671017.pdf

0

10

20

30

40

50

0 5 10 15 20

Axial strain (%)

Deviation stress (

100

kPa)

(a)

0 5 10 15 20

Experimental result ( 300 kPa) MPS model ( 300 kPa)

DC model ( 300 kPa) MPS model ( 500 kPa)

Experimental result ( 500 kPa) DC model ( 500 kPa)

DC model ( 800 kPa) Experimental result

MPS model ( 800 kPa) (^800 kPa)

Axial strain (%)

Vo l

umetric strain (%)

4

3

2

1

0

− 1

− 2

− 3

− 4

(b)

Figure 2: Calculation and test results for triaxial test of rockfill material.

휇푡=

퐺−퐹푙푔(휎 3 /푃푎)

(1−퐴∗)^2

, (65a)

퐴∗=

퐷(휎 1 −휎 3 )

퐾푃푎(휎 3 /푃푎)푛[1 − 푅푓(1 −sin휙)(휎 1 −휎 3 )/(2푐cos휙+2휎 3 sin휙)]

, (65b)

where푐is the cohesion of the soil,휙is the friction angle of
the soil,푃푎is the atmospheric pressure, 100 kPa;퐾,퐾푢푟,푛,
푅푓,퐺,퐹,and퐷are parameters.

The parameters in the calculation are taken as푐=0kPa,
휙=38∘,퐾 = 1116,퐾푢푟= 1500,푛 = 0.65,푅푓= 0.88,퐹=0,
and퐷=0, which are the same for both the DC and MPS
models.Thevalueof퐺for the DC model is taken as 0.45 while
for the MPS model it is 0.8, which is larger than 0.5. Although
the calculation results for deviation stress are identical for the
two models, the MPS model can reproduce the dilation of
soil. Because of the limitation that휇푡< 0.5in the DC model,
the dilatation of soil is not revealed and휀V<0is not achieved.

Figure 2 showsthecalculationandtestresultsof
consolidated-drained triaxial compression test (CD test) of
a rock-fill material from Hengshan Dam in China. The unit

weight of the material is 20.7 kN/m^3. The confining pressures
were 300, 500, and 800 kPa, respectively.
The parameters for퐸푡are푐 = 178kPa,휙=40.4∘,K=
1915,퐾푢푟= 2490,푛 = 0.18,and푅푓= 0.85,whicharealsothe
same for both the DC and MPS models.휇푡in the DC model is
still calculated using (65a)and(65b), and퐺 = 0.6,퐹 = 0.37,
and퐷 = 0.023in the calculation, while휇푡in the MPS model

is calculated using the method proposed by Shen and Zhang

[ 38 ],

휇푡=

1

2

−푐푑(

휎 3

푃푎

)

푛푑 퐸푖푅푓

(휎 1 −휎 3 )푓

1−푅푑

푅푑

×(1−

푅푓푆푙

1−푅푓푆푙

1−푅푑

푅푑

),

(66a)

퐸푖=퐾푃푎(

휎 3

푃푎

)

푛

, (66b)

in which푆푙=(휎 1 −휎 3 )/(휎 1 −휎 3 )푓;(휎 1 −휎 3 )푓is the deviation

stress at failure,(2푐cos휙+2휎 3 sin휙)/(1 −sin휙);푐푑,푛푑,and

푅푑are parameters;푐푑= 0.000224,푛푑= 2.24,and푅푑=0.85

in the calculation.

Again, the calculation results for deviation stress are

identical for the two models, while the MPS model repro-

duces the dilatation of soil giving better results than the DC

model. Obviously, more appropriate results of volumetric

strain can be acquired using the MPS model if we improve

the calculation method of휇푡.However,thisisimpossiblefor

the DC model due to the limitation that휇푡cannot exceed 0.5

for the nonlinear elastic model.