LESSON 8 GEOLOGY

• Subsidence


  happens when the ground material is displaced into some sort of underground voids, which can only occur in certain rock type
• Shear Failure


  Characterized by heaving at the ground surface accompanied by tilting of foundation in it.
• Macrovoids


  Happens in larger cavities, solution caves in limestone, rare natural cavities in other rocks including salt and basalt, mined cavities in any rocks of economic value.
• Slope Failure


  A slope collapses abruptly due to weakened self-retainability of the earth under the influence of a rainfall or an earthquake.
• Subsidence


  • cannot occur on solid, unmined rock.

  • can occur when a rock experienced either shear failure or rotational displacement to the surface under excessive load.

  • also occur by landsliding where slope profiles permit.
• Hydrocompaction


  Some fine soils collapse due to restructuring when saturated for the first time, only occurs in a process known as
• Earthquake Liquefaction


  is the temporary loss of effective stress of sand during a period of earthquake vibration, where it tends to look like a liquid.
• Surcharge


  Consolidation accelerates under a few meters of placed fill and almost stops when surcharge is removed, usually after one year of preconstruction.
• Drainage


  • Accelerates water expulsion, so accelerates consolidation. • May allow settlement beneath embankment to be compacted during construction time
• Grouting


  • Mixing of cement to improve soil strength
• Vibrocompaction


  • Densifying sandy, non-cohesive soils using a crane-supported vibrating poker.