DEEP EXCAVATION & DEEP EXCAVATION & DEEP EXCAVATION & DEEP EXCAVATION & EARTH EARTH EARTH EARTH RETAINING RETAINING RETAINING RETAINING

STABILISTABILISTABILISTABILIZZZZING STRUCTURESING STRUCTURESING STRUCTURESING STRUCTURES

PREPARED BY : THANUJAN. T

CONTENTSCONTENTSCONTENTSCONTENTS

� Earth Pressure Theories………………………………………..……... 1-16 1. Earth Pressure Theory………………………………………………........…... 1-2

2. Rankine Method………………………………………………………...……. 3-7

� Active condition for c-f soil

� Active condition for Su material

� Rankine earth pressures for non-vertical wall & slopping backfill

3. Coulomb Method……………………………………………………………… 8-9

4. Water Pressures due to seepage behind the wall……………………………. 10-11

5. Short term Vs Long term response – Stress path…………………………... 12-16

� Retaining Structures…………………………………………………… 17-29

1. Rigid Retaing Structures……………………………………………………... 18-21

� Sliding or Translational failure

� Rotational failure

� Bearing capacity failure

� Deep seated failure

� Seepage induced instability

2. Design Examples based on BS and Eurocode……………………………….. 22-30

� Gravity retaining wall

� Cantilever retaining wall

3. Flexible Retaining structures…………………………………………………. 31-37

� Cantilever sheet pile wall

� Single propped or Anchored walls

� Finite Element Modelling of Excavations…………………………….. 38-46

1. Modelling of Drained Excavation using Plaxis………………………………. 38-39

2. Modelling of Undrained Excavation using Plaxis……………………………. 39-46

� Undrained A

� Undrained B

� Undrained C

� Description of stress path for undrained A, B & C

� Stability Issues in Excavation Support System………………………. 47-46

1. Basal Heave Failure……………………………..………………………………. 47-53

� Rankine theory (Lower bound)

� Coulomb theory (Upper bound)

� Base stability of circular shaft in soft CLAY

� Summary of Basal heave equations

2. Hydraulic Failure (Piping)……………………..………………………………… 53

3. Slurry Wall Design………………………………………………………………... 53

4. Hydraulic Uplift…………………………………………………………………… 54