Annexure
5.3
Guidelines for Operation of Tamping Machine in design Mode
1.0 Datum
rail:
The datum rail for carrying out attentions to longitudinal profile and alignment should be selected as given below:
(i) Longitudinal section: Non-cess rail on straight track in double line section and inner rail in curves.
(ii) For alignment: non-cess rail on straight track in double line section and outer rail on curves.
(iii) For single and middle line in multiple line sections, any of the two rails which is less disturbed may be selected as datum rail, both for alignment and L-section in straight track.
2.0 Survey
for vertical profile correction:
2.1 The section identified for surfacing should be divided by stations marked at 10 m interval. The starting point should be opposite a km post and the starting station should be marked 0. Station locations and station numbers should be painted in yellow paint on the web of the datum rail.
2.2 Bench
marks:
Bench marks should be established at 200-1000 m interval, relating them to the GTS bench mark levels so that the plotted drawings are properly related to the existing index section. Fixing bench marks in relation to arbitrary levels should be avoided. These bench marks could be established on the top of concrete foundation of OHE masts in electrified sections.
2.3 Recording
of Actual Rail levels:
The SE/JE (P. Way) should record the actual rail levels at all the stations of the datum rail, making use of the established bench marks. However, on the stretches where the datum rail is super-elevated, being on a horizontal curve, the rail levels should be taken on the other rail of the track, opposite the station locations. The stretch for which station levels are taken on "non- datum" rail, should be noted in the level book.
In view of the voluminous survey work involved, autosetting levelling instruments should be used to save time and to achieve accurate results.
2.4 Formation
levels:
At every 5th station i.e. Station No. 0, 5, 10 etc., the Section Engineer/P. way should remove ballast below the rail seat where rail levels are recorded, upto a level, below which it is not desirable to go, while carrying out deep screening work. This level is referred to as Formation Level. The SE/JE (P. Way) should also record the formation levels. For example, in the redesigned vertical profile the rail level should be 700 mm and 680 mm above the formation level in case of 60 kg and 52 kg rail respectively on PSC sleepers with 300 mm ballast cushion, if sub-ballast is not provided.
2.5 Obligatory
Points:
While carrying out the survey, the SE/JE (P. Way) should record the location of obligatory points like level crossings, girder bridges, points and crossings, overhead structures etc., in reference to the station numbers as well as running kilometre. In addition, the location of km posts and gradient posts should also be noted.
3.0 Plotting
of vertical Profile:
3.1 The existing vertical rail profile (of datum rail) and formation profile should be plotted on a graph sheet with the length of track as abscissa and elevation of rail top and formation as ordinate. The scale adopted should be:
Horizontal Scale: 1:1000 or 1 cm = 10 m and
Vertical Scale: 1:10 1 mm = 10 mm
3.2 Having plotted the formation levels the desired rail levels should be marked on the graph e.g. by adding 70 cm to the formation level, in case of 60 kg rail on PSC sleepers with 30 cm ballast cushion and 68 cm in case of 52 kg rail on PSC sleepers. The desired rail level so plotted should be taken into account, while marking the proposed vertical profile on the graph.
3.3 Proposed rail Profile:
While deciding the final levels, the following considerations shall be taken into account:
i) Sub sections shall be selected keeping in view high points and obligatory points.
ii) As far as possible, long stretches of uniform gradient shall be planned keeping in view the depth of construction to be provided, and relative implications of lifting or lowering of track. In no case the grade should exceed the ruling gradient of the section. While designing vertical curves, provisions of para 419 of IRPWM should be observed.
iii) The clearance to overhead structures (including OHE ) shall be maintained within permissible limits.
iv) The redesigned profile should not normally involve lifting or lowering of obligatory points like girder bridges, Level crossing and turnouts.
v) The redesigned profile should aim at easing the sags and humps with manageable lift and lowering. It is not necessarily the intention that the original longitudinal section of the line should be restored.
vi) Generally, the redesigned profile should be so arrived at as to have lifting only, as machines have lifting facility only, and lowering shall be resorted to in exceptional circumstance.
vii) Prescribed minimum ballast cushion should be ensured. However the requirement of ballast over and above that for the prescribed cushion can be optimised by designing suitable vertical curves.
viii) At locations where lifting or lowering is not possible, suitable ramping out preferably in the form of reverse curves in vertical plane should be provided on both approaches. In case lift is proposed at level crossings, the field staff should be prepared to simultaneously raise the road surface and regrade the approaches.
4.0 In redesigning the profile, the requirements to be met are:
i) For other than vertical curves-
The unevenness on 80 m chord should not exceed as under:
a) on high speed routes with speed above 110 kmph - 40mm (corresponding to 20000m vertical radius).
b) on other lines - 65 mm (corresponding to about 12000 m vertical radius).
ii) for vertical curves - The unevenness on 20 m chord should not exceed 10 mm (corresponding to 5000 m vertical radius)
The profile designed should be analytically verified so that the above mentioned unevenness limits are not exceeded. The final levels at various points should be calculated rather than scaling out from the drawing which mainly serves the purpose of visual appreciation..
4.1 The proposed levels should be approved by an officer not below the rank of DEN. The working plan so prepared should be distributed to the concerned field staff and AEN.
4.2 Designing
Vertical Profile With the help of Computer
For designing of vertical profile, aid of a computer with a software developed by IRICEN/Pune may be taken to speed up the design work.
5.0 Surfacing
Operation
5.1 The filially proposed levels of rail top may be marked on the OHE masts for executing the lifting/lowering operation. In case of non-electrified section, permanent level pegs should be provided at every 5th station.
5.2 Actual work of lifting and lowering may be carried out in keeping with the instructions laid down in paras 233 of P. way Manual.
5.3 The finished profile may not exactly conform to the redesigned profile, and the resurfaced levels may vary from the design profile. It is, therefore, necessary to check the finished levels in relation to the levels marked on the OHE posts or other reference points. The difference between the finished levels and designed levels should not exceed 10 mm, provided the variation of unevenness from station to station is not more than 20 mm. To ensure this, SE/JE (P. Way) will workout the unevenness at all stations in relation to the finished levels and the machine incharge shall apply correction to levels, to bring the station to station variation of unevenness within the prescribed limit.
6.0 Survey
For Alignment Correction:
6.1 All the weld and rail kinks should be rectified/eliminated by dekinking or cutting and welding, before measurement for alignment defects are taken. Hydraulic jim-crows may be used for removing kinks.
6.2 In case some horizontal curves on the section to be surfaced warrant realignment, then the process of realignment should be carried out along with surfacing.
6.3 Alignment should be measured on a 40 m chord on straight track and required slew at alternate sleeper should be worked by measuring the offsets at every 5 m interval and interpolating the offsets. The slews are marked on every alternate sleeper.
6.4 On curved track, versines should be measured on 20 m chord at 10m intervals. The required slews at the stations are worked out taking note of the obligatory points and interpolated to give slews at every alternate sleeper. The slews are then marked on alternate sleepers.
6.5 While working out slews, position of fixed structures should be noted and infringement to moving dimensions shall not be allowed.
6.6 Pre-tamping and Post-tamping operation and machine related track works as detailed in Chapter 3 shall be ensured by the Section Engineer P. Way.
