Experiments of creep rate for over-consolidated clay under plain strain condition and a simple correlation

Figures & data

Figure 1. Illustration of plain strain creep consolidometer

Figure 2. Photos of the test process

Table 1. Basic soil properties of Yuedong clay

Property	Value
Initial water content, w0	56 ~ 60%
Compression index, Cc	0.5 ~ 0.7
Recompression index, Cs	0.05 ~ 0.08
Liquid limit, wL	62.5
Plastic limit, wP	37.2
Coefficient of consolidation, cv100-200(10^−3 cm^2/s)	1.05

Table 2. Detailed steps for reloading

Group	Test	Loading procedure (σX, σZ)
		Initial loading 24 h	Maximum preloading	Unloading 24 h	Consolidation, 168 h
					Loading(or Reloading) step
					1	2	3	4
1 (K = 0.5)	-	(25,25)	-	-	(50,100)	-(100,200)^^	-(150,300)	-(200,400)
2 (K = 0.5)	a	(25,25)	(200,400)	(25,25)	(50,100)	-(100,200)	-(150,300)	-(200,400)
	b		(150,300)		(50,100)	-(100,200)^#	-(150,300)
	c		(100,200)		(50,100)	-(100,200)
3 (K = 0.33)	a		(100,300)		(40,120)	-(60,180)	-(80,240)	-(100,300)
	b		(80,240)		(40,120)	-(60,180)	-(80,240)
	c		(60,180)		(40,120)*	-(60,180)

Note: designation of secondary consolidation step, e.g. ^{^} is T1-2, ^# is T2b-2 and * is T3c-1.

Figure 3. Comparison of stress in zero strain direction (σ_y) under normal and over-consolidation states

Figure 4. Variations of σ_y with time for OC soils in test 2a, b and c

Figure 5. Variations of σ_y with time for OC soils in test 3a, b and c

Figure 6. Relationship between final σ_y and (a) σ_z, (b) σ_x for K = 0.5

Figure 7. Relationship between final σ_y and (a) σ_z, (b) σ_x for K = 0.33

Figure 8. Variations of volumetric strain with time for tests T1 and T2 (a, b, c)

Table 3. Calculated results of volumetric creep coefficient and volumetric stress defined over-consolidation ratio

Group	Test	Cα(10^−2), OCRP
		Steps
		1	2	3	4
1 (K = 0.5)	-	1.000, 0.730	1.000, 0.744	1.000, 0.814	1.000, 0.773
2 (K = 0.5)	a	0.192, 4.845	0.372, 2.142	0.603, 1.405	0.656, 0.985
	b	0.262, 3.460	0.467, 1.604	0.829, 1.029
	c	0.404. 2.127	0.692, 1.044
3 (K = 0.33)	a	0.513, 2.591	0.638, 1.723	0.913, 1.281	1.173, 1.008
	b	0.570, 2.042	0.812, 1.353	0.573, 0.991
	c	0.693, 1.512	0.706, 1.010

Table 4. Calculated results of vertical creep coefficient and volumetric stress defined over-consolidation ratio

Group	Test	β(10^−2), OCRP
		Steps
		1	2	3	4
2 (K = 0.5)	a	0.026, 4.845	0.064, 2.142	0.096, 1.405	0.150, 0.985
	b	0.035, 3.460	0.085, 1.604	0.022, 1.029
	c	0.047. 2.127	0.172, 1.044
3 (K = 0.33)	a	0.059, 2.591	0.159, 1.723	0.484, 1.281	0.683, 1.008
	b	0.093, 2.042	0.287, 1.353	0.573, 0.991
	c	0.184, 1.512	0.431, 1.010

Figure 9. Graphic procedure for determining C_α: plot the ε_v ~ log (t) curve firstly, project a straight line along the final linear part of the ε_v ~ log (t) curve secondly, and calculate the slope of the straight line finally

Figure 10. Vertical creep coefficient β for OC clay under plain strain and 1D condition

Figure 11. (a) C_α and (b) β as a function of OCR_P.

Figure 12. (a) C_α and (b) β as a function of K∙OCR_P.

Data availability statement

The data that support the findings of this study are available from the corresponding author, Y. Zhou, upon reasonable request.