Chapter 6, Problem 6.1CTP

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9th Edition

Braja M. Das + 1 other

ISBN: 9781305970939

Textbook Problem

Since laboratory or field experiments are generally expensive and time consuming, geotechnical engineers often have to rely on empirical relationships to predict design parameters. Section 6.6 presents such relationships for predicting optimum moisture content and maximum dry unit weight. Let us use some of these equations and compare our results with known experimental data. The following table presents the results from laboratory compaction tests conducted on a wide range of fine-grained soils using various compactive efforts (*E*). Based on the soil data given in the table, determine the optimum moisture content and maximum dry unit weight using the empirical relationships presented in Section 6.6.

**a.**Use the Osman et al. (2008) method [Eqs. (6.15) through (6.18)].**b.**Use the Gurtug and Sridharan (2004) method [Eqs. (6.13) and (6.14)].**c.**Use the Matteo et al. (2009) method [Eqs. (6.19) and (6.20)].**d.**Plot the calculated*w*_{opt}against the experimental*w*_{opt}, and the calculated γ_{d}_{(max)}with the experimental γ_{d}_{(max)}. Draw a 45°*line of equality*on each plot.**e.**Comment on the predictive capabilities of various methods. What can you say about the inherent nature of empirical models?

(a)

To determine

Find the optimum moisture content and maximum dry unit weight using Osman et al. (2008) method.

Explanation

**Calculation:**

Determine the plasticity index *PI* using the relation.

Here, *LL* is the liquid limit for soil 1 and *PL* is the plastic limit for soil 1.

Substitute 17 % for *LL* and 16 % for *PL*.

Similarly, calculate the *PI* for remaining soils.

Determine the optimum moisture content for soil 1 using the relation.

Here, *E* is the compaction energy for soil 1.

Substitute *E* and 1 % for *PI*.

Similarly, calculate the optimum moisture content for remaining soils.

Determine the value of *L* using the relation.

Substitute *E*.

Determine the value of *M* using the relation.

Substitute *E*.

Determine the maximum dry unit weight of the soil 1 using the relation.

Substitute 23.78 for *L*, 0.387 for *M*, and 0.69 % for

(b)

To determine

Find the optimum moisture content and maximum dry unit weight using Gurtug and Sridharan (2004) method.

(c)

To determine

Find the optimum moisture content and maximum dry unit weight using Matteo et al. method.

(d)

To determine

Plot the graph between the calculated

(e)

To determine

Comment on the predictive capabilities of various methods and comment about the inherent nature of empirical models.

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