,~- [: {- TA I 111r; ur1r12fP This paper ia not for . publication. The views expressed are those ot the authors and not necessarily those of the World Bank. SECTORAL LIBRARY INTERNATIONAL ir,i.NK FOR RECONSTRUCTION AND DEVELOPMENT WRLD BANK STUDY OF THE SUBSTITlJTION OF LABOR AND EQUIPMENT IN CIVIL CONSTRUCTION MAY 301986 Technical Msnorandum No. 2 Increasin1 Output ot Hamal Excavation 13.7' Work Reorganization: An Example of Passing Place Construction on a Mountain Road January 1975 The paper demonstrates the need for prq:>er organization or labor-intensive tasks of civil construction. It is shown that for excavation and hauling activities, labor productivity can be increased two to three told with: i) proper work organization; ii) incentive payment methods; and iii) proper selection and maintenance of hand tools. · Work was carried out on a passing place construction on a mountain road in northern India. Using the improved organization and work procedures, output per man-hour for excavation and haulage of earth was increased ti:-om 0.11 cubic meters to 0.28 cubic meters. Transport Raaurch Division Transportation and Urban Projects !8partment (i) Preface This paper is one of a series of papers prepared in the course of the Study of the Substitution of Labor and Fiquipment in Civil Construction. The paper is prepared with the objective or genere.ting discussion on the results of the study as and when they are available. 'Iba conclusions or this paper are therefore tenitative and subject to revision in light or further field work and analysis. It is hoped that engineers would find these results useful in exeeutµig labor-intensive civil construction projects. Comments are solicited from all interested persons. This paper is based on the field work in India undertaken by Scott Wilson Kirkpatrick and Partners (consultants) in collaboration with the Director Genere.l of Border Roads. The overall study is directed by Inder K. Sud of the World Bank. Financial support tor the study is being provided by the World Bank and the Governments of Canada, Denmark, Federal Republic of Germany, Finland, Japan, Norway, Sweden, United Kingdom and the United States. I. IN'lmDUCTION I 1. Proper work organisation can have an important bearing on the productivity- of both labor and equipment. IJ:Tespective ot the lietbods employed, work lllUst be organized so that there is a minimum of interference •emong the various gangs ot labor (or equipment) and the different activities are scheduled to allow for smooth progress of work. In addition it is necas'sary ·to ensure that work procedures involve a minimum of wasted effort or men or machines. When equipment~intensive methods are used, the site engineers are {generally) conscious of the need for proper work organization ~- the main reason 'to?t this being that most construction equipment is "lumpy" in nature (i.e. high cost, high prodUctivity) : and therefore, inefficiencies in their utilization are apparent. On the other hand, orp.nization of labor-intensive works is generally neglected because of the not-so-obvious inetficienciesJlabor being a devisible, lqw unit coat resource. . In..JJtl.s paper, an exaaple of excavation along hillside _/ is given to demonstrate ho~lith simple work z,eorganization it was possible to significantly increase the . ,, ~abor productivi t7. 2. The work was carried out at a site in not,them India where a nwnber of passing places were being constructed on_ a 390 .km length or mountain road. . The . work consisted of cutting into -iba •hill to a depth of about 4 meters . and spoiling the excavated material down the slope of the road embanlanent. The dimensions of a typical passing place are glven Figure 1. With a aax::l.nrum. length of 27 .4 meters and width of 3.7 meters, the volume of excavation varies between 150-.350 cubic meters, depending on the ground profile. Some of the passing places were in ~.~~ and the othera were mainly- 1n soft rock. These were studied separately. ~ 'I • ~-- •. ll. EXISTING METHOOO OF CONSTRUCTION 3. All work was being c&J:Tied out b7 manual labor. A work gang of 20-25 men were daploy-ed at each site under the supervision of a ganger or mate. The gang was split into excavators and haulers. The excavation gang was using crow bars and shovels for excavation. Earth was being excavated and shovelled down the hillside where he,ulders could pick it up and move it across the road to spoil. The haulage gang was using a n.riet7 or haulage modes. These included manual carrying of rocks, shovels, two-man t.ra7 (stretcher), headpans and wheelbarrow. Work in progress on the construction o~ a passing place is depicted in Figu.re 2. 4. The passing place in soil required 260 113 or excavation and the complete task of excavation and haulage to spoil tor this output required a labor input of 2,450~-bours. The co""9aponding•figures for the passing place in soft rock were 165 m and 2,S7S man-hours respectively. A summary- of the data obtained over a period ot 20 daya at the tvo passing places is S\lllllarized 1n Table 1 • 1/ This is an impo:btant activity in construction of new roads across sidelong ground or in widening or existing mountain roads. -2- ra A -------------i7•4--------------. Hill side Excavation Existing Road Valley side PLAN SCALE 1:200 '' '' ' ' ',so• existing slope Batter 1 in 10 '' '' ' \ Valley side LH_JN-+---J·J -+-UJ Excgv. ation ~ Surfacing Sto,lder for Passing Place &Drain DIMENSIONS IN METR~S SECTION A-A SCALE 1: 100 Figure 1; Typical Passing Place Excavation -3- (a) Loaders and haulers for passing place in soft rock. t . / l I '. I . . .,-~ " ~ ::_\~~: _ /}~t '(b) Typical working arrangement for passing place in soft rock. (Note: excavators working above loaders/haulers) Figure 2. Existing Methods of Passing Place Construction Table 1 . Measured Outputs and Inputs for Existing Methods of Construction l Predominant Excavation Haulage I Material Type Productivity (m3 /man-hour) Pr~ductivity (m /man-hour) ' Parameters Soil 0.42 0.1, Haul length - 8.0 m Soft Rocle 0.18 0.10 Payment method - daily paid Rocle 0.19 - I .5. The following sources of inefficiency were re_cognized in the existing methods of construction: a) There was an improper balance between the excavators and the haulers. b) With excavators and haulers working simultaneously at the same stretch, there was some interference in their working as the haulers had to avoid being hit by the material being excavated above them. c) Excavation was being caITied out starting from the edge of the hill and moving into it. This required longer haul lengths than could be obtained if the work were organized differently (see para 6 below). d) The tools were generally of poor quality and were not being maintained properly. e) The labor was paid on a daily wage system which generally results in lower productivity. III. IMPROVED METHODS OF CONSTRUCTION 6. Bearing in mind the factors discussed above contributing to low labor productivity, tm following changes were introduced in the work organization, procedures, supervision and tools: Work Organization and Procedures a) Each passing place was divided into two sections. Excavation and hauling gangs were employed on different sections to avoid loaders being hit by falling boulders pried loose by the excavators, the relative positions of each group of workers being changed each day. -5- b) Excavation was planned to take pl ace in a series of benches world.ng generally from the upper levels downwards to allow the spoil to fall to the road level with a minimum of hauling on the slop~. This method of excavation :ts:_shown diagrammat- ically in Figure 3 and illustrated in practice in Figure 4. As can be seen from these figures, each step or bench is divided vertically into two parts. Excavation along half the length of the passing place was carried out while soil was being cleared from the other half. Tlrus there was a minimum of double handling, as excavation could usually start above a cleared section. c) With the use of benches, the mode of excavation was changed by allowing the laborers to face outwards and to excavate in front of and below their working posit ion ( see Figure 4) • In this way more effort could be applied to loosening the soil or rock. Tools d) The tools were maintained by regularly shal1)ening crowbars and picks, by lubricating wheelbarrows and by replacing unservice- able items (particularly shovels). e) Wheelbarrows were introduced for all haulage. f) Heavier crowbars and crowbars with enlarged -chisel end and digging forks were introduced. Supervision g) Task work method of payment was introduced. h) Workers were supplied with canvas shoes to reduce the difficulty of working barefoot on broken rock or scattered stones and rock fra~ents. 7. Two passing places ( one in soil and the other in soft rock) were constructed using the improvements indicated above. The passing place in soil required 326 cubic meters of excavation and the complete task of excavation and haulage to spoil required a labor input of 1,166 man-hours. The corresponding figures for the passing place in soft rock were 211 cubic meters and 1,007 man~hours. A summary of the date obtained is given in Table 2. spoil heap CROSS SECTION A-A ELEVATION 8-8 DAY . . I 2 3 4 5 6 7 8 9 10 11 12 13 • EXCAVATION A-1 A-2 EH 8~ C-1 C-2 D-1 D-2 E-1 E-2 F-1 F-2 HAULAGE A·1 A-2 8-1 8-2 C-1 C-2 D-1 0-2 E-1 E-2 F-1 F-2 SCHEDULE OF EXCAVATION & HAULAGE Figure J: Bench Method of Excavation Working at Altemate Ends -7- . . --.: - . .,.~-~ . -,;. ; _ •. :.. . . • ~ ., .- . ,;;. · ~~~ ··:: • .. . ~ ._ - " ~ --~ •. .. . . (a) General arrangement of work for passing place in soil. (Note: Rock exposure, resulting in some double handling of spoil) (b) Loading and haulage activities for passing place in soil. (Note: 1. Excavators and roaders/haulers working on separate sections. 2. Excavators facing away from slope.) Figure 4: Reorganized Method of Construction of Passing Places -8- Table 2: Measured Productivity for Improved Methods of Construction Predominant Excavation Haulage Material P~ductivity Productivity Type m /man-hour m3/man-hour Parameters Soil o.87 o.44 Haul length 8 meters (average) Soft Rocle 0.62 0.32 Payment Method Task Work 8. A comparison of the overall labor productivity for construction of passing places under the existing work organization and the improved work organ- ization is given in Table 3. It can be seen that there was an improvement in the overall labor productivity of 155% to 2.50% for soil and soft rock respectively using the improved methods. It is difficult to detennine the effect of each individual aspect of the improvements implemented. It is, however, estimated that the main sources of improvement were: i) the bench method of excavation; ii) the incentive method of payment; and iii) proper maintenance of tools and the use of the heavy crowbar. Table 3: Comparison of Productivity of Improved Work Organization with the Existing Methods of Passing Place Construction ' ·,I l I Predominant Productivity of Existing Methods of Excavation & Productivity of Improved Methods Excavation and Percentage Increase in Productivity Material Haulage Haulage over Existing Type (m3/man-hour) (m3/man-hour) Methods Soil 0.11 0.28 Soft Rock I 0.06 o. 21 15.5 250 I -9- 9. :Earlier studies_g/have indicated that incentive methods of payment increase productivity of labor in this type of work by 50-75 percent. Thus, it is apparent that at least a 100 percent increase in output has been obtained by siJnrle nlorganization and scheduling of work. IV. CONCLUSIONS 1 o. The findings of this paper are highly significant. Even though the results have been derived for one particular type of labor-intensive work, it is believed that similar possibilities for productivity improvement exist for other labor-intensive activities. The study has demonstrated that with proper planning of work and with the use of simple principles of good supervision (e.g. emphasis on maintenance of tools), output of manual labor can be increased significantly. Success _w ith using certain types of "modified" ~~