TRANSPORTATION RESEA RC H RECORD ] 13 ] Track Evaluation and Ballast Performance Specif ications M. J. KLAsseN, A. W. CrlrroN, eNp B. R. Werrrns A variety of laboratory tests has traditionally been used in the MAINTENANCE AND BALLAST REPLACEMENT selection of a material and gradation for ballast. The results of the laboratory tests are commonly used to reject or accept Ballast on CP Rail historically was selected on the basis of material for use as ballast and rarely imply benefits or costs of geologic engineering properties of the rock and its past selecting alternative materials or gradations. In this paper are r r rL- ¿---l- performance as ballast. Primary consideration was given to preseflt€u lllË --^--¡¿-I tssurrt u¡^f a- tl auÀ ÐalllP¡rlrE^^--l:-- arru^-l ç^-,^1..^¿:^- v arq4r¡u¡r uËr 4rr¡ Pr materials in proximity or within reasonable train haul of the to determine the performance of ballast, subballast, and the subgrade on Canadian Pacific (CP) Rail. A simple method was required location. developed to determine if a signilTcant portion of maintenance of Surfacing is planned according to historical maintenance the track structure is attributable to the subballast and subgrade. schedules and deterioration oftrack surface. As the condition presented The concept of ballast life is with a relationship of the ballast deteriorates, the track surface becomes difficult quality grading. CP Rail specifications for between ballast and to maintain and maintenance costs increase. Reballasting is the selection of a ballast material and the processing of ballast scheduled be completed when the old ballast has are also presented. to deteriorated. A literature review of ballast performance in 1985 (4) found about properties that are important to The economics of selecting a track ballast is a function of general disagreement Ballast and Subgrade production, transportation, and placement costs and main- ballast life. The consensus of the of the AAR (J) is that decisions on ballast tenance costs during the period the ballast is in the track. A Working Group subjective in nature and state-of-the-art review by the Association of American and subgrade maintenance are by local personnel. Railroads (AAR) Technical Center (l) in 1979 indicated that usually made (ó) there were economic incentives for selecting superior quality A proposed model for subgrade performance is shown ballast materials, although there was avariety of opinions on in Figure l. Permanent settlement decreases with tonnage for the appropriate standards and tests for ballast. a good subgrade but increases with tonnage for a poor Field observations at the Facility for Accelerated Service subgrade. Track maintenance for a poor subgrade, and Testing (FAST) (2) indicated that track maintenance is possibly the threshold condition, will be controlled by the required as a result of a combination of deflections of the permanent settlement of the subgrade. Track maintenance on ballast, subballast, and subgrade. Fouling of ballast is a good subgrade will be controlled by the ballast. perfbrmance model on good subgrade considered a combination of ballast degradation and con- A conceptual ballast Figure 2. The model has been modified to tamination from outside sources, both above and below the (ó) is shown in life and portrays repetitive surfacing cycles ballast. illustrate ballast as the ballast A track ballast sampling and evaluation program was with an increasing maintenance frequency to an undertaken on Canadian Pacific (CP) Rail during 1979 and condition deteriorates. When track roughness increases level, ballast replacement is required. A similar 1980 to evaluate the performance ofballast, subballast, and unacceptable costs is shown in Figure 3. Curves for subgrade at selected locations. A CP Rail specification for model for maintenance ballast (see Appendi*, pp. 59-63 in this Record), which a particular ballast indicate the individual performance of the ballast considers the economic factors of ballast production, ballast properties of the ballast, which affect the life of the life. and ballast and subgrade maintenance, was developed. and maintenance frequency. Research by Raymond et al. (3) developed a track-class ballast ranking and recommended a radical change in ballast grading to an extremely broadly graded ballast for heavy TRACK EVALUATION PROGRAM tonnage main lines. A secondary consideration of the ballast track evaluation program was to evaluation program was to determine if the Raymond track- The purpose of the CP Rail class ballast rankings and ballast gradation should be adopted performance of for the CP Rail main line. l. Develop an understanding of the ballast, subballast, and subgrade by evaluating existing track structures; M. J. Klassen, Canadian Pacific Rail, Calgary, Alberta T2G 0Pó, Determine the significance of ballast-the importance Canada. A. W. Clifton, Clifton Associates Ltd., Regina, Sas- 2. katchewan S4N 5Y5, Canada. B. R. Watters, Department of of ballast material quality, grading, and stability-and the Geology. University of Regina, Saskatchewan S4S 042, Canada. predominant properties of ballast; 36 TRAN SPORTATION RESEARCH RECORD 1 131. Samples were carefully collected and identified on a ballast sample location diagram similar to that shown in Figure 4. F z, Technical information for each location was cataloged on an l¡J E inspection foim (Figure 5). The samples were subjected to UJ J laborátory testing (see paper by Clifton et al. in this Record) 1- l- (tl¡J zt- zl¡J =É. ¡¡J (L CUMULATIVE TONS OF RAIL TRAFFIC FIGURE I Subgrade performance model. PLAN at af, zl¡J (,I oD 0z Y PROFILE ct t-É, LEcErlo CUMULATIVE TONS OF RAIL TRAFFIC SECTION A.A !-aerweeru rres FIGURE 2 Ballast performance model, track quality. EE-BELow TlE-TAMPED ffi-eeLow lE-cENTRE FIGURE 4 Ballast sample location. (tt'- GENERAL INFORMATION o() suBDtvtsroN __ MILEAGE -_ DATE BALLAST SOURCE YEAR BALLASTED l¡J BALLASTGRADATION BALLASTING- METHOD zC) -..- 2 DESCRIPTION OF BALLAST l¡J zP MATERIAL -- - FOULING - - SEGREGATION CEMENTNG MOISIURE CUMULATIVE TONS OF RAIL TRAFFIC DESCRIPTON OF SUB-BALLAST MATERIAL FIGURE 3 B¡llast performance model, mainten¡nce cost. CEMENTNG MOISruRE DESCRIPnON OF SUBGRADE 3. Develop an understanding of subballast and subgrade MATERIAL conditions and performance; and STFENGTH 4. Develop a CP Rail specification for ballast, evaluation MOISTURE of ballast sources, and processing of ballast. TRACK PERFORMANCE Track sections were evaluated by hand excavating the ballast between two ties to the subgrade. The rails were raised to allow a tie adjacent to the excavation to be removed. FIGURE 5 Inspection form. Klassen et al. 37 and petrographic examination (see paper by Watters et al. in An excavation in uniformly graded Kimberley Float this Record) to develop an understanding ofperformance of ballast at Mile 52.2, Mountain Subdivision, is shown in ballast in track. Figure 8. The ballast had been in service for I7 years with 52 An excavation in broadly graded Kimberley Float ballast MGT rail traffic annually. The location was adjacent to a at Mile 65.0, Mountain Subdivision, is shown in Figure 6. siding switch at a sawmill, and the fines in the ballast showed The ballast had been in service for 5 years with 52 million signs of contamination from woodchips. Subsequent excava- gross tons (MGT) of rail traffic annually. The tamped ballast tion showed neither mixing of the pit run subballast and the on the left side of the photograph was dense with significant ballast nor permanent deflection of the ballast-subballast fines filling the voids. Below the center ofthe tie, in the center contact. of the photograph, the ballast was looser with less fines in the An excavation in uniformly graded Uhtoff ballast at Mile voids. Subsequent excavation showed neither mixing of the 13.2, Mactier Subdivision, is shown in Figure 9. The ballast pit run subballast and the ballast nor permanent deflection of had been in service for 29 years with 16 MGT of rail traffic the ballast-subballast contact. annually. The fines below the tie had filled the voids and were An excavation in broadly graded Walhachin ballast at holding water. The visible ballast between the ties also Mile 37 .2, Shuswap Subdivision, is shown in Figure 7. The appeared to have the voids filled with fines. The visible ballast had been in service for 8 years with 52 MGT of rail contact between the ballast and the pit run subballast showed traffic annually. The photograph shows dense ballast in the neither signs of mixing of the ballast and pit run subballast tamped area below the tie with sufficient fines in the voids to nor signs of permanent deflections of the ballast-subballast hold water below the tie. The voids in the visible ballast contact. between the ties appeared to be filled with fines when Old, strong, fouled ballast was examined at Mile I10.4, compared with the clean ballast below the center of the tie. Ignace Subdivision, as shown in Figure 10. The clear color Subsequent excavation showed neither mixing of the pit run differentiation between the old subballasts and the darker subballast and the ballast nor permanent deflection of the fouled ballast indicated neither mixing nor permanent de- ballast-subballast contact. flections of the ballast-subballast contact. FIGURE 6 Mile 65.0, Mountain Subdivision. FIGURE E Mile 52.2, Mountain Subdivision. FIGURE 7 Mile 37.2, Shuswap Subdivision. FIGURE 9 Mile 13.2, Mactier Subdivision. 38 TRA N S PO RTA TION RES EA RC H RECO RD 1 13 1 A clear contact between the newer ballast and the older DEVELOPMENT OF A GRADATION SPECIFICATION darker fouled ballast was observed at Mile 13.8, Kaministiquia Subdivision, as shown in Figure ll. No mixing of the Field Studies materials was apparent, although the convex shape of the visible contact below the tie indicated that subgrade deflections The ballast field study consisted of the evaluation of 54 track were occurring.