Notes

Outline

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INTRODUCTION Increasing interest in mechanized logging in PNW as harvest  of second growth increased

PREVIOUS STUDIES Economic advantages: Cut-to-length system produced wood at a lower cost compared to skidders (Greene et al. 1987) Cut-to-length system followed by tractor and skyline in logging planning and layout cost (Kellogg et al. 1998)

Soil Disturbance Excessive machine downtime Relocation of operation Extra cost of increased stockpiling of timber Increased manpower for building stockpiles Reduction in wood quality in stockpiles Increased processing costs

Objectives Developing a model that minimizes the sum of road construction costs plus forwarding costs with the constraint that rut depth caused by the forwarder cannot exceed a maximum depth during the anticipated season of operation

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

Wheel Sinkage NGP = 2000´W/(b´d) b = tire width (mm) d = tire diameter (mm) W = dynamic wheel load (Newton)

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

Slash Adjustment NGP is adjusted due to slash laid on trails (Wronski et al. 1994): Fs =1/(0.0033´SD + 0.93) Fs = slash adjustment factor SD  = slash density

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

MODEL DESCRIPTION Model Assumptions Forwarding Operation Optimum Road Spacing Minimizing Total Cost Loading and Unloading (Constant Activities) Traveling inhaul and outhaul (Variable Activities) Cumulative Rut Depth

Model Assumptions Two-way forwarding is possible

MODEL DESCRIPTION Model Assumptions Forwarding Operation Optimum Road Spacing Minimizing Total Cost Loading and Unloading (Constant Activities) Traveling inhaul and outhaul (Variable Activities) Cumulative Rut Depth

Forwarding Operation

MODEL DESCRIPTION Model Assumptions Forwarding Operation Optimum Road Spacing Minimizing Total Cost Loading and Unloading (Constant Activities) Traveling inhaul and outhaul (Variable Activities) Cumulative Rut Depth

Optimum Road Spacing

MODEL DESCRIPTION Model Assumptions Forwarding Operation Optimum Road Spacing Minimizing Total Cost Loading and Unloading (Constant Activities) Traveling inhaul and outhaul (Variable Activities) Cumulative Rut Depth

Minimizing Total Cost Min Total Cost = Road Cost + Forwarding Cost subject to : S Rut depth < Max Rut depth

MODEL DESCRIPTION Model Assumptions Forwarding Operation Optimum Road Spacing Minimizing Total Cost Loading and Unloading (Constant Activities) Traveling inhaul and outhaul (Variable Activities) Cumulative Rut Depth

Constant Activities Loading and Unloading Cost ($/m3) = MR ($/min) ´ Cycle time (min) / Load (m3)

MODEL DESCRIPTION Model Assumptions Forwarding Operation Optimum Road Spacing Minimizing Total Cost Loading and Unloading (Constant Activities) Traveling inhaul and outhaul (Variable Activities) Cumulative Rut Depth

Variable Activities Cost of traveling inhaul plus outhaul ($/m3) = MR ($/min) ´ Cycle time (min) / Load (m3)

Vehicle Speed Rolling Resistance(Newton) (Ashmore et al. 1985): RR = W ((0.22/Cn)+0.20-0.10 (W/WR))

MODEL DESCRIPTION Model Assumptions Forwarding Operation Optimum Road Spacing Minimizing Total Cost Loading and Unloading (Constant Activities) Traveling inhaul and outhaul (Variable Activities) Cumulative Rut Depth

Cumulative Rut Depth Updating Cone Index (Brixius, 1988):

Cumulative Rut Depth (Continued) ZFirstTrip= Z1+Z2+Z3+Z4 Initial: CI, Mobility, ACI Z1= Rut depth caused by the rear tire unloaded Update: BCI, Mobility, ACI Z2 = Rut depth caused by the front tire unloaded Update: BCI, Mobility, ACI Z3 = Rut depth caused by the front tire loaded Update: BCI, Mobility, ACI Z4 = Rut depth caused by the rear tire loaded S Z = ZFirstTrip + ZSeconTrip + ZThirdTrip +…+ ZnthTrip If S Z > Zmax  =>

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

Model Application Max. Z < 150 mm

Data Range Rut depth tested from 100 mm to 500 mm

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

RESULTS Cycle time and cost summary of constant activities:

RESULTS (Continued) The total cost summary for the forwarders:

RESULTS (Continued)

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

DISCUSSION The large forwarder equipped with wider tires produced larger contact area

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

CONCLUSION A decrease in trail spacing requires a longer trail distance to accumulate a load and leads to an increased road spacing to minimize costs

CONTENTS Soil Trafficability Wheel Sinkage Slash Adjustment Model Description Model Application Results Discussions Conclusion Future Studies

FURTHER STUDIES Field study on ability of slash to distribute the weight of the machine after passage of each tire (Before Fs, After Fs) Developing additional regression equations for tire deflection under various tire inflation pressures to investigate the effect of tire pressures on soil strength

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