Lateral Earth Pressure

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Transcript of Lateral Earth Pressure

  • *Lateral Earth PressureWe can calculate vNow, calculate h which is the horizontal stressh/ v = KTherefore, h = Kv (V is what?)vhH

  • *Lateral Earth PressureThere are 3 states of lateral earth pressureKo = At RestKa = Active Earth Pressure (wall moves away from soil)Kp = Passive Earth Pressure (wall moves into soil) Passive is more like a resistancevhzH

  • *At Rest Earth PressureAt rest earth pressure occur when there is no wall rotation such as in a braced wall (basement wall for example)

    Ko can be calculated as follows:Ko = 1 sin for coarse grained soilsKo = .44 + .42 [PI / 100] for NC soilsKo (oc) = Ko (NC) (OCR)1/2for OC soilsvhzH

  • *Active Earth PressureActive earth pressure occurs when the wall tilts away from the soil (a typical free standing retaining wall)

  • *Active Earth PressureActive earth pressure occurs when the wall tilts away from the soil (a typical free standing retaining wall)

  • *Active Earth PressureActive earth pressure occurs when the wall tilts away from the soil (a typical free standing retaining wall)

  • *Active Earth PressureActive earth pressure occurs when the wall tilts away from the soil (a typical free standing retaining wall)Ka can be calculated as follows:Ka = tan2 (45 /2)thus: a = Ka v 2 c (Ka)1/245 + /2Failure wedgeHSoil sliding down pushing the wall

  • *Passive Earth PressurePassive earth pressure occurs when the wall is pushed into the soil (typically a seismic load pushing the wall into the soil or a foundation pushing into the soil)Kp can be calculated as follows:Kp = tan2 (45 + /2)thus: p = Kp v + 2 c (Kp)1/245 - /2Failure wedgeHSoil being pushed up the slope

  • *Active Stress Distribution (c = 0)c = 0dry soilHa = Ka v 2 c (Ka)1/2a = Ka v0a is the stress distribution Pa is the force on the wall (per foot of wall)How is Pa found? Pa = ?? - What is this value

  • *Passive Stress Distribution (c = 0)c = 0dry soilH0p is the stress distribution Pp is the force on the wall (per foot of wall)How is Pp found? Pp = ?? - What is this valuep = Kp v 2 c (Kp)1/2p = Kp v

  • *Stress Distribution - Water Table (c = 0)H1Ka H1orPa = areas = Ka H12 + Ka H1H2 + Ka H22 + 1/2wH22 H2Ka H1Ka H2Ka ( H1 + H 2)Effective StressPore Water PressurePaw H2

  • *Stress Distribution With Water TableH1Ka H1orH20Ka H1Ka H2Ka ( H1 + H 2)Effective StressPore Water PressurePaw H2Why is the water pressure considered separately? (K)

  • *Active Stress Distribution (c 0)-c 0dry soilHKa Hzo2 c (Ka)1/2Ka H 2 c (Ka)1/2=Find zo:Ka zo 2 c (Ka)1/2 = 0Zo = 2c / (Ka)1/2Pa = ?_

  • *Passive Stress Distribution (c 0)-c 0dry soilHKp H2 c (Kp)1/2Kp H + 2 c (Kp)1/2=Pp = ?+

  • *Practice ProblemsChapter 12 Problems:1315(part c is using equation 12.47 and part d uses equation 12.49)25

    13 and 25 are the same problem just one is active calcs and the other is passive calcs