Matasovic and Vucetic Model for Clay
Matasovic and Vucetic (1995) propose the following equation for the excess pore water pressure generation for clays:
 | Eq. 1 |
Table 1: Description of Matasovic and Vucetic Model Parameters
| VARIABLE | DESCRIPTION |
| uN | Normalized excess pore pressure (ru) |
| Neq | Equivalent number of cycles |
| γc | The most recent reversal shear strain. |
| γtvp | Threshold shear strain value. |
| r | Curve fitting parameter. |
| s | Curve fitting parameter. |
| A | Curve fitting coefficients |
| B | Curve fitting coefficients |
| C | Curve fitting coefficients |
| D | Curve fitting coefficients |
The uN parameter is the same as in normalized excess pore water pressure ratio (ru = u’ / σv’)
Neq is the equivalent number of cycles calculated for the most recent strain reversal. For uniform strain cycles, the equivalent number of cycles is the same as the number of loading cycles. For irregular strain cycles, since the cycle number does not increase uniformly, and Neq is calculated using the uN obtained from the previous step and is then incremented by 0.5 for the current step.
γtvp is the threshold shear strain value below which reversals will not generate excess pore water pressure.
Suggested Values
Carlton (2014) presents empirical correlations for the curve fitting parameters s, r, A, B, C, and D. Table 2 and Figure 1 (solid black lines) are used in the correlations. The parameter t in the figure corresponds to s*(γc - γtvp)r. The empirical correlations take the following functional forms:
 | Eq. 2 |
 | Eq. 3 |
 | Eq. 4 |
 | Eq. 5 |
 | Eq. 6 |
 | Eq. 7 |
where OCR is the over consolidation ratio, and PI is the plasticity index.
Table 2: Material parameters for the Matasovic and Vucetic (1995) clay pore pressure generation model (From Carlton, 2014)
Material |
Reference |
γtvp (%) |
Pore Water Pressure and Degradation Model Parameter |
|||||
s |
r |
A |
B |
C |
D |
|||
Marine Clay (OCR = 1.0) |
Matasovic and Vucetic (1995) |
0.1 |
0.075 |
0.495 |
7.6451 |
-14.7174 |
6.3800 |
0.6922 |
Marine Clay (OCR = 1.4) |
Matasovic and Vucetic (1995) |
0.1 |
0.064 |
0.520 |
14.62 |
-30.5124 |
18.4265 |
-2.5343 |
Marine Clay (OCR = 2.0) |
Matasovic and Vucetic (1995) |
0.1 |
0.054 |
0.480 |
12.95 |
-26.3287 |
15.3736 |
-1.9944 |
Marine Clay (OCR = 4.0) |
Matasovic and Vucetic (1995) |
0.1 |
0.042 |
0.423 |
11.263 |
-21.4595 |
11.2404 |
-1.0443 |