Forest road planting and control by mathematical programming and time study analysis

Abstract

Planning and construction of forest roads have until very recently been geared towards establishment and tending of plantation forests. Now that most of the plantations are nearing maturity, it is essential to plan and construct proper roads for harvesting purposes. Hi is study was designed to develop a comprehensive methodology that can be used by forest managers in the planning and control of forest roads. Specifically, the objectives of the study were: - To evaluate the application of mathematical programming methods to the design of safe and minimum-cost forest roads - To test the feasibility of improving and controlling forest­ road construction by mathematical programming - To develop a comprehensive methodology for measuring and estimating production rates and costs associated with forest road construction. To be able to plan, execute and control work operations for this study, a representative 1.3 km access road was planned and constructed at the Training Forest of the Sokoine University of Agriculture between February 1981 and May 1984. A number of mathematical models and time study methods were tested and incorporated in this study in order to develop a comprehensive methodology aimed at improving plan­ ning, control and cost estimation procedures. Based on the results of this study, the following observatxons and conclusions are made;Planning and construction of forest roads have until very recently been geared towards establishment and tending of plantation forests. Now that most of the plantations are nearing maturity, it is essential to plan and construct proper roads for harvesting purposes. Hi is study was designed to develop a comprehensive methodology that can be used by forest managers in the planning and control of forest roads. Specifically, the objectives of the study were: - To evaluate the application of mathematical programming methods to the design of safe and minimum-cost forest roads - To test the feasibility of improving and controlling forest­ road construction by mathematical programming - To develop a comprehensive methodology for measuring and estimating production rates and costs associated with forest road construction. To be able to plan, execute and control work operations for this study, a representative 1.3 km access road was planned and constructed at the Training Forest of the Sokoine University of Agriculture between February 1981 and May 1984. A number of mathematical models and time study methods were tested and incorporated in this study in order to develop a comprehensive methodology aimed at improving plan­ ning, control and cost estimation procedures. Based on the results of this study, the following observatxons and conclusions are made;Planning and construction of forest roads have until very recently been geared towards establishment and tending of plantation forests. Now that most of the plantations are nearing maturity, it is essential to plan and construct proper roads for harvesting purposes. Hi is study was designed to develop a comprehensive methodology that can be used by forest managers in the planning and control of forest roads. Specifically, the objectives of the study were: - To evaluate the application of mathematical programming methods to the design of safe and minimum-cost forest roads - To test the feasibility of improving and controlling forest­ road construction by mathematical programming - To develop a comprehensive methodology for measuring and estimating production rates and costs associated with forest road construction. To be able to plan, execute and control work operations for this study, a representative 1.3 km access road was planned and constructed at the Training Forest of the Sokoine University of Agriculture between February 1981 and May 1984. A number of mathematical models and time study methods were tested and incorporated in this study in order to develop a comprehensive methodology aimed at improving plan­ ning, control and cost estimation procedures. Based on the results of this study, the following observatxons and conclusions are made;(a) With some modifications (in order to fit them to local conditions), the standard engineering procedures used for road design, layout and culvert size determination proved to be fully satisfactory for use in Tanzania. (b) Detailed time and work analyses conducted during the study resulted in the establishment of production rates and costs of forest road construction in Tanzania. (c) Microcomputer-based linear programming and a transportation tableau method were shown to be equivalent in determining optimal allocation of earthwork during forest road planning. Because it can be done by hand without recourse to a micro­ computer, however the transportation tableau method is the one likely to be favoured and adopted by most forest projects in Tanzania. (d) Before the actual road construction starts, the distance between net cut and net fill areas can be used as a surrogate for earthwork cost to determine the optimal road design. The study found that the design alternative selected on the basis of minimum earth moving distance was also the one that mini­ mized earthwork cost. (e) A distance of 30 m between instrument stations along the road appears to provide better accuracy for road layout and design than using either intervals of 60 m or utilizing "terrain breaks" to define instrument stations. In this study, both of these latter interval lengths provided data (a) With some modifications (in order to fit them to local conditions), the standard engineering procedures used for road design, layout and culvert size determination proved to be fully satisfactory for use in Tanzania. (b) Detailed time and work analyses conducted during the study resulted in the establishment of production rates and costs of forest road construction in Tanzania. (c) Microcomputer-based linear programming and a transportation tableau method were shown to be equivalent in determining optimal allocation of earthwork during forest road planning. Because it can be done by hand without recourse to a micro­ computer, however the transportation tableau method is the one likely to be favoured and adopted by most forest projects in Tanzania. (d) Before the actual road construction starts, the distance between net cut and net fill areas can be used as a surrogate for earthwork cost to determine the optimal road design. The study found that the design alternative selected on the basis of minimum earth moving distance was also the one that mini­ mized earthwork cost. (e) A distance of 30 m between instrument stations along the road appears to provide better accuracy for road layout and design than using either intervals of 60 m or utilizing "terrain breaks" to define instrument stations. In this study, both of these latter interval lengths provided data which tended to u. i erestimate actual road construction cost by about 30 Z. (f) The influence of road grade and alignment on log-truck haul­ ing speed can satisfactorily be determined through the prin­ ciples of engineering mechanics. For instance, when deter­ mining the hauling speed over a given road with a good number of sharp curves, time to decelerate into and accelerate out of the curve, the designed curve speed and the maximum safe speed have to be considered. (g) Of three road grade alternatives analysed in this study (6 Z, 8 Z and 10 Z), the 8 Z maximum grade recommended by the Forest Division was found to be the grade that minimized the total of earthwork and hauling costs. (h) The use of the critical path method during culvert installa­ tion resulted in the reduction of total installation time by about 28 Z. (i) Road construction is an expensive undertaking, but costs can be reduced to about 1/3 to 1/2 of those estimated by road contractors if proper applied. planning and control procedures are The construction cost of this research road was found to be shs 220 587/km, with earthwork and gravelling operations taking 33 Z and 30 Z of the total construction costs respectively, while road alignment/clearing and culvert installation took 24 Z and 13 Z respectively.In addition to these conclusions, the methodological procedures described in detail in this thesis provide a foundation on which forest managers can base decisions related to the planning and cons­ truction of forest roads.