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

Youcef Mahmoudi; Abdellah Cherif Taiba; Leila Hazout; Wiebke Baille; Mostefa Belkhatir

doi:10.2478/sgem-2018-0011

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

Studia Geotechnica et Mechanica

Volume 40 (2018): Issue 2 (October 2018)

By: Youcef Mahmoudi, Abdellah Cherif Taiba, Leila Hazout, Wiebke Baille and Mostefa Belkhatir

Open Access

|Oct 2018

Figures & Tables

Determination of the instability line (Yamamuro and Lade, 1997).

(a) Photograph and (b) SEM image of Chlef sand (Algeria).

Grain size distribution curves of tested soils.

Void ratios index of tested soils. (a) Void ratio index versus fines content and (b) maximum void ratio versus minimum void ratio.

Table 1

Index properties of sand and silt under study.

Properties	Materials Chlef sand	Silt
Gs	2.652	2.667
D_max(mm)	2.000	0.08
D₁₀ (mm)	0.266	-
D₅₀ (mm)	0.596	0.023
C_u (.)	2.634
C_c (.)	0.999
e_max(.)	0.795	1.563
e_min(.)	0.632	0.991
W_L(%)	-	31.72
W_p (%)	-	26.71
I_p (%)	-	5.12
USCS	SP	ML
Grain Shape	Rounded	Rounded

Table 2

Index properties of Chlef sand-silt mixtures.

Properties	Sand-silt mixtures
F_c (%)	20	40
Gs	2.655	2.658
D₁₀(mm)	0.023	0.003
D₅₀(mm)	0.488	0.236
C_u (.)	27.24	120.51
C_c(.)	3.997	3.300
e_max(.)	0.697	0.759
e_min(.)	0.458	0.505

Schematic illustration of sample preparation; (a) wet deposition and (b) dry funnel pluviation.

View of (a) dry funnel pluviated and (b) wet deposited samples after shearing.

Undrained monotonic response of dry funnel pluviated sand–silt mixtures (F_c = 0%, OCR = 1, D_r = 52 %): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Undrained monotonic response of dry funnel pluviated sand–silt mixtures (F_c = 40%, OCR = 1, D_r = 52%): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Undrained monotonic response of dry funnel pluviated sand–silt mixtures (F_c = 0%, OCR = 2, D_r = 52%): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Undrained monotonic response of dry funnel pluviated sand–silt mixtures (F_c = 40%, OCR = 2, D_r = 52%): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Undrained monotonic response of wet deposited sand–silt mixtures (F_c = 0%, OCR = 1, D_r = 52%): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Undrained monotonic response of wet deposited sand–silt mixtures (F_c = 40%, OCR = 1, D_r = 52%): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Undrained monotonic response of wet deposited sand–silt mixtures (F_c = 0%, OCR = 2, D_r = 52%): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Undrained monotonic response of wet deposited sand–silt mixtures (F_c = 40%, OCR = 2, D_r = 52%): (a) deviator stress versus axial strain, (b) excess pore water pressure versus axial strain and (c) stress path diagram.

Table 3

Summary of monotonic triaxial tests of silty sand.

Test No	D_r (%)	F_c (%)	Method	OCR	P’_c (kPa)	η	ϕ’_ins(°)	ϕ’_s(°)	q_ins(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

Instability and steady-state lines of Chlef sand–silt mixtures = (D_r = 52%): (a) Fc = 0%, (b) Fc = 20% and(c) Fc = 40%.

Instability friction angles versus fines content of sand–silt mixtures (D_r = 52%): (a) OCR = 1 and (b) OCR = 2.

Table 4

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

DFP instability friction angle versus WD friction angle of Chlef sand–silt mixtures (D_r = 52%).

Table 5

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

Overconsolidated instability friction angle versus normally consolidated friction angle of sand–silt mixtures (D_r = 52%).

Table 6

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

Instability friction angle of sand–silt mixtures versus instability friction angle of sand (D_r = 52%).

Instability shear strength of sand–silt mixtures versus fines content (D_r = 52%): (a) P’_c = 100 kPa;(b) P’_c = 200 kPa; (c) P’_c = 300 kPa.

Table 7

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

Instability shear strength versus the instability friction angle of sand-silt mixtures (D_r = 52%): (a) OCR = 1, DFP; (b) OCR = 2, DFP; (c) OCR = 1, WD; (d) OCR = 2, WD.

Table 8

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

Mobilised friction angles versus fines content of sand–silt mixtures (D_r = 52%): (a) OCR = 1 and (b) OCR = 2.

Table 9

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

Mobilised friction angles versus instability friction angle of Chlef sand–silt mixtures.

Instability friction angles versus global void ratio: (a) OCR = 1 and (b) OCR = 2.

Instability friction angles versus intergranular void ratio: (a) OCR = 1 and (b) OCR = 2.

References

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Articles in this issue

DOI: https://doi.org/10.2478/sgem-2018-0011 | Journal eISSN: 2083-831X (formerly 0137-124X) | Journal ISSN: 0137-6365

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Language: English

Page range: 96 - 116

Submitted on: Mar 31, 2018

Accepted on: May 29, 2018

Published on: Oct 3, 2018

Published by: Wroclaw University of Science and Technology

In partnership with: Paradigm Publishing Services

Keywords:

Instability lines,

Dry funnel pluviation,

Wet deposition,

Overconsolidation ratio,

Related subjects:

Physics,

Mechanics and fluid dynamics

© 2018 Youcef Mahmoudi, Abdellah Cherif Taiba, Leila Hazout, Wiebke Baille, Mostefa Belkhatir, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Volume 40 (2018): Issue 2 (October 2018)

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

Figures & Tables

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