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Examples - Determination of Coefficient of Consolidation of Soil, Soil Mechanics | Soil Mechanics Notes- Agricultural Engineering PDF Download

Problem 1

Determine the total settlement of two layered soil system as shown in Figure 24.3. A strip loading of intensity 50 kN/m3 of width 3 m is applied at the ground surface. The water table is at a depth of 1.0 m below ground level.

Examples - Determination of Coefficient of Consolidation of Soil, Soil Mechanics | Soil Mechanics Notes- Agricultural Engineering

Fig. 24.3. Settlement calculation of two layered soil system.

Solution:

The thickness of the Layer I and II is 3m and 2.5m, respectively. Choose one point at the middle of each normally consolidated clay layer. Here point A is chosen at a depth of 1.5 m from the ground level (if loading is applied at any depth from the ground level, then the point in the layer I will be chosen as middle of the soil layer in between the loading depth and top of the layer II. In layer II, point will be chosen at the middle of the layer II). The point B is chosen at a depth of 1.25m from the top of the layer II (or 4.25 m below the ground level).

Layer I

At point A,

σ'v0 = 18 × 1 + (1.5 – 1) × (20 – 10) = 23 kN/m2

Δσ'v = 50 × 3 /(3+1.5) = 33.33 kN/m2 (taking 1:2 distribution of loading)

H1 = 3m (if loading is applied at a depth, then Hwill be taken as total thickness of layer I minus the depth of the loading).

\[{S_1}={{{C_c}} \over {1 + {e_0}}}{H_1}{\log _{10}}\left( {{{{{\sigma '}_{v0}} + \Delta {{\sigma '}_v}} \over {{{\sigma '}_{v0}}}}} \right) = 0.12 \times 3 \times {\log _{10}}\left( {{{23 + 33.33} \over {23}}} \right)=140mm\]                      

Layer II

At point B,

σ'v0 = 18 × 1 + 2 × (20 – 10) + 1.25 (19-10) = 49.25 kN/m2

Δσ'v = 50 × 3 /(3+4.25) = 20.69 kN/m2 (taking 1:2 distribution of loading)

H2 = 2.5m (if loading is applied at a depth, then H2 will be taken as total thickness of layer II).

\[{S_2}={{{C_c}} \over {1 + {e_0}}}{H_2}{\log _{10}}\left( {{{{{\sigma '}_{v0}} + \Delta {{\sigma '}_v}} \over {{{\sigma '}_{v0}}}}} \right) = 0.16x2.5x{\log _{10}}\left( {{{49.25 + 20.69} \over {49.25}}} \right)=60.93mm\]

Total settlement = S1+S2= 140 +60.93 = 200.93 mm

The document Examples - Determination of Coefficient of Consolidation of Soil, Soil Mechanics | Soil Mechanics Notes- Agricultural Engineering is a part of the Agricultural Engineering Course Soil Mechanics Notes- Agricultural Engineering.
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FAQs on Examples - Determination of Coefficient of Consolidation of Soil, Soil Mechanics - Soil Mechanics Notes- Agricultural Engineering

1. What is the coefficient of consolidation of soil?
Ans. The coefficient of consolidation of soil is a measure of the rate at which water can flow through the soil under a constant pressure. It represents the ability of the soil to undergo consolidation, which is the process of soil particles settling and compressing under applied pressure.
2. Why is it important to determine the coefficient of consolidation of soil?
Ans. Determining the coefficient of consolidation of soil is important in geotechnical engineering and agricultural engineering as it helps in understanding the settlement behavior of soil under load. It provides valuable information for designing foundations, embankments, and other structures on soil, ensuring their long-term stability.
3. How is the coefficient of consolidation of soil determined?
Ans. The coefficient of consolidation of soil can be determined through laboratory tests, specifically the oedometer test. In this test, a soil sample is placed in an oedometer cell and subjected to a constant load. The resulting settlement of the soil sample is then measured over time, allowing the calculation of the coefficient of consolidation.
4. What factors affect the coefficient of consolidation of soil?
Ans. Several factors can influence the coefficient of consolidation of soil. These include the permeability of the soil, the compressibility of the soil matrix, the thickness of the soil layer, and the magnitude and duration of the applied load. Additionally, the type and composition of the soil also play a role in determining its coefficient of consolidation.
5. How can the coefficient of consolidation of soil be used in agricultural engineering?
Ans. In agricultural engineering, the coefficient of consolidation of soil can be used to assess the drainage characteristics of agricultural fields. By understanding the rate at which water can flow through the soil, farmers and agricultural engineers can make informed decisions regarding irrigation, drainage, and crop selection, optimizing agricultural practices for improved crop yields and soil health.
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