Block Wall Details & Callout Tool

Block Wall Details & Callout

Gravity & reinforced segmental block walls

MethodNCMA / Coulomb / AASHTO M-O

Project

Location

Parcel

Wall ID

Date

Preliminary tool. Output is a check of the models in the reference memo, not a sealed design. Soil parameters, seismic values and wall locations are site-specific — a licensed geotechnical/structural engineer must confirm inputs and stamp the final design. Global (deep-seated) stability, settlement, internal geogrid rupture/pullout and drainage adequacy are not checked here.

Inputs

Preset

Reference cases reload the memo's inputs so you can compare against its printed results.

Wall geometry

Exposed heightft

Embedmentft

Batter from verticaldeg

Leveling pad thicknessft

Leveling pad widthft

Toe slope (foreslope)

Block unit

Unit

Course heightft

Unit depth (base width)ft

Unit lengthft

Weight per ft of wallplf

Centroid from faceft

Unit-to-unit friction factor—

Allow half-height cap block

Connection

Type

Lug diameter (at base)in

Lug projectionin

Lugs per unitea

Socket travel (fore/aft)in

Socket travel is the fore/aft play before the lug binds — a fit tolerance only. Batter is built by inclining the leveling pad, with units stacked flush, so socket travel does not limit batter.

Connection shear capacityplf

Peak connection shear from ASTM D6916 testing of your unit, entered as the intercept at zero normal load. Leave at 0 until you have test data — the wall is then carried by friction alone, which is conservative.

Backslope

Backslope angledeg

Slope run to crest (0 = infinite)ft

Soil parameters

Retained φdeg

Retained cohesionpsf

Unit weightpcf

Foundation φdeg

Leveling pad φdeg

Foundation friction factor—

Wall friction δ (× φ)—

Surcharge

Live loadpsf

— offset from back faceft

— strip widthft

Dead load (building)psf

— offset from back faceft

— strip widthft

Include surcharge in the trial wedge search (recommended; the reference design software drops loads that fall outside the critical wedge)

Seismic

PGAg

Site factor F_PGA—

Allowable displacementin

Add wall inertia P_if to seismic driving forces (more conservative; the reference run omits it)

Ignore vertical component of earth pressure (NCMA, as used in the reference run)

Targets

FS sliding — static / seismic—

FS overturning — static—

FS bearing — static—

Seismic targets are taken as 75 % of static (1.125 / 1.125 / 1.50), per the reference method.

Bearing length / width ratio—

Section — wall

block unit drain rock retained soil / fill critical failure plane

Stability checks

Course-by-course

Interfaces are checked top-down. Driving force is the earth pressure retained above that interface; resisting force is unit-to-unit friction plus whatever connection shear capacity you have entered.

Layout, quantities & loads

Layout

Loads

Quantities per LF of wall

Tiering & setback

Plan callout

Verification against the reference memo

Run each preset and compare. Differences and why they occur are listed under Assumptions below.

Assumptions and known deviations from the reference software.
1. Active pressure is a Coulomb trial wedge (failure plane searched in 0.05° steps); it reproduces the closed-form Coulomb equation for a planar backslope and handles broken backslopes and strip surcharges directly.
2. Moment arms use h_eff = h + B·tan ω, with the earth resultant at h_eff/3 and the seismic increment at h_eff/2 — calibrated to reproduce the reference output.
3. Base sliding is checked at the block-to-pad interface using tan φ_pad, and at foundation level using the foundation friction factor; the lower of the two governs.
4. Bearing eccentricity uses the standard Meyerhof convention (e measured from the base centroid), and q_ult uses the effective width B′ = B − 2e + pad thickness. The reference software prints a wider internal bearing width, so its FS_bearing runs higher than this tool's. Bearing has never governed for walls in this height range.
5. Seismic K_AE uses Mononobe-Okabe (AASHTO A11.3.1.1) with k_h = 0.74·k_max·(k_max/d)^0.25. Where K_AE ≤ K_A the dynamic increment is taken as zero.
6. Cohesion is carried through the wedge but should normally be left at zero for granular retained soil.

Not evaluated: global/deep-seated slope stability, settlement and differential settlement, geogrid rupture and pullout, compound failure through reinforced mass, hydrostatic pressure (the drainage detail is assumed to work), scour, and any surcharge from adjacent walls in a tiered arrangement beyond the spacing rules noted.