Index Properties MCQ Quiz in मराठी - Objective Question with Answer for Index Properties - मोफत PDF डाउनलोड करा

Explanation:

The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit. Depending on its water content, a soil may appear in one of four states: solid, semi-solid, plastic, and liquid as shown below:

Shrinkage Limit: Water content below which, no further reduction in the volume of soil is possible, irrespective of change in the water content.

Plastic Limit: Water content just above which the soil just turns into a plastic state.

Liquid Limit: Water content at which soil changes from a liquid state to a plastic state.

Concept:

The formula for finding the dry unit weight of soil is given by:

\({γ _d} = \frac{γ }{{1 + w}}\)

where, 

γd = Dry unit weight of soil

γ = Total Unit weight of soil

w = Water content

Calculations:

Given Data:

\(γ\) = 5 kN/m3

w = 17 % = 0.17

So, 

\({γ _d} = \frac{5 }{{1 + 0.17}}=4.27\;kN/m^3\)

Explanation:

Methods used for finding water content:

Explanation:

Consistency Index: It is defined as a ratio of the difference between the liquid limit and the natural water content of the soil to the plasticity index.

\({I_c} = \frac{{{w_{L - W}}}}{{{I_p}}}\)

Where,

w_L = water content at liquid limit

w = Natural water content

I_p = Platicity index

Concept:

Shrinkage ratio: It is the ratio of a given volume change expressed as a percentage of dry volume to the corresponding charge in water content above the shrinkage limit expressed as a percentage of the weight of the oven dried soil.

\(\text{SR}=\frac{\frac{\left( {{\text{V}}_{1}}-{{\text{V}}_{2}} \right)}{{{\text{V}}_{\text{d}}}}\times 100}{{{\text{w}}_{1}}-{{\text{w}}_{2}}}=\frac{{{\text{V}}_{1}}-{{\text{V}}_{2}}}{{{\text{V}}_{\text{d}}}\left( {{\text{w}}_{1}}-{{\text{w}}_{2}} \right)}\times 100\)

Where,

V1 = Volume of soil mass at water content (w1)

V2 = Volume of soil mass at water content (w2)

Vd = Volume of dry soil mass

Note: Shrinkage ratio is equal to mass specific gravity of soil in its dry state.

Calculation:

WL = 42%

WP = 30%

As per given data,

(VL – Vd )/V_d= 35

(VP – Vd )/V_d= 22

Also, \(\frac{{{V_L} - {V_d}}}{{{W_L} - {W_s}}} = \frac{{{V_p} - {V_d}}}{{{W_p} - {W_s}}}\)

\(\frac{{35}}{{0.42 - {W_s}}} = \frac{{22}}{{0.3 - {W_s}}}\)

Solving we get WS = 9.69%

Shrinkage Ratio, \(SR = {{{{{V_L} - {V_d}} \over {{V_d}}} \times 100} \over {{w_L} - {w_s}}}\)

∴ \(S.R = \frac{{35}}{{42 - 9.69}} = 1.1\)

Concept:

Plasticity Index:

• Plasticity index (PI) is the range of water content over which the soil remains in the plastic state. Mathematically defined as,
• Plasticity Index = Liquid Limit - Plastic Limit.
• The plasticity of soil is its ability to undergo deformation without cracking.
• It is an important index property of fine-grained soil, especially for clayey soils.

Activity:

• The activity of the soil is given by the ratio of the plasticity index (Ip) and the percentage of clay fraction (C) in the soil.
• It indicates water absorption capacity or indicates swelling and shrinkage characteristics.

Activity \(= \frac{{Plasticity\;Index}}{{Per\;cent\;of\;clay\;particles\;finer\;than\;2\;\mu m}}\)

Consistency Index or Relative consistency:

• It is useful in the study of the field behavior of saturated fine-grained soil.
• It is given as subtraction of natural water content from the liquid limit to the plasticity index of the soil.

\({{\rm{I}}_{\rm{c}}} = \frac{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{n}}}}}{I_P}\)

IP = Plasticity Index = wl - wP

\({{\rm{I}}_{\rm{c}}} = \frac{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{n}}}}}{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{p}}}}}\)

\({{\rm{w}}_{\rm{l}}}\) = liquid limit, \({{\rm{w}}_{\rm{P}}}\) = plastic limit, \({{\rm{w}}_{\rm{n}}}\) = water content of the soil at the natural state

Calculation:

Given, W_l = 40%, W_p = 20%, Clayey silt = 70%

W_n = 30%, Clay content = 100 - silt content = 100 - 70 = 30%

a) Plasticity Index

Plasticity Index = Liquid Limit – Plastic Limit

Plasticity Index = 40 - 20 = 20%

b) Activity

Activity \(= \frac{{Plasticity\;Index}}{{Per\;cent\;of\;clay\;particles\;finer\;than\;2\;\mu m}}\)

Activity \(= \frac{{20}}{{30}}\) = 0.67

Consistency Index:

\({{\rm{I}}_{\rm{c}}} = \frac{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{n}}}}}{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{p}}}}}\)

\({{\rm{I}}_{\rm{c}}} = \frac{40 \ - \ 30}{40 \ -\ 20}\) = 0.5

Consistency Index or Relative consistency: 

It is useful in the study of the field behaviour of saturated fine-grained soil.

It is given as subtraction of natural water content from liquid limit to the plasticity index of the soil.

\({{\rm{I}}_{\rm{c}}} = \frac{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{n}}}}}{I_P}\)

I_P = Plasticity Index = w_l - w_P

\({{\rm{I}}_{\rm{c}}} = \frac{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{n}}}}}{{{{\rm{w}}_{\rm{l}}} - {{\rm{w}}_{\rm{p}}}}}\)

\({{\rm{w}}_{\rm{l}}}\) = liquid limit

\({{\rm{w}}_{\rm{P}}}\) = plastic limit

\({{\rm{w}}_{\rm{n}}}\) = water content of the soil at the natural state

Range: It can be greater than or less than 1.

For

Ic = 1, the soil is at its plastic limit

Ic = 0, the soil is at its liquid limit

Ic > 1, the soil is in semi-solid state and is stiff

Ic < 0, it indicates that the natural water content is greater than the liquid limit and hence behaves like a liquid.

Concept:

Consistency index

 \({I_C} = \frac{{{w_L} - w}}{{{w_L} - {w_P}}}\)

So, consistency index is – ve means, w > wL i.e. soil is in the liquid state and behaves like a liquid. 

\({I_C} = 0;w = {w_L}\; \Rightarrow Soil\;is\;in\;liquid\;limit.\)

\({I_C} = 1;w = {w_P}\; \Rightarrow Soil\;is\;in\;plastic\;limit.\)

\({I_C} > 1\;;\left( {{w_L} - w} \right) > \left( {{w_L} - {w_P}} \right) \Rightarrow w < {w_P}\;i.e;soil\;is\;stiff.\)

Calculation:

Given data,

Liquid limit, wL = 45%, 

Plastic limit, wp = 25%,

Shrinkage limit, ws = 15% , and

Natural moisture content, w = 30%

Consistency index

\({I_C} = \frac{{{w_L} - w}}{{{w_L} - {w_P}}}\)

\(\therefore {{\rm{I}}_{\rm{C}}} = \frac{{45 - 30}}{{45 - 25}} = \frac{{15}}{{20}}\) = 0.75

Hence, the consistency index is 75%.

Concept:

The Activity of the soil (A)

The activity of the soil is given by the ratio of the plasticity index (Ip) and the percentage of clay fraction (C) in the soil.

It indicates water absorption capacity or indicates swelling and shrinkage characteristics.

Activity \(A_c= \frac{{Plasticity\;Index}}{{Per\;cent\;of\;clay\;particles\;finer\;than\;2\;\mu m}}\)

So, C = Percentage of clay fraction finer than 2 μ

Kaolinite:

• The basic Kaolinite mineral is a two-layer unit that is formed by stacking a gibbsite sheet on a silica sheet
• These basic units are then stacked one on top of the other to form a lattice of the mineral
• These units are held together by hydrogen bonds
• The strong bonding does not permit water to enter the lattice
• Thus, kaolinite minerals are stable and do not expand under saturation