and free from porosity and other imperfections. Thewaterstop is specially shaped, so it will interlock with the concrete. Figure 76 showsa waterstop with ribbed sides and a centerbulb profile. This type of waterstop (alsoreferred to as dumbbell shaped) is very versatile, and the centerbulb canaccommodate lateral, transverse, and shear movements. Larger centerbulb diametersare available to accommodate larger anticipated movements.107