Citation:

j.margeo.2015.08.012

Name: (Table 1) Experimental details and results
Published: 2015
License: https://creativecommons.org/licenses/by/3.0/

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Abstract:

Factor-of-safety analyses of submarine slope failure depend critically on the shear strength of the slope material, which is often evaluated with residual strength values and for normally consolidated sediments. Here, we report on direct measurements of both shear strength and cohesion for a quartz–clay mixture over a wide range of overconsolidation ratios (OCRs). For normally consolidated sediment at low stresses, cohesion is the dominant source of shear strength compared to friction. Significant increases in peak shear strength occur for OCR > 4, and the primary source of this strength increase is due to increased cohesion, rather than friction. The proportion of added shear strength due to cohesion depends log-linearly on the OCR. We show that at shallow depths where OCR values can be high, overconsolidated clays can be stronger than pure or nearly pure quartz sediments, which are cohesionless under near-surface conditions. Our data also suggest that areas which have experienced significant unroofing due to previous mass movements are less likely to experience subsequent failure at shallow depths due to increased peak strength, and if failure occurs it is expected to be deeper where the OCR is lower. In seismically active areas, this is one potential explanation for the general observation of lower slope failure recurrence compared to rates expected from triggering due to local earthquakes.

Project(s):

Center for Marine Environmental Sciences (MARUM)

Comment:

GT = Grüne Tonerde, SQ = silt quartz, NC = normally consolidated, OC = overconsolidated.* Tau as measured in B126.

Parameter(s):

#	Name	Short Name	Unit	Principal Investigator	Method/Device	Comment
1	Experiment	Exp		Ikari, Matt J
2	Sample material	Samp mat		Ikari, Matt J
3	Comment	Comment		Ikari, Matt J		Test
4	Normal stress	SigmaN	kPa	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Consolidation
5	Normal stress	SigmaN	kPa	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Shearing
6	DEPTH, sediment, experiment	Depth sed exp	m	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Geocode – Simulated maximum burial depth (mbsf)
7	DEPTH, sediment, experiment	Depth sed exp	m	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Geocode – Simulated depth of failure (mbsf)
8	Overconsolidation ratio	Pc/Po		Ikari, Matt J	Direct shear apparatus (GIESA, Germany)
9	Shear stress	Tau	kPa	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Peak
10	Shear stress	Tau	kPa	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Residual
11	Cohesion	C	kPa	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)
12	Cohesion	C	kPa	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Sliding cohesion
13	Cohesion	C	%	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	component of shear stress attributed to sliding cohesion
14	Friction coefficient	µ		Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Peak, apparent coefficient of friction
15	Friction coefficient	µ		Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Residual, apparent coefficient of friction
16	Residual friction coefficient	µres		Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	of sliding cohesion
17	Cohesion coefficient	C coef		Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Chi
18	Displacement	DIS	mm	Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	at cs measurement
19	Residual friction coefficient	µres		Ikari, Matt J	Direct shear apparatus (GIESA, Germany)
20	Friction coefficient	µ		Ikari, Matt J	Direct shear apparatus (GIESA, Germany)	Peak

License:

Creative Commons Attribution 3.0 Unported (CC-BY-3.0)

Size:

525 data points

Data

Download dataset as tab-delimited text — use the following character encoding:

1 Exp	2 Samp mat	3 Comment (Test)	4 SigmaN [kPa] (Consolidation)	5 SigmaN [kPa] (Shearing)	6 Depth sed exp [m] (Simulated maximum burial dept...)	7 Depth sed exp [m] (Simulated depth of failure (m...)	8 Pc/Po	9 Tau [kPa] (Peak)	10 Tau [kPa] (Residual)	11 C [kPa]	12 C [kPa] (Sliding cohesion)	13 C [%] (component of shear stress att...)	14 µ (Peak, apparent coefficient of...)	15 µ (Residual, apparent coefficien...)	16 µres (of sliding cohesion)	17 C coef (Chi)	18 DIS [mm] (at cs measurement)	19 µres	20 µ (Peak)
B482gds_iq0pt016	50% GT, 50% SQ	NC, increasing load	16	16	2	2	1.0		9.0		5	56.2		0.55		0.311	8.3	0.24
B291gds_iq0pt032			32	32	4	4	1.0		19.0		11	58.0		0.58		0.339	8.5	0.25
B292gds_iq0pt056			56	56	7	7	1.0		31.0		15	47.1		0.56		0.263	8.4	0.29
B293gds_iq0pt128			128	128	16	16	1.0		70.0		18	25.9		0.55		0.142	8.6	0.41
B181gds_iq0pt24			240	240	30	30	1.0		131.0		34	25.6		0.55		0.140	8.6	0.41
B115gds_iq0pt4			411	411	51	51	1.0		220.0		50	22.5		0.54		0.121	8.4	0.42
B104gds_iq0pt8			810	810	101	101	1.0		421.0		79	18.9		0.52		0.098	9.4	0.42
B113gds_iq1pt2			1212	1212	151	151	1.0		643.0		94	14.7		0.53		0.078	8.6	0.45
B107gds_iq1pt6			1610	1610	201	201	1.0		845.0		103	12.2		0.52		0.064	8.3	0.46
B79gds_iq2		(cohesion only)	1985	0	248					55					0.028
B126gds_iq2			2010	2010	251	251	1.0		1033.0		132	12.8		0.51		0.066	8.4	0.45
B474gds_q0pt016	SQ	NC, increasing load	16	16	2	2	1.0		13.0					0.79
B472gds_q0pt032			32	32	4	4	1.0		24.0					0.73
B473gds_q0pt056			56	56	7	7	1.0		41.0					0.73
B192gds_q0pt128			138	138	17	17	1.0		93.0					0.67
B191gds_q0pt24			250	250	31	31	1.0		177.0					0.71
B190gds_q0pt4			400	400	50	50	1.0		276.0					0.69
B189gds_q0pt8			810	810	101	101	1.0		544.0					0.67
B188gds_q1pt2			1210	1210	151	151	1.0		859.0					0.71
B187gds_q1pt6			1600	1600	200	200	1.0		1114.0					0.70
B81gds_q2			1985	1985	248	248	1.0		1276.0	10	10	0.8		0.64	0.005	0.005	9.1	0.64
B240gds_iq0pt016	50% GT, 50% SQ	OC, constant max load	2000	16	250	2	125.0	48			34	70.8	3.02			2.138	0.7		0.88
B236gds_iq0pt016			2000	16	250	2	125.0	46	43.5		31	71.2	2.86	2.72		1.936	1.0	0.78	0.93
B287gds_iq0pt016			2000	16	250			41	18.1		17	92.7	2.59	1.13		1.049	8.2	0.08	1.54
B246gds_iq0pt032			2000	32	250	4	62.5	60			40	66.5	1.88			1.249	0.8		0.63
B122gds_iq0pt06			1985	53	248	7	37.7	88			53	60.7	1.67			1.013	1.4		0.66
B123gds_iq0pt13			1985	122	248	15	16.2	114			56	48.6	0.94			0.455	1.3		0.48
B269gds_iq0pt24			2000	240	250	30	8.3	186			54	28.8	0.77			0.223	1.1		0.55
B127gds_iq0pt4			1985	405	248	51	4.9	243			69	28.2	0.60			0.169	1.2		0.43
B103gds_iq0pt8			1985	810	248	101	2.5		431.0		97	22.5		0.53		0.120	8.3	0.41
B111gds_iq1pt2			1985	1212	248	151	1.6		648.0		107	16.5		0.53		0.088	8.7	0.45
B57gds_iq1pt6			1985	1610	248	201	1.2		796.0		117	14.7		0.49		0.073	7.2	0.42
B167gds_iq0pt016	50% GT, 50% SQ	OC, constant unload	416	16	52	2	26.0	30			19	62.5	1.89			1.183	1.1		0.71
B169gds_iq0pt032			432	32	54	4	13.5	38			22	58.0	1.18			0.684	1.1		0.49
B170gds_iq0pt056			456	56	57	7	8.1	51			19	38.3	0.91			0.347	1.1		0.56
B171gds_iq0pt128			528	128	66	16	4.1	76			24	32.0	0.60			0.191	1.8		0.41
B157gds_iq0pt24			640	240	80	30	2.7		135.0		45	33.2		0.56		0.186	8.5	0.38
B165gds_iq0pt4			810	400	101	50	2.0		211.0		56	26.6		0.53		0.140	8.8	0.39
B278gds_iq0pt8			1210	810	151	101	1.5		435.0		76	17.4		0.54		0.093	8.3	0.44
B81gds_q2	SQ	clay mineral content	1985	1985	248	248	1.0		1409.0	10	10	0.7		0.71	0.005	0.005	9.1	0.70
B50gds_iq2	25% GT, 75% SQ		1985	1985	248	248	1.0		1259.0	26	67	5.3		0.63	0.013	0.034	8.6	0.60
B51gds_iq2	40% GT, 60% SQ		1985	1985	248	248	1.0		1146.0	47	123	10.7		0.58	0.024	0.062	7.9	0.52
B79gds_iq2	50% GT, 50% SQ		1985	1985	248	248	1.0		985.0	55	127	12.9		0.50	0.028	0.064	9.4	0.43
B54gds_iq2	60% GT, 40% SQ		1985	1985	248	248	1.0		829.0	77	164	19.7		0.42	0.039	0.082	7.6	0.34
B56gds_iq2	75% GT, 25% SQ		1985	1985	248	248	1.0		711.0	93	197	27.7		0.36	0.047	0.099	7.6	0.26
B49gds_i2	GT		1985	1985	248	248	1.0			177					0.089
B52gds_i2	GT		1985	1985	248	248	1.0	564	494.0				0.28	0.25
B58gds_i2	GT		1985	1985	248	248	1.0	544	495.0				0.27	0.25
B85gds_iq2	50% GT, 50% SQ	230 kPa shear load (22% Tau)*	1985		248			224		66					0.033
B78gds_iq2	50% GT, 50% SQ	475 kPa shear load (48% Tau)*	1985		248			494		90					0.045
B84gds_iq2	50% GT, 50% SQ	685 kPa shear load (71% Tau)*	1985		248			733		96					0.048