Effect of Specimens’ Height to Diameter Ratio on Unconfined Compressive Strength of Cohesive Soil

Parameters	Pit sites
Parameters	Ajib	Aweytu	Saris Sefer	JIT campus	Mariam Church
Liquid limit, %	79	49	72	86	75
Plastic limit, %	32	22	36	28	49
Plastic index, %	47	27	36	58	26
Percentage of course soil, %	0.0	10.7	0.0	0.0	0.2
Percentage of sandy soil, %	16.7	33.6	1.6	2.7	1.6
Percentage of fine soil, %	83.3	55.7	98.4	97.3	98.1
Soil classification
USCS	CH	CL	MH	CH	MH
Group name	High-plasticity clay soil	Low-plasticity clay soil	High-plasticity silty soil	High-plasticity clay soil	High High-Plasticity plasticity silty
AASHTO	A-7-5	A-7-6	A-7-5	A-7-6	A-7-5
Group name	Clayey soil	Clayey soil	Clayey soil	Clayey soil	Clayey soil
Standard Proctor compaction test
Optimum moisture content, %	34	23	26.5	39	37.5
Maximum dry density, g/cm³	1.27	1.51	1.38	1.3	1.31

Table 2

Specimens’ height for each diameter, with respect of their H/D ratio at stain rate of 1%/min.

H/D ratio	Specimen's diameter
	38 mm		50 mm		100 mm
	Height (mm)	Strain mm/min	Height (mm)	Strain mm/min	Height (mm)	Strain, mm/min
3.0	114	1.14	150	1.50	300	3
2.75	104.5	1.05	137.5	1.38	2750	2.75
2.5	95.0	0.95	125	1.25	250	2.50
2.25	85.5	0.86	112.5	1.13	225	2.25
2.0	76.0	0.76	100	1.00	200	2.00
1.75	66.5	0.67	87.5	0.88	175	1.75
1.5	57.0	0.57	75.0	0.75	150	1.50
1.25	47.5	0.48	62.5	0.63	125	1.25
1.00	38.0	0.38	50.0	0.50	100	1.00

Peak value of unconfined compressive strength for specimens with diameter of 38, 50, and 100 mm with their respective H/D ratio.

Percentage of UCS difference from the mean value for 38, 50, and 100 mm specimen diameters.

Stress–strain curves for 38 mm, 50 mm, and 100 mm specimen diameters of Ajip test pit from top to bottom.

Stress–strain curves for 38 mm, 50 mm, and 100 mm specimen diameters of Aweytu test pit from top to bottom.

Stress–strain curves for 38 mm, 50 mm, and 100 mm specimen diameters of JIT campus test pit from top to bottom.

Stress–strain curves for 38 mm, 50 mm, and 100 mm specimen diameters of Mariam Church test pit from top to bottom.

Stress–strain curves for 38 mm, 50 mm, and 100 mm specimen diameters of Saris Sefer test pit from top to bottom.

Failure pattern of 38 mm specimen diameter: (a) Ajip, (b) Aweytu, (c) JIT campus, (d) Saris Sefer, and (e) Mariam Church.

Failure pattern of 50 mm specimen diameter: (a) Ajip, (b) Aweytu, (c) JIT campus, (d) Saris Sefer, and (e) Mariam Church.

Failure pattern of 100 mm specimen diameter: (a) Saris Sefer and (b) Mariam Church.

Failure pattern of 100 mm specimen diameter: (a) Ajip, (b) Aweytu, (c) JIT campus.

Table 3

Descriptive statistics of the peak UCS value for specimens of diameter 38 mm.

	Number of observations	Minimum (kPa)	Maximum (kPa)	Mean (kPa)	Std deviation	Skewness	Skewness std error	Kurtosis	Kurtosis std error
Mariam Church	9	200.54	348.63	271.96	42.55	0.177	0.717	0.649	1.400
Ajip	9	299.33	525.21	395.97	71.13	0.527	0.717	−0.046	1.400
Aweytu	9	238.07	474.49	332.04	75.12	0.776	0.717	0.114	1.400
Saris Sefer	9	206.53	428.74	307.54	68.45	0.308	0.717	−0.111	1.400
JIT campus	9	397.37	728.32	528.64	108.76	0.682	0.717	−0.293	1.400

Table 4

Descriptive statistics of the peak UCS value for specimens of diameter 50 mm.

	Number of observations	Minimum (kPa)	Maximum (kPa)	Mean (kPa)	Std deviation	Skewness	Skewness std error	Kurtosis	Kurtosis std error
Mariam Church	9	196.73	321.97	254.91	41.74	0.132	0.717	−0.909	1.400
Ajip	9	245.42	503.90	358.01	79.63	0.529	0.717	0.005	1.400
Aweytu	9	203.80	396.40	285.28	62.33	0.627	0.717	−0.180	1.400
Saris Sefer	9	174.75	391.34	272.07	71.92	0.313	0.717	−0.757	1.400
JIT campus	9	292.35	546.82	401.37	85.46	0.525	0.717	−0.755	1.400

Table 5

Descriptive statistics of the peak UCS value for specimens of diameter 100 mm.

	Number of observations	Minimum (kPa)	Maximum (kPa)	Mean (kPa)	Std deviation	Skewness	Skewness std error	Kurtosis	Kurtosis std error
Mariam Church	9	155.66	313.46	222.71	50.06	0.434	0.717	−0.176	1.400
Ajip	9	209.21	372.44	281.48	58.61	0.338	0.717	−1.415	1.400
Aweytu	9	181.44	321.42	251.30	48.41	0.130	0.717	−1.134	1.400
Saris Sefer	9	126.06	281.43	210.98	56.46	−0.386	0.717	−1.181	1.400
JIT campus	9	225.62	465.21	340.70	77.48	0.142	0.717	−0.629	1.400

Table 6

Shapiro–Wilk normality test.

	38 mm specimen diameter			50 mm specimen diameter			100 mm specimen diameter
	Statistic	Degrees of freedom	Sig.	Statistic	Degrees of freedom	Sig.	Statistic	Degrees of freedom	Sig.
Mariam Church	0.989	9	0.995	0.974	9	0.926	0.968	9	0.879
Ajip	0.974	9	0.925	0.977	9	0.946	0.936	9	0.538
Aweytu	0.952	9	0.709	0.956	9	0.759	0.959	9	0.784
Saris Sefer	0.988	9	0.994	0.974	9	0.925	0.935	9	0.532
JIT campus	0.953	9	0.725	0.958	9	0.776	0.981	9	0.969

The scatter plot of UCS versus H/D ratio for 38, 50, and 100 mm specimen diameter from left to right.

Table 7

Significance level (Sig.) and Pearson correlation coefficient (R) of UCS value for 38 mm specimen diameter.

		Height to diameter ratio	UCS of Mariam Church test pit	UCS of Ajip test pit	UCS of Aweytu test pit	UCS of Saris Sefer	UCS of JIT campus test pit
Height to diameter ratio (H/D)	R	1	−0.968^**	−0.979^**	−0.970^**	−0.984^**	−0.979^**
	Sig.		0.000	0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Mariam Church test pit	R	−0.968^**	1	0.984^**	0.977^**	0.993^**	0.971^**
	Sig.	0.000		0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Ajip test pit	R	−0.979^**	0.984^**	1	0.991^**	0.996^**	0.992^**
	Sig.	0.000	0.000		0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Aweytu test pit	R	−0.970^**	0.977^**	0.991^**	1	0.988^**	0.995^**
	Sig.	0.000	0.000	0.000		0.000	0.000
	n	9	9	9	9	9	9
UCS of Saris Sefer test pit	R	−0.984^**	0.993^**	0.996^**	0.988^**	1	0.986^**
	Sig.	0.000	0.000	0.000	0.000		0.000
	n	9	9	9	9	9	9
UCS of JIT campus test pit	R	−0.979^**	0.971^**	0.992^**	0.995^**	0.986^**	1
	Sig.	0.000	0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9

n – number of valid observations for the variable

** Correlation is significant at the 0.01 level (two-tailed)

Table 8

Significance level (Sig.) and Pearson correlation coefficient (R) of UCS value for 50 mm specimen diameter.

		Height to diameter ratio	UCS of Mariam Church test pit	UCS of Ajip test pit	UCS of Aweytu test pit	UCS of Saris Sefer	UCS of JIT campus test pit
Height to diameter ratio (H/D)	R	1	−0.994	−0.978	−0.973	−0.993	−0.986
	Sig.		0.000	0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Mariam Church test pit	R	−0.994	1	0.983	0.981	0.997	0.987
	Sig.	0.000		0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Ajip test pit	R	−0.978	0.983	1	0.989	0.988	0.991
	Sig.	0.000	0.000		0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Aweytu test pit	R	−0.973	0.981	0.989	1	0.992	0.992
	Sig.	0.000	0.000	0.000		0.000	0.000
	n	9	9	9	9	9	9
UCS of Saris Sefer test pit	R	−0.993	0.997	0.988	0.992	1	0.995
	Sig.	0.000	0.000	0.000	0.000		0.000
	n	9	9	9	9	9	9
UCS of JIT campus test pit	R	−0.986	0.987	0.991	0.992	0.995	1
	Sig.	0.000	0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9

n – number of valid observations for the variable

** Correlation is significant at the 0.01 level (two-tailed)

Table 9

Significance level (Sig.) and Pearson correlation coefficient (R) of UCS value for 100 mm specimen diameter.

		Height to diameter ratio	UCS of Mariam Church test pit	UCS of Ajip test pit	UCS of Aweytu test pit	UCS of Saris Sefer	UCS of JIT campus test pit
Height to diameter ratio (H/D)	R	1	−0.979	−0.988	−0.992	−0.987	−0.990
	Sig.		0.000	0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Mariam Church test pit	R	−0.979	1	0.965	0.965	0.958	0.979
	Sig.	0.000		0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Ajip test pit	R	−0.988	0.965	1	0.989	0.960	0.983
	Sig.	0.000	0.000		0.000	0.000	0.000
	n	9	9	9	9	9	9
UCS of Aweytu test pit	R	−0.992	0.965	0.989	1	0.972	0.993
	Sig.	0.000	0.000	0.000		0.000	0.000
	n	9	9	9	9	9	9
UCS of Saris Sefer test pit	R	−0.987	0.958	0.960	0.972	1	0.974
	Sig.	0.000	0.000	0.000	0.000		0.000
	n	9	9	9	9	9	9
UCS of JIT campus test pit	R	−0.990	0.979	0.983	0.993	0.974	1
	Sig.	0.000	0.000	0.000	0.000	0.000
	n	9	9	9	9	9	9

n – number of valid observations for the variable

** Correlation is significant at the 0.01 level (two-tailed)

Plot of *UCS*/*UCS*_2.00 versus height to diameter ratio for a specimen diameter of 38 mm.

The plot of *UCS*/*UCS*_2.00 versus height to diameter ratio of 50 mm specimen diameter.

The plot of *UCS*/*UCS*_2.00 versus height to diameter ratio of 100 mm specimen diameter.

Table 10

Model summary of UCS/(UCS at 2 H/D ratio)-38 mm diameter and H/D ratio.

Model summary^b
Model	R	R²	Adjusted R²	Std error of the estimate
1	0.963^a	0.928	0.926	0.053191

a Predictors: (constant), H/D ratio

b Dependent variable: UCS/(UCS at 2 H/D ratio)-38 mm diameter

Table 11

Coefficients of UCS/(UCS at 2 H/D ratios)-38 mm diameter and H/D ratio.

Coefficients^a
Model		Unstandardized coefficients		Standardized coefficients	t	Sig.
Model		B	Std. Error	beta	t	Sig.
1	(Constant)	1.596	0.026		61.838	0.000
H/D ratio	−0.288	0.012	−0.963	−23.469	0.000

a Dependent variable: UCS/(UCS at 2 H/D ratio)-38 mm diameter

Table 12

Model summary of UCS/(UCS at 2 H/D ratios)-50 mm diameter and H/D ratio.

Model summary^b
Model	R	R²	Adjusted R²	Std error of the estimate
2	0.969^a	0.938	0.937	0.0540444

a Predictors: (constant), H/D ratio

b Dependent variable: UCS/(UCS at 2 H/D ratio)-50 mm diameter

Table 13

Coefficients of UCS/(UCS at 2 H/D ratios)-50 mm diameter and H/D ratios.

Coefficients^a
Model		Unstandardized coefficients		Standardized coefficients	t	Sig.
Model		B	Std error	beta	t	Sig.
2	(Constant)	1.658	0.026		63.201	0.000
H/D ratio	−0.318	0.012	−0.969	−25.509	0.000

a Dependent variable: UCS/(UCS at 2 H/D ratio)-50 mm diameter

Table 14

Model summary of UCS/(UCS at 2 H/D ratios)-100 mm diameter and H/D ratio.

Model summary^b
Model	R	R²	Adjusted R²	Std error of the estimate
3	0.970^a	0.941	0.940	0.0540500

a Predictors: (constant), H/D ratio

b Dependent Variable: UCS/(UCS at 2 H/D ratio)-100 mm Diameter

Table 15

Coefficients of UCS/(UCS at 2 H/D ratios)-100 mm diameter and H/D ratios.

Coefficients^a
Model		Unstandardized coefficients		Standardized coefficients	t	Sig.
Model		B	Std error	beta	t	Sig.
3	(Constant)	1.671	0.026		63.699	0.000
H/D ratio	−0.328	0.012	−0.970	−26.238	0.000

a Dependent variable: UCS/(UCS at 2 H/D ratio)-100 mm diameter

Table 16

Regression equations of UCS(measured)/UCS_2.00 ratio for different specimen diameters versus H/D ratio.

Specimens’ diameter	Regression equations	R²	Correlation state	Equation number
38 mm	UCS_2.00=(UCS(measured))/(1.596-0.288(H/D))	0.928	Strong	3
50 mm	UCS_2.00=(UCS(measured))/(1.658-0.318(H/D))	0.938	Strong	4
100 mm	UCS_2.00=(UCS(measured))/(1.671-0.328(H/D))	0.941	Strong	5

Table 17

Regression model accuracy for the developed equations.

Specimens’ diameter of regression equations	MAE	MSE	RMSE	MAPE
38 mm	13.44	289.05	16.70	3.84%
50 mm	12.53	215.77	14.64	4.15%
100 mm	11.21	232.69	14.86	4.42%

References

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Articles in this issue

DOI: https://doi.org/10.2478/sgem-2023-0001 | Journal eISSN: 2083-831X (formerly 0137-124X) | Journal ISSN: 0137-6365

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Language: English

Page range: 112 - 132

Submitted on: Jun 5, 2022

Accepted on: Nov 29, 2022

Published on: Mar 9, 2023

Published by: Wroclaw University of Science and Technology

In partnership with: Paradigm Publishing Services

Keywords:

Height to diameter ratio,

Unconfined compression strength,

Related subjects:

Physics,

Mechanics and fluid dynamics

© 2023 Haile Tsegay Gebresamuel, Damtew Tsige Melese, Yada Tesfaye Boru, Alemu Mosisa Legese, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution 4.0 License.

Volume 45 (2023): Issue 2 (June 2023)

Effect of Specimens’ Height to Diameter Ratio on Unconfined Compressive Strength of Cohesive Soil

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