Unit 1

Unit 1: Railway Planning and Construction - Section Summary¶

This unit has 10 major sections. Here's a comprehensive breakdown:

Section 1.1: Introduction¶

Context: Imagine you need to transport coal from mines to a power plant 500 km away, or move thousands of passengers daily between cities. This section explains why railways became civilization's answer to mass transportation.

Key Concept: Transportation = Index of economic growth

Without efficient transport, one region might starve while another has surplus crops
Railways unite nations by connecting production centers with markets

Comparison:

With transport: Regional specialization possible (mangoes from one state, steel from another)
Without transport: Each region must be self-sufficient (inefficient)

Section 1.2: Modes of Transport¶

Context: You need to move 10,000 tons of coal. Do you use trucks, trains, planes, or ships? Each mode has its "sweet spot."

Quick Comparison Table (exam favorite):

Mode	Best For	Speed	Cost	Capacity
Rail	Bulk goods, long distance	Moderate	Medium	Very High
Road	Door-to-door, short distance	Fast	Medium	Low
Air	Time-critical, passengers	Fastest	Highest	Low
Water	Heavy/bulky, long distance	Slowest	Lowest	Highest

One-glance insight: Rail = "bulk + safety + long distance"

Section 1.3: Road vs Rail Transport¶

Context: Why build a railway when we have roads? This comparison answers that.

Critical Distinctions (frequently asked):

Feature	Road	Rail
Tractive Resistance	5× higher	1× (baseline)
Gradients	Up to 1 in 30 (steep)	Max 1 in 100 (flat)
Flexibility	Door-to-door	Station-to-station only
Ownership	Private sector	Government
Environment	More pollution	Less pollution

Common Confusion: Students mix up "right of way" - roads are open to all, railways are exclusive tracks.

Section 1.4: Indian Railways Development¶

1.4.1: Role of Indian Railways¶

Context: How does transporting coal help India's economy? This section connects railways to national development.

Seven Functions (memorize this list):

Integrates markets → modern economy
Links industries with raw materials
Connects farms with distant markets
Moves energy resources (coal to power plants)
Low-cost mass passenger movement
Symbol of national integration
Defense preparedness tool

1.4.2: Gauges¶

Context: Why do some tracks look wider than others? Gauge = track width.

Three Gauges in India:

Gauge	Width	Where Used
Broad Gauge (BG)	1676mm (5'6")	Main/trunk lines
Metre Gauge (MG)	1000mm (3'3.37")	Feeder lines
Narrow Gauge (NG)	762mm or 610mm	Mountains

Key Insight: Speed ∝ Gauge (wider gauge = larger wheels = higher speed)

Common Confusion: Don't confuse gauge measurement points:

✓ Correct: Minimum distance between running faces of rails
✗ Wrong: Outer edge to outer edge

Section 1.5 & 1.6: Alignment Selection¶

Context: You're planning a Mumbai-to-Goa railway. Do you go straight through mountains or take a longer coastal route? This is alignment.

Alignment = Route planning in horizontal + vertical planes

Six Selection Factors:¶

1. Obligatory Points (must-pass locations)¶

Example: Bangalore to Madurai must pass through Salem (commercial hub) and Thoppur Pass (only mountain crossing)

Exam Tip: Draw Fig 1.1 - shows how intermediate towns become obligatory points

2. Traffic Considerations¶

More traffic = more revenue = better route selection

3. Geometrical Standards¶

Keep gradients ≤ 1 in 150 (plains) for safety/comfort

4. Topography (exam favorite - 15-20 marks)¶

SourceExplained

Four Terrain Types:

Terrain	Challenge	Solution
Plain	None	Straight alignment
Valley	Simple	Follow valley floor
Cross-Country	Multiple watersheds	Steep varying gradients
Mountain	Too steep	Development methods ↓

Mountain Development Methods (frequently asked with diagrams):

Zigzag Line:
Track goes back-and-forth in horseshoe patterns
Like hiking switchbacks
Gains height without steep grade
Switch-Back:
Train reverses direction at switches
Must stop at switch points
Used on very steep slopes
Spiral/Loop:
Track loops and crosses itself via bridge/tunnel
Train at higher elevation second time
Most elegant but expensive

Common Confusion: - Zigzag = continuous movement - Switch-back = must stop and reverse

The Crystal Clear Picture - Topography Section

*What This Section Is REALLY About (One Sentence):*

"Different types of land = different railway route strategies"

*The Overall Picture - Dead Simple:*

You're building a railway. The land shape determines:

✅ Can you go straight? (Plain terrain = yes, Mountains = no)
✅ What gradient? (Valley = gentle, Mountains = too steep)
✅ Special tricks needed? (Mountains = yes, need zigzag/loops)

That's it. Nothing more complicated.

*Exam Importance: ⭐⭐⭐⭐⭐ (Very High)*

*Why Examiners Love This:*

Diagram questions: 10-15 marks guaranteed
"Draw and explain mountain alignment methods"
"Sketch zigzag alignment with labels"
Comparison tables: 8-10 marks
"Compare four terrain types"
"Differentiate zigzag vs switch-back"
Application problems: 10 marks
"Railway from elevation 100m to 800m. Gradient 1 in 100. Is straight line possible? Suggest methods."

Total potential: 25-35 marks out of 100 in this unit!

*What You're Expected to Know:*

*Level 1: Must Know (80% of marks)*

4 terrain types and their ONE main characteristic
3 mountain methods with basic difference
ONE good diagram of zigzag

**Level 2: Should Know (15% of marks) **

Why each terrain needs different approach
Detailed differences between 3 mountain methods

*Level 3: Nice to Know (5% of marks)*

Calculations, cost comparisons, real examples

Focus on Level 1. That's your bread and butter.

*THE ULTIMATE DISTILLATION - 5 Core Points*

Memorize these. Expand in exam using common sense.

*POINT 1: Four Terrain Types*

1. PLAIN → Straight line → Easy
2. VALLEY → Follow valley floor → Still easy  
3. CROSS-COUNTRY → Up-down-up-down → Moderate difficulty
4. MOUNTAIN → Too steep → Need special tricks

Exam Expansion Template:

"Railway alignment depends on topography: - Plain terrain presents no problems, straight alignment with gentle gradients - Valley terrain is simple if both points in same valley, uniform gradient - Cross-country crosses watersheds, has varying gradients and multiple drainage - Mountain terrain requires development methods as natural gradient too steep"

(That's 4 marks right there for just naming and one-line explaining each)

*POINT 2: Mountain Problem (The Core Issue)*

One sentence: Normal gradient would be too steep (like 1 in 30), but trains need 1 in 100 maximum.

Solution: Make the track longer artificially!

Exam Expansion:

"If mountain rises 700m over 20km straight distance: - Natural gradient = 700/20,000 = 1 in 28 (TOO STEEP) - Ruling gradient = 1 in 100 (required) - Therefore track length needed = 700 × 100 = 70 km - Must add 50 km extra length artificially → Development methods"

(That's 5 marks for showing you understand THE problem)

*POINT 3: Three Mountain Methods - The ONLY Differences That Matter*

One comparison table - memorize this:

Method	Does train stop?	Track shape	When used
ZIGZAG	❌ NO (continuous)	Back-and-forth with horseshoe curves	Moderate slopes
SWITCH-BACK	✅ YES (must reverse)	Has switches/buffers	Very steep slopes
SPIRAL	❌ NO (continuous)	360° loop	Narrow valley with space

That's the ENTIRE difference. Nothing else matters for exams.

Exam Expansion - Just elaborate each column:

"Zigzag: Train moves continuously forward, track makes horseshoe curves to change direction. No stopping. Used when side slopes moderate."

"Switch-back: Train must stop at buffer, reverse direction using switches. Requires stopping. Used when slopes too steep for curves."

"Spiral: Track makes complete 360° loop, crosses itself via flyover/tunnel. Continuous movement. Used in valleys with circular space."

(That's 6 marks - 2 per method)

*POINT 4: ONE Diagram - Master This*

Draw ONLY the Zigzag (Figure 1.5):

Simple version for exam:

90m  ___B___
        \
        _\__ ← Horseshoe turn
       /
85m  _/
     |
80m  |  ← Straight section climbing
     |
75m  |
     |___A___
70m

Labels needed:
- "Horseshoe curve" at turns
- "Train moves continuously"  
- "Follows side slope"
- Heights on left

Practice this 5 times. You can draw it in 1 minute.

Why only zigzag? - Most commonly asked (80% of diagram questions) - Simplest to draw - If asked switch-back, just add: "Similar but has switches where train stops and reverses" - If asked spiral, add: "Instead of back-forth, makes complete circle"

*POINT 5: Exam Question Pattern Recognition*

3 question types. Same answers work for all:

Type A: "Explain mountain alignment methods" (10 marks)

Your template answer: 1. State the problem (Point 2) - 2 marks 2. Name three methods - 1 mark
3. Explain each using Point 3 - 6 marks 4. Draw zigzag diagram - 1 mark

Type B: "Differentiate zigzag and switch-back" (5 marks)

Your template answer: 1. Draw the comparison table from Point 3 - 3 marks 2. Add one line: "Both add track length but zigzag uses curves, switch-back uses reversals" - 2 marks

Type C: "Railway line 50 km, rises 500m. Ruling gradient 1 in 100. What to do?" (8 marks)

Your template answer: 1. Calculate: 500m needs 500×100 = 50km track length (2 marks) 2. Available distance = 50km (given) (1 mark) 3. Say: "Straight alignment just possible, but mountains likely have ups-downs, so actual requirement more" (2 marks) 4. Suggest: "Use zigzag or spiral development" (1 mark) 5. Draw zigzag - (2 marks)

*Your Study Strategy (30 Minutes Total):*

*Day 1 (15 minutes):* 1. Memorize Point 1 table (4 terrains) - 5 min 2. Memorize Point 3 table (3 methods) - 5 min 3. Practice drawing zigzag - 5 min

*Day 2 (15 minutes):* 1. Practice writing Point 2 explanation - 5 min 2. Practice drawing zigzag again (faster) - 5 min 3. Mock answer one Type A question - 5 min

That's it. You're done.

*What You Can Skip (For Now):*

❌ Detailed switch-back/spiral diagrams (unless specifically asked)
❌ Valley alignment details (too easy, rarely asked separately)
❌ Cross-country saddles/watersheds (mention briefly if asked)
❌ Cost calculations (unless question explicitly asks)
❌ Real railway examples (nice to add but not necessary)

*The Absolute Minimum (If You Have Only 10 Minutes):*

Learn these 3 things:

Four terrains: Plain (easy) → Valley (easy) → Cross-country (moderate) → Mountain (hard, needs tricks)
Three tricks: Zigzag (continuous) vs Switch-back (stops) vs Spiral (loops)
One diagram: Zigzag with horseshoe curves [practice once]

Even with just this, you can score 12-15 marks out of 20.

*Final Reality Check:*

Question: "Can you explain why zigzag is used?"

❌ Over-complicated answer: "Due to the mountainous topography and the requirement to maintain the ruling gradient within permissible limits while negotiating steep terrain that would otherwise result in gradients steeper than 1 in 100..."

✅ Perfect exam answer: "Mountain too steep. Normal track = 1 in 30 gradient (unsafe). So track goes back-forth in zigzag to make length longer. Longer track = gentler gradient (1 in 100). Train moves continuously through horseshoe curves."

Same information. Half the words. Full marks.

*Your Confidence Checklist:*

After studying, you should be able to:

✅ Name 4 terrain types in 10 seconds
✅ Draw zigzag diagram in 1 minute
✅ Explain why mountains need special methods (30 seconds)
✅ State difference between zigzag and switch-back (one sentence)

If you can do these 4 things, you're ready. Period.

The rest is just adding more words to these core ideas.

*Bottom Line:*

This section seems complicated because the document is detailed. But for exams:

Master: 1 table + 1 diagram + 1 problem statement = 20 marks guaranteed

Don't overthink it. Railways need different routes for different land. Mountains need tricks. Three tricks exist. Learn one trick well (zigzag). Done.

5. Economic Considerations¶

Capital cost + operational cost + maintenance = final decision

6. Other Factors¶

Geology, material sources, political issues

---

Section 1.7: Engineering Surveys¶

Context: Before laying a single track, you need 5 types of surveys. Think of it as "measure five times, build once."

sourcenotes

Survey Progression (in order):¶

1. Traffic Survey¶

Purpose: Will enough people/goods use this railway? Collects: Population data, industry locations, trade patterns

Report Contents (12 points - know structure for long answers):

* History & terms of reference * Economic development projections * Passenger/goods traffic estimates * Financial appraisal (revenue vs cost)

2. Map Study¶

Purpose: Desktop analysis using satellite images, topographic maps

Key: Identify contours, hill passes, river crossings on paper first

3. Reconnaissance Survey¶

Purpose

Rapid field inspection - "Is this feasible?"

Equipment

* Conventional: Barometer (heights), Abney level (slopes), Prismatic compass (bearings) * Modern: GPS, Total Station, EDM

What's Collected:

* General topography * River positions * Rough station locations * Controlling points

4. Preliminary Survey¶

Purpose: Detailed measurement for cost estimation

Equipment: Theodolite, Tacheometer, Dumpy Level, Plane Table

What's Collected (8 specific items):

1. Geological data (soil types) 2. Construction material sources 3. Labour/water availability 4. Land acquisition details 5. Bridge/culvert details 6. Road crossing locations 7. High flood levels (HFL) 8. Station site requirements

5. Final Location Survey¶

Purpose: Working drawings + accurate costs

Key Differences from Preliminary:

Preliminary	Final
May not stake fully	Fully staked every 20m
Basic report	Detailed project report
No working drawings	All working drawings

Tasks: - Masonry pillars at curve points - Compensate gradients for curves - Demarcate station yards - Prepare 7 types of drawings (know list)

Modern Techniques (for difficult terrain): - Satellite imagery (updated monthly) - Aerial photographs (Survey of India) - Digital Terrain Modeling (DTM) - computer finds economical route - Used in Kashmir valley railway (terrorist areas, hard fieldwork)

---

Section 1.7: Engineering Surveys - The "Obviously" Guide

The Big Picture: Basically, you do 5 surveys that ask the same question with increasing paranoia: "Should we build this railway?" Start vague, end obsessive.

*1.7.1: Stages - The Anxiety Ladder*

Think of it like buying a house: 1. Check Zillow (Map Study) 2. Drive by the neighborhood (Reconnaissance) 3. Actually tour the house (Preliminary) 4. Hire an inspector (Final Location) 5. Oh wait, will anyone actually live here? (Traffic Survey - runs parallel)

That's it. Five surveys. Always in this order. Easy.

*1.7.2: Traffic Survey - "Will Anyone Use This Thing?"*

The Only Question: Is this railway going to make money or are we building a monument to bureaucratic optimism?

Example: You're proposing a railway from Thrissur to Guruvayur.

What you do (just common sense):

Count how many people visit the temple annually → passenger traffic
Check if there's a coconut oil factory → goods traffic
Talk to the district collector (obligatory bureaucratic theater)
Ask local businesses: "Would you ship stuff by train?"
Google: "Thrissur industrial development plan 2025"

The Report (12 sections - but it's all fluff around one number):

Honestly, it's just: * Sections 1-2: "Here's what we were asked to do and here's the area" * (bureaucratic throat-clearing) * Sections 3-6: "Here's how much money/people/stuff will use this railway" * ← THE ONLY PART THAT MATTERS * Sections 7-9: "Here's where stations go and how many trains" (logistics) * Sections 10-11: "Revenue minus expenses = profit/loss" ← THE ACTUAL * DECISION MAKER * Sections 12-14: "Engineering stuff and telecom" (padding)

Memory trick: It's a business plan disguised as engineering. Economics students could write 80% of it.

*1.7.3: Map Study - "Google Earth But Official"*

What it is: You sit in an air-conditioned office and draw lines on maps. Don't go outside yet. That's for peasants (and the next survey).

Example: Thrissur to Guruvayur railway

You open:

Topographic maps (shows hills - avoid those)
Satellite imagery (updated monthly by ISRO - flex this in exams)
Contour maps (squiggly lines = elevation changes)

You draw 2-3 possible routes with a pencil:

Route A: Straight line (shortest) but crosses a hill
Route B: Curves around hill (longer) but flat
Route C: Goes through that town you forgot existed

Key insight: You're just connecting the dots between "obligatory points" (important towns, low mountain passes, obvious bridge locations) while respecting contour lines.

Exam padding: Mention "man-made features like buildings, road/rail networks, rural and urban settlements are also marked." (Nobody cares, but it sounds thorough.)

*1.7.4: Reconnaissance Survey - "The Lazy Field Trip"*

Translation: "Rapid and rough" = binoculars and educated guessing

What you do: Drive around in a jeep, stop occasionally, squint at the landscape, take notes. You're collecting just enough data to tell your boss, "Yeah, Route B is definitely possible, Route A is insane."

Example: Thrissur-Guruvayur

You drive Route B with:

Conventional Equipment (sounds fancier than it is):

Barometer: "This hill is approximately 80m tall" (measure air pressure)
Abney level: "This slope is about 1 in 40" (tilt meter, basically)
Prismatic compass: "We're heading northeast" (fancy magnetic compass)
Binoculars: "There's a river 2 km ahead" (literally just binoculars)
Pedometer: "We walked 5 km" (counts steps like your phone)

Modern Equipment (for when you have budget): * GPS: Coordinates of anything * Total Station: All-in-one angle/distance measurement * EDM: Laser distance meter

What you note down (8 obvious things): 1. "It's hilly here" (topography) 2. "This point is about 60m elevation" (approximate heights) 3. "There's a river here and it floods to this mark" (rivers + hydrology) 4. "The highway crosses here" (roads) 5. "Mostly red soil" (soil type) 6. "Station could go here" (rough location) 7. "Must pass through Irinjalakuda" (controlling points) 8. "There's a quarry 5 km away" (construction facilities)

Exam trick: List all equipment in a table (Table 1.2 style) - instant 4 marks for writing barely anything.

*1.7.5: Preliminary Survey - "Now We're Serious (But Not Too Serious)"*

What changes: You bring actual surveying instruments. Theodolites, not binoculars. Numbers, not adjectives.

Example: Thrissur-Guruvayur, Route B

Equipment (Table 1.3 - memorize for easy marks): 1. Theodolite: Measures angles (for traversing the route) 2. Tacheometer: Measures distance + elevation simultaneously 3. Dumpy Level: Measures elevation differences precisely 4. Plane Table: Sketches interior details on paper outdoors 5. Prismatic Compass: Still need bearings

The 8 Things You Collect (exam loves this as an 8-mark question):

Just answer: "What would a contractor need to know before bidding?"

Geology: "Is this rock or clay? Will tunneling cost ₹1 crore or ₹10 crore?" 2. Construction materials: "Is there a sand quarry nearby or do we truck it 100 km?" 3. Construction facilities: "Can we hire 500 laborers locally? Is there drinking water?" 4. Land acquisition: "Whose land are we taking? How much will we pay?" 5. Bridge details: "Existing bridges nearby? Any irrigation tanks that'll flood our track?" 6. Road crossings: "Where do roads cross? At what angle? How much traffic?" (affects level crossing design)
High Flood Level (HFL): "How high does the river rise during monsoon?" (Critical for bridge height) 8. Station sites: "Where exactly will stations be? How big? Parking needed?"

Memory trick: It's a contractor's shopping list. "Rock type, material sources, labor, land cost, bridge heights, road crossings, flood levels, station locations." Done.

*1.7.6: Final Location Survey - "Okay, NOW We're Actually Serious"*

What it is: Preliminary Survey, but you're writing a doctoral thesis instead of a term paper.

The 3 Differences (easy exam question):

Preliminary	Final
"We might stake it"	Peg every 20m, masonry pillars at curves (no jokes now)
Basic report	Detailed project report with 7 types of drawings
Rough estimates	Working drawings for contractors

What you actually do (4 tasks):

Example: Thrissur-Guruvayur final alignment

Mark every 20m with pegs:
Small pegs every 20m
Big pegs every 100m
Masonry pillars at every curve point
Why? So contractors know exactly where to build
Longitudinal & cross leveling:
Measure elevation every 20m along the route
Measure cross-slopes (for cutting/embankment design)
Compensate gradients for curves (remember Section 1.9.4? Apply it here)
Demarcate station yards:
"Thrissur Station will be from km 0.0 to km 0.8, this exact area"
Prepare 7 drawings:
General map (20 km to 1 cm scale) - "Here's Kerala, here's our line"
Index map (2.5 km to 1 cm) - "Zoomed in"
Detailed plans & sections - "Every curve, every gradient"
Cross-sections - "Cut here, fill there"
Station yard plans - "Platform 1 here, parking there"
Structure drawings - "Bridge design, culvert size"
Junction plans - "How this connects to existing lines"

The 8 Objectives (philosophical padding for 8-mark answers): 1. Correct obligatory points ← (Did we actually hit all the towns we promised?) 2. Easy grades, flat curves ← (Physics) 3. Minimum construction cost ← (Money) 4. Minimum environmental damage ← (Politics) 5. Easy construction ← (Contractor happiness) 6. Potential for high speeds ← (Future-proofing) 7. No constraints for expansion ← (Double-tracking later?) 8. Minimum maintenance ← (Lifecycle costs)

Reality: Objectives 1-3 matter. The rest are buzzwords for the report.

*1.7.7: Modern Surveying Techniques - "Because It's 2024, Not 1924"*

When you use this: Difficult terrain (mountains, forests, terrorist zones like Kashmir)

Why: Can't send 50 surveyors to climb mountains with theodolites if they'll get shot or fall off cliffs.

The Example That Appears in Every Textbook: Udhampur to Qazigund railway (Kashmir) - mountains + security issues = perfect use case

The 5 Techniques (just list these, instant 5 marks):

Satellite Imagery:
ISRO updates monthly
Bird's eye view of large areas
"Oh look, there's a valley we can use"
Aerial Photographs:
Survey of India does whole country every 3-5 years
"Zoom in to see exact river crossing locations, tunnel sites"
Topographic/Contour Maps:
Old reliable, now combined with satellite data
Digital Terrain Modeling (DTM) ← The Fancy One:
Computer algorithm finds most economical alignment
Input: Start point, end point, terrain data
Output: "Build here, dummy"
Photogrammetric Plotted Sheets:
Convert aerial photos to precise measurements
Basically fancy mapping software

The Process (sounds complex, is trivial): 1. Use satellites/photos to shortlist 2-3 routes (office work) 2. Use DTM to find cheapest route (computer work) 3. Mark ground stations 1 km apart on the chosen route (minimal field work) 4. Use contour maps + computers for all other details (back to office)

Key benefit: Instead of 500 surveyors spending 6 months in a war zone, 5 engineers spend 2 months in an office with computers.

Exam strategy: If question says "difficult terrain," vomit this entire list. If it says "Kashmir" or "mountains" or "security issues," definitely vomit this list.

*Memory Trick for All 5 Surveys*:

The Dating Analogy:

Map Study: Stalking their Instagram (desktop research) 2. Reconnaissance: Seeing them across the room (quick look) 3. Preliminary: First date (getting details) 4. Final Location: Meeting the parents + ring shopping (total commitment) 5. Traffic Survey: Asking "Can we actually afford this relationship?" (runs throughout)

Or the Home Renovation Analogy:

Map: Browsing Pinterest 2. Reconnaissance: Walking through house noting issues 3. Preliminary: Contractor gives estimate 4. Final: Architect draws blueprints, you get permits 5. Traffic: "Will this increase home value?"

*Exam Template for "Explain the survey process" (15 marks)*:

Introduction (2 marks): "Before constructing a railway line, preliminary investigations are conducted using topo sheets, trade/population data, and statistical data from similar terrains. Once feasibility is established, five types of surveys are undertaken: Traffic, Map Study, Reconnaissance, Preliminary, and Final Location surveys."

Body (10 marks): [Vomit the 5 surveys with one example and one equipment list each - 2 marks per survey]

Modern Techniques (2 marks): "For difficult terrains like the Udhampur-Qazigund line in Kashmir, modern techniques such as satellite imagery (ISRO), aerial photographs (Survey of India), DTM, and photogrammetric sheets are employed to minimize field work in hazardous conditions."

Conclusion (1 mark): "This systematic approach ensures technical feasibility, cost optimization, and safety before construction begins."

Done. 15/15 marks with minimal actual thinking.

The Ultimate Truth: Section 1.7 is 90% "list things in order" and 10% "use common sense about what you'd want to know before building a railway." If you forget specifics, just ask yourself: "What would I want to know if I were spending ₹1000 crore on this?"

Section 1.8: Railway Track (Permanent Way)¶

Context: What you see when you stand on a platform - rails, sleepers, stones. But why this specific arrangement?

Definition: Permanent Way = rails + sleepers + ballast + formation

Why "Permanent"?: Initially, temporary tracks were laid to carry construction materials. The final track is "permanent."

1.8.1: Four Components¶

Component 1: RAILS¶

Shape: Unsymmetrical I-section steel beams

Functions (6 points):

* Act as girders (transmit load to ballast)
* Provide smooth surface
* Guide wheels laterally
* Low friction (1/5 of road friction)

Rail Types:

Three types of rails:

1. Double headed rails/Dumb-bell rails: less strength compared to flat footed. 2. Bull headed rails 3. Flat footed rails

* India uses Flat-Footed Rails (90% worldwide)
* Can be spiked directly to sleepers

6 Merits (compare with bull-headed):

* Lower initial cost (fewer fittings)
* Higher strength (for same weight)
* No chairs required
* Simpler at points/crossings
* Less liable to kinks
* Better load distribution

Gauge Concept (frequently confused):

* ✓ Correct: Clear distance between inner faces of rails at top * ✗ Wrong: Britain originally used outer-to-outer (flanges were outside) * Why changed: Wheels were coned, flanges moved inside for better turning

Rail Lengths:

Type	BG	MG
Standard	13m	12m
Short Welded Rails (SWR)	39m	36m
Long Welded Rails (LWR)	>250m	>500m
Continuously Welded Rails (CWR)	One full block section	One full block section

Benefits of Welding:

↓ maintenance,
↓ creep,
↑ stability,
↓ sabotage risk

Speed-Gauge Relationship:

* Wheel diameter ≈ 0.75 × gauge
* Larger gauge → Larger wheels → Higher speed

Critical Phenomenon: CREEP¶

Definition: Longitudinal movement of rails in track

Causes:

1. Wave formation from moving wheels 2. Push/pull during braking/acceleration 3. Impact at rail joints

Effects:

* Sleepers go out of square * Gauge distorted * Joints open up → fishplate failure * Signals fail (critical safety issue)

Adjustment (when creep >150mm):

1. Loosen fishplates at one end 2. Pull back rails manually/mechanically 3. Use creep adjusters/anti-creepers

Critical Phenomenon: KINKS¶

Definition: Rail ends move slightly out of position

Causes:

Loose joints
Gauge/alignment defects
Uneven wear

Effect: Unpleasant jerks, safety hazard

Common Confusion:

Creep = gradual longitudinal sliding of entire rail
Kink = sudden misalignment at joints

Coning of Wheels¶

Definition: Wheels shaped like cones, 1:20 slope on treads

Why? (Exam favorite - draw Fig 1.13):

On straight track: Wheels stay centered
On curves:
Outer wheel moves outward (centrifugal force)
Cone shape means outer wheel travels longer distance
No slipping needed!

4 Purposes:

Smooth curve negotiation
Reduces slipping/skidding
Less wheel/rail wear
Smooth riding

Disadvantages:

Pressure on inner edge → accelerated wear
Rails tend to turn outward → gauge widens
Damages outer rail edge

Solution: CANTING OF RAILS

Tilt rails inward (1:20 slope)
Use inclined base plates
Adzing of Sleepers: Cut wooden sleeper tops to match rail tilt

Common Confusion:

Coning = wheel shape
Canting = rail tilt
Both work together at 1:20 slope

Component 2: SLEEPERS¶

Function: Transverse ties holding rails

Component 3: BALLAST¶

Material: Broken stone, gravel, moorum (India uses stone ballast)

Functions (memorize): 1. Hold sleepers in position 2. Transfer/distribute load to formation 3. Provide elasticity (riding comfort) 4. Effective drainage 5. Medium for super-elevation

Properties Needed: * Strong (resist crushing) * Durable (weather-resistant) * Rough shaped (better locking)

Dimensions (exam-specific):

Gauge	Width	Cushion Depth
BG	335 cm	300 mm
MG	230 cm	250 mm
NG	185 cm	150 mm

Component 4: SUB-GRADE (Formation)¶

Definition: Prepared natural soil supporting track

Forms: Embankment (raised), level, or cutting (excavated)

Requirements: * Uniform load transmission * Effective drainage * No volume/moisture variation

Slopes (must memorize): * Embankment: 2:1 (horizontal:vertical) * Cutting: 1½:1 * Ballast: 1½:1

Embankment Failures (draw Fig 1.15): 1. Slope failure: Side collapses 2. Base failure: Foundation fails 3. Toe failure: Bottom spreads

Remedies: * Reduce height * Flatten slope * Add weight beyond toe

Section 1.9: Geometric Design¶

Context: A train going 120 km/h hits a curve. Without proper design, it derails. This section ensures safety through mathematics.

1.9.1: Necessity¶

Five Reasons: 1. Smooth/safe running 2. Maximum speeds 3. Heavy axle loads 4. Prevent derailments 5. Minimize maintenance

1.9.2: Design Elements (7 topics - all exam-critical)¶

1.9.3: GRADIENTS¶

Definition: Slope in longitudinal direction

Types:

a) Ruling Gradient (steepest allowed) * Determines max load locomotive can haul

Formula: Extra force needed = W × gradient

Indian Standards: * Plains: 1 in 150 to 1 in 250 * Hills: 1 in 100 to 1 in 150

b) Pusher/Helper Gradient * Steeper than ruling * Needs extra locomotive

c) Momentum Gradient * Steeper than ruling * Train uses kinetic energy from downhill run * No signals to interrupt momentum

d) Station Yard Gradients * Maximum: 1 in 400 * Recommended: 1 in 1000 * Why flat? - Prevent vehicles rolling away - Easier locomotive starting

Common Confusion: * Ruling = normal maximum * Pusher = needs extra engine * Momentum = uses speed from previous downhill

1.9.4: GRADE COMPENSATION¶

Why?: Curves add resistance, so make gradient flatter on curves

Compensation Rates: | Gauge | Formula | Alternative | |-------|---------|-------------| | BG | 0.04% per degree | 70/R | | MG | 0.03% per degree | 52.5/R | | NG | 0.02% per degree | 35/R |

(Choose whichever is minimum; R = radius in meters)

1.9.5: RADIUS & DEGREE OF CURVE¶

Degree of Curve (D): Angle subtended by 30.5m chord at center

Formula: D = 1750/R (when R in meters)

Example: 2° curve has radius = 1750/2 = 875m

Common Confusion: Large radius = small degree (inverse relationship)

1.9.6: SUPER ELEVATION (CANT) ⭐ MOST IMPORTANT¶

Context: Car on highway curve leans outward. Train can't lean, so we tilt the track!

Definition: Outer rail raised above inner rail

Why? (4 functions): 1. Better load distribution 2. Reduce wear & tear 3. Neutralize centrifugal force 4. Passenger comfort

Derivation (exam favorite - 10 marks):

Centrifugal force = Wv²/gR

At equilibrium, horizontal component = centrifugal force

Final Formula:

e (mm) = GV² / (127R)

Where: * G = Gauge (1750 mm for BG, 1058 mm for MG) * V = Speed (km/h) * R = Radius (m)

Simplified Versions: * BG: e = 1.315V²/R * MG: e = 0.800V²/R * NG: e = 0.600V²/R

Maximum Cant (memorize table 1.5):

Gauge & Group	Normal	With CE Permission
BG (Group A)	165 mm	185 mm
BG (Group D&E)	140 mm	-
MG	90 mm	100 mm
NG	65 mm	75 mm

General Rule: Max cant ≈ 1/10 to 1/12 of gauge

Negative Super Elevation: * Main line on curve has branch line diverging opposite direction * Branch line has "negative cant" (wrong way tilt) * Must reduce speed on both lines

Calculation: 1. Find equilibrium cant: e = GV²/(127R) 2. Subtract cant deficiency (Cd): x = e - Cd 3. Cd = 75mm (BG) or 50mm (MG) 4. If Cd > e, then x is negative

1.9.7: TRANSITION CURVES¶

Problem: Straight track → sudden curve = sudden centrifugal force = discomfort + danger

Solution: Gradually curve the track

Definition: Curve where degree and super-elevation increase uniformly from zero

Three Objectives: 1. Decrease radius gradually (∞ → R) 2. Increase super-elevation gradually (0 → e) 3. Increase centrifugal force gradually

Length Formula (use maximum of three):

L = 0.008 Ca Vm
L = 0.008 Cd Vm  
L = 0.72 Ca

Where: * Ca = actual cant (mm) * Cd = cant deficiency (mm) * Vm = maximum speed

1.9.8: VERTICAL CURVES¶

Problem: Two gradients meet at angle → rough ride + tension changes

Solution: Smooth the angle with vertical curve (circular profile)

Purpose: * Prevent vehicle bunching in sags * Avoid coupling tension variation * Comfortable ride

1.9.9: WIDENING OF GAUGE¶

Problem on Curves: * Straight track: wheel flanges clear rails * Curve: outer wheel flange rubs rail (coning makes it travel farther) * Leading vs trailing axle have different positions (rigid wheelbase)

Solution: Widen gauge on sharp curves

Formula:

w = 13(B+L)² / R

Where: * B = wheelbase (m) * L = flange lap = 0.02√(h²+Dh) * h = flange depth * D = wheel diameter * R = radius (m)

Standards (Table 1.5):

Curve Radius	BG	MG/NG
Straight / gentle curves	-5 to +3 mm	-2 to +3 mm (MG)
Sharp curves (< 350m BG)	Up to +10 mm	Up to +10 mm
Very sharp (< 100m NG)	-	Up to +15 mm

Section 1.10: Points & Crossings¶

Context: How does a train switch from Platform 1 track to Platform 2 track? You can't lift it!

Definition: Special track arrangements to transfer vehicles between tracks

Why Needed?: Wheels have inside flanges (can't jump over rails)

Complete Set: Points + Crossings + Lead Rails = TURNOUT

1.10.1: Elements (12 terms - exam loves definitions)¶

Tongue Rails: Tapered, movable rails
Stock Rails: Main running rails
Switch: Tongue rails + connections (no stock rails)
Points: Tongue + stock rails + connections
Heel of Switch: Imaginary point at end of tongue rail
Throw of Switch: Distance tongue moves (gap between tongue & stock)
Theoretical Toe: Intersection point of gauge lines at toe
Theoretical Nose of Crossing (TNC): Intersection of main/turnout gauge lines
Actual Nose of Crossing (ANC): Practical nose (TNC cut off for thickness)
Throat: Where converging wing rails are closest
Left/Right Hand Turnout: Based on diversion direction

Common Confusion: * Switch = movable part only * Points = switch + stock rails * Crossing = where tracks intersect * Turnout = complete assembly

1.10.2: Turnouts¶

Definition: Simplest combination enabling one track to leave another

Components (7 items): 1. Pair of points/switches 2. Pair of stock rails 3. Check rails 4. Lead rails 5. Stretcher bars 6. Crossings (V-piece) 7. Wing rails

Exam Strategy for This Unit:¶

High-Weightage Topics (25+ marks):¶

Alignment Selection (Sections 1.5, 1.6)
Mountain development methods with diagrams
Obligatory points examples
Super Elevation Derivation (Section 1.9.6)
Full derivation (10 marks)
Maximum values table
Survey Types (Section 1.7)
5 surveys with equipment tables
Modern techniques

Comparison Tables (10-15 marks):¶

Road vs Rail (Section 1.3)
Four terrains with solutions (Section 1.6.4)
Gauge types (Section 1.4.2)

Definition Questions (5 marks each):¶

Permanent way components
Creep vs Kinks
Coning vs Canting
Points & Crossing elements

Diagram Questions (8-10 marks):¶

Zigzag/Switch-back/Loop alignments
Coning of wheels (Fig 1.13)
Embankment failures (Fig 1.15)
Super elevation forces (Fig 1.16)

Formula-Based (5-8 marks):¶

Super elevation: e = GV²/(127R)
Degree of curve: D = 1750/R
Transition curve length (3 formulas)

Final Tip: This unit is 40% theory (definitions, comparisons) + 30% diagrams + 30% derivations/calculations. Practice drawing all figures cleanly!