Some aspects of the use of labour - intensive methods for road construction

Ulj Ae- "SOME ASPECTS OF THE USE OF LABOUR-INTENSIVE METHODS FOR ROAD CONSTRUCTION" By P. A. GREEN t & PETER D. BROWN ft CONTENTS Page 1. Introduction .. 36 2. System of Analysis .. 36 3. Construction Methods Available .. 39 4. Incentives and Supervision . . 42 5. Productivity & Costing .. 46 6. Cost Comiparisons for Selected Tasks .. 64 7. Break-Even Wage Rates .. 67 8. Other Factors Affecting Choice of Technology .. 72 9. Conclusions .. 73 SYNOPSIS This Paper to some extent complements that submitted to the Congress by the IBRD (World Bank). Based on field stuclies carried out on behalf of the IBRD, mainly in Indlia and Tiidonesii, the Paper summarises some of the more important engineerinig findings, with particular reference to road construction in In dia. The Paper describes the syslenm developed and used to measure and to analyse the produictivities and costs of a project, and lists the range of methods available to the enginieer for the more impo-rlailt activities anrd taslks in road construction. It has been found that, once the elTects of certain specific parameters have been eliminated, the variation in labour productivity data between different groups of workers and between different sites can be largely explained by variations in incerilives and uLIpervisioni; a relation between these two factors and scatter of proLILclitvity data is formulated. ProdLctiC'iyV and cost data for importanit activities is given for labour, animals anid eqIuipment and for intermediate methods using combinations of these three, alonii, xvith a brief mention of possible ways of increasing productivities investigat- ed, during the study. Costs of alternative methods for select'ed tasks are compared, + Partner, Scott \\'ilsoil Kirkpatrik and Partners, Consulting Engineers, Ba.i'iqbtlok., U.IK. it Assi4.Lml Eimiiicoer. Scott Wilson I<irkpatrick and Partners. hi 7.  36 GREEN & BROWN ON at typical Indian wage rates, and the concept of a 'break-even' wvage is discussed, with particular regard to eartlhworks, arqiregale productioni and haulage of road materials. The IPaper concludes with a brief mention of otlher factors, includinig road design, wlhich have an important bearing upon the choice of technology. 1. INTRODUCTION 1 . l. Labour-intensive construction methods in road buildings have been wVidely used in India for many years, but in other parts of the world (excluding the Republic of China) equipnment-intenisive methcds have predominated. The recent and very rapid growth of population in many less developed countries has created a serious unemployinent problem, leading politicians, economiiists, engineers and planners to examine the potential for efficient use of men instead of machines in civil construction. 1.2. This Paper summarises some of the more important engineering findings from a Study of the Substitution of Labour and Equipment in Civil Construction (" the Study ") carried out on behalf of the IBIRD (World Bank) with particular relevance to road construction in India of. By way of cost comparisons based on observations and experiments carried out during the Study, some conclusions are drawn as to which construction tasks are best suited to labour-intensive methods ; possible means of improving labour productivity are described briefly, and the role of intermediate technology is identified. Manual and interme- diate methods of course have a better chance of success if the project is designed with such methods in mind, and the Paper ends with some notes on the relationship between design and choice of technology. 2. SYSTEN; OF ANALYSIS 2.1. In the analytical framework set up in the Study to measure productivity and cost data, a project is usually broken down successively into sub-projectst, operations, tasks and activities. A sub-project is a section of work coming under the 0 However, thle views expressed in this Paper are those of the Authors and not necessarily those of thle World Bank. t Full -letails of the Study findings can be found in a series of Technttical ,Aellnorunclu published by the \Vorld Bank, a list of wlhich Is appended to the Paper presented by the Bank to this same Session of the Inidian Roads Congress. : \Words printed in italics thle first time they appear in the text have specifically defined rneanhiigs in the Study.  USE OF LABOUR-INTENSIVE METHODS FOR 37 ROAD CONSTRUCTION conitrol on one site enigineer and encomiipassing one or two seasons' work, Operatiol7s are jobs which can be carried out indepen- dtently of one another in time, the important operations in a road project comprising -site clearance - earthworks -sub-grade improvement (niutrum or gravel course) -Rslb-base conistruction -base constructior - surfacing - drainiage workst - structutres (bridges anid major culverts)- A task is the smallest description of work which can be performed by an independent group of resources, for example the earth- wVorks operation may consist of two tasks: (a) excavate soi! from borrow to fill, spread and dress, all of which can be done by a ganig of labotir on thle one lhand or by a gang of dozers, scrapers and graders on the other; (b) water and comripact fill material, which may require a wrater tanker and roller operatinig together. Tasks miiay be split into comiiponent activities, in the case of task (a) above, for example: - excavate soil - load (headbasket, wlheelbarrow, scraper, etc.) - haul (i.e., transport or ' lead ') -unlloadl -spread (inieluding dresshig2) 2.2. The produtctivity of a task or an activity is the ratio of the ouztptut to the inzput. The OlutpUt is the quantity of work donie, ilsasured in cubic metres, tonnes, litres or square metres, etc. The input is a measure of the resource-tinie spent in doing the work, for examiple iiman-hours or mail-days, specified in terms of either total time (TT), available time (AT) or workilng time t Structural and drainage works hiave not been givenl muchi colnsideration in the Study.  38 GREEN & BROWN ON (WT)'. It is conivernient to express productivity as its invterse, that is as all inpIt coefficietnt, e.g. - ian-hour (\WT)/cu.rm. or - dozer-lhour (AT)/tonne. 2.3. Prodtuctivity of both mnen and machines is strongly influenced by various conditions which are described as pal- meters. These fall generally into three categories, the first two of wvhich are measurable: (a) genteral paramiieters, wlich apply to all tasks (b) specific paraleters, applying to specific tasks and activities only (c) side paramiieters, which are not readily measurable, or if ineasrll'able, are difficult to apply.t * Total Tilune is defined as either the hours during whiclh the resource is involved in the work process, or the hours during wlhich work on site would normally be done, It is generally assumed that the alternative giving the largest number of hours applies. No time outside ' working houirs ', such as niglht time and official meal breaks, is iuchlded in total time unless it is aclually used for doing work. Total time divided is into lost time and available litiie. Lost Tilune occasions during total time when production may not be practical or possible are called lost time. Included in this are stoppages due to maclhine breakdown, severe climatic conditions, strikes, epidemics etc. Available Titme (AT) = Total Time (TT) - Lost time (LT). Available time divided into working timiie (WT) anc non-worlking tilmie (NT). Nonz-working Time is any time durinig available time when the resource being considered is fulfilling no useful purpose as far as the progress of work is concernecl and is temporarily not involved in the work process. Non-Working time includes starting work late, finishing work early or time spent waiting for another resource to complete a piece of work where the wait could have been avoided. Non-working time does not include necessary rest fr time spent, on ancillary tasks (whichi are often essential to the conistruction process) such as fetching water, repairing tools, listening to instructions and walking to the next job site ; nor does it include delays to vehicles wvaiting while loading. IW'orkitng Tine (WT) - Available Time (AT)-Non-Working Time (NT). t The full list of parameters is given below: Getieral Paramileters Specific Paramleters Site Paraln eters Air temperature Soil/rock Reduction Health and Type of work Relative huinidity lhardness factor nutritioni Terrain Payment method Loading hieiglht Rock hardness Traditional Rainfall Haul distance In-situ density skill ltLiltIde (lead) Loose density Local customs Traflic inter- Haul route rise Compacted Equipment ference (lift) or fall denisity condition Supervision HaLul route Maintenance Labour condition level Spares relations .ul~itbiIil, Type of contract Trainin1g on site  USE, OF LABOUR-INTENSIVE ME1THODS FOR 39 R,OAD CONSTRUCTION 3. CONSTRUCTION METHODS AVAILABLE 3.1. Even the most labour-intensive construction methods employ a little capital in the form of hand tools, while the most equipment-intensive mnethods require operators. In between the two extremes lie miiany techniquies employing larger amounts of both equlipment and labour, so there is no clear dividinig line between labour-and equipment-intensive methods. For the purposes of this Paper, however, three categories of method are distinguished: (1) Equipinent-lniensive methods employ no unskilled labour except in pLurely ancillary capacity, for instance for dressing of slopes cut by dozer. (2) Labour-inlensive methods involve nothilng more than hand tools. (3) Iite-inediate methods employ a certain amount of capital to aid or replace labour in a part of a task which can be least efficiently done by an unaided labourer. They may involve one or more of the following (a) siUn1ple equtipmiienit, manually powered, suclh as hand-operated rop) ^i ' s ancd rail systems (b) uNinals with or without items of 'simple equipment' such as carts; (c) imiixett resouirces wvhere labour and machines work together, for instance hand-loaded trLucks or tractor/trailers. While xwheelbarrows are often classified as hand tools, they are treated in this Paper as simple equipment. 3.2. Based on the above definitions, a selection of methods whichl are teclhnically feasible-t for the more important activities and tasks in road construction are listed in Table 1. Methods w1lich hla\e little relevance to India are ignored. t Note that there is no sharp dividillg line L'ti Wct0Ii the meanings of teclnical and econiomic fcjililiv, Those methods are igniored wlich could in theorv be usedl to do a job according to bltiis.ati(,I1s hut wlich are so uneconomic that no practical man wouild eve- consider LuSilng them0l.  TABLE I A\A\ILABLE CONSTRUCT'ION MIETHODS Actijitt or Task Laboir-Intensive Intermediate Methods Equipment-Intensive Meths Methodis Excavation of soft soil j Hoe1 A \\'Iieeled Scraper