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Casagrande’s Logarithm of Time Fitting Method- Determination of Coefficient of Consolidation of Soil | Soil Mechanics Notes- Agricultural Engineering PDF Download

Casagrande’s Logarithm of Time Fitting Method

From the oedometer test (explained in Lesson 23) the dial reading (settlement) corresponding to a particular time is measured.  From the measured data, dial reading vs time graph can be drawn (as shown in Figure 24.2). Select two points t1 and t2 in initial part of the curve such that t= 4 t1. The points corresponding to the chosen times are marked on the curve. The vertical distance (z) between the two points on the curve is measured. Select another point R0 such that the vertical distance between that point and point on the curve corresponding to the ttime is also z. R is corrected zero reading i.e U = 0%. Determine the U=100% line by drawing two tangents form the straight portion of the curve as shown in Figure 24.2. Once U=0% and 100% lines are identified, U= 50% line is also determined by choosing the middle point between the U=0% and 100% lines. Time (t50) corresponding to the 50% degree of consolidation is determined from the curve. The Coefficient of consolidation (cv) is determined from Eq.(24.1).

Casagrande’s Logarithm of Time Fitting Method- Determination of Coefficient of Consolidation of Soil | Soil Mechanics Notes- Agricultural Engineering

Fig. 24.2. Casagrande’s Logarithm of Time Fitting Method.

The document Casagrande’s Logarithm of Time Fitting Method- Determination of Coefficient of Consolidation of Soil | Soil Mechanics Notes- Agricultural Engineering is a part of the Agricultural Engineering Course Soil Mechanics Notes- Agricultural Engineering.
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FAQs on Casagrande’s Logarithm of Time Fitting Method- Determination of Coefficient of Consolidation of Soil - Soil Mechanics Notes- Agricultural Engineering

1. What is Casagrande's Logarithm of Time Fitting Method?
Ans. Casagrande's Logarithm of Time Fitting Method is a technique used in agricultural engineering to determine the coefficient of consolidation of soil. It involves plotting the logarithm of time against the change in void ratio of the soil sample during consolidation testing. By fitting a straight line to the plotted data, the coefficient of consolidation can be calculated.
2. Why is the coefficient of consolidation important in soil engineering?
Ans. The coefficient of consolidation is an important parameter in soil engineering as it helps determine the rate at which soil consolidates under applied loads. It provides information on the time required for soil to achieve a certain degree of consolidation, which is crucial for designing foundations, embankments, and other structures on soil. It also helps in understanding the settlement behavior of soil and predicting its long-term stability.
3. How is the coefficient of consolidation calculated using Casagrande's Logarithm of Time Fitting Method?
Ans. The coefficient of consolidation can be calculated using Casagrande's Logarithm of Time Fitting Method by first plotting the change in void ratio of the soil sample against the logarithm of time. Then, a straight line is fitted to the plotted data using linear regression analysis. The slope of this line represents the coefficient of consolidation, which can be determined by dividing the slope by the square of the length of the soil sample.
4. What are the advantages of Casagrande's Logarithm of Time Fitting Method?
Ans. Casagrande's Logarithm of Time Fitting Method offers several advantages in determining the coefficient of consolidation of soil. Firstly, it is a relatively simple and straightforward method that can be easily implemented in laboratory tests. Secondly, it allows for the calculation of the coefficient of consolidation using the logarithm of time, which helps in analyzing data over a wide range of time durations. Lastly, it provides a graphical representation of the consolidation process, aiding in better understanding and interpretation of the results.
5. Are there any limitations to Casagrande's Logarithm of Time Fitting Method?
Ans. Yes, there are certain limitations to Casagrande's Logarithm of Time Fitting Method. One limitation is that it assumes one-dimensional consolidation, which may not be applicable in all soil engineering scenarios. Additionally, it assumes that the soil sample is homogeneous and isotropic, which may not always be the case in actual field conditions. Lastly, the method relies on the assumption of constant hydraulic conductivity, which may not hold true for all soil types. Therefore, it is important to consider these limitations and use the method in conjunction with other tests and analyses to obtain accurate results.
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