Chance Technical Design Manual

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Allowable Nail Strength Punching Limit

20 25 30 35 40 45

Flexural Limit

Anchor 2

10 15

Anchor 1

Nail Strength (kip)

0 5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Distance Along Nail Behind Wall Face (ft) Level 1

Distance Along Nail Behind Wall Face (ft) Level 2

DESIGN EXAMPLES

Allowable Nail Strength Punching Limit

20 25 30 35 40 45

Flexural Limit

Anchor 3

Anchor 4

10 15

Nail Strength (kip)

0 5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Distance Along Nail Behind Wall Face (ft) Level 3

Distance Along Nail Behind Wall Face (ft) Level 4

ANCHOR PULLOUT LIMITS FIGURE 8-16

STEP 15 - CHECK GLOBAL STABILITY Analysis was performed for the given slope geometry by the computer program PCSTABL6H, developed by Purdue University and modified by Harald Van Aller, and the pre processor STED, developed by Harald Van Aller. The resulting Global Factor of Safety (FS global ) = 1.93. Refer to Attachment EX2 in the Chance Soil Screw Retention Wall System Design Manual for printout results of this global stability analysis.

look like that shown for Anchor 1. If the pullout envelope work ing from the back of the nail exceeds the flexural limit, then construct a pullout envelope working from the flexural limit at the head of the nail.

STEP 14 - EVALUATE INTERNAL AND COMPOUND STABILITY

GoldNail 3.11, “A Stability Analysis Computer Program for Soil Nail Wall Design,” developed by Golder and Associates, was used to perform the internal and compound stability analysis. Refer to Attachment EX1 in the Chance® Soil Screw® Retention Wall System Design Manual for printout result of this stability analysis. The following discussion is based on these results. The anchor strength envelope developed in Step 13 needs to be modified for GoldNail. The increase in pullout capacity along the length of the nail is estimated for GoldNail as straight lines, not step functions. An example of this modification for Anchor Level 2 is shown in Figure 8-17. Within GoldNail there are several analysis options. The option used for this example is “Factor of Safety.” Using this option, the Internal Factor of Safety (FS internal ) = 2.11 for the anchor pattern defined in Step 7. The GoldNail output printout lists “Global Stability” not “Internal Stability.” However, the location of the critical failure surface (Circle #13) indicates an internal mode of failure, as shown on the GoldNail geometry printout.

STEP 16 - CHECK CANTILEVER AT TOP OF WALL

In Step 7 the layout of anchors was assumed. The cantilever at the top of the wall from Step 7 is 3 feet. Check cantilever mo ment (M c ) using Equation 8-52. EQUATION 8-52

= 326.7 ft∙lb/ft

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