Hi, I am working on a micropile design to stabilize an active landslide, for which we are required to use the procedures in the 2005 FHWA manual for micropile design (NHI-05-039). The procedure gets pretty convoluted when it reaches the step of determining the shear capacity of a single vertical micropile.
The procedure directs you to break the micropile in two at the slip surface (location is known), flip the top portion upside-down such that the 'pile head' is the slip surface, and run p-y analyses (e.g. with LPILE) on the the two portions separately. The shear capacity is determined by applying shear force and bending moment boundary conditions at the slip surface, such that both analyses result in (1) equal slopes at the pile head (i.e. slip surface) and (2) maximum moment equal to the bending moment capacity of the micropile, determined in a previous step.
Per the procedure, the bending moment BC is adjusted until the slopes are equal, then the shear force BC is adjusted until the max moment = moment capacity. But of course, adjusting the shear force BC also affects the slopes, so the iterative procedure becomes a bit of a tail-chaser.
Or at least that is what I am seeing. Is anyone familiar enough with the FHWA micropile procedure to offer some guidance on this tortured p-y analysis?
The procedure directs you to break the micropile in two at the slip surface (location is known), flip the top portion upside-down such that the 'pile head' is the slip surface, and run p-y analyses (e.g. with LPILE) on the the two portions separately. The shear capacity is determined by applying shear force and bending moment boundary conditions at the slip surface, such that both analyses result in (1) equal slopes at the pile head (i.e. slip surface) and (2) maximum moment equal to the bending moment capacity of the micropile, determined in a previous step.
Per the procedure, the bending moment BC is adjusted until the slopes are equal, then the shear force BC is adjusted until the max moment = moment capacity. But of course, adjusting the shear force BC also affects the slopes, so the iterative procedure becomes a bit of a tail-chaser.
Or at least that is what I am seeing. Is anyone familiar enough with the FHWA micropile procedure to offer some guidance on this tortured p-y analysis?
