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Approval of Guidelines by Railway Board

New Formation Specifications for Heavy Axle Load ( Case Study For Availability Of Blanket Material). Approval of Guidelines by Railway Board. RDSO prepared the Guidelines Critical items Reviewed by CAO/Cs Committee

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Approval of Guidelines by Railway Board

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  1. New Formation Specifications for Heavy Axle Load(Case Study For Availability Of Blanket Material)

  2. Approval of Guidelines by Railway Board RDSO prepared the Guidelines Critical items Reviewed by CAO/Cs Committee Formation Specifications for New Lines/Doubling/GC Works to be carried out on IR, for existing axle loads in the range 22.5t to 25t , should also be kept as same as those for 25 T as per new specifications. Railway Board has approved the committee’s recommendations & the New Secifications/Guidelines vide letter No.2007/CE-I/Geotech/02dated 26.10.09. - The guidelines is to be put to use only on new works and would not apply to on going project. - This may be first tried for a year and half to get the field appreciation and correction, if any. The approved guidelines have been already circulated to the Zonal Railways for adoption. Also available on website http://www.rdso.gov.in/engineering/literature/geo_reports/0014.pdf

  3. Formation Heavy Axle Load • New Formation Specifications vis a vis Existing GE: G-1 2003 • Availability of blanket material • Cost Comparison (New Formation specification verses Existing Guidelines)

  4. The Existing ‘Guidelines of Earthwork in Railway Projects, GE:G-1, July 2003 stipulates :(A) – Organic soils, Dispersive soils will be treated as Unsuitable Soils etc.

  5. (B) There is provision of additional blanket thickness to cater for Heavy Axle Loads in Existing Guidelines, GE:G-1 also which is : For axle load > 22.5t and up to 25t there is a provision of additional blanket thickness of 30cm of superior quality material in upper part For axle load > 25t up to 30t there is a provision of additional blanket thickness of 45cm of superior quality material in upper part The same is shown in the enveloping curve in the next slide

  6. Advantages of Blanket Layer Let us understand advantages of blanket 1 It reduces traffic induced stresses at top of sub-grade to a tolerable limit to avoid track foundation failure. 2 It prevents penetration of ballast into sub-grade and upward migration of sub-grade fines into ballast. 3It intercepts downward percolation of water, facilitates run off of water from top surface of blanket layer and provide drainage path for upward movement of water from subgrade. 4 Blanket provide separation layer to prevent mud pumping by checking the attrition of subgrade particles by ballast.

  7. New Specification & Guidelines of Formation for Heavy Axle Loads’ Consists of: Soil Exploration Surveys Methodology for Ground Improvement Formation Layers Thickness & Material Specification including blanket Quality Assurance Tests

  8. Concept adopted in New Specifications / Design It is with objective of selecting the granular layer thickness based on threshold strength of the subgrade soil. To limit the stress on the subgrade soils to less than a threshold stress To prevent subgrade failure due to excessive plastic deformation, which is more pertinent in case of cohesive soils viz – clay type soil. CBR value and particle size distribution are governing factor for the formation design.

  9. New Specification consists of : Multi layer system which includes blanket, prepared subgrade over embankment fill. The 2 different system are as under:

  10. Subsoil Requirements We have talked about the multilayer system however subsoil parameters are equally important since subsoil is the foundation of the Formation Ground Conditions requirements are given below 2.1 Ground Soil/Sub-soil Strata should have Minimum Undrained shear strength of soil, = 25 KPa or SPT (N-value > 5) 2.2 Otherwise Ground Improvement is required, if Undrained shear strength of soil, < 25 KPa or SPT (N-value < 5)

  11. Soil Grouping The soils to be used in earth fill is locally available soils. The soil grouping has been done for embankment fill & prepared subgrade both, as under : SQ3 (fines <12%) (CBR > 10 Min.) SQ2 (fines : 12 to 50 %) CBR 5-8 (min) SQ1 (fines > 50%) & CBR 3-4 (min) Fines – Particles finer than 75 micron For prepared subgrade, additional requirements is to have Plasticity Index < 12

  12. Comparision of Soil Grouping of New Specifications with GE:G-1 Therefore, it can be concluded that all usable soils as per GE:G-1 are also falling in the new soil grouping & combination (multi layer) thereof in the new specifications.

  13. New Blanket Specification i) Cu > 7 and Cc between 1 and 3. ii) Fines (passing 75 microns) :3% to 10% iii) Los Angeles Abrasion value < 35-40% iv) Minimum CBR value 25 of the blanket material compacted at 100% of MDD v) Size gradation within specified range or enveloping curves. vi) Filter Criteria should be satisfied with subgrade layer, as given below :(OPTIONAL) Criteria–1: D15 (blanket) < 5 x D85 (sub-grade) Criteria–2: D15(blanket) >4to5 D15 (sub-grade) Criteria–3: D50(blanket) < 25 x D50 (sub-grade)

  14. Gradation of Blanket Material

  15. Gradation of Blanket Material & Comparison with Highway Granular Sub-base

  16. Explanation of Blanket Enveloping curves w.r.t. Railway Embankment & Highways 1. Distribution of larger size particles is more as per new enveloping curve to meet with Heavy Axle Load requirements. 2. Railway new enveloping curves covers larger %age and range of finer particles than Highways. 3. Railway Blanket Specifications are liberal in comparison to Highways.

  17. Single Layer System (Blanket on Embankment Fill) Blanket Embankment Fill (Top Layer) SQ3 Embankment Fill (Top Layer) SQ2 200 Embankment Fill (Top Layer) SQ1 180 160 100 140 1 75 80 120 80 100 100 Thickness (cm) 75 80 60 60 75 75 40 50 20 0 SQ1* SQ2 SQ3 SQ2 SQ3 SQ2 SQ3 Soil Type Below Blanket Min. CBR of Top Layer of Embankment Fill CBR  6 generally but not < 5 in isolated cases CBR  6 generally but not < 5 in isolated cases CBR  7 generally but not < 6 in isolated cases 30 T 32.5 T 25 T Axle Load

  18. Two Layer System (Blanket + Prepared Subgrade on Embankment Fill) Blanket (Min. CBR – 25) Prepared Subgrade of SQ3 Soil 200 180 160 140 60 60 45 45 45 120 30 100 Thickness (cm) 80 100 60 100 100 40 20 0 Soil Type Below Blanket SQ2 SQ3 SQ2 SQ3 SQ2 SQ3 Min. CBR of Prepared Subgrade CBR  7 generally but not < 6 in isolated cases CBR  7 generally but not < 6 in isolated cases CBR  8 generally but not < 7 in isolated cases 25 T 32.5 T 30 T Axle Load Prepared Subgrade of SQ2 Soil

  19. Comparison of Blanket Thickness (25 T) With the New Formation Specifications, following reduction in Blanket Thickness have been achieved.

  20. Comparison of Blanket Thickness (30 T) With the New Formation Specifications, following reduction in Blanket Thickness can be achieved :

  21. Advantages of New Specifications 1. Requirement of Blanket Material is reduced considerably which will reduce the overall cost. 2. Materials like prepared subgrade have been brought in requiring lesser stringent specifications. 3. This will enhance use of locally available materials. 4. Economic optimization is possible by varying thickness depending upon available materials.

  22. Quality Assurance Tests There are three Quality assurance tests 1. CBR Test :CBR test is required to be conducted for ground soil, embankment fill, prepared sub-grade & blanket material to ensure the minimum specified CBR value of these materials to be used in construction. This test is carried out on soil sample in laboratory as per procedure, detailed in IS : 2720 (Part 16) - 1987.

  23. Quality Assurance Tests 2. Compaction Test:Heavy compaction Test is required to be conducted to determine the Maximum Dry Density of soil. In-situ density is measured in the field by Sand Replacement Method (IS: 2720 – part 28) or Core Cutter Method (IS: 2720 – part 29) to calculate the degree of compaction w.r.t. MDD.

  24. Quality Assurance Tests 3. Plate Load test for Ev2 Value (Optional) EV2 – Elastic Modulus at 2nd Loading in Plate Load Test Plate Load Test is required to be conducted in-situ for measurement of EV2, as per procedure detailed in German Code DIN:18134, 2001, titled – “Determining Deformation & Strength Characteristics Of Soil By Plate Loading Test”.

  25. Case studyMechanical Production of Blanket Material • Most of the time naturally available materials do not meet the desired specifications of blanket material. • Blanket material can be produced by mechanical process from crushing or blending method or combination of these two methods.

  26. Crushing Methodology • Rock Boulders are crushed & sieved from different sieves to produce aggregates of different sizes. • Trials and permutations of feed speed, crushing cycle, sieve combinations may be required to arrive at the required particle size gradation. • These aggregates are mixed in pre-determined proportions over conveyers and mixed with water, stored.

  27. Blanketing in Chandigarh – Ludhiana New BG Line Crusher Plant visited in the month of May 2005 & Nov. 2009 at Chandigarh to inspect crushing methodology for production of blanket material. Details are as follows: Name of crusher owner: Hargobind Stone crusher Site : Panchkula, Chandigarh Make of crusher: Gurudev, Lalkuwan, Delhi Source of stone: River Ghaggar Plant capacity: 830 cft/hour (Approximately)

  28. Unloading of Blanket Material at site

  29. Compaction of Blanket Material with Vibratory Roller

  30. Finished Blanket after Compaction

  31. In-situ density measurement of Blanket Layer

  32. Gradation of Blanket Material in Chandigarh – Ludhiana project

  33. Gradation of Blanket Material in Chandigarh – Ludhiana project

  34. Case Study BLENDING METHODOLOGY FOR BLANKET PRODUCTION Components :Four bin aggregate unitPug mill mixer unitWater tank and metering systemConveyor beltsStorage silos (optional)Anti segregation surge hopperAutomation and controlsDifferent available materials, coarse aggregate, local sand/soil are blended in pre-determined ratio.

  35. Blanket by Blending in Southern Rly • Gauge conversion project between Manamadurai and Virudhunagar • Most of the alignment of track passes through the land of black cotton soil. • A gravel quarry was identified at 35 km away from the work site. • This material not satisfying blanket Specification. • Blending of Gravelly material was done with available sand using Pug-mill Blender.

  36. Gradation of Available Gravelly Material

  37. Gradation of available Sand for Blending

  38. Mix ration of gravel to sand was taken 4 (Gravel) : 1 Sand and tested for gradation found OK.

  39. Materials : storage, conveying, blending and loading process

  40. Blanket : Laying, Compaction, Finished Surface & Quality check Degree of Compaction achieved : 98.1 to 99.6 %

  41. Tentative Cost Comparison of Existing GE-1 and new specifications (all 2 alternatives) For working out the cost we have taken actual rate of blanket material & earth fill being used of Section Chandigarh - Morinda (NR) & rates of SQ1 & SQ3 soil has been assumed bearing in mind the transportation cost aspect. Analysis has been done for Bank Height of 1.75m ( maximum depth of variation in Formation Layers) & Single Line

  42. Tentative Cost Comparison (Chandigarh - Morinda, NR)

  43. Tentative Cost Comparison of Existing GE-1 and new specifications (all 2 alternatives) For working out the cost we have taken actual rate of blanket material & earth fill being used of Section Manmadurai - Virudhunaagar (SR) & rates of SQ1 & SQ3 soil has been assumed bearing in mind the transportation cost aspect. Analysis has been done for Bank Height of 1.75m (maximum depth of variation in Formation Layers) & Single Line

  44. Tentative Cost ComparisonManmadurai - Virudhunaagar (SR)

  45. Tentative Cost Comparison of Existing GE-1 and New specifications (all 2 alternatives) For working out the cost we have taken actual rate of blanket material & earth fill being used of Section Palval _ Bhooteswar (RVNL) & rates of SQ2, SQ3 soil has been assumed adding the transportation cost over and above the soil being used in earth fill Analysis has been done for Bank Height of 1.75m (maximum depth of variation in Formation Layers) & Double Line

  46. Tentative Cost Comparison (Palval – Bhooteshwar, NR)

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