1. Classification, Engineering Properties & Consolidation Methods

2. Why Do We Classify Soils? From experience and historic data, we know the engineering behavior of most soil types: From experience and historic data, we know the engineering behavior of most soil types: Strength when wet Strength when wet Strength when loaded Strength when loaded Behavior when disturbed (earthquake, vibration) Behavior when disturbed (earthquake, vibration) From the historic data and research of our predecessors, soil classification systems have been developed. From the historic data and research of our predecessors, soil classification systems have been developed. Therefore, if a soil can be classified accordingly, we can predict its behavior under specific conditions Therefore, if a soil can be classified accordingly, we can predict its behavior under specific conditions

3. Silt: What is It? Silt is VERY fine sand Silt is VERY fine sand Produced by the mechanical weathering of rock Produced by the mechanical weathering of rockweathering Grinding by glaciers, Grinding by glaciers,glaciers sandblasting by the wind, sandblasting by the wind, sandblasting water erosion of rocks on the beds of rivers and streams. water erosion of rocks on the beds of rivers and streams.erosionbedserosionbeds Silt particles are larger than clay but smaller than sand. Silt particles are larger than clay but smaller than sand.clay sandclay sand Mineralogically, silt is mainly quartz and feldspar Mineralogically, silt is mainly quartz and feldsparquartzfeldsparquartzfeldspar Silt is sometimes known as 'rock flour' or 'stone dust' Silt is sometimes known as 'rock flour' or 'stone dust'

4. Engineering Properties of Silt Little or no dry strength Little or no dry strength Non-plastic Non-plastic Volume change (settlement) under load is rapid Volume change (settlement) under load is rapid Moderate to low permeability Moderate to low permeability Susceptible to frost heave Susceptible to frost heave Minimal changes in volume due to wet/dry Minimal changes in volume due to wet/dry VERY DIFFICULT TO COMPACT VERY DIFFICULT TO COMPACT VERY DIFFICULT TO EXCAVATE BELOW WATER TABLE VERY DIFFICULT TO EXCAVATE BELOW WATER TABLE

5. Clay: What is it? Produced by the chemical weathering: Produced by the chemical weathering:chemical Low concentrations of naturally occurring solvents migrate through rock and take mineral particles along. Low concentrations of naturally occurring solvents migrate through rock and take mineral particles along. solvents Clay deposits are formed as the result of deposition after they have been eroded and transported from their original location of formation. Clay deposits are formed as the result of deposition after they have been eroded and transported from their original location of formation.

6. Engineering Properties of Clay Clay particles are plate-shaped & have highly charged surfaces Clay particles are plate-shaped & have highly charged surfaces The electrical charge on the surface attracts and holds water. The electrical charge on the surface attracts and holds water. Strongest when dry due to cohesion of particles Strongest when dry due to cohesion of particles Plastic when wet & over a range of w% Plastic when wet & over a range of w% Load carrying capacity is linked to load history Load carrying capacity is linked to load history Previously compressed = higher current strength Previously compressed = higher current strength Settlement occurs over time (under static load) Settlement occurs over time (under static load) Not compressible under dynamic load Not compressible under dynamic load Susceptible to freeze-thaw Susceptible to freeze-thaw Volume changes due to wet/dry Volume changes due to wet/dry Easy to compact in thin layers (lifts) Easy to compact in thin layers (lifts)

7. Consolidation of Clay Soils Spring analogy : Spring analogy : Consolidation is explained with an idealized system composed of a spring, a container with a hole in its cover, and water. In this system, the spring represents the compressibility of the soil, and the water which fills the container represents the pore water in the soil. Consolidation is explained with an idealized system composed of a spring, a container with a hole in its cover, and water. In this system, the spring represents the compressibility of the soil, and the water which fills the container represents the pore water in the soil.spring

8. 1. The container is filled with water, and the hole is closed. (Fully saturated soil) 2. A load is applied onto the cover, while the hole is still unopened. At this stage, only the water resists the applied load. (Development of excessive internal pore pressure) 3. When hole is opened, water starts to drain out through the hole and the spring shortens. (Loss of excessive pore water) 4. After some time, the drainage of water no longer occurs. Now, the spring alone resists the applied load. (Full dissipation of excessive pore water pressure. End of consolidation)

9. Sheeps Foot Roller or Static Roller Applies heavy load in a slow/rolling action. Applies heavy load in a slow/rolling action. Used to compact cohesive soils in lifts Used to compact cohesive soils in lifts

10. Consolidation of Granular Materials It is necessary to densify loose granular soils to achieve acceptable foundation performance of structures. It is necessary to densify loose granular soils to achieve acceptable foundation performance of structures. Compaction of granular soils is achieved by vibration: Compaction of granular soils is achieved by vibration: By use if a vibrator roller By use if a vibrator roller By frequent drops of a large mass from a great height (deep dynamic compaction). By frequent drops of a large mass from a great height (deep dynamic compaction). By insertion of a large vibrating poker into the ground (vibro- compaction By insertion of a large vibrating poker into the ground (vibro- compaction

11. “Vibratory Roller” Used to compact sand & gravel Used to compact sand & gravel Delivers a dynamic blow as it rolls Delivers a dynamic blow as it rolls “Shakes” particles into a more dense configuration “Shakes” particles into a more dense configuration

12. Vibro-Compaction Penetration The vibroprobe penetrates to the required depth by vibration and jetting action of water and/or air Compaction The vibroprobe is retracted in 0.5 m intervals. The in situ sand or gravel is flowing towards the vibroprobe. Completion After compaction the platform needs to be leveled and eventually roller compacted at the surface.

13. The principle of sand compaction (Vibroflotation): The compaction process consists of a flotation of the soil particles as a result of vibration, which then allows for a rearrangement of the particles into a denser state. The compaction process consists of a flotation of the soil particles as a result of vibration, which then allows for a rearrangement of the particles into a denser state.

14. Test Pattern

15. Deep Dynamic Compaction Natural soil deposits and undocumented fills can be densified by dropping large weights from great heights repeatedly on the ground surface. Natural soil deposits and undocumented fills can be densified by dropping large weights from great heights repeatedly on the ground surface. The energy imparted is considerable & compaction can be achieved at significant depths below the ground surface. The energy imparted is considerable & compaction can be achieved at significant depths below the ground surface.

16. This mass of concrete, weighing about 12,000 pounds, was used for deep dynamic compaction at the site of an oil storage tank in Japan.

17. Here the mass is lifted to a height of 50 feet and is ready to be dropped. When it hits the surface of the ground, the blow will impart about 600,000 foot- pounds of energy.

18. These craters are the result of dropping the weight.

19. The treatment pattern, energy level, number of passes and phasing of passes are designed based on soil conditions, required bearing capacity and settlement characteristics.The treatment pattern, energy level, number of passes and phasing of passes are designed based on soil conditions, required bearing capacity and settlement characteristics.