Question

You are a field engineer for a construction services testing firm. Your current job assignment is
to evaluate fill placement for a new roadway being constructed in Tg, Lumpur, Pahang. The
project specifications for the roadway require fill compaction to 98% of the ASTM D1557
compaction test results. Your lab manager sends you the results of the Standard and Modified
Proctor compaction testing on the fill being placed. These results are presented in Figure 2. Your
field compaction test results for the second soil lift taken at the intervals required by the project
specifications are listed in Table 2.
a) Identify the maximum dry unit weight and the optimum moisture content from Modified
Proctor Test (ASTM D1557).
(2 Marks)
b) Calculate the amount of water required to fully saturate the soil at maximum dry unit
weight, if the specific gravity Gs is 2.7.
(18 Marks)
c) Estimate the percentage of air entrapped in the soil assuming the compaction done fail to
fulfill the specification. Use this formula:
Gsp,(1 —Va)
Pa = 1+ wG,

06:23N. K AA2513 SOIL MECHANIC. a CONFIDENTIAL BAA/ITISIL QUESTION 2 125 MARKS You are a field engineer for a construction services testing firm. Your current job assignment is to evaluate fill placement for a new roadway being constructed in T. Lumpur, Pahang. The project specifications for the roadway require fill compaction to 98% of the ASIM D1557 compaction test results. Your lab manager sends you the results of the Standard and Modified Proctor compacticn testing on the fill being placed. These results are presented in Figure 2. Your fleld compaction test results for the second soil lift taken at the intervals required by the project specifications are listed in Table 2. a) Identify the maximum dry unit weight and the optimum moisture content from Modified Proctor Test (ASTM D1557) (2 Marks) b) Caculate the amount of water required to fully saturate the soil at maximum dry unit weight, if the specific gravity G, is 2.7 (18 Marks) c) Estimate the percentage of air entrapped in the soil assuming the compaction done fail to fulfill the specification. Use this formula (5 Marks) 11.8 1.0 10.2 025 ,5 10 125 15 175 20 225 25 WATER CONTENT (w) (%) Figure 2: Prector compaction curve Table 2: Sol properties Soil Unit weight, Angle of kN/m friction, Sandy clay Dry 17.5 30 Sandy clay Wet 30 Silty elay Wet 38

Answer 1

Ans a) According to figure 2 , Maximum dry density(MDD) = 16.2 kN/m³ and Optimum moisture content (OMC) ,

OMC = 9.4 %

Ans b) We know,

$\rho$_d = G $\rho$_w/ (1 + e)

where, $\rho$_d = dry unit weight

$\rho$_w = unit weight of water

e = void ratio

Therefore, void ratio at MDD = (2.7 x 9.81/ 16.2) - 1

e = 0.635

water content at  fully saturation can be determined using,

   s e = G w

where, s = degree of saturation =1

w = e/G = 0.635 / 2.7

=> 23.51 %

From part a , OMC = 9.4 %

Water to be added = 23.51 - 9.4

= 14.11 %

Ans) Given ,

  $\rho$_d = G $\rho$_w ( 1 - Va) / (1+wG)

Putting values,

16.2 = 2.7 x 9.81 ( 1 - Va) / ( 1 + 0.635)

1 - Va = 1.635 x 16.2 / 9.81 x 2.7

1 - Va = 1

=> Va = 0 %