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Re: RetainPro

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I disagree that Pv=0 with a level backslope. In Professor Bowles book, p.
685, 5th ed., he states in the caption to fig. 12-12 that Pav=Pah*tan(phi)
"..since the 'slip' along ab is soil-to-soil."

Regards,
Bill Allen

----------
> From: Michael Brooks <mdbrooks(--nospam--at)enercalc.com>
> To: Bill Allen, S.E. <BAllenSE(--nospam--at)pacbell.net>; Kevin McCune
<kmccune(--nospam--at)willdan.com>
> Subject: RetainPro 
> Date: Thursday, August 21, 1997 2:12 PM
> 
> Dear Sirs:
> 
> I'm responding by private email to clarify your question regarding
RetainPro.
> 
> The "EFP" method calculates a Pv using tan(slope), where for level
backfill
> there is no Pv, and then with increasing slope the force is higher. Years
> ago we used a straight 1/3 value, but this proved to be inaccurate after
> reviewing the more accurate Coulomb and Rankine equations for active
pressure.
> 
> Also, when the heel does not project past the back of the stem we do not
> use Pv, since I believe it develops from inter-soil friction. With no
> projecting heel there is no theoretical failure plane within the soil for
> the inter-soil friction to develop. We will probably add a soil/wall
> friction coefficient for this situation in the future.
> 
> When you use the Rankine method in RetainPro the angle of internal
friction
> is supplied by the user, hence both active and passive pressures can be
> calculated.
> 
> After nearly 15 years designing and maintaining the software for
retaining
> wall design, it still amazes me that there is no definitive work
published
> on both cantilevered and restrained walls.
> 
> Unfortunately I have been unable to pursue the task, but recently we have
> begun an intensive program of software improvement and hopefully some
good
> redesign will become of it.
> 
> Respectfully,
> Michael D. Brooks, S.E.
> President, ENERCALC Engineering Software