Soil Reaction Forces Research Articles

Exploring memory mechanisms for friction fatigue in vibratory pile driving

This paper studies the mechanism that leads to the reduction of frictional soil reaction forces during pile driving, termed friction fatigue. We focus on axial vibratory driving, an environmentally friendly monopile installation method, and examine two friction fatigue formulations, i.e. a penetration-based and a cyclic memory mechanism. Friction fatigue plays a pivotal role in pile drivability and post-installation bearing capacity for piles installed via axial vibratory driving. Through numerical analyses and validation against field data from onshore experiments, the efficacy of these memory mechanisms is assessed. The results reveal that the proposed cyclic memory mechanism provides consistently more accurate predictions than the corresponding penetration-based approach, offering a promising option for modelling friction fatigue in vibratory driving. This study advances our understanding of friction fatigue in the context of vibratory driving for offshore monopile installation, emphasizing the need for further numerical and experimental works in this topic.

A novel analytical solution for horizontal vibration of partially embedded offshore piles considering the distribution effect of wave loads

According to the Novak's plane strain theory and Biot's wave equation, this paper proposes an analytical model for horizontal vibration of partially embedded offshore piles under distribution effect of wave loads (DEWL) incorporating the diffraction effects of waves. Firstly, for the pile above the mudline, the wave force acting on the pile is obtained through the method of separation of variables. Secondly, for the embedded section of offshore piles, the governing equations of the seabed are decoupled by introducing potential functions, and then the boundary condition of the seabed and the continuity condition at the soil-pile contact surface are combined to obtain the frequency domain analysis of the soil reaction forces. Furthermore, by applying the continuity condition of displacement at mudline and using the matrix transfer method, the analytical solution for the horizontal vibration characteristics (HVC) is derived. Finally, a comparison analysis with existing theoretical solutions is conducted to validate the rationality and accuracy of the analytical solution proposed in this paper. Based on this, a parametric analysis is conducted to discuss the effects of the parameters of the soil, the pile and the wave on the HVC of partially embedded offshore piles.

Study of the dynamic interactions between helix-stiffened cement mixing piles and soft soil under oblique incidence of SV waves in arbitrary space

Helix stiffened cement mixing (HSCM) piles are extensively utilized in soft soil sites due to their excellent seismic and pullout resistance. Initially, the equivalent nodal force formulas for each face under the oblique incidence of SV waves in any spatial direction are derived based on the viscous-spring artificial boundary. The method's applicability in studying pile–soil interactions is verified based on existing pile–soil tests. Subsequently, the HSCM pile–soil model is constructed using finite element software through a Python program. Various analyses of accelerations, relative displacements, soil reactions, and pile–soil dynamic p-y curves are conducted using two different directions of incidence angles (horizontal and vertical) and various types of seismic waves. Subsequently, the backbone line of the dynamic p-y curve is plotted, revealing the pile–soil interaction mechanism under spatial oblique incidence. Finally, Matlock's formula is modified to ensure its applicability to pile–soil interactions under spatially oblique incidence. The results demonstrate that loading the Kobe wave causes the peak acceleration in the x direction, the peak pile–soil relative displacement, and the peak pile-side soil reaction force to increase by 22.64 %, −18.90 % and 18.42 %, respectively, compared to those of the El Centro wave.

Enhancing Afforestation Practices in Hilly Terrain: A Study on Soil Disturbance by Earth Augers Based on the Discrete Element Method

Afforestation operations in hilly regions are both arduous and unsafe. The mechanized afforestation method that takes into account soil and water conservation measures is deemed highly important. This paper examines the operational process and the auger’s mechanism of digging below the ground using the discrete element method (DEM). Using this model, soil disturbance parameters and reaction forces are satisfactorily predicted, exhibiting similar trends to experimental observations. This research also examines the influence of key parameters on soil disturbance and distribution patterns and analyzes the conditions and mechanisms of the formation of fish-scale pits to preserve soil and water. A field experiment of pit digging in woodland is carried out to test the performance of the device. The error rates for the actual and simulated values of the efficiency of conveying soil and the distance of throwing soil on plain terrain and slopes were 12.7% and 8.2%, and 8.6% and 15.7%, respectively. Overall, this research provides a theoretical basis for the innovative exploration, development, and optimized design of earth augers in hilly regions.

Performance Evaluation of Jerusalem Artichoke Digging Tool in Cohesive Soil Using Discrete Element Method

Highlights Response surface methodology is suitable for DEM input parameter optimization. Soil reaction forces reduced at velocity ratios greater than one (1.2-3.9). Vibration reduced soil reaction forces at the target depth of 350 mm by 70%. In general, soil reaction forces increase with speed but decrease with frequency. Abrasive wear predominantly occurred at the tool’s cutting section. Abstract. The discrete element method (DEM) and response surface methodology (RSM) were used to determine the input parameters and combination of operational factors required for optimizing the Jerusalem artichoke (Helianthus tuberosus L.) harvesting tool in cohesive soil. The DEM soil model consisted of particles with different radii in three shapes calibrated using angle of repose and cone penetration data. Compared with data from a soil bin subsoiler evaluation, the DEM model showed acceptable relative errors for draught force (6.7%), vertical force (4.5%), and furrow width (9.3%). The effects of operational factors, including forward speed, vibration frequency, and amplitude, on response variables such as draught and vertical forces, drawbar power, and abrasive wear were analyzed for three harvesting shovels (S-shape, step-shape, and fork-shape). The ratio of vibratory speed to forward speed (velocity ratio, Vr) was used to analyze the combined effect of the factors. The operational factors significantly affected all the response variables (p<0.05). At Vr > 1 (1.2-3.9), soil reaction forces and drawbar power were considerably reduced. The optimal parameters for minimizing the response variables were 2.5 km h-1 forward speed, 14.5 Hz frequency, 30 mm amplitude, and S-shape shovel at Vr = 3.9. The minimum draught force, vertical force, drawbar power, and Archard wear depth were 4.64 kN, 0.41 kN, 2.64 kW, and 2.36 mm, respectively, at an operating depth of 350 mm. Operating in vibratory mode reduced draught force by 54% with the full width of the implement. Future work should include Jerusalem artichoke tubers in the simulation and experimental validation. Keywords: Abrasive wear, Clay, Numerical optimization, Soil reaction forces, Velocity ratio, Vibration.

Experimental study on vertical–lateral coupling pipe–soil interaction characteristics and speed amplification effect of marine pipelines

ABSTRACT Under actual marine environment, the steel catenary pipeline’s touchdown zone frequently interacts with the seabed. The existing understanding of vertical–lateral coupling effect and speed amplification effect is insufficient at present. In this paper, the mechanism tests for the vertical and lateral soil resistance of small-scale pipes are carried out in both dry soil and saturated soil environments. The pipe–soil interaction presents quite different characteristics in dry soil and saturated soil due to the soil liquefaction effect. The pipe movement speed affects the soil reaction force significantly, especially in the high-speed range. During the vertical penetration of the pipe, soil shear strength follows a tri-linear relation. The lateral pipe–soil interaction could be classified into three phases i.e. fast growth, fast descent and stable fluctuation. The vertical–lateral coupling has a significant influence on pipe–soil interaction, presenting that the penetration depth greatly affects the lateral soil resistance.

Terramechanics models augmented by machine learning representations

The field of terramechanics focuses largely on two types of simulation approaches. First, the classical semi-empirical methods that rely on empirically determined soil parameters and equations to calculate the soil reaction forces acting on a wheel, track or tool. One major drawback to these methods is that they are only valid under steady-state conditions. The more flexible modelling approaches are discrete or finite element methods (DEM, FEM) that discretize the soil into elements. These computationally demanding approaches do away with the steady state assumption at the cost of including more model parameters that can be difficult to accurately tune. Model-free approaches in which machine learning algorithms are used to predict soil reaction forces have been explored in the past, but the use of these models comes at the cost of the valuable insight that the semi-empirical models provide. In this work, we presume that in a dynamic simulation, the soil reaction forces can be divided into a steady state component that can be captured using semi-empirical models and a dynamic component that cannot. We propose an augmented modelling approach in which a neural network is trained to predict the dynamic component of the reaction forces. We explore how this theory can be applied to the simulation of a soil-cutting blade using the Fundamental Earthmoving Equation and of a wheel driving over soft soil using the Bekker wheel-soil model.

Model Test Study of the Synergistic Interaction between New and Existing Components of Sheet Pile Walls

New and existing components of retaining structures are often combined in the width section. When combining the design and use requirements of the existing and new structures, the synergistic interactions between the existing and new structures and the design and working conditions require clarification. In conjunction with an actual project, a sheet pile wall consisting of existing and new components is proposed to retain an embankment. Indoor model tests were carried out to simulate the excavation and compaction and investigate changes in earth pressure, pile bending moment, shear force, and load-sharing ratio of the new and existing sheet pile walls at different stages. The results show that the earth pressure of the cantilever section of the existing and new piles increases with an increase in the fill volume or the upper uniform load. An inflection point is observed in the earth pressure curve halfway between the pile top and the ground due to sudden changes in the pile and soil stiffness. The bending moment of the new and existing piles increases and decreases with the distance from the top of the pile under different working conditions, and the maximum bending moment occurred at 0.485 and 0.9 m from the bottom of the existing pile and the bottom of the new pile, respectively. The lateral displacement of the new and existing piles decreases with the distance from the top of the pile. Due to the adjustment of the structural force in the cantilever section and the soil reaction force in front of the pile, the displacement curves of the new and existing piles are similar in the cantilever section. The displacement in the anchored section is initially larger for the existing pile than for the new pile but then becomes similar for both piles. In working condition 5, the top displacement of the existing pile was 6.531 mm, exceeding the control value (5.6 mm). The earth-pressure-sharing ratio of the existing pile decreases with an increase in the width of the filling material or the load. When the load was applied, the earth-pressure-sharing ratio of the existing pile was 0.451, indicating that the structural design of the combined sheet pile wall is reasonable.

Effects of Rotary Tine Tool Velocity on Soil Reaction Forces, Power, and Energy Intensity

Highlights Draft force and torque on a vertical rotary tine tool were studied for various longitudinal velocities and speed ratios. Draft force increased with longitudinal velocity but decreased with speed ratio, and soil reaction torque increased with both longitudinal velocity and speed ratio. Total power required by the tool increased with speed ratio, and energy intensity increased with speed ratio and longitudinal velocity, with substantial changes observed at higher velocities. Abstract. Studying soil-tool interaction can provide valuable information on the actuation force and energy requirements of a weeding tool operating in soil. Soil-tine interaction was investigated for a vertical rotary tine tool that was intended to be used as a weeding tool for an automated mechanical intra-row weeder. The main objective of the research was to investigate the effects of linear and rotational velocities on soil reaction forces and power associated with actuation of the rotary tine tool in soil. A series of soil bin experiments were conducted in loam soil. Soil horizontal (draft) force and torque on the tool were measured at three longitudinal/travel velocities of 0.09 m s-1, 0.29 m s-1, and 0.5 m s-1 that were used to move the tool linearly across the soil bin length. The speed ratio, defined as the ratio of the longitudinal velocity to the peripheral velocity of the rotary tines, determined the rotational speeds required for the study. The draft force and torque were evaluated at four speed ratio levels (0, 1, 1.5, and 2). An Analysis of Variance (ANOVA) performed for statistical analysis using p < 0.05 showed that both longitudinal velocity and speed ratio had significant main and interaction effects on the draft force and torque. In most cases, the draft force decreased while torque increased with increasing speed ratios for the different longitudinal velocities used in the study. Power and energy intensity were also calculated using draft force and torque measurements for different experimental settings. For increases in speed ratios, the power requirements for tool draft force decreased, whereas the power requirements for rotating the tool increased for each longitudinal velocity. At the highest test travel speed of 0.5 m s-1, the power decreased from 66 W to 28 W for draft and increased from 0 W to 76 W for rotation of the tool at increasing speed ratios. The maximum total power calculated for the tool was 110 W at 0.5 m s-1 and a speed ratio of 2. The study shows the changes in power and energy requirements of a vertical rotary tine tool for different operating parameters for weed control. This information could be valuable for optimizing the physical weeding process. Keywords: Energy intensity, Power, Rotary tool, Soil-tine interaction, Weed control.

SIMULATION OF VIBRATORY PLATE INTERACTION WITH THE GROUND SURFACE

The paper presents a three-mass rheological model of the system "soil – vibration plate base – vibration plate frame". The rheological model makes it possible to reproduce different modes of interaction between the vibratory plate base and soil: with different types of plate decoupling and without decoupling. We verify this model by comparing the experimental values of the vertical oscillation span of the base and frame of the Zitrek CNP 20 vibrating plate with the previously calculated values. As a whole, the calculated values of the span of vertical oscillations of the base and frame of the Zitrek CNP 20 vibrating plate correlate with the experimental data in the range of the dynamic modulus of soil deformation of 13…30 MPa. During the experiment we used the rheological model and obtained results are as follows: the mass of the vibrating plate (50; 150; 250; 350; 450; 550; 650; 750 kg), the coefficient of the elastic resistance of soil (30; 60; 90; 120 MN / m), and the coefficient of viscous resistance of soil (100; 200; 300 kN • s / m). The total number of combinations of parameters was 96. The processed results of the computational experiment provide the regression dependences for calculating the maximum soil reaction force, the time of soil loading (increasing the values of the reaction force of soil) t1, and the time of soil unloading (decrease the values of the reaction force of soil) t2. The simulation results show that, within one exposure cycle, the soil loading time t1 is less than the soil unloading time t2. The ratio t1/t2 is influenced by the weight of the vibratory plate, as well as the factors of elastic and viscous resistance of soil. This feature (t1/ t2  1) is typical for both vibratory rollers and rammers, which is confirmed by the results of the relevant experimental studies. The obtained regression dependences of parameters Fs, t1, and t2 on the vibratory plate mass and the factors of elastic and viscous resistance of soil are important for calculating the distribution of stresses and strains on the depth of the compacted soil.

PENGUKURAN GAYA REAKSI TANAH DENGAN SATU BUAH SIRIP RODA SANGKAR TRAKTOR TANGAN DI BAK PENGUJIAN TANAH

The ability of a cage wheel to climb slopes depends on the grip of the lug on the sloped soil. A lug wheel that sinks deeper will generate more force when climbing. This study aimed to measure the soil reaction force on a single flat lug wheel in the slope soil bin so that the optimal lug angle is obtained to enhance the ability of cage wheels to climb sloped soil. The experiment was carried out using a model of a single flat lug wheel (length of 10 cm, width of 3.5 cm, radius of 30.4 cm, and slope of 30o). Measurements of soil reaction forces on the lug were carried out on five lug angles (-15o, 0o, 15o, 30o, 45o) at three various sinkage depths (2.5 cm, 5 cm, 7.5 cm) at a rotational speed of 11 rpm. The moisture content, density, porosity used in this study were 45.61% (d.b.), 1.02 (g/cm), 44.02%. In addition, the particle size distribution of sand, clay, and silt are 8.038%, 13.396%, and 78.564%, respectively. The limits of soil consistency used in this study, including the plastic limit, water limit, and index limit, were 64.57%, 80.86%, and 16.29%, respectively. A set of measurement and data logger equipment is used to measure the reaction forces of the soil. The results showed that at the angles of -15 and 0 the lugs were able to penetrate the soil faster and deeper to produce a greater pulling force. This implies that a smaller angle of inclination will be more beneficial to the tractors wheel applied for climbing than a greater angle of inclination.

Parametric analysis and numerical optimisation of Jerusalem artichoke vibrating digging shovel using discrete element method

Commercial potato harvester is inefficient in harvesting Jerusalem artichokes due to the vast development area of tubers in the soil and the wide-ranging sizes and shapes, some growing up to a depth of about 35 cm. Harvesting artichoke tubers, mainly at such deep depth, is problematic, necessitating optimisation of parameters for the harvesting operations to account for the effect of soil-tool dynamics on the digging performance. However, vibration can substantially reduce soil reaction forces and increase the soil-crushing effect, improving harvesters’ production efficiency. Therefore, the effect of travel speed, vibration frequency, amplitude, and rake angle and the shovel geometry on soil reaction forces, drawbar power, and Archard wear were studied using the discrete element method (DEM) and response surface methodology (RSM) at a targeted shovel’s operating depth of 35 cm. Laboratory experiments of the static angle of repose and cone penetration tests were successfully used to calibrate the soil model using multi-sphere particles. Also, Design-Expert® Software (2021) version 13 was used to determine the optimised geometry design and operating parameters values from the soil-to-shovel interaction simulation based on numerical optimisation and desirability functions procedure. Two optimal solutions were obtained, with the first one having 0.556 m s− 1 speed, 13.864 Hz frequency, 20 mm amplitude, 15˚ rake angle, and S-shape geometry. Contrariwise, the second solution was at the same geometry design with 1.111 m s− 1 speed, 20.300 Hz, 20 mm amplitude, 15˚ rake angle. Analysis of variance showed that all the individual factors influenced draught force, vertical force, and drawbar power. However, only frequency, amplitude, and geometry design significantly influenced Archard wear. Soil reaction forces increased with increasing speed. Vibration significantly affected soil reaction forces by reducing draught force and vertical force by 43.61% and 36.67%. DEM and RSM are effective techniques for designing and optimising soil-engaging implements.

Model tests on horizontal load-bearing and deformation resistance capacities of pile-bucket foundation in soft seabed soil

Large-diameter pile-bucket foundations are a new type of foundation used for offshore wind turbines. In this study, model tests were performed on pile-bucket foundations to investigate their load-bearing and deformation resistance capacities. The strains of the pile and bucket and the horizontal displacements at the loading point were measured using strain gauges and displacement transducers, respectively. The variations in moments of the pile and bucket with depth were calculated and fitted into polynomial functions of sixth to eighth orders. Based on the moment polynomials, the distributions of the horizontal displacements and soil reaction of the pile and bucket were determined according to the beam bending theory. Improvements in the load-bearing and deformation resistance capacities were quantitatively determined by comparing the test results for the pile-bucket foundation with those of the monopile foundation. The initial stiffness and ultimate horizontal bearing capacity of the pile-bucket foundation were 50% and 20%, respectively, higher than those of the monopile foundation. For sections within the bearing depth of the bucket, the ultimate soil reaction force of the pile-bucket foundation was 20 times that of the monopile foundation. However, a 10%–20% improvement in the ultimate soil reaction was observed for deeper sections.

Analysis of effect of bentleg opener geometry on performance in cohesive soil using the discrete element method

Bentleg furrow openers can significantly reduce soil disturbance and reaction forces relative to conventional narrow point openers used in no-tillage farming. The effect of bentleg opener geometry on soil disturbance and reaction forces in a cohesive soil was assessed in a virtual soil bin using the discrete element method. Soil disturbance and reaction forces at an operating depth and a speed of 100 mm and 8 km h −1 , were shown to be minimised by using (1) a shank lateral offset of 70 mm, (2) a side leg bend angle that ensures the elbow, which is the transition between the side leg and vertical shank, is not located below the soil surface, (3) an arched instead of angled elbow, (4) a cutting edge chamfer angle as low as practical, and (5) tine thickness as small as practical. Furrow size was found to be more dependent on shank lateral offset and side leg bend angle than side leg forward angle. Though side leg forward angles >90° reduce particle displacement and will work better in fields with stones and roots, they also considerably increase draught and penetration resistance. A low rake angled foot minimises soil reaction forces and drives soil loosening. Reducing foot height and interaction of the vertical shank with soil particles minimises surface soil displacement. These results have expanded the understanding of bentleg opener mechanics and are in close agreement with those reported for sandy soils. Therefore, similar criteria can be followed to optimise bentleg opener design for different soil types. • Discrete element method predicted bentleg opener geometry effects in Black Vertosol. • Geometries that cause minimum soil disturbance and reaction forces were identified. • Shank lateral offset should be large and arched elbow protrude above soil surface. • Cutting edge chamfer angle and thickness as small as practical are recommended. • Low foot rake angle and foot height reduce soil forces and soil throw, respectively.

Analysis of effects of operating speed and depth on bentleg opener performance in cohesive soil using the discrete element method

High operating speeds are desirable, different seeding depths are required, and low soil disturbance is necessary for sowing in no-tillage farming. The effects of operating speed (8–16 km h−1) and depth (60–120 mm) on bentleg opener (four variations) performance were analysed in comparison to straight openers in a virtual soil bin using the discrete element method (DEM). Generally, increasing operating depth and speed resulted in increased soil disturbance and reaction forces. However, the bentleg openers loosened furrows down to the furrow bottom and caused less lateral soil throw at all operating depths and speeds. Bentleg openers, particularly without foot, increased furrow width by lower magnitudes compared with straight openers as operating speed was increased. The greatest lateral soil throw beyond furrow banks recorded for the bentleg openers at operating speed and depth of 16 km h−1 and 60 mm were less than the least for the straight openers, except for the footless bentleg with forward raked side leg. Backward raked side leg had the lowest impact on lateral soil throw and spill over distance with increasing operating speed. Increasing operating speed shifted the main ridge created by the bentleg openers above the furrow’s centre outward to the left. Furrow backfill of 97–100% was achieved with the bentleg openers. Bentleg openers with 45° foot rake angle required the lowest draught and vertical forces. Backward raked side leg resulted in the highest draught force among the bentleg openers and the greatest vertical (penetration) force among all the openers.

Next-generation NATO reference mobility model complex terramechanics – Part 1: Definition and literature review

The US army along with NATO member and partner nations’ militaries need an accurate software tool for predicting ground vehicle mobility (such as speed-made-good and fuel-consumption) on world-wide terrains where military vehicles may be required to operate. Currently, the NATO Reference Mobility Model (NRMM) is the only NATO recognized tool for assessing ground vehicle mobility. NRMM was developed from the 1960s to the 1980s and relies on steady-state empirical formulas which may not be accurate for new military ground vehicles. A NATO research task group (RTG-248) was established from 2016 to 2018 to develop the NG-NRMM (next-generation NRMM) software tool requirements and an NG-NRMM prototype which uses high-fidelity “simple” or “complex” terramechanics models for the terrain/soil along with modern 3D multibody dynamics software tools for modeling the vehicle. NG-NRMM Complex Terramechanics (CT) models are those that utilize full 3D soil models capable of predicting the 3D soil reaction forces on the vehicle surfaces (including tires, tracks, legs, and under body) and the 3D flow and deformation of the soil including both elastic and plastic deformation under any 3D loading condition. In Part 1 of this paper, an overview of the full spectrum of terramechanics models from the highest fidelity to the lowest fidelity is presented along with a literature review of CT ground vehicle mobility models.

Analytical description of the interaction process of a rigid vibratory drum with a compacted surface using the general dynamics equation

This study has solved the task of creating the theory of the soil compaction by a rigid vibratory drum on the basis of the usage of the general dynamics equation. When rolling over the deformable soil the vibratory drum performs a compaction operation and represents a mechanical system that is influenced by stationary dynamic forces. A design diagram has been created for the consideration of dynamic interaction processes of the vibratory drum with the compacted soil, where the main parameters are represented by the angle α of the vibratory drum interaction with the soil, angle β of the inclined plane, which simulates the vibratory drum resistance rolling during the soil compaction and vibratory drum geometric parameters. The general dynamics equation allows to obtain an analytical solution of the problem of the vibratory drum interaction with the soil in the form of the sum of elementary works of the tractive force T, load Q on the wheel axles, soil reaction forces on the vibratory drum, and rolling resistance forces. The solution is presented in the equation form of the sum of the elementary works of all the indicated forces, which is equal to zero. Analytical dependences of the vibratory drum rolling moment, rolling resistance force and vibratory drum rolling resistance coefficient over the deformable soil in relation to construction soils of the 1st – 4th strength categories have been obtained. The obtained results can be used when designing vibration rollers for the compaction of deformable media.

Modeling Soil Forces on a Rotary Tine Tool in Artificial Soil

HighlightsA mathematical model of soil reaction forces on a rotary tine tool was developed.Soil bin experiments using artificial soil enabled observation of soil failure due to soil-tine interaction.The model-predicted forces were similar to experimentally measured forces.Abstract. Understanding soil-tool interaction can enable better control of weeding tools to achieve higher weeding efficacy. The interaction between a vertical tine (mounted on a rotating disc) and soil was investigated using a mathematical model that estimated soil horizontal forces on the tine operating at different linear and rotational velocities. The kinematics associated with the linear and rotational velocities of the rotary tine tool were modeled, and the shearing and inertial forces were estimated. To evaluate model performance with different experimental factors, two sets of soil bin experiments were conducted using an artificial soil: with one tine to estimate model parameters and with two tines 180° apart. Experimental factors were longitudinal velocity (travel speed) at three levels (0.09, 0.29, and 0.5 m s-1) and speed ratio, i.e., the ratio of longitudinal velocity to peripheral velocity of the tines, at three levels (1, 1.5, and 2). Soil horizontal force and torque on the rotary tine tool were measured. A nonlinear least squares method was used to estimate model parameters from the experimental data, resulting in shearing force coefficients ranging from 2.9 to 37 N and inertial force coefficients ranging from 16 to 528 N s2 m-2. The variations in the shearing and inertial forces on the tine were due to differences in soil failure patterns among the treatments. The predicted longitudinal and tangential forces for two tines using the model showed trends that were similar to the forces measured in the experiment. However, the model overestimated the predicted forces because it did not account for the reduced force on a tine due to soil disturbance created by the other tine. Keywords: Soil-tine interaction, Weed control.

Modeling soil-bulldozer blade interaction using the discrete element method (DEM)

Limited studies have been conducted to establish scaling relationships of soil reaction forces and length scales of bulldozer blades using the Discrete Element Method (DEM) technique. With a DEM-based similitude scaling law, performance of industry-scale blades can be predicted at reduced simulation efforts provided a calibrated and validated DEM soil model is developed. DEM material properties were developed to match soil cone penetration testing. The objectives of the study were to develop a DEM soil model for Norfolk sandy loam soil, establish a scaled relationship of soil reaction forces to bulldozer blade length scales (n = 0.24, n = 0.14, n = 0.10, and n = 0.05), and validate the DEM-predicted soil reaction forces on the scaled bulldozer blades to the Norfolk sandy loam soil bin data. Using 3D-scanned and reconstructed DEM soil aggregate shapes, Design of Experiment (DOE) of soil cone penetration testing was used to develop a soil model and a soil-bulldozer blade simulation. A power fit best approximated the relationship between the DEM-predicted soil horizontal forces and the bulldozer blade length scale (n) (R2 = 0.9976). DEM prediction of soil horizontal forces on the bulldozer blades explained the Norfolk sandy loam soil data with a linear regression fit (R2 = 0.9965 and slope = 0.9634).

Strength-based design analysis of a Para-Plow tillage tool

In this research, experimental field tests and an advanced computer aided design and engineering (CAD and CAE) based application algorithm was developed and tested. The algorithm was put into practice through a case study on the strength-based structural design analysis of a Para-Plow tillage tool. Para-Plow is an effective tractor attached tillage tool utilised as an alternative to the conventional deep tillage tools used in agricultural tillage operations. During heavy tillage operations, the Para-Plow experiences highly dynamic soil reaction forces which may cause undesired deformations and functional failures on its structural elements. Here, prediction of the deformation behaviour of the tool structure during tillage operation in order to describe optimum structural design parameters for the tool elements and produce a functionally durable tool become an important issue. In the field experiments, draft force and strain-gauge based measurements on the tool were carried out simultaneously. Subsequently, Finite Element Method based stress analysis (FEA) were employed in order to simulate deformation behaviour of the tool under consideration of the maximum loading (worst-case scenario) conditions tested in the field. In the field experiments, average and maximum resultant draft forces were measured as 33,514 N and 51,716 N respectively. The FEA revealed that the maximum deformation value of the tool was 9.768 mm and the maximum stress values impart a change on the most critical structural elements of between 50 and 150 MPa under a worst-case loading scenario. Additionally, a validation study revealed that minimum and maximum relative differences for the equivalent stress values between experimental and simulation results were 5.17% and 30.19% respectively. This indicated that the results obtained from both the experimental and simulation are reasonably in union and there were no signs of plastic deformation on the Para-Plow elements (according to the material yield point) under pre-defined loading conditions and a structural optimisation on some of the structural elements may also be possible.This research provides a useful strategy for informing further research on complicated stress and deformation analyses of related agricultural equipment and machinery through experimental and advanced CAE techniques.