The external sleeve installation requires the use of the hydraulic drive cylinder. The installation time for the external sleeve is generally equivalent to the time required for installing pier pipe, but only to the required depth for the pier sleeve.
The combination of the Model 350 pier pipe plus the inertia sleeve provides 92% of the axial stiffness of the ECP Model 400 system when there is a lack of sufficient lateral support for a distance of 8 feet. If the designer provides 4” diameter exterior sleeve and grouts the Model 350 pier pipe, the allowable load on the system will be 160% that of the grouted Model 400 pier system. One must keep in mind that the pier sleeve is required only in the areas of weak soil or exposed pier pipe. The cost savings should be very evident especially on projects that require extra strength only in the upper several feet of soil.
When specifying sleeve, the designer must extend the sleeve at least three feet into competent material. For example, if a site has 6 feet of peat with blow counts from 0 to 2 blows per foot followed by sand having suitable density as indicated by an SPT reading of 5 blows per foot or greater; the designer should specify sleeve to a depth of 9 feet in order to provide adequate protection through 6 feet of weak soil.
Click on the links for more information about the Model 300 and Model 350 piers.
