Summary of results on remolded samples

CHAPTER 4. TEST RESULTS & DISCUSSIONS

4.11.2 Summary of results on remolded samples

Table 4.31 and table 4.32 presents the comparison of cv and cr,PD obtained from remolded samples for root t method and non-graphical method.

Table 4.31. Summary of correlations for CD method on remolded samples

Pressure (kPa)

cr,Root CD / cv cr,NG CD / cv

a (y = ax) R - square

No. of data point

(n)

a (y = ax)

R - square

No. of data point (n)

50 0.50 0.72 3 0.78 0.49 5

100 0.88 0.67 5 0.94 0.67 5

200 0.44 0.63 4 0.36 0.67 4

400 0.66 0.65 3 0.54 0.46 4

800 0.58 0.60 4 0.55 0.77 4

All data 0.53 0.61 15 0.55 0.79 16

Table 4.32. Summary of boundary for CD method on remolded samples Pressure

(kPa)

cr,Root CD / cv cr,NG CD / cv

Lower Upper Distribution

area Lower Upper Distribution area

50 0.42 1.12 80.00% 0.35 2.96 80.00%

100 0.72 1.84 80.00% 0.57 1.82 80.00%

200 0.34 0.61 80.00% 0.27 0.47 80.00%

400 0.39 1.23 80.00% 0.36 1.14 80.00%

800 0.39 0.95 80.00% 0.39 0.78 80.00%

All data 0.36 0.82 80.00% 0.41 0.82 80.00%

The authors obtain the result in Table 4.31 and Table 4.32 for correlations of cv and cr CD from remolded samples for Root t method and Non-graphical method.

Average correlations of cr CD/cv and boundary of cr CD/cv with 80% distribution area ratio of cr CD/cv can be determined:

a. For Root method

- cr CD = 0.53cv & R2 is 0.61, cr CD = (0.36 – 0.82)cv (4.34) b. For Non-graphical method

- cr CD = 0.55cv & R2 is 0.79, cr CD = (0.41 – 0.82)cv (4.35)

CHAPTER 5. CONCLUSIONS & RECOMMENDATIONS

The following are key conclusions drawn from this study.

1. The most reliable methods for determining the horizontal coefficient of consolidation (cr):

- Best method is Non-graphical method for determining cr for all case and the function of linear

p = 1.0m & R2 = 0.99 (5.1)

This is the best method because this method determines cr is by matching to find the best curve for the data series

- Rank as 2 or 3 is usually log de2/t or log t.

- These two methods are matching methods, so it gives good results.

- Root method is usually rank as 4 and the function of linear

p = (0.98 - 1.00)m & R2 = (0.95 – 0.99) (5.2) - Result of p from root t method is almost equal to m in the both test (CD and

PD) tests on the both samples (intact and remolded). Therefore, Root t method may become the standard for determining cr values as it is the standard method for determining cv values.

- The root method is matching data within Ur = 20% to Ur = 60% but it is usually ranked 4 because the most appropriate method with measured curves is similar to predicted curve. Especially actual samples with sand or mixed impurities such as seashells, small rocks ... make measured settlement curve different from the theory.

- Full-match method also uses the principle of matching but does not rank well because determining two straight lines on the logarithmic coordinate system is often difficult.

- The remaining methods also do not have high rankings because the value of 0 varies greatly in the range Ur = 20%. Range Ur = 20% is the initial compression.

The initial compression phase takes place due to the compression of small air

pockets in pore spaces and partly due to the rearrangement of particles in the soil, and a small percentage may be due to elastic compression due to the value of 0 varies greatly in this range

- Determining 0 from steepest tangent method is incorrect. It is only true in the vertical consolidation.

2. Correlations between cr values obtained from central drain (CD) test and peripheral drain (PD) test.

Due to differences in drainage boundary, so

, ,

, , , ,

w w

r PD r CD

r PD r CD r PD r CD

r r

k k

k k c c

m m

 

    

  (5.3) Where: kr PD (kr CD) is the permeability coefficient from PD case (CD case), w is water unit weight and mr is soil stiffness from radial consolidation.

Correlations of cr PD/ cr CD changes difference by level of pressure loading:

a. On intact samples For Root method

cr PD = 0.47cr CD & R2 is 0.80, cr PD = (0.26 – 0.62)cr CD (5.4) For Non-graphical method

cr PD = 0.47cr CD & R2 is 0.81, cr PD = (0.32 – 0.64)cr CD (5.5) b. On remolded samples

For Root method

cr PD = 0.33cr CD & R2 is 0.87, cr PD = (0.30 – 0.56)cr CD (5.6) For Non-graphical method

cr PD = 0.41cr CD & R2 is 0.87, cr PD = (0.33 – 0.58)cr CD (5.7) 3. Correlations between cr and vertical coefficients of consolidation (cv)

Due to differences in drainage boundary, so

w w

v r

r v r v

r v

k k c k c

m m

 

    

  (5.8)

Where: kr (kv) is the permeability coefficient from radial consolidation (vertical consolidation), w is water unit weight and mr (mv) is soil stiffness from radial consolidation (vertical consolidation)

Correlations of cr PD/cv and cr CD/cv changes difference by level of pressure loading:

a. On intact samples For Root method

- cr PD = 1.59cv & R2 is 0.78, cr PD = (0.90 – 2.33) cv (5.9) - cr CD = 3.38cv & R2 is 0.76, cr CD = (2.14 – 5.12) cv (5.10) For Non-graphical method

- cr PD = 1.31cv & R2 is 0.71, cr PD = (0.86 – 2.26) cv (5.11) - cr CD = 2.41cv & R2 is 0.63, cr CD = (1.52 – 4.29) cv (5.12) b. On remolded samples

For Root method

- cr PD = 0.46cv & R2 is 0.71, cr PD = (0.35 – 1.01) cv (5.13) - cr CD = 0.53cv & R2 is 0.61, cr CD = (0.36 – 0.82)cv (5.14) For Non-graphical method

- cr PD = 0.58cv & R2 is 0.79, cr PD = (0.41 – 1.09) cv (5.15) - cr CD = 0.55cv & R2 is 0.79, cr CD = (0.41 – 0.82)cv (5.16) The limitation of the study is that the amount of data is still limited due to the urgent time, so it has not been able to perform many samples a and there is no permeability test to verify the ratio in theory.

In the future, the author intends to carry out consolidation and permeability tests for different sites to test the theory. In thesis has not been evaluated and selected the best value 0 & 100, developed the equation of correlations cr with CPTu.

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