Tire compaction capacity rating on non-standard soil

Tire Compaction Capacity rating system with its CC index was evolved to support the choice of proper tires for off-road vehicles or machines operating on crop producing land with aim to prevent harmful compaction of the ground. This system, fundamentally presented in the Journal of Terramechanics, Vol. 52/2014, is based on a great number of laboratory compaction tests in common clay–loam soil (here marked as standard soil). The presented article deals especially with more accurate application of numerical rating to sandy and clay soils (very different grain size) under the designation equivalent Compaction Capacity (eCC) index, however, is applicable to an arbitrary soil type. The features and practical use of eCC rating are explained and discussed in this technical note.     

Tire tread pattern design trigger on the stress distribution over rigid surfaces and soil compaction

Studies comparing the structural differences of tires have not qualitatively or quantitatively considered the effects of tread geometry on tire behaviour or the interactions of the tire with the surface. Therefore, to determine the effects of different tire tread patterns on the stress distribution of the tire and soil compaction, we compared the structural behaviours of a high-flotation tractive-tread (TT) tire and a smooth-tread (ST) tire. The experiments were conducted over a rigid and over a deformable surface. The results from the rigid surface shows the influences of the tread pattern and sidewalls is dependent of the loads. Over the deformable surface, the contact area of the TT tire was larger than that of the ST tire. The inflation pressure (IP) was mainly responsible for the load support before the soil reached its maximum deformation. Next, the tread and sidewalls exhibited the same behaviour as observed on the rigid surface. In addition, we observed alterations in the balloon point with the tread geometry and the type of surface due to changes in the contact pressure. With carcass deformation, the volume of the tire was visibly reduced, which indicated that the IP could increase.     

Finite element modeling of tire/terrain interaction: Application to predicting soil compaction and tire mobility

Tire/terrain interaction has been an important research topic in terramechanics. For off-road vehicle design, good tire mobility and little compaction on terrain are always strongly desired. These two issues were always investigated based on empirical approaches or testing methods. Finite element modeling of tire/terrain interaction seems a good approach, but the capability of the finite element has not well demonstrated. In this paper, the fundamental formulations on modeling soil compaction and tire mobility issues are further introduced. The Drucker-Prager/Cap model implemented in ABAQUS is used to model the soil compaction. A user subroutine for finite strain hyperelasticity model is developed to model nearly incompressible rubber material for tire. In order to predict transient spatial density, large deformation finite element formulation is used to capture the configuration change, which combines with soil elastoplastic model to calculate the transient spatial density due to tire compaction on terrain. Representative simulations are provided to demonstrate how the tire/terrain interaction model can be used to predict soil compaction and tire mobility in the field of terramechanics.     

Modeling compaction in agricultural soils

Research was conducted to quantify the effect of tire variables (section width, diameter, inflation pressure); soil variables (soil moisture content, initial cone index, initial bulk density); and external variables (travel speed, axle load, number of tire passes) on soil compaction and to develop models to assess compaction in agricultural soils. Experiments were conducted in a laboratory soil bin at the Asian Institute of Technology in three soils, namely: clay soil (CS), silty clay loam soil (SCLS), and silty loam soil (SLS). A dimensional analysis technique was used to develop the compaction models. The axle load and the number of tire passes proved to be the most dominant factors which influenced compaction. Up to 13% increase in bulk density and cone index were observed when working at 3 kN axle load in a single pass using a 8.0–16 tire. Most of the compaction occurred during the first three passes of the tire. It was also found that the aspect ratio, tire inflation pressure and soil moisture content have significant effect on soil compaction. The initial cone index did not show significant effect. The compaction models provided good predictions even when tested with actual field data from previous studies. Thus, using the models, a decision support system could be developed which may be able to provide useful recommendations for appropriate soil management practices and solutions to site-specific compaction problems.     

A tyre option for sugarcane haulout trucks to minimise soil compaction

Change in soil cone resistance was used as an indicator of soil compaction after the passage of haulout trucks running dual tyres or super single tyres. Cone resistance was measured to a depth of 0.6 m in the inter-row and in transects from the middle of one crop row to the middle of the adjacent row. Treatments consisted of one, two, three and four passes by both dual tyres and super single tyres and one and two passes of reduced pressure and standard pressure super single tyres aligned down the inter-row. Soil cone resistance increased with an increasing number of passes under the dual tyres. There was less change in soil cone resistance after the passage of super single tyres. A small reduction in soil cone resistance resulted when low tyre pressure was used compared with the standard tyre pressure in the super single tyres. Soil cone resistance was greater in the row after passage of the dual tyres compared with low-pressure super single tyres. There is an advantage in using super single tyres on haulout trucks compared with conventional dual tyres to minimise soil compaction.     

Numerical prediction of soil compaction in geotechnical engineering

Soil compaction involves a reduction in volume of the soil mass instead of settlement, which has been considered as one of the most important methods to increase geomaterials' strength in geotechnical engineering practice. This paper presents a numerical model to simulate soil compaction using the finite-element method with finite deformation. The fundamental formulations for soil compaction are introduced first. Then the model is employed to simulate the compaction process and predict spatial density, in which the soil is modeled as elastoplastic material. The Drucker–Prager/Cap model is integrated in the large-deformation finite-element code and used to model the gradual compaction process of soil. Representative simulations of practical applications in geotechnical/pavement engineering are provided to demonstrate the feasibility of predicting soil compaction density using the proposed large-deformation finite-element model.     

Influence of the axle load, tyre size and configuration on the compaction of a freshly tilled clayey soil

Enhancement of the potential root growth volume is the main objective of farmers when they establish a conventional tillage system. Therefore, the main function of primary tillage is to increase soil’s structural macroporosity. In spite of this, during secondary tillage operations on these freshly tilled soils, the traffic on seedbeds causes significant increases in soil compaction. The aim of this paper was to quantify soil compaction induced by tractor traffic on a recently tilled non consolidated soil, to match ballast and tyre size on the tractors used during secondary tillage. The work was performed in the South of the Rolling Pampa region, Argentina. Secondary tillage traffic was simulated by one pass of a conventional 2WD tractor, using four configurations of bias-ply rear tyres: 18.4×34, 23.1×30, 18.4×38 and 18.4×38 duals, two ballast conditions were used in each configuration. Soil bulk density and cone index in a 0 to 600 mm profile were measured before and after traffic. Topsoil compaction increased as did ground pressure. Subsoil compaction increased as total axle load increased and was independent from ground pressure. At heavy conditions, topsoil levels always showed higher cone index values. From 150 to 450 mm depth, the same tendency was found, but with smaller increases in the cone index parameter, 22 to 48%, averaging 35%. Finally, at the deepest layer considered, 600 mm, differential increases due to the axle load are great enough as to be considered similar to those found in the upper horizon, 36 to 64%, averaging 55%. On the other hand, bulk density tended to be less responsive than cone index to the traffic treatments. Topsoil compaction can be reduced by matching conventional bias-ply tyres with an optimized axle weight.     

Measuring soil compaction and soil behavior under the tractor tire using strain transducer

Soil compaction can occur due to machine traffic and is an indicator of soil physical structure degradation. For this study 3 strain transducers with a maximum displacement of 5 cm were used to measure soil compaction under the rear tire of MF285 tractor. In first series of experiments, the effect of tractor traffic was investigated using displacement transducers and cylindrical cores. For the second series, only strain transducers were used to evaluate the effect of moisture levels of 11%, 16% and 22%, tractor velocities of 1, 3 and 5 km/h, and three depths of 20, 30 and 40 cm on soil compaction, and soil behavior during the compaction process was investigated. Results showed that no significant difference was found between the two methods of measuring the bulk density. The three main factors were significant on soil compaction at a probability level of 1%. The mutual binary effect of moisture and depth was significant at 1%, and the interaction of moisture, velocity, and depth were significant at 5%. The soil was compressed in the vertical direction and elongated in the lateral direction. In the longitudinal direction, the soil was initially compressed by the approaching tractor, then elongated, and ultimately compressed again.     

Measurement of compacted soil density in a compaction of thick finishing layer

The compaction of a soil is one of the important construction operations that influences the durability of soil structure. Therefore, the measurement of soil density, used to judge the degree of compaction, has to be performed exactly. Since a compaction of a thick finishing layer could be executed with the enlargement of compaction machinery and the improvement of productivity, new equipment which can measure the soil density in a deep stratum has to be developed. In this paper, we propose a method of accurately estimating compacted soil density based on the three dimensional stresses measured in the ground during compaction by a stress state transducer (SST). A tracked vehicle mounted with a vertical oscillator was used to compact a decomposed granite soil of 45 cm depth. A model experiment was executed at a frequency that was varied from 16 to 25 Hz, setting the load ratio of maximum oscillating force to the vehicle weight (4.9 kN) to be 1.2, 1.6 and 2.0. The three dimensional stresses in the ground were measured by use of the SST. Comparing the dry density converted from cone penetrometer test results and the dry density estimated from Baily’s formula, the compacted soil density at the lowest soil stratum could be estimated by measuring earth pressure using SST.     

Effect of multiple passes of tractor with varying normal load on subsoil compaction

A field experiment was conducted on alluvial soil with sandy loam texture, in a complete randomized design, to determine the compaction of sub-soil layers due to different passes of a test tractor with varying normal loads. The selected normal loads were 4.40, 6.40 and 8.40 kN and the number of passes 1, 6, 11 and 16. The bulk density and cone penetration resistance were measured to determine the compaction at 10 equal intervals of 5 cm down the surface. The observations were used to validate a simulation model on sub-soil compaction due to multiple passes of tractor in controlled conditions. The bulk density and penetration resistance in 0–15 cm depth zone continuously increased up to 16 passes of the test tractor, and more at higher normal loads. The compaction was less in different sub-soil layers at lower levels of loads. The impact of higher loads and larger number of passes on compaction was more effective in the soil depth less than 30 cm; for example the normal load of 8.40 kN caused the maximum bulk density of 1.53 Mg/m³ after 16 passes. In 30–45 cm depth layer also, the penetration resistance increased with the increase in loads and number of passes but to a lesser extent which further decreased in the subsoil layers below 45 cm. Overall, the study variables viz. normal load on tractor and number of passes influenced the bulk density and soil penetration resistance in soil depth in the range of 0–45 cm at 1% level of significance. However, beyond 45 cm soil depth, the influence was not significant. The R² calculated from observed and predicted values with respect to regression equations for bulk density and penetration resistance were 0.7038 and 0.76, respectively.     

Soil compaction management: Reduce soil compaction using a chain-track tractor

Modern agricultural production requires research for new design and layout plans of the track-chained mover, providing a reduction in soil compaction. One of many ways to improve the efficiency of machine-tractor aggregate (MTA) use is to improve the geometry of the support part of the chain-track tractor. Flat geometry of the support part of a chain-track tractor with a semi-rigid suspension creates maximum pressure on soil with the first and last track rollers, which causes increased soil compaction. Research objective is to ensure the uniform pressure on soil from the tractor with a semi-rigid suspension by justifying the geometry of the supporting part of the track-chained mover.Based on experimental and theoretical studies a model of pressure distribution along the length of the support part was developed. Thus, the geometry of the support part of a track-chained tractor with a semi-rigid suspension was substantiated. Pressure decrease on soil and compaction reduction are achieved by changing the geometry of the support part and rational location of the tractor mass center. To achieve the elliptical geometry of the support part of a track-chained tractor with a semi-rigid suspension lower track rollers were placed at different heights.To test the formulas and to study the influence of the support part geometry, of the hitch height and the force on the hook of a track-chained tractor on soil compaction, experiments were conducted. As a model for experiment, the tractor actively used in agriculture was modernized; chain-track tractor T-170M1.03-55 with flat and elliptical caterpillar bypasses. The pressure was measured directly by pressure sensors that were placed into the ground. Soil density in the track left by a track-chained tractor mainly depends on mover pressure and the number of impacts per pass. Track-chained mover makes two impacts on soil with the flat support part. If the support part geometry is changed, the number of impacts on soil is reduced to one. To create typical working conditions for T-170M1.03-55 track-chained tractor the third and fourth support rollers should be lowered by 9.5 ± 1.5 mm, the second and fifth-by 4.5 ± 0.5 mm relatively, which leads to a decrease in the maximum pressure on soil and reduces its compaction in the track left by the mover by 15–25%.     

Laboratory experimental study of tire tractive performance on soft soil: Towing mode,traction mode,and multi-pass effect

Tire tractive performance, soil behavior under the traffic, and multi-pass effect are among the key topics in the research of vehicle off-road dynamics. As an extension of the study (He et al., 2019a), this paper documents the testing of a tire moving on soft soil in the traction mode or towing mode, with a single pass or multiple passes, and presents the testing results mainly from the aspects of tire tractive performance parameters, soil behavior parameters, and multi-pass effect on these parameters. The influence of tire inflation pressure, initial soil compaction, tire normal load, or the number of passes on the test data has been analyzed; for some of the tests, the analysis was completed statistically. A multi-pass effect phenomenon, different from any phenomenon recorded in the available existing literature, was discovered and related to the ripple formation and soil failure. The research results of this paper can be considered groundwork for tire off-road dynamics and the development of traction controllers for vehicles on soft soil.     

Several contributions to soil compactibility induced by cyclic loading test

To investigate the soil compactibility during the cyclic loading, three different kinds of paddy field soils were prepared so as to clarify interrelationships among stress amplitude ratio, bulk density, soil water content and pore water pressure. The presetting values of specimen include the soil water content(percent dry basis) and bulk density of 25% d.b. and 1.1 Mg/m³ respectively. The relation between the number of cyclic loading and axial strain exhibited an asymptotically increasing trend, converging toward a specific value for each experimental condition. Possible effect caused by elastic–plastic characteristics could be recognized, when axial strain for 0.5 Hz excitation becomes greater than the one of 1.0 Hz under same stress amplitude ratio. When the stress amplitude ratio took 0.1, the absolute value of axial strain of 0.5 Hz was greater than the one of 1.0 Hz, whereas its decreasing trend was recognized in the sequence of silt, clay and silty sand. The qualitative relations between pore water pressure and number of cyclic loading were also examined to scrutinize the effect of effective water pressure to the soil compactibility.     

Soil compaction and over-winter changes to tracked-vehicle ruts, Yakima Training Center, Washington

We monitored two experimental areas at the Yakima Training Center (YTC) in central Washington to measure changes to M1A2 Abrams (M1) tank-rut surface geometry and in- and out-of-rut saturated hydraulic conductivity (K_fs), soil penetration resistance (SPR) and soil bulk density (BD). Profile-meter data show that rut cross-sectional profiles smoothed significantly and that turning ruts did so more than straight ruts. Rut edges were zones of erosion and sidewall bases were zones of deposition. K_fs values were similar in and out of ruts formed on soil with 0–5% moisture by volume, but were lower in ruts formed on soil with about 15% water. Mean SPR was similar in and out of ruts from 0- to 5-cm depth, increased to 2 MPa outside ruts and 4 MPa inside ruts at 10- to 15-cm depth, and decreased by 10–38% outside ruts and by 39–48% inside ruts at the 30-cm depth. Soil BD was similar in and out of ruts from 0- to 2.5-cm depth, and below 2.5 cm, it was generally higher in ruts formed on moist soil with highest values between 10- and 20-cm depth. Conversely, BD in ruts formed on dry soil was similar to out-of-rut BD at all depths. This information is important for determining impacts of tank ruts on water infiltration and soil erosion and for modifying the Revised Universal Soil Loss Equation (RUSLE) and the Water Erosion Prediction Project (WEPP) models to more accurately predict soil losses on army training lands.     

Overwinter changes to near-surface bulk density, penetration resistance and infiltration rates in compacted soil

Previous studies at Yakima Training Center (YTC), in Washington State, suggest freeze-thaw (FT) cycles can ameliorate soil compacted by tracked military vehicles [J. Terramechanics 38 (2001) 133]. However, we know little about the short-term effects of soil freezing over a single winter. We measured bulk density (BD), soil penetration resistance (SPR), and steady-state runoff rates in soil newly tracked by an Abrams tank and in uncompacted soil, before and after a single winter at YTC. We similarly measured BD, SPR and saturated hydraulic conductivity (k_fs) in simulated tank tracks at another site near Lind Washington. Average BD was significantly greater in tank ruts at YTC and in simulated tracks at the Lind site than in uncompacted soil soon after tracking and did not change significantly during the winter of 1997–1998. Measurements of SPR were strongly influenced by soil moisture. When soil was moist or tracks were newly formed, SPR was significantly higher in tank ruts than in uncompacted soil from the surface to a depth of about 10–15 cm. The greatest average SPR in compacted soil was observed between 4 and 6 cm depth. We observed less difference in SPR between tank ruts and uncompacted soil near-surface at YTC as the time after trafficking increased. We observed highest SPR ratios (compacted rut:undisturbed) in fresh tracks near the surface, with lower ratios associated with increasing track age or soil depth, indicating that some recovery had occurred at YTC near-surface. However, we did not observe a similar over-winter change in SPR profiles at the Lind site. Rainfall simulator data from YTC showed higher steady-state runoff rates in tank ruts than over uncompacted soil both before and after winter. However, more time was required to reach steady-state flow in tank ruts and the proportion of runoff was slightly lower in May 1998 than in August 1997. At the Lind site, k_fs was lower in newly compacted soil than in one-year old compacted soil or uncompacted soil. Our data suggest that indices of water infiltration such as steady-state runoff rates or k_fs, are more sensitive indicators of soil recovery after compaction than are BD or SPR.     

Response of railway track system on poroelastic half-space soil medium subjected to a moving train load

Based on the dynamic poroelastic theory of Biot, dynamic responses of a track system and poroelastic half-space soil medium subjected to moving train passages are investigated by the substructure method. The whole system is divided into two separately formulated substructures, the track and the ground, and the rail is described by introducing the Green function for an infinitely long Euler beam subjected to the action of moving axle loads of the train and the reactions of the sleeper. Sleepers are represented by a continuous mass and the effect of the ballast is considered by introducing the Cosserat model for granular medium. Using the double Fourier transform, the governing equations of motion are then solved analytically in the frequency-wave-number domain. The time domain responses are evaluated by the inverse Fourier transform computation for a certain train speed. Computed results show that the shape of the rail displacements of the elastic and poroelastic soil medium are in good agreement with each other of the low train velocity, but the result of the poroelastic soil medium is significantly different to that of the elastic soil medium for the high train velocity which is higher than Rayleigh-wave speed in the soil. The influence of the soil intrinsic permeability on soil responses is discussed with great care in both time domain and frequency domain. The dynamic responses of the soil medium are considerably affected by the fluid phase as well as the load velocity.