1. What are some types of soils that will swell when adding water to it, and why
ID: 119046 • Letter: 1
Question
1. What are some types of soils that will swell when adding water to it, and why? How do we define the soil’s swelling behavior? How do you deal with the expansive soil when you design pile foundations?
2. What are the main challenges of the permanent frozen soils when you apply the cast-in-place concrete piles to a very thick layer in a cold environment (-30Co )?
3. How do we define the soil sensitivity? What does the soil sensitivity means? When sensitive soil is “disturbed”, the excessive pore water pressure increases and structural bounding (strength) disappears. The former is referred as “general liquefaction behavior” due reducing effective stress. What is soil liquefaction?
Explanation / Answer
Usually clay swells when water is added to it. This is because clay contains different molecules that are ready to absorb water. When they absorb water they will increase their size and this causes swelling of the clay. This is a dangerous property of clay when used in construction. The only way we can avoid this problem in making pile foundation is to extend the process of making a foundation so that it goes beyond the water zone.
2. Permanently frozen soil has improper packing of the particles. The shearing strength will be very low and the formation cannot take heavy loads on it. These soils are easily deformed as they have very less strength.
3. Sensitivity of a soil means it is the ratio. When a soil is at it's own state where it is formed and left undisturbed it has some strength. But when it is moulded or changed then the strength will change. This ratio is called sensitivity of soil.
When the soil has enough moisture and supporting factors that keep the soil strong then the soil is undisturbed. But when any change takes place in those factors will result in the weakening of the soil. This is what we call soil disturbance or disturbed soil. When the soil is saturated it loses it's strength and when some external stress is applied then the soil gets disturbed and flows and moves. This is soil liquefaction.
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