liquefaction of soil

soil liquefaction of soil ppt

1. MUSLIM YOUTH UNIVERSITY CIVIL ENGINEERING DEPARTMENT SOIL MECHANICS LAB INSTRUCTER: ENGR. MUHAMMAD UMER JADOON

2. Group Members HUSSIAN GHAZI (G.L) MOBIN KHAN MUHAMMAD WAQAS SAHAR GUL UMER AFTAB SATTI

3. Liquefaction Change from solid to liquid state

4. LIQUIFICATION Liquefaction is the name given to the process that converts a solid soil mass into a liquid . Liquefaction is the process that leads to a soil suddenly losing strength, most commonly as a result of ground shaking during a large earthquake

5. What is Soil Liquefaction A phenomenon where by a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid .

6. Cont.. Soil liquefaction occurs when water logged soil behaves like a liquid. Some people refer to it as earthquake liquefaction. The vibrations of earthquake shockwaves in water-saturated soils trigger the phenomenon . Earthquakes are a very common origin of soil liquefaction damage, but other vibration-creating events can be a factor. This includes construction activities, such as blasting, soil compaction, and similar tasks .

7. LIQUIFICATION

8. Why it is a problem? During an earthquake or other vibration in the ground, the liquid consistency of the ground cannot support objects. Buildings, bridges, trees and other objects collapse or sink into the soil . In most countries, modern building codes require builders and architects to analyze the viscosity of the soil before developing the land . Collapsed buildings are not the only problem that liquefaction causes. Since minor earthquakes, vibrations from construction and other incidents happen frequently; soil liquefaction happens often

9. Soil liquefaction October 17, 1989—Soil Liquefaction in the East Bay During the Earthquake

10. when the effective stress of soil is reduced to essentially zero, which corresponds to a complete loss of shear strength May be initiated due to Monotonic Loading Cyclic loading

11. How It Works When the seismic waves pass through the soil, the vibrations cause the individual grains in the soil to  move around  re-adjust their positions This ultimately results in a decrease in volume of the soil mass as  the grains pack more tightly together  a reduction in porosity

12. Principle and Causes of Liquefaction The soil in normal condition is closely packed to each other . The soil particles are closely packed due to the contact forces of each particle. This tight packing contributes to the soil strength. When the soil is in the saturated condition, the pores and the soil are fully filled with water. These water molecules present in the soil exerts pressure on the neighboring particles.  The water pressure exerted by these water molecules increases with rapid load action or earthquake forces. During liquefaction, the water pressures become high enough to counteract the gravitational pull on the soil particles.

13. In the figer the soil particle and water in saturated state

14. The figure shows the forces that are created between the soil particles during their interaction.

15. The figure shows the soil condition at an elevated water pressure. Here, the soil is said to be in a completely saturated condition where the increased water pressure makes the soil grains to “float” as shown in figure This floating activity decreases the interaction between the soil grains. This promotes the properties of liquefaction .

16. The occurrence of liquefaction is the result of rapid load application and break down of the loose, saturated sand and the loosely-packed individual soil particles . Under the action of earthquake force or rapid loading condition, there is no time to completely squeeze out the pore water within the soil. Instead of being squeezed out, the soil particles are prevented from moving closer to each other. This increases the water pressure within the soil system. This water pressure created is very high compared to the contact forces within the soil particles. This softens and weakens the soil deposit. Other than the earthquake and large load actions, the liquefaction of soil can be happened due to construction practices like blasting and dynamic compaction.( Mechanical compaction)

17. Effects of Liquefaction 1). Sand Boiling When liquefaction occurs below the surface that is fully compacted, the water pressure below the surface makes the water to break out like a bubble. These come out as boiling water. This is called as sand boiling.

18. Sand Boiling:

19. Effects of Liquefaction 2). Damage the structures: Liquefaction is common in soil that is submerged. These conditions cause huge damage for the bridge construction, structures supporting submerged soil deposits.

20. Effects of Liquefaction 3).Failure of Dams and Retaining Walls: The soils supporting Dams and Retaining walls undergoes liquefaction, which results in the collapse of these structures. As the structures lose the ability to control the huge water it further results in floods that are uncontrollable

21. Effects of Liquefaction 4 ). Surface Landslides: The failure of water carrying bodies can result in surface landslides. 5 ). Failure of Structures under Earthquake: Liquefaction followed by earthquake forces make the structures to lose its stability. They can either split or lean bringing complete collapse of the structure . Past earthquake records have shown a huge failure of building structures due to liquefaction . These hazards do not provide enough time for evacuation that it results in a huge loss of life and property.

22. Damages Liquefied soil, like water, cannot support the weight of whatever is lying above it – be it the surface layers of dry soil or the concrete floors of buildings. The liquefied soil under that weight is forced into any cracks and crevasses it can find, including those in the dry soil above, or the cracks between concrete slabs. It flows out onto the surface as boils, sand volcanoes and rivers of silt. In some cases the liquefied soil flowing up a crack can erode and widen the crack to a size big enough to accommodate a car .

23. How to Identify? There are a number of different ways to evaluate the liquefaction susceptibility of a soil deposit. 1 Historical Criteria 2 Geological Criteria 3 Compositional Criteria

24. Historical Criteria Observations from earlier earthquakes provide a great deal of information Soils that have liquefied in the past can liquefy again in future earthquakes. If you are building a house and want to find out if your site is susceptible to liquefaction, you could investigate previous earthquakes to see if they caused liquefaction at your site. Information is also available in the form of maps of areas where liquefaction has occurred in the past and/or is expected to occur in the future

25. Geological Criteria The type of geologic process that created a soil deposit has a strong influence on its liquefaction susceptibility. Saturated soil deposits that have been created by sedimentation in rivers and lakes (fluvial or alluvial deposits ), deposition of debris or eroded material (colluvial deposits ), or deposits formed by wind action (aeolian deposits) can be very liquefaction susceptible .

26. Compositional Criteria Liquefaction susceptibility depends on the soil type. Clayey soil , particularly sensitive soils, may exhibit strain- softening behavior similar to that of liquefied soil, but do no liquefy in the same manner as sandy soils are.

27. Compositional Criteria  Soils composed of particles that are all about the same size are more susceptible to liquefaction than soils with a wide range of particle sizes.  In a soil with many different size particles, the small particles tend to fill in the voids between the bigger particles thereby reducing the tendency for densification and pore water pressure development when shaken.

28. Types of Failure  Cyclic Mobility  Overturning  Sand Boiling

29. Cyclic Mobility  Deformations due to cyclic mobility develop incrementally because of static and dynamic stresses that exist during an earthquake.  Lateral spreading, a common result of cyclic mobility, can occur on gently sloping and on flat ground close to rivers and lakes .

30. Overturning  Liquefaction can cause Overturning of large lateral loads on foundations. Foundation must also be able to resist horizontal loads bending moments induced and by lateral movements.  Liquefaction Damage: 1964 Niigata, Japan

31. Sand Boiling  A sand boil is sand and water that come out onto the ground surface during an earthquake as a result of liquefaction at shallow depth.  The Damage of Port Structures (at Kushiro Port)

32. S o luti o n  To minimize liquefaction, one successful approach to lower into the ground, a self digging apparatus till the desired depth is reached; then it is set in motion vibrating the soil surrounding it. This consolidates the sediment layer itself, and de-waters it up to the surface.  The ground surface will naturally alter during this process, and the surface is graded to the desired contours, filled as necessary with overburden, and smoothed off.  The equipment used at Pegasus Town north of Christchurch New Zealand, originated from Bahrein, where presumably this is the technique used to create the 'sand islands'. PAM JAMERA

33. Conclusion: It can clearly be concluded that the ill effects caused by liquefaction have devastating damages to structures built on liquefied soils. Hence the various methods in which the severity of damage as a result of liquefaction can be reduced. the behavior of soils under the influence of loading forces and water interactions .

34. QUESTION?