LATERAL EARTH PRESSURE

GENERAL Lateral earth pressure represents pressures that are “to the side” (horizontal) rather than vertical. Caused by soil self weight and or external load 3 categories: At rest earth pressure Active earth pressure Passive earth pressure

AT REST EARTH PRESSURE The at rest pressure develops when the wall experiences no lateral movement. This typically occurs when the wall is restrained from movement such as a basement wall that is supported at the bottom by a slab and at the top by a floor framing system prior to placing soil backfill against the wall.

ACTIVE EARTH PRESSURE The active pressure develops when the wall is free to move outward such as a typical retaining wall and the soil mass stretches sufficiently to mobilize its shear strength.

PASSIVE EARTH PRESSURE If the wall moves into the soil, then the soil mass is compressed sufficiently to mobilize its shear strength and the passive pressure develops.

AT REST EARTH PRESSURE q vv hh z  v = . z + q At rest, K = K o Jaky, Broker and Ireland  Ko = M – sin  ’ Sand, normally consolidated clay  M = 1 Clay with OCR > 2  M = 0.95 Sherif and Ishibashi  K o = +  (OCR – 1) = (LL – 20)  = (LL – 20) LL > 110%  = 1.0 ;  = 0.19 Broker and Ireland K o = PI, 0  PI  40 K o = PI, 40  PI  80

ACTIVE EARTH PRESSURE

RANKINE ACTIVE EARTH PRESSURE Ka = tan 2 (45 -  /2)  1 =  3. tan 2 (45+  /2)+2c.tan (45+  /2)  a =  v. tan 2 (45-  /2) – 2c. tan (45-  /2)  a =  v. Ka – 2c  Ka

RANKINE ACTIVE EARTH PRESSURE (INCLINED BACKFILL) (for granular soil, c = 0) For c-  soil

COULOMB ACTIVE EARTH PRESSURE Assumptions: -Fill material is granular soil - Friction of wall and fill material is considered - Soil failure shape is plane (BC 1, BC 2 …) Pa = ½ Ka. . H 2

COULOMB ACTIVE EARTH PRESSURE (SURCHARGE ON BACKFILL)

RANKINE PASSIVE EARTH PRESSURE

 p =  v. tan 2 (45+  /2) + 2c. tan (45+  /2)

RANKINE PASSIVE EARTH PRESSURE Kp = tan 2 (45 +  /2)  h =  v. Kp + 2c  Kp

COULOMB PASSIVE EARTH PRESSURE Pp = ½ Kp. . H 2

LATERAL EARTH PRESSURE DUE TO SURCHARGE a > 0,4 a  0,4

LATERAL EARTH PRESSURE DUE TO SURCHARGE

PURPOSE OF LATERAL EARTH PRESSURE STABILITY ANALYSIS GRAVITY WALL AGAINST SLIDING OVERTURNING

PURPOSE OF LATERAL EARTH PRESSURE