DESIGN OF CANTILEVER RETAINING WALLS Stability Checks STABILITY
DESIGN OF CANTILEVER RETAINING WALLS Stability Checks
STABILITY • OVERTURNING • SLIDING • BEARING
OVERTURNING Traffic Loading (Surcharge)
OVERTURNING Overturning Forces No Surcharge Here Full Surcharge Here Active Pressure Soil + Surcharge
OVERTURNING No Passive Pressure Restoring Forces Weight of Wall Weight of Soil (with care) Weight of Soil
OVERTURNING FOS = Restoring Moment Overturning Moment A FOS = 2 is considered sufficient
SLIDING Sliding Forces No Surcharge Here H 1 Full Surcharge Here Active Pressure Soil+Surcharge
SLIDING Resisting Forces No Surcharge Here Resisting Forces H 2 + μ V μ =Co-eff of Friction Vs 2 Vc 1 Vs 1 H 2 Vc 3
SLIDING without KEY FOS = Passive Earth Pressure Force + μ V Active Earth Pressure Force A FOS = 1. 5 is considered sufficient
SLIDING with KEY Sliding Forces No Surcharge Here Active Pressure Soil+Surcharge
SLIDING with KEY Resisting Forces No Surcharge Here Vs 2 Vc 1 Vs 1 H Vc 2 Vc 3
SLIDING with KEY Find Vertical forces acting in front and back of key No Surcharge Here RESULTANT Vs 2 Vc 1 Vs 1 Active Pressure Soil+Surcharge Vc 2 Vc 3
SLIDING with KEY Determine Pressure Distribution Under Base A=B e x S=B 2/6 V B B/2
SLIDING with KEY Determine Force in Front of KEY y 1 P 2 y 3 y 3=y 2+(y 1 -y 2) (B-x 1)/B B x 1 P 1=(y 1+y 3) x 1/2 P 2=V-P 1
SLIDING with KEY When Pressure Distribution Under Base is Partially Negative V e B B/2
SLIDING with KEY V e B x 2 V 3 x P 1 3 x P 2 Determine P 1 and P 2 once again
SLIDING with KEY Active Earth Pressure Force Total Sliding Force = H 1 Total Resisting Force = P 1 tan f + μ P 2 + H 2 Force in Front of Key Internal Friction of Soil Friction b/w Soil, Concrete Passive Earth Pressure Force on and Back of Key
BEARING There are two possible critical conditions 1. No surcharge on heel 2. Surcharge on heel
BEARING No Surcharge on Heel This case has been dealt already RESULTANT Vs 2 Vc 1 Vs 1 Active Pressure Soil + Surcharge Vc 2 Vc 3
BEARING Surcharge on Heel Determine the pressure distribution under base slab Vs RESULTANT Vs 2 Vc 1 Vs 1 Active Pressure Soil+Surcharge Vc 2 Vc 3
BEARING Determine Pressure Distribution Under Base A=B e x S = B 2/6 V B B/2
BEARING Compare Pressure with Bearing Capacity B FOS = Allowable Bearing Capacity Max Bearing Pressure
BEARING ALTERNATELY B 2 V/3 x 3 x FOS vs Bearing = Allowable Bearing Capacity Max Bearing Pressure 2 V/3 x
Concluded
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