Riprap wedge active or passive
Riprap wedge active or passive
(OP)
I have a similar question to the one that Kenny posted in thread255-367340: Passive Resistance on Sheet Pile Wall back in 2014. We are in the process of designing a sheet pile to bisect a WWTP lagoon into two sections which will allow the municipality to keep the WWTP running while they first lower the water level on one side of the sheet pile, install a liner, and then refill that side of the lagoon before doing the same procedure to the other half of the lagoon. The water level in the lagoon is 15' deep which results in significant pressures on the sheet pile. The site also has weathered rock and/or bedrock approximately 15' below grade so the depth of embedment of the sheet pile below grade is limited. We are proposing to drive the sheet pile and install class 1 riprap on the side of the lagoon that will be drained to act as a wale to laterally brace the sheet pile at a height of H/3 (5') above the base of the lagoon.
If the angle of the riprap is roughly installed at the angle of repose, can we use passive pressure to determine the resultant force from the riprap? Also as suggested in the referenced thread, should Culmann's solution be used to determine this force or another method?
Thanks.
Scott Francis
If the angle of the riprap is roughly installed at the angle of repose, can we use passive pressure to determine the resultant force from the riprap? Also as suggested in the referenced thread, should Culmann's solution be used to determine this force or another method?
Thanks.
Scott Francis





RE: Riprap wedge active or passive
f-d
ípapß gordo ainÆt no madre flaca!
RE: Riprap wedge active or passive
Mike Lambert
RE: Riprap wedge active or passive
Maybe I'm just being pedantic. . . ?
f-d
ípapß gordo ainÆt no madre flaca!
RE: Riprap wedge active or passive
https://res.cloudinary.com/engineering-com/image/upload/v1469031001/tips/20160720104121_df7isd.pdf
Does this seem right?
RE: Riprap wedge active or passive
Log spiral charts allow you to determine this passive resistance. My first reply suggested you look at these log-spiral charts, which are found in DM7.1 or 7.2. You'd need to take some wall friction into account - i.e., the interface friction angle between the rip-rap and the sheeting.
The friction angle of rip-rap is likely 50 degrees. The Rankine passive wedge is taken as the wedge of soil with an angle of 45+phi/2 as measured from the vertical line and as marked from the toe of the sheets. That'd be 70 degrees! If the rip rap is 5 ft up the side of the wall, you'd need a wedge of at least 14 ft (5*tan70).
Or you can just bank the rip rap on the angle of repose against the sheets and calculate the passive resistance for that non-Rankine wedge of resistance using log-spiral charts.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Riprap wedge active or passive
I have used the Culmann's or trial method before.
Berm Study
Berm Passive Pressure
Embedded Wall - Berm Overview
EIT
www.HowToEngineer.com