2400
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
Figure 2 (a). Wire Reinforced Membrane (b). Stacked Rings
(Baxter et al 2010)
The cyclic shear response of natural low-plastic Fraser
River silt was investigated using constant-volume direct simple
shear (DSS) testing (Wijewickreme 2010). Maria V. Sanin et
al., (2011) studied the cyclic shear response of undisturbed and
reconstituted Fraser River Silt. A soil can be subjected to many
different stress conditions, being purely cyclic stress, static or
average stress, or a combination of both. Andersen (2009)
shows this clearly in a study on Drammen clays at the NGI.
Drammen clays samples are tested in cyclic triaxial and cyclic
simple shear conditions for different combinations of static and
cyclic shear stresses. In this study cyclic simple shear tests have
been performed with static or average shear stress,
= 0 or
symmetrical cyclic loading.
1.2
Sample Preparation
Air Pluviation with dry compaction approach was developed to
produce samples of the silty sand with consistent heights and
initial relative densities. The equipment used consists of the
shear box having bottom cap, two o-rings, wire-reinforced
membrane, top cap, triaxial pressure panel, and compacting
hammer. Sample diameter is 63.5mm and height is varied from
20 to 25 mm to maintain height to diameter ratio less than 0.4,
in order to fulfill the ASTM D6528-07 criteria. In this study
marine silty sand is obtained from the West coast of South
Korea. Specific gravity of material tested is Gs =2.65. Marine
silty sand has minimum voids ratio of 0.74 and maximum voids
ratio of 1.18. Details of properties of soil tested are given in
Table 1.
Table 1 Properties of marine silty sand.
Figure 3 Stress-path responses of NC Fraser River silt under constant
volume cyclic DSS loading (σ’
v
= 97 kPa; CSR = 0.20;
=0; OCR =
1.0) (Maria V. Sanin et al., 2011).
Figure 5 Constant volume cyclic DSS test on undisturbed Fraser River
Delta silt. (
σ
’
v
= 100 kPa, CSR = 0.14) (Maria V. Sanin et al., 2011).
Figure 5 Stress-strain behavior under different loading conditions
(Andersen, 2009)
1.3
Testing Program
The laboratory testing program for this study was designed to
analyze the behavior of marine silty sand when subjected to
cyclic loads for different combinations of parameters such as
cyclic stress ratio, no. of loading cycles and relative density.
For marine silty sand, the tests were performed at a
frequency of 0.1 Hz. Effect of Relative Density (Dr %) for 65,
and 70 percent is studied for various CSR and no. of loading
cycles. Marine silty sand has minimum voids ratio of 0.74 and
maximum voids ratio of 1.18. Specific gravity of Gs=2.65.
To produce in-situ (K
0
) stress conditions, a vertical
consolidation stress must be applied to the sample prior to
shearing. Applied vertical stresses simulate the loads from
overburden material located over the soil sample. For marine
