Predicting forwarder rut formation on fine-grained mineral soils

Figures & data

Figure 1. Map of experimental area. Locations of study tracks are marked with red lines. Contains data from the National Land Survey of Finland Topographic map series (raster) 10/2017.

Figure 2. Particle size distribution for the study tracks.

Figure 3. Average profiles of cone penetration resistance (CI) on the study tracks. Averages between 0 and 20 cm were used in the modelling.

Table 1. Soil characteristics at the study tracks.

Track	CI	ARP	Clay	MGS	BD	VWC	Soil type
	Mean (SD), MPa	Mean (SD), cm	Mean (SD), %	Mean (SD), µm	Mean (SD), g/cm^3	Mean (SD), %
1	1.89 (0.84)	20.26 (5.55)	5.00	465.50	0.87	14.54 (2.65)	clSa/grclSa
2	1.35 (0.59)	15.00 (6.59)	5.20	296	0.91	19.03 (4.78)	clSa
3	0.57 (0.33)	40.91 (10.33)	14.88	188.50	0.91	70.22 (14.45)	clSa
4	1.28 (0.36)	55.00 (0.00)	43.44	3.50	0.71	30.59 (4.75)	Cl
5	1.48 (0.72)	17.92 (7.83)	4.27	291.50	0.85	14.61 (1.92)	grclSa/grsiSa
6	0.51 (0.09)	55.00 (0.00)	7.91	123.00	0.92	80.42 (9.72)	clSa/Sa
7	1.53 (0.24)	55.00 (0.00)	32.40	17.50	0.85	22.69 (3.36)	sasiCl
Overall	1.23 (0.71)	36.17 (18.30)	15.76 (14.18)	203.39 (154.36)	0.87 (0.07)	35.80 (26.40)

Notes: CI = Cone penetration resistance 0-20 cm, ARP = average rod penetration depth, Clay = percentage of clay in soil, MGS = median grain size, BD = soil bulk density, VWC = volumetric water content, Soil type (EN ISO 2002, 2004): Cl = Clay, sasiCl = sandysiltyClay, clSa = clayeySand, Sa = sand, grclSa = gravelyclayeySand, grsiSa = gravelysiltySand.

Figure 4. Average rut depths in the study tracks (1–7) after machine passes. Pass 1 = harvester (mass 22,500 kg), 2 = forwarder passes with load (mass 30,000 kg).

Table 2. Pearson correlation coefficients between rut depths (after one harvester pass and three forwarder passes) and soil properties calculated as averages for the test tracks.

	CI (kPa)		ARP (cm)	Clay (%)	MGS (µm)	BD (g/cm^3)	VWC (%)	Average rut depth (cm)	Harvester rut depth (cm)
CI (MPa)		1	−0.336**	0.030	0.259**	−0.244**	−0.627**	−0.400**	−0.272**
			0.000	0.485	0.000	0.000	0.000	0.000	0.000
		140	140	7	7	7	140	561	140
ARP (cm)			1	0.698**	−0.840**	−0.322**	0.483**	0.242**	0.102*
				0.000	0.000	0.000	0.000	0.000	0.016
				140	7	7	140	561	140
Clay (%)				1	−0.826**	−0.794**	−0.042	−0.078	−0.034
					0.000	0.000	0.321	0.063	0.423
					7	7	140	561	140
MGS (µm)					1	0.472**	−0.320**	−0.094*	0.011
						0.000	0.000	0.026	0.801
						7	140	561	140
BD (g/cm^3)						1	0.373**	0.258**	0.210**
							0.000	0.000	0.000
							140	561	140
VWC (%)							1	0.584**	0.401**
								0.000	0.000
								561	140
Average rut depth (cm)								1	0.579**
									0.000
									140
Harvester rut depth (cm)									1
									140

Notes: The P-values and number of observations are given in the rows below the coefficient. CI = average cone penetration resistance 0–20 cm, ARP = average rod penetration, Clay = percentage of clay in soil, MGS = median grain size, BD = soil bulk density, VWC = volumetric water content. **, The correlation is significant at the level of 0.01 (2-tailed).

*, The correlation is significant at the level of 0.05 (2-tailed).

Table 3. Mixed-linear models predicting the logarithm of the average rut depth (ln (y_tmi)) of measurements in a measurement line.

Model	1		2		3		4		5
Parameter	Estimate	Sig.	Estimate	Sig.	Estimate	Sig.	Estimate	Sig.	Estimate	Sig.
Fixed
Intercept	0.571	0.037	0.285	0.192	0.677	0.000	0.329	0.007	0.818	0.003
CM	0.000011	0.000	0.000011	0.000	0.0000068	0.000	0.0000068	0.000	0.0000069	0.000
VWC	0.013	0.010	0.016	0.005	0.012	0.000	0.015	0.000
CI	−0.166	0.095			−0.191	0.020
Hr					0.108	0.000	0.110	0.000	0.121	0.000
Random
${\sigma }_{track}^2$	0.111	0.175	0.109	0.191	0.115	0.061	0.122	0.044	0.224	0.104
${\rho }_{track}$	0.969	0.000	0.967	0.000	0.534	0.017	0.483	0.014	0.999	0.000
${\sigma }_{meas}^2$	0.528	0.000	0.534	0.000	0.234	0.000	0.234	0.000	0.322	0.000
${\rho }_{meas}$	0.761	0.000	0.764	0.000	0.746	0.000	0.746	0.000	0.816	0.000
AIC	1013.0		1013.0		507.7		510.0		506.2

Notes: CM = cumulative mass driven over measurement point (kg), VWC = volumetric water content (%), CI = cone penetration resistance (MPa), Hr = harvester rut depth (cm), ${\sigma }_{track}^2$ =variance within the track, ${\sigma }_{meas}^2$ = variance between the measurement points, ${\rho }_{track}$ and ${\rho }_{meas}$ = correlation coefficients for measurement lines within a track and for consecutive measurements after each pass. AIC = Akaike’s Information Criterion.

Figure 5. The influence of the cumulative overdriven mass and soil volumetric water content on the rut depth.

EN ISO 14688-1:2002. Geotechnical investigation and testing – Identification and classification of soil – Part 1: Identification and description (ISO 14688-1:2002). 14 pp. https://www.iso.org/standard/25260.html

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EN ISO 14688-2:2004. Geotechnical investigation and testing. Identification and classification of soil. Part 2: Principles for a classification (ISO 14688-2:2004). 15 pp. https://www.iso.org/standard/34082.html

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