Rock Mechanics Lab Report — UCS, Crack Thresholds, Creep and Relaxation in Word

Sample report — synthetic data · StrataPlot Pro builds this from your own

Synthetic limestone suite — sample report

Scientific analysis report

Client: Demonstration
Laboratory: Rock mechanics laboratory
Prepared by: StrataPlot sample
Date: 9 November 2026
Rock: micritic limestone (synthetic data)
Specimens: 10

Summary

5 specimens were tested in compression. Peak strength averaged 119.6 MPa (SD 8.9 MPa). Crack initiation, by crack volumetric strain reversal, averaged 52.6 MPa, 43.9 % of peak; crack damage, by reversal of the volumetric strain, averaged 103.0 MPa, 86.0 % of peak. Young’s modulus averaged 42.7 GPa and Poisson’s ratio 0.22. 4 specimens were creep tested; 2 failed under constant load.

Part 1 — Methodology and theoretical framework

1.1 Scope and test programme

The programme covered 10 specimens of micritic limestone (synthetic data):

Uniaxial or triaxial compression with axial and lateral strain and acoustic emission: 5 specimens.
Uniaxial creep under constant load: 4 specimens, 4 load stages.
Stress relaxation under constant strain: 1 specimen.

Only compressive time-dependent behaviour is reported; indirect tensile (Brazilian) creep is outside the scope of this report.

1.2 Analytical tools

Readings were imported from the laboratory files and reduced in StrataPlot (Rock Mechanics Lab Report, web edition, 9 November 2026). Each test type was analysed by the same engine as the corresponding StrataPlot tool, so every number below can be reproduced on that tool page from the same readings. No reading was edited; the data checks behind each result are listed with its specimen in Part 3. The methods themselves are those of the published sources cited beside each parameter; StrataPlot is credited only for applying them.

1.3 Calculation procedures

Stress–strain tests

Peak strength is the largest axial stress on the loading branch (ISRM, 1979; ASTM D7012). Young’s modulus and Poisson’s ratio are the average modulus, a least-squares fit over the linear portion between σcc and σci, both slopes found by least squares as ASTM D7012 permits (ASTM D7012). Volumetric strain is the sum of the axial strain and twice the lateral strain, compression positive. All slopes come from a moving least-squares window rather than from differencing raw readings.

Uniaxial compressive strength

σ_{c} = \frac{P_{max}}{A_{0}}

(1)

Young’s modulus

E = \frac{Δ σ}{Δ ε_{a}}

(2)

Poisson’s ratio

ν = - \frac{Δ ε_{l}}{Δ ε_{a}}

(3)

Volumetric strain

ε_{v} = ε_{a} + 2 ε_{l}

(4)

Creep tests

Each creep record was analysed stage by stage, time and strain measured from the load step. Primary, secondary and tertiary creep were identified from the strain rate against log time, secondary creep being the stretch where the rate is at its minimum (Brantut et al., 2013); the strain was smoothed by a moving least-squares slope before it was differentiated. The steady-state rate is the least-squares slope across the readings within 20 % of the minimum rate. The Burgers model (Wang & Li, 2018), Andrade’s power law (Andrade, 1910) and the logarithmic law (Weiss & Amitrano, 2023) were fitted by least squares, up to the onset of tertiary creep where it occurred.

Burgers model (uniaxial)

ε (t) = \frac{σ}{E_{M}} + \frac{σ t}{η_{M}} + \frac{σ}{E_{K}} (1 - \exp (- \frac{E_{K} t}{η_{K}}))

(5)

Power law (Andrade form)

ε = ε_{0} + A t^{n}

(6)

Logarithmic (Lomnitz) law

ε = ε_{0} + A \ln (1 + α t)

(7)

For comparison with published tables, the Burgers constants are also given as shear moduli and viscosities of the isotropic Burgers body (Wang & Li, 2018, Eqs. 6–8): E_K = 3G_K, η = 3η_shear and G_M = E_M/2(1 + ν), with ν from each specimen’s compression test where there is one (Eq. 5 becomes the shear form below). The Norton–Bailey power law (Norton, 1929; Bailey, 1935) was fitted to every stage at once by least squares in log space.

Burgers model, shear-modulus form

ε_{1} (t) = \frac{σ}{9 K} + \frac{σ}{3 G_{M}} + \frac{σ}{3 G_{K}} (1 - \exp (- \frac{G_{K} t}{η_{K}})) + \frac{σ t}{3 η_{M}}

(8)

Norton–Bailey law

ε_{c} = A σ^{n} t^{m}

(9)

Relaxation tests

Stress against time since the strain was applied was fitted with Maxwell, Prony-series and logarithmic models (Lakes, 2009). No ISRM or ASTM method for the stress relaxation of rock exists.

Maxwell relaxation

σ (t) = σ_{0} \exp (- \frac{t}{τ})

(10)

Prony series

σ (t) = σ_{∞} + \sum_{i = 1}^{N} σ_{i} \exp (- \frac{t}{τ_{i}})

(11)

Logarithmic relaxation

σ (t) = σ_{0} (1 - r log₁₀ (1 + \frac{t}{t_{0}}))

(12)

1.4 Crack initiation and crack damage

There is no agreed way to pick the crack initiation (σci) and crack damage (σcd) stresses, and the published methods disagree by several MPa on the same record (Nicksiar & Martin, 2012). Every method below was therefore applied to every specimen and is listed in Part 3. The summary quotes σci by crack volumetric strain reversal (Martin & Chandler, 1994) and σcd by reversal of the volumetric strain (Bieniawski, 1967; Martin & Chandler, 1994), except where a threshold was picked by hand, which is marked (1 specimen). Where a chosen method could not run on a record, the next method in the order of Table 1 was used and the result is marked.

Crack volumetric strain

ε_{v}^{crack} = ε_{v} - \frac{1 - 2 ν}{E} σ

(13)

Lateral strain response

Δ ε_{l} (σ) = ε_{l} (σ) - \frac{ε_{l} (σ_{cd})}{σ_{cd}} σ

(14)

Departure from linearity

σ_{ci} = min {σ : - \frac{d ε_{l}}{d σ} \geq (1 + τ) c_{0}}

(15)

The deviation-from-linearity picks fire when the smoothed tangent has drifted 10 % from its straight-line value; that tolerance is StrataPlot’s statement of a judgement the original authors made by eye. The acoustic emission thresholds are the corners of a three-segment least-squares fit to log₁₀(1 + AE per stress bin): a StrataPlot construction, after the AE thresholds of Eberhardt et al. (1998) and Zhao et al. (2015).

Table 1. Derived parameters, the method behind each, and its source

Parameter	Symbol	Method	Source	Applied as
Uniaxial compressive strength	σc (UCS)	Peak axial stress	ISRM (1979); ASTM D7012	Plateau-safe maximum of the loading branch
Young’s modulus	E	average modulus, a least-squares fit over the linear portion between σcc and σci	ASTM D7012	Least squares over the stated range
Poisson’s ratio	ν	Negative ratio of lateral to axial slope	ASTM D7012	Over the same range as E
Crack closure stress	σcc	Axial stiffness levels off; crack volumetric strain	Eberhardt et al. (1998); Martin & Chandler (1994)	Tolerance on the plateau, printed in Part 3
Crack initiation stress (quoted)	σci	crack volumetric strain reversal	Martin & Chandler (1994)	Automated; see 1.4
Crack damage stress (quoted)	σcd	reversal of the volumetric strain	Bieniawski (1967); Martin & Chandler (1994)	Automated; see 1.4
Crack initiation stress (comparison)	σci	lateral strain response	Nicksiar & Martin (2012)	Part 3 only
Crack initiation stress (comparison)	σci	departure of the lateral strain from linearity	Brace et al. (1966); Bieniawski (1967); Lajtai & Lajtai (1974)	Part 3 only
Crack initiation stress (comparison)	σci	onset of acoustic emission	Eberhardt et al. (1998)	Part 3 only
Crack damage stress (comparison)	σcd	departure of the axial strain from linearity	Lajtai (1974)	Part 3 only
Crack damage stress (comparison)	σcd	acceleration of acoustic emission	Eberhardt et al. (1998)	Part 3 only
Strength estimated from σci	UCS*	Least-squares slope through the origin of UCS on σci	StrataPlot	StrataPlot regression
Creep stages and steady-state rate	ε̇s	Minimum strain rate against log time	Brantut et al. (2013)	Moving least-squares slope
Burgers constants	E_M, E_K, η_K, η_M	Burgers model	Wang & Li (2018)	Least squares, linearised standard errors
Transient creep laws	A, n; A, α	Power law; logarithmic law	Andrade (1910); Weiss & Amitrano (2023)	Least squares, linearised standard errors
Burgers constants, shear form	G_M, G_K, η_K, η_M, K	Isotropic Burgers body	Wang & Li (2018)	Converted from the fitted constants
Norton–Bailey constants	A, n, m	Power law in stress and time	Norton (1929); Bailey (1935)	Least squares in log space
Driving-stress ratios, time to failure	σ/UCS, σ/σci	Last-stage stress over strength; static fatigue	Brantut et al. (2013)	Own UCS where tested, else the suite mean
Relaxation constants	σ∞, σi, τi	Maxwell, Prony and logarithmic models	Lakes (2009)	Least squares

“StrataPlot” in the Source column marks a construction of the software itself rather than a published method.

1.5 Statistics

Suite statistics are the arithmetic mean, the sample standard deviation (n − 1) and the coefficient of variation of the specimens that gave a value.

Mean, standard deviation, coefficient of variation

x̄ = \frac{1}{n} \sum_{i} x_{i}, s = \sqrt{\frac{\sum_{i} {(x_{i} - x̄)}^{2}}{n - 1}}, CoV = \frac{s}{x̄}

(16)

Strength estimated from σci

UCS* = a \cdot σ_{ci}, a = \frac{\sum_{i} {UCS}_{i} σ_{ci,i}}{\sum_{i} {σ_{ci,i}}^{2}}

(17)

Driving-stress ratios

R_{UCS} = \frac{σ_{creep}}{UCS}, R_{CI} = \frac{σ_{creep}}{σ_{ci}}

(18)

Part 2 — Consolidated summary

2.1 Strength, crack thresholds and elastic constants

Table 2. Results by specimen — σci by crack volumetric strain reversal, σcd by reversal of the volumetric strain

Specimen	Lithology	UCS (MPa)	σci (MPa)	σcd (MPa)	σci/UCS	σcd/UCS	E (GPa)	ν
LS-01	Micritic limestone (synthetic)	118.0	51.8	101.6	0.44	0.86	42.0	0.22
LS-02	Micritic limestone (synthetic)	126.0	53.0 m	110.9	0.42	0.88	44.5	0.22
LS-03	Micritic limestone (synthetic)	109.0	46.3	91.5	0.42	0.84	39.9	0.22
LS-04	Micritic limestone (synthetic)	131.1	61.2	113.9	0.47	0.87	45.5	0.22
LS-05	Micritic limestone (synthetic)	113.9	50.6	96.9	0.44	0.85	41.5	0.22
Mean		119.6	52.6	103.0	0.44	0.86	42.7	0.22
SD		8.9	5.5	9.4	0.02	0.02	2.3	0.00
CoV (%)		7.5	10.4	9.1	4.2	1.9	5.3	0.3
n		5	5	5	5	5	5	5

m: picked by hand (user-selected); f: the chosen method could not run on this record and the next method was used. Methods and sources: Table 1.

Figure 1. Crack initiation, crack damage and peak strength of each specimen (values in Table 2); dashed lines are suite means.

Figure 1 draws Table 2. Each specimen’s thresholds by every other method are in Part 3.

Figure 2. σci and σcd as fractions of each specimen’s peak strength.

2.2 How far the threshold methods disagree

Table 3. Suite statistics of σci and σcd by every method

Threshold	Method	Source	Mean (MPa)	SD (MPa)	CoV (%)	n
σci	Crack volumetric strain	Martin & Chandler (1994)	53.8	6.2	11.6	5
σci	Lateral strain response	Nicksiar & Martin (2012)	61.3	6.2	10.1	5
σci	Lateral strain non-linearity	Lajtai & Lajtai (1974)	50.8	5.2	10.2	5
σci	AE onset (change point)	Eberhardt et al. (1998)	41.5	—	—	1
σcd	Volumetric strain reversal	Martin & Chandler (1994)	103.0	9.4	9.1	5
σcd	Axial strain non-linearity	Lajtai (1974)	70.1	6.5	9.3	5
σcd	AE acceleration (change point)	Eberhardt et al. (1998)	91.6	—	—	1

Figure 3. σci of each specimen by each method. The vertical extent at each specimen is the disagreement between methods, a measure of how uncertain any single pick is.

Across 4 methods the suite-mean σci ranges from 41.5 to 61.3 MPa. The largest disagreement on one specimen is 12.2 MPa (LS-03). This spread is of the same order as the specimen-to-specimen scatter in Table 2 and should be read as part of the uncertainty of σci, as Nicksiar & Martin (2012) found for six methods on one dataset.

2.3 Strength estimated from crack initiation

Figure 4. Peak strength against σci with the least-squares line through the origin, UCS* = 2.27·σci (n = 5).

The ratio a = 2.267 (Figure 4) lets the strength of a specimen that went straight into a creep test be estimated from the σci of its own loading stage (Eq. 17), so its driving-stress ratio does not rest on the suite mean alone.

2.4 Creep

Table 4. Creep results by specimen (last load stage)

Specimen	σ (MPa)	Stages	Held (h)	ε̇s (%/h)	Tertiary	σ/UCS	σ/σci	Failed
LS-06	71.8	1	240	7.98 × 10^-6	no	0.60 †	1.37	no
LS-07	89.7	1	168	9.85 × 10^-6	no	0.75 †	1.71	no
LS-08	105.2	1	6.00	2.74 × 10^-3	yes	0.88 †	2.00	yes
LS-09	113.6	1	3.00	1.11 × 10^-2	yes	0.95 †	2.16	yes

† ratio to the suite-mean UCS: this specimen had no compression test of its own. “Failed” is the laboratory’s statement, not inferred from the record.

Table 5. Burgers constants of the last stage in shear-modulus form

Specimen	G_M (Pa)	G_K (Pa)	η_K (Pa·s)	η_M (Pa·s)	K (Pa)	ν used
LS-06	1.72 × 10¹⁰	8.67 × 10¹⁰	3.12 × 10¹⁴	1.08 × 10¹⁸	2.51 × 10¹⁰	0.22
LS-07	1.72 × 10¹⁰	8.67 × 10¹⁰	3.12 × 10¹⁴	1.09 × 10¹⁸	2.51 × 10¹⁰	0.22
LS-08	1.72 × 10¹⁰	8.71 × 10¹⁰	3.12 × 10¹⁴	1.76 × 10¹⁷	2.51 × 10¹⁰	0.22
LS-09	1.72 × 10¹⁰	8.85 × 10¹⁰	3.14 × 10¹⁴	4.06 × 10¹⁶	2.51 × 10¹⁰	0.22

Converted from the fitted E-form constants (Eq. 5 to Eq. 8).

Norton–Bailey A: 1.61 × 10^-8 (ε dimensionless, σ in MPa, t in h)
Stress exponent n: 1.92 ± 0.29
Time exponent m: 0.64 ± 0.02
r² (log space): 0.873
Data: 231 readings, 4 stages

Figure 5. Time under constant load against driving-stress ratio. Filled: failed (time to failure); open with arrow: did not fail in the time held. Dashed: the suite-mean σci/UCS and σcd/UCS from the compression tests.

Figure 5: The 2 specimens that failed were loaded at σ/UCS = 0.88–0.95. The 2 that did not fail were loaded at 0.60–0.75. No specimen failed below the suite-mean σcd/UCS of 0.86. No specimen was loaded below the suite-mean σci/UCS of 0.44, so the data do not test the long-term strength below crack initiation.

2.5 Relaxation

Table 6. Relaxation results by specimen and stage

Specimen	Stage	σ₀ (MPa)	σ end (MPa)	Relaxed (%)	Per decade (%)	Model	r²
LS-10	1	62.86	51.98	17.3	4.88	Prony (2 terms)	1.0000

Part 3 — Specimen sheets

A.1 LS-01

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: stress–strain

Table 7. LS-01: thresholds by every method

Threshold	Method	Source	Stress (MPa)	Of peak	Quoted
σcc	Axial stiffness	Eberhardt et al. (1998)	14.7	12.4 %
σcc	Crack volumetric strain	Martin & Chandler (1994)	13.4	11.4 %
σci	Crack volumetric strain	Martin & Chandler (1994)	51.8	43.9 %	✓
σci	Lateral strain response	Nicksiar & Martin (2012)	60.9	51.6 %
σci	Lateral strain non-linearity	Lajtai & Lajtai (1974)	48.9	41.5 %
σcd	Volumetric strain reversal	Martin & Chandler (1994)	101.6	86.1 %	✓
σcd	Axial strain non-linearity	Lajtai (1974)	68.8	58.3 %
σpeak	Maximum axial stress	ASTM D7012	118.0	100.0 %	✓

Young’s modulus, average (σcc–σci): 42.0 GPa over 14.7–51.8 MPa
Young’s modulus, tangent at 50 %: 39.6 GPa
Young’s modulus, secant to 50 %: 39.2 GPa
Poisson’s ratio (as quoted): 0.22
Readings: 438, with lateral strain

Check: peak held within 0.2 % over 5 readings; the centre of that plateau is taken as the peak.

A.2 LS-02

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: stress–strain
Notes: σci picked by hand from the lateral strain curve, to show a manual pick.

Table 8. LS-02: thresholds by every method

Threshold	Method	Source	Stress (MPa)	Of peak	Quoted
σcc	Axial stiffness	Eberhardt et al. (1998)	16.8	13.3 %
σcc	Crack volumetric strain	Martin & Chandler (1994)	15.4	12.2 %
σci	Crack volumetric strain	Martin & Chandler (1994)	59.2	47.0 %
σci	Lateral strain response	Nicksiar & Martin (2012)	66.7	53.0 %
σci	Lateral strain non-linearity	Lajtai & Lajtai (1974)	55.7	44.2 %
σcd	Volumetric strain reversal	Martin & Chandler (1994)	110.9	88.1 %	✓
σcd	Axial strain non-linearity	Lajtai (1974)	76.1	60.4 %
σci	Manual (user-selected)	picked by hand	53.0	42.1 %	✓
σpeak	Maximum axial stress	ASTM D7012	126.0	100.0 %	✓

Young’s modulus, average (σcc–σci): 44.5 GPa over 16.8–59.2 MPa
Young’s modulus, tangent at 50 %: 42.5 GPa
Young’s modulus, secant to 50 %: 41.6 GPa
Poisson’s ratio (as quoted): 0.22
Readings: 438, with lateral strain

Check: peak held within 0.2 % over 6 readings; the centre of that plateau is taken as the peak.

A.3 LS-03

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: stress–strain
Notes: Acoustic emission recorded.

Table 9. LS-03: thresholds by every method

Threshold	Method	Source	Stress (MPa)	Of peak	Quoted
σcc	Axial stiffness	Eberhardt et al. (1998)	14.1	12.9 %
σcc	Crack volumetric strain	Martin & Chandler (1994)	12.3	11.3 %
σci	Crack volumetric strain	Martin & Chandler (1994)	46.3	42.5 %	✓
σci	Lateral strain response	Nicksiar & Martin (2012)	53.7	49.3 %
σci	Lateral strain non-linearity	Lajtai & Lajtai (1974)	45.0	41.3 %
σci	AE onset (change point)	Eberhardt et al. (1998)	41.5	38.0 %
σcd	Volumetric strain reversal	Martin & Chandler (1994)	91.5	83.9 %	✓
σcd	Axial strain non-linearity	Lajtai (1974)	62.5	57.4 %
σcd	AE acceleration (change point)	Eberhardt et al. (1998)	91.6	84.0 %
σpeak	Maximum axial stress	ASTM D7012	109.0	100.0 %	✓

Young’s modulus, average (σcc–σci): 39.9 GPa over 14.1–46.3 MPa
Young’s modulus, tangent at 50 %: 37.4 GPa
Young’s modulus, secant to 50 %: 37.1 GPa
Poisson’s ratio (as quoted): 0.22
Readings: 438, with lateral strain, with AE

Check: peak held within 0.2 % over 6 readings; the centre of that plateau is taken as the peak.

A.4 LS-04

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: stress–strain

Table 10. LS-04: thresholds by every method

Threshold	Method	Source	Stress (MPa)	Of peak	Quoted
σcc	Axial stiffness	Eberhardt et al. (1998)	17.0	12.9 %
σcc	Crack volumetric strain	Martin & Chandler (1994)	16.0	12.2 %
σci	Crack volumetric strain	Martin & Chandler (1994)	61.2	46.7 %	✓
σci	Lateral strain response	Nicksiar & Martin (2012)	68.1	51.9 %
σci	Lateral strain non-linearity	Lajtai & Lajtai (1974)	56.9	43.4 %
σcd	Volumetric strain reversal	Martin & Chandler (1994)	113.9	86.9 %	✓
σcd	Axial strain non-linearity	Lajtai (1974)	77.6	59.2 %
σpeak	Maximum axial stress	ASTM D7012	131.1	100.0 %	✓

Young’s modulus, average (σcc–σci): 45.5 GPa over 17.0–61.2 MPa
Young’s modulus, tangent at 50 %: 42.9 GPa
Young’s modulus, secant to 50 %: 42.5 GPa
Poisson’s ratio (as quoted): 0.22
Readings: 438, with lateral strain

Check: peak held within 0.2 % over 5 readings; the centre of that plateau is taken as the peak.

A.5 LS-05

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: stress–strain

Table 11. LS-05: thresholds by every method

Threshold	Method	Source	Stress (MPa)	Of peak	Quoted
σcc	Axial stiffness	Eberhardt et al. (1998)	14.4	12.6 %
σcc	Crack volumetric strain	Martin & Chandler (1994)	15.2	13.4 %
σci	Crack volumetric strain	Martin & Chandler (1994)	50.6	44.4 %	✓
σci	Lateral strain response	Nicksiar & Martin (2012)	56.9	49.9 %
σci	Lateral strain non-linearity	Lajtai & Lajtai (1974)	47.6	41.8 %
σcd	Volumetric strain reversal	Martin & Chandler (1994)	96.9	85.0 %	✓
σcd	Axial strain non-linearity	Lajtai (1974)	65.6	57.6 %
σpeak	Maximum axial stress	ASTM D7012	113.9	100.0 %	✓

Young’s modulus, average (σcc–σci): 41.5 GPa over 15.2–50.6 MPa
Young’s modulus, tangent at 50 %: 38.8 GPa
Young’s modulus, secant to 50 %: 38.6 GPa
Poisson’s ratio (as quoted): 0.22
Readings: 438, with lateral strain

Check: peak held within 0.2 % over 6 readings; the centre of that plateau is taken as the peak.

A.6 LS-06

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: creep
Notes: Single-stage creep at 0.60 of the suite-mean UCS.

Table 12. LS-06: creep models fitted to each stage

Stage	Model	Parameters (± SE)	r²	AIC
1	Burgers *	E_M = 42.0 ± 4.9×10⁻⁴ GPa; E_K = 260 ± 0.030 GPa; η_K = 260 ± 0.10 GPa·h; η_M = 9.03×10⁵ ± 3400 GPa·h	1.0000	-2113.6
1	Power law	ε₀ = -0.155 ± 0.79 %; A = 0.342 ± 0.79 %/hⁿ; n = 0.0100 ± 0.023	0.8991	-1014.7
1	Lomnitz	ε₀ = 0.169 ± 0.0013 %; A = 0.00383 ± 1.9×10⁻⁴ %; α = 78.0 ± 43 1/h	0.9144	-1040.7

* the model drawn and quoted. Burgers moduli in GPa and viscosities in GPa × time unit when the stress unit is MPa.

A.7 LS-07

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: creep
Notes: Single-stage creep at 0.75 of the suite-mean UCS.

Table 13. LS-07: creep models fitted to each stage

Stage	Model	Parameters (± SE)	r²	AIC
1	Burgers *	E_M = 42.0 ± 3.9×10⁻⁴ GPa; E_K = 260 ± 0.024 GPa; η_K = 260 ± 0.078 GPa·h; η_M = 9.06×10⁵ ± 4000 GPa·h	1.0000	-2071.1
1	Power law	ε₀ = -0.158 ± 0.84 %; A = 0.392 ± 0.84 %/hⁿ; n = 0.0112 ± 0.024	0.9004	-955.1
1	Lomnitz	ε₀ = 0.211 ± 0.0015 %; A = 0.00502 ± 2.5×10⁻⁴ %; α = 62.9 ± 31 1/h	0.9192	-984.6

* the model drawn and quoted. Burgers moduli in GPa and viscosities in GPa × time unit when the stress unit is MPa.

A.8 LS-08

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: creep
Notes: Single-stage creep at 0.88 of the suite-mean UCS.

Table 14. LS-08: creep models fitted to each stage

Stage	Model	Parameters (± SE)	r²	AIC
1	Burgers *	E_M = 42.0 ± 3.4×10⁻⁴ GPa; E_K = 261 ± 0.60 GPa; η_K = 260 ± 0.12 GPa·h; η_M = 1.46×10⁵ ± 5.8×10⁴ GPa·h	1.0000	-1349.0
1	Power law	ε₀ = 0.248 ± 4.2×10⁻⁴ %; A = 0.0253 ± 6.0×10⁻⁴ %/hⁿ; n = 0.545 ± 0.021	0.9884	-768.2
1	Lomnitz	ε₀ = 0.250 ± 1.2×10⁻⁴ %; A = 0.0187 ± 5.1×10⁻⁴ %; α = 2.79 ± 0.16 1/h	0.9977	-877.2

* the model drawn and quoted. Burgers moduli in GPa and viscosities in GPa × time unit when the stress unit is MPa.

Stage 1: Models fitted up to the tertiary onset at 3.14 h.

A.9 LS-09

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: creep
Notes: Single-stage creep at 0.95 of the suite-mean UCS.

Table 15. LS-09: creep models fitted to each stage

Stage	Model	Parameters (± SE)	r²	AIC
1	Burgers *	E_M = 42.0 ± 3.6×10⁻⁴ GPa; E_K = 266 ± 2.5 GPa; η_K = 261 ± 0.76 GPa·h; η_M = 3.38×10⁴ ± 1.5×10⁴ GPa·h	1.0000	-1225.7
1	Power law	ε₀ = 0.270 ± 1.9×10⁻⁴ %; A = 0.0278 ± 2.8×10⁻⁴ %/hⁿ; n = 0.678 ± 0.015	0.9959	-774.5
1	Lomnitz	ε₀ = 0.270 ± 4.2×10⁻⁵ %; A = 0.0256 ± 4.5×10⁻⁴ %; α = 1.91 ± 0.056 1/h	0.9996	-912.6

* the model drawn and quoted. Burgers moduli in GPa and viscosities in GPa × time unit when the stress unit is MPa.

Stage 1: Models fitted up to the tertiary onset at 1.66 h.

A.10 LS-10

Lithology: Micritic limestone (synthetic)
Origin: Demo block A
Diameter × height (mm): 54.0 × 135.0
Tests: relaxation
Notes: Stress relaxation at 0.18 % held strain.

Table 16. LS-10: relaxation models fitted to each stage

Stage	Model	Parameters (± SE)	r²	AIC
1	Maxwell	σ₀ = 58.6 ± 0.38 MPa; τ = 893 ± 130 h	0.4183	173.7
1	Prony (2 terms) *	σ∞ = 52.0 ± 0.0033 MPa; σ1 = 6.00 ± 0.0055 MPa; τ1 = 0.400 ± 9.5×10⁻⁴ h; σ2 = 5.00 ± 0.0054 MPa; τ2 = 15.0 ± 0.044 h	1.0000	-696.8
1	Logarithmic	σ₀ = 64.4 ± 0.57 MPa; r = 0.0495 ± 0.0014 per decade; t₀ = 0.00902 ± 0.0047 h	0.9836	-102.8

Acknowledgement and references

How to cite StrataPlot

StrataPlot. (2026). StrataPlot: Rock Mechanics Lab Report [Computer software]. https://www.strataplot.com/lab-report

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