Influence of Soil Fabrics and Stress State on the Undrained Instability of Overconsolidated Binary Granular Assemblies

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Index properties of Chlef sand-silt mixtures_

Properties	Sand-silt mixtures
Fc (%)	20	40
Gs	2.655	2.658
D10(mm)	0.023	0.003
D50(mm)	0.488	0.236
Cu (.)	27.24	120.51
Cc(.)	3.997	3.300
emax(.)	0.697	0.759
emin(.)	0.458	0.505

Coefficients a, b and R2 for equation (3)_

OCR	1	2
a	108.81	206.48
b	–2.03	–4.40
R2	0.96	0.99

Coefficients a, b and R2 for equation (2)_

Methods	DFP		WD
OCR	1	2	1	2
a	44.08	47.44	31.72	36.19
b	–0.21	–0.20	0.11	0.03
R2	0.80	0.99	0.93	0.83

Index properties of sand and silt under study_

Properties	Materials Chlef sand	Silt
Gs	2.652	2.667
Dmax(mm)	2.000	0.08
D10 (mm)	0.266	-
D50 (mm)	0.596	0.023
Cu (.)	2.634
Cc (.)	0.999
emax(.)	0.795	1.563
emin(.)	0.632	0.991
WL(%)	-	31.72
Wp (%)	-	26.71
Ip (%)	-	5.12
USCS	SP	ML
Grain Shape	Rounded	Rounded

Coefficients a, b and R2 for equation (5)_

P’c (kPa)	100				200				300
Method	DFP		WD		DFP		WD		DFP	WD
OCR	1	2	1	2	1	2	1	2	1	2	1	2
a	55.4	83.2	34.2	51.0	132.5	174.2	78.0	122.1	207.3	297.3	125.9	208.3
b	–0.17	–0.66	0.05	0.097	–1.25	–1.04	0.09	0.19	–1.99	–2.01	0.13	0.16
R2	0.99	0.86	0.98	0.87	0.92	0.82	0.95	0.99	0.78	0.84	0.99	0.98

Coefficients a, b and R2 for equation (4)_

Method	DFP	WD
a	10.57	23.17
b	0.82	0.41
R2	0.89	0.99

Summary of monotonic triaxial tests of silty sand_

Test No	Dr (%)	Fc (%)	Method	OCR	P’c (kPa)	η	ϕ’ins(°)	ϕ’s(°)	qins(kPa)	P’ins(kPa)
1					100				55.56	56.11
2				1	200	1.01	45.28	25.61	136.77	138.14
3			DFP		300				219.72	21.92
4					100				86.34	94.97
5				2	200	1.10	47.73	27.70	1 79.88	197.87
6		0			300				307,45	338,19
7					100				34.26	20.90
8				1	200	0.61	31.38	16.07	78.24	47.72
9			WD		300				125.96	76.83
10					100				51.46	37.36
11				2	200	0.72	36.01	18.75	122.01	88.58
12					300				208.06	151.05
13					100				51.48	39.12
14				1	200	0.65	37.47	19.85	98.89	75.15
15			DFP		3 00				1 42.67	108.43
16					100			23.51	63.64	58.93
17				2	2 00	0.93	42.82		142.05	131.54
18		20			300				236.87	219.34
19	52				100				35.02	24.16
20				1	200	0.69	34.60	18.02	79.31	54.72
21			WD		300				128.19	88.45
22					100				52.11	40.12
23				2	200	0.77	37.59	19.95	126.16	97.14
24					300				211.95	163.20
25					100				48.58	36.43
26				1	200	0.75	36.87	19.47	86.78	65.08
27			DFP		300				139.97	104.98
28					100				59.78	49.01
29				2	200	0.83	39.58	21.14	138.05	113.20
30		40			300				227.03	186.16
31					100				36.33	26.16
32				1	200	0.72	35.75	18.75	81.89	58.96
33					300				131.05	94.36
34			WD		100				55.34	42.94
35				2	200	0.78	37.83	20.12	129.75	100.68
36					300				214.43	166.40

Coefficients a, b and R2 for equation (7)_

Methods	DFP		WD
OCR	1	2	1	2
a	24.71	27.39	16.27	18.92
b	– 0.15	– 0.16	0.0 6 7	0.03
R2	0.80	0.97	0.94	0.84

Coefficients a, b and R2 for equation (6)_

Method	DFP						WD
OCR	1			2			1			2
P’c (kPa)	100	200	300	100	200	300	100	200	300	100	200	300
a	24.01	110.8	216.8	76.24	78.36	186.7	20.88	55.18	92.37	–3.15	10.18	95.39
b	0.70	5.74	9.64	3.37	5.34	10.23	0.42	0.73	1.06	1.51	3.66	3.12
R2	0.88	0.97	0.99	0.93	0.90	0.92	0.83	0.77	0.89	0.52	0.88	0.93