Effect of soil compaction intensity under wheel on the stress under passage track

Transcription

1 Annals of Warsaw University of Life Sciences SGGW Agriculture No 60 (Agricultural and Forest Engineering) 2012: (Ann. Warsaw Univ. Life Sci. SGGW, Agricult. 60, 2012) Effect of soil compaction intensity under wheel on the stress under passage track JERZY BULIŃSKI, LESZEK SERGIEL Department of Agricultural and Forest Machinery, Warsaw University of Life Sciences SGGW Abstract: Effect of soil compaction intensity under wheel on the stress under passage track. There are presented the laboratory investigation results on the effect of soil compaction intensity, diversified by number of wheel passages over the same track, load and passage speed, on the stress in soil profile at depth of 0.24 and 0.34 m. The investigations were carried out in a soil bin on fine-sandy clay of moisture content 12%. A distinct connection of stress values with number of passages and loads was found in all measurement variants. In the shallow soil layer (0.24 m) the highest stress changes were found after the wheel passages at the lowest load of 2011 N, while in the deep soil layer (0.34 m) the stress values were lower on the average by 39%. A regression equation to describe the investigated dependences was developed. Key words: wheel, load, number of passages, soil stress. INTRODUCTION Problems of soil compaction have been investigated in many scientific centers for many years; the unfavourable effects for soil environment and plants are well known. However, the investigations are still carried out, since field operations intensity in agriculture increases continuously and more and more heavy tractor outfits occur. Along with an increase in vehicle mass, the soil stress changes can be found in deeper layers of soil profile [Keller et al. 2007; Lamande et al. 2007; Zink et al. 2010; Lamande and Schjønning 2011]. The soil reaction to wheel pressures is an increase in compaction that limit the biological soil activity. According to researchers, the dynamic loading and pressure area significantly affect the stress under wheel, while the highest compaction zone (volumetric deformation) depends on soil type and pressure values. These values depend, among other things, on tyre type, pressure and first of all on ground characteristics. On a rigid surface the area is always smaller than on deformable [Alakukku et al. 2003]. According to the authors, the pressure distribution under wheel is not uniform and largely depends on tyre type. Under the tyre tread lugs it can greatly (4 10 times) exceed the average pressure value estimated for the entire contact area, although this differentiation is limited to superficial layer. It is evident from laboratory investigations [Gysi 2001], a single passage of wheel loaded to about 107 kn caused soil compaction only in upper soil layer to a depth of 25 cm, without measurable changes in deeper layers. One can note, that under real field conditions such small wheel loads in implements and machines are rare. The mass of current agricultural heavy tractors exceeds 10 Mg, while in the case of fully equipped three-axle sugar beet combine harvesters it can reach even 50 Mg. Ac-

2 16 J. Buliński, L. Sergiel cording to Horn and Fleige [2009], the load of wheel with typical inflation pressure should not exceed 3.3 Mg to avoid compaction of deeper soil layer; beside the vehicle axle load, the main factor that determines soil compaction is number of passages over the same track [Canillas and Salokhe 2001]. Investigations carried out in this respect [Słowińska- -Jurkiewicz and Domżał 1991; Buliński 1998; Gysi et al. 2000; Gysi 2001; Powałka 2005] pointed out that the highest soil compaction increase was caused by the first passage over loosened soil. Duration of loading as well as degree of exceeding the soil limiting stress are also important [Jurga 2008; Błażejczak 2010]. Many researchers [Kruszewski, Michalak 1989; Pukos 1990; Walczyk 1995; Błaszkiewicz 1997] found that apart from axle loading, the soil moisture content is among factors affecting the range of quantitative and qualitative changes in soil properties connected with its compaction. According to Abu-Hamdeh and Reeder [2003], predicting of soil compaction calls for understanding of accompanied phenomena, learning of mathematical description of forces that cause the soil volumetric deformation and increase in soil density. For many years there have been carried out the field and laboratory investigations in this respect. This work aimed at evaluation of the effect of multiple passages of wheel at various load and speed on the stress changes in soil under the passage track. MATERIAL AND METHODS Investigations were carried out in a soil bin [Buliński and Leszczyński 2012], filled with fine-sandy clay of sand content 61.5%, dust content 22% and fluming particle content 16.5%. Soil moisture content in the bin amounted to 12%. The soil was loosened with a set of tines and compacted with the wheel designated as ANP-5 (steering wheel of tractor Ursus 4512) that moved times over the same track along the bin at speed 0.82 m s 1. The wheel load during investigations amounted to G 1 = 2011 N, G 2 = 3600 N, G 3 = 5199 N, while the tire inflation pressure was equal to 180 kpa. Soil stresses were measured with piezoresistive pressure gauges placed along the track axis on supports of such length that allowed for the sensor tip position at depth 0.24 and 0.34 m (Fig. 1) in relation to soil surface in the bin. The supports rested on the bin bottom and ensured sensor s stability in soil, making impossible changes in its position under pressure of moving wheel. The support with sensor was placed in soil with the use of a special device. The measuring cycle consisted in soil loosing over the entire width and length of measuring length, leveling of soil surface and execution of appropriate number of runs with the loaded wheel. Sensor signals were recorded continuously with the use of a digital measuring-recording unit of Hottinger Baldwin DMCplus and a computer with CATMAN 2.1 program that run the

3 Effect of soil compaction intensity under wheel on the stress under passage Direction of motion Bottom of soil bin FIGURE 1. Layout of pressure gauge position in soil bin measuring system. In analysis of results there were taken the maximal stress values. For each variant of soil compaction (load number of passages) the measurements were repeated three times. RESULTS OF INVESTIGATIONS Changes in soil stresses at depth 0.24 m and 0.34 m are presented in Figures 2a, b for various load (G) and number of passages (Kr). A distinct connection of stress values with number of passages and loads was found in all measurement variants. The stress values at depth 0.24 m ranged from kpa at the lowest load and single wheel passage to kpa at the highest load (5199 N) and 8 compacting passages. Considering the results of measurements one can find that an increase in wheel load caused an increase in stress at both considered profile depths. The increased wheel load from 2011 N (G 1 ) to 3600 N (G 2 ) at depth 0.24 m caused an increase in average stress of 14.5 kpa (28.2%), while increasing of load from G 1 to G 3 (5199 N) resulted in the increased average load of 38 kpa (35.6%). In deeper layer (0.34 m) the effect of wheel load was lower. An increase in load from G 1 to G 2 caused an average increase in stress of 13.8 kpa (43%), while at G 3 load the stress was increased on the average by 26.2 kpa (25.7%) in relation to values at G 1 load. The extreme load values reflected the extreme intensity of wheel load effects (G 1, Kr1 and G3, Kr8) and ranged from 23.2 kpa to 75.8 kpa. In the deeper layer of 0.34 m the stress under the track, as a result of damping soil action, were not so dynamic as that close to the surface, and were lower (than on deep layer 0.24 m) by 25 54% (on the average 39%); it may result from the stabilizing action of under-surface layer that transfers pressures deeper in the profile. The changes ranged from 13 to 49 kpa. The number of compacting passages over the same track also affected significantly the changes in stresses under the track; a positive correlation between these factors was found. It was found in the shallower layer (Fig. 3a) that in relation to soil state after the single compact-

4 18 J. Buliński, L. Sergiel a Soil stress [kpa] Kr1 Kr2 Multiplicity of passages Kr4 Kr8 G3 G2 Wheel G1 load b Soil stress [kpa] Kr1 Kr2 Multiplicity of passages Kr4 Kr8 G3 G2 Wheel G1 load FIGURE 2. Values of soil stress at depth: a) 0.24 m and b) 0.34 m and at multiple wheel passage (Kr) and three loads (G) ing passage, the highest stress increments were found after the wheel passages at the highest load (G3). Following the initial stress increase caused by the first wheel passage, the subsequent passages increased systematically the stress increments in this layer, to maximal increase of 54.6 kpa after eight compacting passages (Kr8 Kr1). The similar level of maximal stress increase after eight passages was found also for the wheel passages at load G 1 (54.8 kpa) and G 2 (52.6 kpa); maybe, at such soil moisture content, the initial compaction by the first wheel passage creates a pressure that displaces air from the soil spaces, while the remaining incompressible water transfers the stress to deeper layers. At deep loosening of soil, the superficial layers are compacted to certain state resulted from the soil resistance against the moved and compressed layers. It is also evident that at maximal load, particular passages cause the similar values of stress changes in relation to the state obtained after a single passage. It can be a significant indication for agri-

5 Effect of soil compaction intensity under wheel on the stress under passage a a = Stress changes [kpa] Kr8 0 Kr4 b G1 Wheel load G2 G3 Kr2 a = 0.34 Multiplicity of passages Stress changes [kpa] G1 Wheel load G2 G3 Kr8 Kr4 Multiplicity Kr2 of passages FIGURE 3. Soil stress changes under tracks after subsequent wheel passages at depth: a) 0.24 m and b) 0.34 m (in relation to Kr1 state) cultural practice on organization of field operations and setting up the tractor-machine outfits. However, taking into consideration the mean stress changes for the three wheel load levels, two compacting passages increased the soil stress at depth 0.24 m by 23.4 kpa, four passages by 35 kpa, and eight passages by 54 kpa, when compared to single passage. In relation to maximal stresses after eight wheel passages, a single passage created stress of 46.5%, two passages of 68.7%, and four passages of 80.3%. In deeper layer (Fig. 3b), the nature of stress changes was different; the soil stresses systematically increased along with the number of compacting passages and wheel load. The soil was systematically compacted. In relation to values obtained after single passage, two wheel

6 20 J. Buliński, L. Sergiel passages increased the stress from 12 to 19.6 kpa (on the average by 14.9 kpa), four passages from 18.3 to 32.8 kpa (on the average by 23.5 kpa), and eight passages from 19.8 to 39.9 kpa (on the average by 30.2 kpa). Assuming the stress values at depth 0.34 m and after eight passages as 100%, single passages created the stress of 49.3%, two passages by 74.9%, four passages by 89.4%. In order to determine significance of the effect of investigated factors on the stress at considered depths, there was carried out analysis of variance by the squares sum method for the entire measuring results. It was found that at confidence level of 95%, the depth, load and number of passages affected highly significantly (P < 0.05) the soil stress values under the wheel tracks (Tab. 1). The obtained results of analysis were confirmed in the multiple range test by Tukey method (95% HSD); its values pointed out that the mean stress values at particular levels of independent factors effects differed significantly from each other. The values presented in Table 2 point out that both the depth of measurement and wheel load significantly diffe- TABLE 1. Analysis of variance for soil stresses (Pk) under wheel tracks Factor Sum of squares Degrees of freedom Mean square F Sig. level Depth, a [m] Wheel load, G [N] Number of wheel passages, Kr Residue Total TABLE 2. Comparison between differences in mean soil stress values after wheel passage Factor Depth, a [m] Wheel load, G [N] Number of wheel passages, Kr * differences statistically significant Level of factor Mean Contrast Calculated difference Limit value * * * * * * * *

7 Effect of soil compaction intensity under wheel on the stress under passage rentiated the soil stresses over the entire range of assumed values. Number of passages caused a statistically significant differentiation of mean values between the first and the remaining passages as well as between the second and eighth passage; it confirms the previous findings of the effect of the two first passages on changes in state of soil under the track. Differences between mean values for 2, 4 and 8 passages were small and statistically insignificant. The obtained results of analysis allow for determination of regression equation that connect the stress (Pk) with depth of measurement (a), wheel load (N) and number of passages: Pk = a G Kr R 2 = 87.5% According to assumed methodic, depth in this equation (a) is expressed in meters and the wheel load (G) in newtons. Comparison between measuring values and calculated ones with the use of the above equation, presented in Figure 4, enables to find that the proposed dependence is well fitted to measuring values within the prevailing range of variability of the obtained investigation results. CONCLUSIONS The investigations carried out in the soil bin showed a highly significant effect of wheel load and number of passages on the stress values in soil profile under the passage track. The highest increase of stress in the investigated levels of soil profile was caused by the first wheel passage. The single passages created the stress of %, two passages of %, and four passages of % of maximal value obtained after eight passages. The mean stress values of corresponded compaction variants at depth 0.34 m were lower than that found at depth 0.24 m, on the average by 30.1 kpa (over 39%); scatter of changes was considerably lower. REFERENCES ABU-HAMDEH N.H., REEDER R.C. 2003: Measuring and predicting stress distribution under tractive devices in undisturbed soils. Biosystems Engineering 85 (4), ALAKUKKU L., WEISSKOPF P., CHA- MEN W.C.T., TIJINK F.G.J., VAN DER LINDEN J.P., PIRES S., SOMMER C., Measured stress Calculated stress [kpa] FIGURE 4. Comparison between soil stress measured values with values calculated by the equation

8 22 J. Buliński, L. Sergiel SPOOR G. 2003: Prevention strategies for field traffic-induced subsoil compaction: a review. Part 1. Machine/soil interactions. Soil & Tillage Research 73, BŁASZKIEWICZ Z. 1997: Analiza wpływu wybranych parametrów opon rolniczych na ugniatanie gleby. Roczniki Akademii Rolniczej w Poznaniu. Rozprawy naukowe, zeszyt 271, 156. BŁAŻEJCZAK D. 2010: Prognozowanie naprężenia granicznego w warstwie podornej gleb ugniatanych kołami pojazdów rolniczych. Wydawnictwo Uczelniane Zachodniopomorskiego Uniwersytetu Technologicznego. Szczecin, 96. BULIŃSKI J. 1998: Zagęszczenie gleby w różnych technologiach i związane z tym opory orki. Rozprawy naukowe i monografie. Wyd. SGGW, Warszawa, 140. BULIŃSKI J., LESZCZYŃSKI Ł. 2012: Effect of multiple passages and wheel load on soil deformation. Annals of Warsaw University of Life Sciences SGGW, Agriculture (Agricultural and Forest Engineering) 59, CANILLAS E.C., SALOKHE V.M. 2001: Regression analysis of some factors influencing soil compaction. Soil & Tillage Research 61, GYSI M. 2001: Compaction of a Eutric Cambisol under heavy traffic in Switzerland: Field data and a critical state soil mechanics model approach. Soil & Tillage Research 61, GYSI M., KLUBERTANZ G., VULLIET L. 2000: Compaction of an Eutric Cambisol under heavy wheel traffic in Switzerland field data and modeling. Soil & Tillage Research 56, HORN R., FLEIGE H. 2009: Risk assessment of subsoil compaction for arable soils in Northwest Germany at farm scale. Soil & Tillage Research 102, JURGA J. 2008: Metoda prognozowania zmian gęstości objętościowej gleby na podstawie geometrycznych parametrów koleiny. Wydawnictwo Naukowe Akademii Rolniczej w Szczecinie. Rozprawy 248, 99. KELLER T., DEFOSSEZ P., WEISSKOPF P., ARVIDSSON J., RICHARD G. 2007: Soil Flex: a model for prediction of soil stresses and soil compaction due to agricultural fieldtraffic including a synthesis of analytical approaches. Soil & Tillage Research 93, KRUSZEWSKI Z., MICHALAK G. 1989: Wybrane zagadnienia z teorii ruchu oraz budowy pojazdów rolniczych. Wydawnictwa Politechniki Warszawskiej. LAMANDE M., SCHJØNNING P. 2011: Transmission of vertical stress in a real soil profile. Part II: Effect of tyre size, inflation pressure and wheel load. Soil & Tillage Research 14, LAMANDE M., SCHJØNNING P., TO- GERSEN F.A. 2007: Mechanical behaviour of an undisturbed soil subjected to loadings: effects of load and contact area. Soil & Tillage Research 97, POWAŁKA M. 2005: Wpływ nacisków kół ciągników rolniczych na zagęszczenie gleby w warstwie ornej. Praca doktorska, SGGW, Warszawa, 84. PUKOS A. 1990: Odkształcenia gleby w zależności od rozkładów wielkości porów i cząstek fazy stałej. Wydawnictwo Polskiej Akademii Nauk. Instytut Agrofizyki. Problemy agrofizyki, zeszyt 61, 5 8. SŁOWIŃSKA-JURKIEWICZ A., DOMŻAŁ H. 1991: The structure of the cultivated horizon of soil compacted by the wheels of agricultural tractors. Soil & Tillage Research 19 (2 3), WALCZYK M. 1995: Wybrane techniczne i technologiczne aspekty ugniatania gleb rolniczych agregatami ciągnikowymi. Zeszyty Naukowe Akademii Rolniczej im. H. Kołłątaja w Krakowie. Rozprawy 202, 107. ZINK A., FLEIGE H., HORN R. 2010: Load risks of subsoil compaction and depths of stress propagation in arable luvisols. Soil Sci. Soc. Am. J. 74,

9 Effect of soil compaction intensity under wheel on the stress under passage Streszczenie: Wpływ intensywności ugniecenia gleby kołem na naprężenia pod koleiną przejazdu. Badania przeprowadzone w kanale glebowym miały na celu określenie wpływu obciążenia koła i liczby przejazdów na odkształcenia gleby na dwóch głębokościach w profilu pod koleiną. Badania przeprowadzono w kanale glebowym napełnionym gliną drobnopiaszczystą o zawartości piasku 61,5%, pyłu 22%, części spławialnych 16,5% i wilgotności 12%. Do ugniatania gleby wykorzystano koło ciągnika o wymiarze ANP-5 i ciśnieniu w oponie 180 kpa, poruszające się z prędkością 0,82 m s 1, krotnie tym samym śladem, z obciążeniem: N. Badania wykazały, że we wszystkich wariantach pomiarowych istniał wyraźny związek wartości naprężeń zarówno z liczbą przejazdów ugniatających, jak i z obciążeniami i głębokością położenia warstwy. Największy wzrost naprężeń w badanych poziomach profilu glebowego powodował pierwszy przejazd koła. W odniesieniu do wartości maksymalnych naprężeń otrzymywanych po ośmiokrotnych przejazdach koła, pojedynczy przejazd koła wytwarzał wartości naprężeń w zakresie 46,5 49,3%, dwukrotne: 68,7 74,9%, czterokrotne: 80,3 89,4%. W warstwie płytszej (0,24 m) największe zmiany naprężeń otrzymywano po przejazdach koła przy największym obciążeniu 5199 N. Wartości średnie naprężeń z odpowiadających sobie wariantów ugniecenia na głębokości 0,34 m były mniejsze niż na głębokości 0,24 m średnio o 30,1 kpa, tj. ponad 39% i rozrzut zmian był znacznie mniejszy. Opracowano równanie regresyjne opisujące badane zależności. MS. received June 2012 Authors address: Jerzy Buliński Leszek Sergiel Katedra Maszyn Rolniczych i Leśnych SGGW Warszawa, ul. Nowoursynowska 166 Poland jbulinski@wp.pl