Dissolved Oxygen and Biochemical Oxygen Demand

 Dissolved Oxygen and Biochemical Oxygen Demand   🔆🔆🔆🔆✔ Corrections pending

What is dissolved oxygen and why is it important?

The stream system both produces and consumes oxygen. It gains oxygen from the atmosphere and from plants as a result of photosynthesis. Running water, because of its churning, dissolves more oxygen than still water, such as that in a reservoir behind a dam. Respiration by aquatic animals, decomposition, and various chemical reactions consume oxygen.

Wastewater from sewage treatment plants often contains organic materials that are decomposed by microorganisms, which use oxygen in the process. (The amount of oxygen consumed by these organisms in breaking down the waste is known as the biochemical oxygen demand or BOD. A discussion of BOD and how to monitor it is included at the end of this section.) Other sources of oxygen-consuming waste include stormwater runoff from farmland or urban streets, feedlots, and failing septic systems.

Oxygen is measured in its dissolved form as dissolved oxygen (DO). If more oxygen is consumed than is produced, dissolved oxygen levels decline and some sensitive animals may move away, weaken, or die.

DO levels fluctuate seasonally and over a 24-hour period. They vary with water temperature and altitude. Cold water holds more oxygen than warm water (Table 5.3) and water holds less oxygen at higher altitudes. Thermal discharges, such as water used to cool machinery in a manufacturing plant or a power plant, raise the temperature of water and lower its oxygen content. Aquatic animals are most vulnerable to lowered DO levels in the early morning on hot summer days when stream flows are low, water temperatures are high, and aquatic plants have not been producing oxygen since sunset.

Temperature (°C)	DO (mg/l)	Temperature (°C)	DO (mg/l)	Table 5.3 Maximum dissolved oxygen concentrates vary with temperature
0	14.60	23	8.56
1	14.19	24	8.40
2	13.81	25	8.24
3	13.44	26	8.09
4	13.09	27	7.95
5	12.75	28	7.81
6	12.43	29	7.67
7	12.12	30	7.54
8	11.83	31	7.41
9	11.55	32	7.28
10	11.27	33	7.16
11	11.01	34	7.16
12	10.76	35	6.93
13	10.52	36	6.82
14	10.29	37	6.71
15	10.07	38	6.61
16	9.85	39	6.51
17	9.65	40	6.41
18	9.45	41	6.41
19	9.26	42	6.22
20	9.07	43	6.13
21	8.90	44	6.04
22	8.72	45	5.95

Sampling and Equipment Considerations

In contrast to lakes, where DO levels are most likely to vary vertically in the water column, the DO in rivers and streams changes more horizontally along the course of the waterway. This is especially true in smaller, shallower streams. In larger, deeper rivers, some vertical stratification of dissolved oxygen might occur. The DO levels in and below riffle areas, waterfalls, or dam spillways are typically higher than those in pools and slower-moving stretches. If you wanted to measure the effect of a dam, it would be important to sample for DO behind the dam, immediately below the spillway, and upstream of the dam. Since DO levels are critical to fish, a good place to sample is in the pools that fish tend to favor or in the spawning areas they use.

An hourly time profile of DO levels at a sampling site is a valuable set of data because it shows the change in DO levels from the low point just before sunrise to the high point sometime in the midday. However, this might not be practical for a volunteer monitoring program. It is important to note the time of your DO sampling to help judge when in the daily cycle the data were collected.

DO is measured either in milligrams per liter (mg/L) or "percent saturation." Milligrams per liter is the amount of oxygen in a liter of water. Percent saturation is the amount of oxygen in a liter of water relative to the total amount of oxygen that the water can hold at that temperature.

DO samples are collected using a special BOD bottle: a glass bottle with a "turtleneck" and a ground glass stopper. You can fill the bottle directly in the stream if the stream is wadable or boatable, or you can use a sampler that is dropped from a bridge or boat into water deep enough to submerse the sampler. Samplers can be made or purchased. Dissolved oxygen is measured primarily either by using some variation of the Winkler method or by using a meter and probe.

Winkler Method

The Winkler method involves filling a sample bottle completely with water (no air is left to bias the test). The dissolved oxygen is then "fixed" using a series of reagents that form an acid compound that is titrated. Titration involves the drop-by-drop addition of a reagent that neutralizes the acid compound and causes a change in the color of the solution. The point at which the color changes is the "endpoint" and is equivalent to the amount of oxygen dissolved in the sample. The sample is usually fixed and titrated in the field at the sample site. It is possible, however, to prepare the sample in the field and deliver it to a lab for titration.

Dissolved oxygen field kits using the Winkler method are relatively inexpensive, especially compared to a meter and probe. Field kits run between $35 and $200, and each kit comes with enough reagents to run 50 to 100 DO tests. Replacement reagents are inexpensive, and you can buy them already measured out for each test in plastic pillows.

You can also buy the reagents in larger quantities, in bottles, and measure them out with a volumetric scoop. The advantage of the pillows is that they have a longer shelf life and are much less prone to contamination or spillage. The advantage of buying larger quantities in bottles is that the cost per test is considerably less.

The major factor in the expense of the kits is the method of titration they use eyedropper, syringe-type titrator, or digital titrator. Eyedropper and syringe-type titration is less precise than digital titration because a larger drop of titrant is allowed to pass through the dropper opening and, on a micro-scale, the drop size (and thus the volume of titrant) can vary from drop to drop. A digital titrator or a buret (which is a long glass tube with a tapered tip like a pipet) permits much more precision and uniformity in the amount of titrant that is allowed to pass.

If your program requires a high degree of accuracy and precision in DO results, use a digital titrator. A kit that uses an eye dropper-type or syringe- type titrator is suitable for most other purposes. The lower cost of this type of DO field kit might be attractive if you are relying on several teams of volunteers to sample multiple sites at the same time.

Meter and Probe

A dissolved oxygen meter is an electronic device that converts signals from a probe that is placed in the water into units of DO in milligrams per liter. Most meters and probes also measure temperature. The probe is filled with a salt solution and has a selectively permeable membrane that allows DO to pass from the stream water into the salt solution. The DO that has diffused into the salt solution changes the electric potential of the salt solution and this change is sent by electric cable to the meter, which converts the signal to milligrams per liter on a scale that the volunteer can read.

DO meters are expensive compared to field kits that use the titration method. Meter/probe combinations run between $500 and $1,200, including a long cable to connect the probe to the meter. The advantage of a meter/probe is that you can measure DO and temperature quickly at any point in the stream that you can reach with the probe. You can also measure the DO levels at a certain point on a continuous basis. The results are read directly as milligrams per liter, unlike the titration methods, in which the final titration result might have to be converted by an equation to milligrams per liter.

However, DO meters are more fragile than field kits, and repairs to a damaged meter can be costly. The meter/probe must be carefully maintained, and it must be calibrated before each sample run and, if you are doing many tests, in between samplings. Because of the expense, a volunteer program might have only one meter/probe. This means that only one team of samplers can sample DO and they will have to do all the sites. With field kits, on the other hand, several teams can sample simultaneously.

Laboratory Testing of Dissolved Oxygen

If you use a meter and probe, you must do the testing in the field; dissolved oxygen levels in a sample bottle change quickly due to the decomposition of organic material by microorganisms or the production of oxygen by algae and other plants in the sample. This will lower your DO reading. If you are using a variation of the Winkler method, it is possible to "fix" the sample in the field and then deliver it to a lab for titration. This might be preferable if you are sampling under adverse conditions or if you want to reduce the time spent collecting samples. It is also a little easier to titrate samples in the lab, and more quality control is possible because the same person can do all the titrations.

How to collect and analyze samples

The procedures for collecting and analyzing samples for dissolved oxygen consist of the following tasks:

TASK 1 Prepare before leaving for the sampling site

Refer to section 2.3 - Safety Considerations for details on confirming sampling date and time, safety considerations, checking supplies, and checking weather and directions. In addition to the standard sampling equipment and apparel, when sampling for dissolved oxygen, include the following equipment:

If Using the Winkler Method

• Labels for sample bottles
• Field kit and instructions for DO testing
• Enough reagents for the number of sites to be tested
• Kemmerer, Van Dorn, or home-made sampler to collect deep-water samples
• A numbered glass BOD bottle with a glass stopper (1 for each site)
• Data sheet for dissolved oxygen to record results

If Using a Meter and Probe

• DO meter and probe (electrode) (NOTE: Confirm that the meter has been calibrated according to the manufacturer's instructions.)
• Operating manual for the meter and probe
• Extra membranes and electrolyte solution for the probe
• Extra batteries for the meter
• Extension pole
• Data sheet for dissolved oxygen to record results

TASK 2 Confirm that you are at the proper location

The directions for sampling should provide specific information about the exact point in the stream from which you are to sample; e.g., "approximately 6 feet out from the large boulder downstream from the west side of the bridge." If you are not sure you are in the exact spot, record a detailed description of where you took the sample so that it can be compared to the actual site later.

TASK 3 Collect samples and fill out the field data sheet

Winkler Method

Use a BOD bottle to collect the water sample. The most common sizes are 300 milliliters (mL) and 60 mL. Be sure that you are using the correct volume for the titration method that will be used to determine the amount of DO. There is usually a white label area on the bottle, and this may already be numbered. If so, be sure to record that number on the field data sheet. If your bottle is not already numbered, place a label on the bottle (not on the cap because a cap can be inadvertently placed on a different bottle) and use a waterproof marker to write in the site number.

If you are collecting duplicate samples, label the duplicate bottle with the correct code, which should be determined prior to sampling by the lab supplying the bottles. Use the following procedure for collecting a sample for titration by the Winkler method:

1. Remember that the water sample must be collected in such a way that you can cap the bottle while it is still submerged. That means that you must be able to reach into the water with both arms and the water must be deeper than the sample bottle.
2. Carefully wade into the stream. Stand so that you are facing one of the banks.
3. Collect the sample so that you are not standing upstream of the bottle. Remove the cap of the BOD bottle. Slowly lower the bottle into the water, pointing it downstream, until the lower lip of the opening is just submerged. Allow the water to fill the bottle very gradually, avoiding any turbulence (which would add oxygen to the sample). When the water level in the bottle has stabilized (it won't be full because the bottle is tilted), slowly turn the bottle upright and fill it completely. Keep the bottle under water and allow it to overflow for 2 or 3 minutes to ensure that no air bubbles are trapped.
4. Cap the bottle while it is still submerged. Lift it out of the water and look around the "collar" of the bottle just below the bottom of the stopper. If you see an air bubble, pour out the sample and try again.
5. "Fix" the sample immediately following the directions in your kit:
• Remove the stopper and add the fixing reagents to the sample.
• Immediately insert the stopper so air is not trapped in the bottle and invert several times to mix. This solution is caustic. Rinse your hands if you get any solution on them. An orange-brown flocculent precipitate will form if oxygen is present.
• Wait a few minutes until the floc in the solution has settled. Again invert the bottle several times and wait until the floc has settled. This ensures complete reaction of the sample and reagents. The sample is now fixed, and atmospheric oxygen can no longer affect it. If you are taking the sample to the lab for titration, no further action is necessary. You can store the sample in a cooler for up to 8 hours before titrating it in a lab. If you are titrating the sample in the field, see Task 4: Analyze the Samples.

Figure 5.7 Taking a water sample for DO analysis Point the bottle downstream and fill gradually. Cap underwater when full.

Using a DO Meter

If you are using a dissolved oxygen meter, be sure that it is calibrated immediately prior to use. Check the cable connection between the probe and the meter. Make sure that the probe is filled with electrolyte solution, that the membrane has no wrinkles, and that there are no bubbles trapped on the face of the membrane. You can do a field check of the meter's accuracy by calibrating it in saturated air according to th e manufacturer's instructions. Or, you can measure a water sample that is saturated with oxygen, as follows. (NOTE: You can also use this procedure for testing the accuracy of the Winkler method.)

1. Fill a l-liter beaker or bucket of tap water. (You may want to bring a gallon jug with water in it for this purpose.) Mark the bottle number as "tap" on the lab sheet.
2. Pour this water back and forth into another beaker 10 times to saturate the water with oxygen.
3. Use the meter to measure the water temperature and record it in the water temperature column on the field data sheet.
4. Find the water temperature of your "tap" sample in Table 5.3. Use the meter to compare the dissolved oxygen concentration of your sample with the maximum concentration at that temperature in the table. Your sample should be within 0.5 mg/L. If it is not, repeat the check and if there is still an error, check the meter's batteries and follow the troubleshooting procedures in the manufacturer's manual.

Once the meter is turned on, allow 15 minute equilibration before calibrating. After calibration, do not turn the meter off until the sample is analyzed. Once you have verified that the meter is working properly, you are ready to measure the DO levels at the sampling site. You might need an extension pole (this can be as simple as a piece of wood) to get the probe to the proper sampling point. Simply secure the probe to the end of the extension pole. A golfer's ball retriever works well because it is collapsible and easy to transport. To use the probe, proceed as follows:

1. Place the probe in the stream below the surface.
2. Set the meter to measure temperature, and allow the temperature reading to stabilize. Record the temperature on the field data sheet.
3. Switch the meter to read dissolved oxygen.
4. Record the dissolved oxygen level on the field data sheet.

TASK 4 Analyze the samples

Three types of titration apparatus can be used with the Winkler method: droppers, digital titrators, and burets. The dropper and digital titrator are suited for field use. The buret is more conveniently used in the lab (Fig. 5.8) Volunteer programs are most likely to use the dropper or digital titrator. For titration with a dropper or syringe, which is relatively simple, follow the manufacturer's instructions. The following procedure is for using a digital titrator to determine the quantity of dissolved oxygen in a fixed sample:

Figure 5.8 Titrating a DO sample using a buret

1. Select a sample volume and sodium thiosulfate titration cartridge for the digital titrator corresponding to the expected dissolved oxygen concentration according to Table 5.4. In most cases, you will use the 0.2 N cartridge and the 100-mL sample volume.
2. Insert a clean delivery tube into the titration cartridge.
3. Attach the cartridge to the titrator body.
4. Hold the titrator with the cartridge tip up. Turn the delivery knob to eject air and a few drops of titrant. Reset the counter to 0 and wipe the tip.
5. Use a graduated cylinder to measure the sample volume (from the "fixed" sample in the 300-mL BOD bottle) according to Table 5.4.
6. Transfer the sample into a 250-mL Erlenmeyer flask, and place the flask on a magnetic stirrer with a stir bar. If you are in the field, you can manually swirl the flask to mix.
7. Place the delivery tube tip into the solution and turn the stirrer on to stir the sample while you're turning the delivery knob.
8. Titrate to a pale yellow color.
9. Add two dropperfuls of starch indicator solution and swirl to mix. A strong blue color will develop.
10. Continue to titrate until the sample is clear. Record the number of digits required. (The color might reappear after standing a few minutes, but this is not a cause for concern. The "first" disappearance of the blue color is considered the endpoint.)
11. Calculate mg/L of DO = digits required X digit multiplier (from Table 5.4).
12. Record the results in the appropriate column of the data sheet.

Some water quality standards are expressed in terms of percent saturation. To calculate percent saturation of the sample:

1. Find the temperature of your water sample as measured in the field.
2. Find the maximum concentration of your sample at that temperature as given in Table 5.3.
3. Calculate the percent saturation, by dividing your actual dissolved oxygen by the maximum concentration at the sample temperature.
4. Record the percent saturation in the appropriate column on the data sheet.

Expected Range	Sample Volume	Titration Cartridge	Digit Multiplier	Table 5.4 Sample volume selection and corresponding values for Winkler titration
1-5 mg/L	200 mL	0.2 N	0.01
2-10 mg/L	100 mL	0.2 N	0.02
10+ mg/L	200 mL	2.0 N	0.10

TASK 5 Return the samples and the field data sheets to the lab/drop-off point

If you are using the Winkler method and delivering the samples to a lab for titration, double-check to make sure that you have recorded the necessary information for each site on the field data sheet, especially the bottle number and corresponding site nu mber and the times the samples were collected. Deliver your samples and field data sheets to the lab. If you have already obtained the dissolved oxygen results in the field, send the data sheets to your sampling coordinator.

What is biochemical oxygen demand and why is it important?

Biochemical oxygen demand, or BOD, measures the amount of oxygen consumed by microorganisms in decomposing organic matter in stream water. BOD also measures the chemical oxidation of inorganic matter (i.e., the extraction of oxygen from water via chemical reaction). A test is used to measure the amount of oxygen consumed by these organisms during a specified period of time (usually 5 days at 20 C). The rate of oxygen consumption in a stream is affected by a number of variables: temperature, pH, the presence of certain kinds of microorganisms, and the type of organic and inorganic material in the water.

BOD directly affects the amount of dissolved oxygen in rivers and streams. The greater the BOD, the more rapidly oxygen is depleted in the stream. This means less oxygen is available to higher forms of aquatic life. The consequences of high BOD are the same as those for low dissolved oxygen: aquatic organisms become stressed, suffocate, and die.

Sources of BOD include leaves and woody debris; dead plants and animals; animal manure; effluents from pulp and paper mills, wastewater treatment plants, feedlots, and food-processing plants; failing septic systems; and urban stormwater runoff.

Sampling Considerations

BOD is affected by the same factors that affect dissolved oxygen (see above). Aeration of stream water by rapids and waterfalls, for example will accelerate the decomposition of organic and inorganic material. Therefore, BOD levels at a sampling site with slower, deeper waters might be higher for a given volume of organic and inorganic material than the levels for a similar site in highly aerated waters.

Chlorine can also affect BOD measurement by inhibiting or killing the microorganisms that decompose the organic and inorganic matter in a sample. If you are sampling in chlorinated waters, such as those below the effluent from a sewage treatment plant, it is necessary to neutralize the chlorine with sodium thiosulfate. (See APHA, 1992.)

BOD measurement requires taking two samples at each site. One is tested immediately for dissolved oxygen, and the second is incubated in the dark at 20 C for 5 days and then tested for the amount of dissolved oxygen remaining. The difference in oxygen levels between the first test and the second test, in milligrams per liter (mg/L), is the amount of BOD. This represents the amount of oxygen consumed by microorganisms to break down the organic matter present in the sample bottle during the incubation period. Because of the 5-day incubation, the tests should be conducted in a laboratory.

Sometimes by the end of the 5-day incubation period the dissolved oxygen level is zero. This is especially true for rivers and streams with a lot of organic pollution. Since it is not known when the zero point was reached, it is not possible to tell what the BOD level is. In this case it is necessary to dilute the original sample by a factor that results in a final dissolved oxygen level of at least 2 mg/L. Special dilution water should be used for the dilutions. (See APHA, 1992.)

It takes some experimentation to determine the appropriate dilution factor for a particular sampling site. The final result is the difference in dissolved oxygen between the first measurement and the second after multiplying the second result by the dilution factor. More details are provided in the following section.

How to Collect and Analyze Samples

The procedures for collecting samples for BOD testing consist of the same steps described for sampling for dissolved oxygen (see above), with one important difference. At each site a second sample is collected in a BOD bottle and delivered to the lab for DO testing after the 5-day incubation period. Follow the same steps used for measuring dissolved oxygen with these additional considerations:

• Make sure you have two BOD bottles for each site you will sample. The bottles should be black to prevent photosynthesis. You can wrap a clear bottle with black electrician's tape if you do not have a bottle with black or brown glass.
• Label the second bottle (the one to be incubated) clearly so that it will not be mistaken for the first bottle.
• Be sure to record the information for the second bottle on the field data sheet.

The first bottle should be analyzed just prior to storing the second sample bottle in the dark for 5 days at 20 C. After this time, the second bottle is tested for dissolved oxygen using the same method that was used for the first bottle. The BOD i s expressed in milligrams per liter of DO using the following equation:

DO (mg/L) of first bottle
- DO (mg/L) of second bottle
= BOD (mg/L)

References

APHA. 1992. Standard methods for the examination of water and wastewater. 18^th ed. American Public Health Associa

tion, Washington, DC.

 

 

                  

Drainage in Tunnels Drainage & water proofing

Drainage & water proofing                              

 Drainage and waterproofing are essential aspects of tunnel construction and maintenance. Tunnels are vulnerable to water ingress due to their underground location, making effective drainage and waterproofing systems crucial for ensuring their structural integrity and functionality. Let's explore these concepts further:

Drainage in Tunnels:

Drainage systems in tunnels are designed to control the flow of water, preventing accumulation and potential damage. Here are some common drainage elements:

Drainage Ditches: These are channels constructed along the sides or base of the tunnel to collect and redirect water away from critical areas.

Sump Pumps: Used to pump out collected water from drainage ditches or sumps, ensuring a continuous flow and preventing flooding.

Gravel or Perforated Pipes: Placed below the tunnel's base or along its sides, these pipes facilitate water collection and transportation to the drainage system.

Drainage Outlets: Located at regular intervals, these outlets allow water to exit the tunnel safely.

Waterproofing in Tunnels:

Waterproofing measures are employed to prevent water from penetrating the tunnel structure. They help maintain the tunnel's durability and protect against potential water-related issues. Here are some common waterproofing techniques:

Membrane Systems: Waterproof membranes, such as bituminous or PVC-based sheets, are applied to the tunnel surfaces. These sheets form a barrier against water penetration.

Injection Grouting: This method involves injecting a waterproofing material, like cementitious grout or chemical resins, into cracks or joints to seal them and prevent water ingress.

Concrete Admixtures: Certain additives can be mixed with concrete during construction to enhance its waterproofing properties.

Shotcrete: A layer of sprayed concrete can be applied to the tunnel surfaces, forming a waterproofing barrier.

Tunnel Lining: Lining materials, such as precast concrete segments or cast-in-place concrete, can be used to create a waterproof layer around the tunnel. Both drainage and waterproofing systems should be designed based on the specific geotechnical conditions, hydrological considerations, and expected water loads in and around the tunnel. Regular inspections and maintenance are essential to ensure the continued effectiveness of these systems.

It's important to note that tunnel design and construction involve complex engineering considerations, and the specific drainage and waterproofing methods can vary depending on factors such as tunnel type, location, and anticipated water conditions. Consulting with tunnel engineering experts and adhering to applicable industry standards and regulations is crucial to ensure a safe and well-fun

History of Tunneling

Different Tunneling Method

Uses of Tunnels

Geology

Geotechnical Investigations

Geophysical Exploration

Numerical Analysis

The New Austrian Tunneling Method (NATM)

Mechanized or TBM Tunneling

Immersed Tunnel

Cut and Cover Tunnel

Underground Stations

Urban Tunneling

Utility Tunneling

Soft Ground Tunneling

Precast Segment Design

Grouting

Instrumentation and Monitoring

Fire and Safety

Ventilation

Maintenance, Repair & Operation o

Risk Asshel971 947 444

Subm

 

 

 

रेलवे के प्रकार Types Of Railways

 रेलवे के प्रकार

दुनिया में कितने प्रकार के रेलवे ट्रैक हैं? शायद आप जितना सोचते हैं उससे कहीं ज़्यादा। रेलवे ट्रैक के प्रकारों को अलग-अलग पहलुओं जैसे कि रेल गेज, निर्माण रूप आदि से विभाजित किया जा सकता है।

विभिन्न रेल गेज वाले रेलवे ट्रैक

रेल गेज रेलरोड ट्रैक की पटरियों या ट्रेन के पहियों के बीच की दूरी है। आम तौर पर, रेलवे ट्रैक गेज के प्रकारों को मानक गेज, नैरो गेज और ब्रॉड गेज में विभाजित किया जा सकता है। सबसे आम गेज मानक गेज 1435 मिमी (4 फीट 8 1/2 इंच) है। 1435 मिमी से कम चौड़े गेज को नैरो गेज कहा जाता है जबकि 1435 मिमी से अधिक चौड़े गेज को ब्रॉड गेज कहा जाता है।

दुनिया में मानक गेज रेलवे ट्रैक की कुल लंबाई 720,000 किलोमीटर है। यह दुनिया के रेलवे का केवल 60% हिस्सा है। नैरो गेज ट्रैक की एक किस्म केप गेज रेलवे उपयोग के मामले में दुनिया में तीसरे स्थान पर है। कुल 110,000 किलोमीटर से ज़्यादा की लंबाई के साथ, केप गेज रेलवे ट्रैक दुनिया के रेलवे का लगभग 11% हिस्सा है। इसके अलावा, भारतीय गेज, इबेरियन गेज, रूसी गेज, मीटर गेज आदि जैसे कई गेज हैं।

मानक गेज रेलवे ट्रैक

मानक गेज 1435 मिमी (4 फीट 8 1/2 इंच) चौड़ा है और सबसे ऐतिहासिक गेज में से एक है। मानक गेज की एक कहानी प्राचीन रोमन युग से जुड़ी है। उस समय सड़कें आज की तुलना में बहुत कम पक्की थीं और उनमें से ज़्यादातर मिट्टी से बनी थीं। इसलिए, गाड़ियाँ आगे-पीछे चलती थीं और धीरे-धीरे ज़मीन पर गहरे पहियों के निशान छोड़ती थीं। इस पहिये के निशान जितनी चौड़ाई वाली गाड़ी बहुत आसानी से चल सकती है, लेकिन अलग चौड़ाई वाली गाड़ी के पहिये गलती से खाई में गिर सकते हैं और गाड़ी को नुकसान पहुँचा सकते हैं। समय के साथ, एक ही क्षेत्र में गाड़ियाँ एक ही ट्रैक बन गई थीं। सम्राट निशिजावा ने साम्राज्य पर शासन करने के बाद, रोम के सभी लोगों को एक ही गाड़ी के व्हीलबेस का उपयोग करने के लिए एक आदेश जारी किया, और यहां तक ​​कि नई पक्की पत्थर की सड़क भी पहियों के चलने के लिए खांचे छोड़ देगी! ऐतिहासिक स्थलों से, हम अब जान सकते हैं कि गाड़ी का गेज 4 फीट 9 इंच है, जो मानक गेज की चौड़ाई के बहुत करीब है। लेकिन क्या इससे कोई फर्क पड़ता है कि इसे पारित किया गया है? इस भाग पर अलग-अलग राय हैं। मानक गेज के सर्जक जॉर्ज स्टीफेंसन हैं। एक और रोमांटिक दृष्टिकोण यह है कि उन्होंने अभी-अभी एक रोमन स्मारक की खुदाई देखी है, इसलिए उन्होंने गेज को इस चौड़ाई पर सेट करने का फैसला किया। लेकिन यह अधिक संभावना है कि यह सिर्फ एक साधारण संयोग है। मानक गेज की चौड़ाई दो घोड़ों के गधों के बराबर होती है। शुरुआती दिनों में, ट्रेन एक ऐसा उत्पाद था जिसने रेल-प्रकार के वैगन को बदल दिया। स्वाभाविक रूप से, यह मौजूदा ट्रैक की चौड़ाई के अनुकूल होगा, इसलिए यह "मानक" दिखाई दिया!

क्या सभी ने शुरुआत से ही 1435 मिमी चौड़ाई का पालन किया? जवाब है नहीं। इसाम्बर्ड ब्रुनेल द्वारा निर्मित ग्रेट वेस्टर्न रेलवे 2140 मिमी की एक अजेय चौड़ी पटरी का उपयोग करता है। इसका मुख्य उद्देश्य यह है कि यह डिज़ाइन स्थिरता को बढ़ा सकता है और एक बड़े स्टीम इंजन के लिए जगह छोड़ सकता है। उन्नीसवीं सदी के मध्य में, इन दो विशिष्टताओं ने यूनाइटेड किंगडम में भी बहुत संघर्ष किया, और अंत में एक मानक गेज के साथ जीता जो कोने में आसान और कम लागत वाला है। एक सरकारी शोध समूह द्वारा अनुशंसित किए जाने के बाद, यूनाइटेड किंगडम ने 1845 में ट्रैक कानून लागू किया ताकि विभिन्न लाइनों के बीच सीधे संचालन की सुविधा के लिए नवनिर्मित लाइनों को 1435 मिमी की चौड़ाई अपनाने के लिए मजबूर किया जा सके। अंतिम विनिर्देश युद्ध 1892 में ग्रेट वेस्टर्न रेलवे के मानक गेज में पूर्ण रूपांतरण के साथ समाप्त हुआ। यूनाइटेड किंगडम से शुरू होकर, यूरोपीय महाद्वीप और संयुक्त राज्य अमेरिका ने शुरुआती दिनों में पहला रेलवे बनाने के लिए या तो ब्रिटिश इंजीनियरों को काम पर रखा या यूनाइटेड किंगडम द्वारा निर्मित लोकोमोटिव और ट्रेनें खरीदीं। इसलिए, यूरोपीय महाद्वीप और संयुक्त राज्य अमेरिका। पलटने और छिद्रण के बाद, मानक गेज मानक है।

नैरो-गेज रेलवे ट्रैक

मानक गेज से संकरे गेज को नैरो गेज कहा जाता है।

• केप गेज

केप गेज 1067 मिमी चौड़ा है, क्योंकि यह 1435 मिमी के मानक गेज से संकरा है, इसलिए यह एक तरह का "संकीर्ण गेज" है। इसका नाम केप गेज इसलिए रखा गया क्योंकि दक्षिण अफ्रीका के भूतपूर्व केप प्रांत ने 1873 में इस गेज को अपनाया था। लेकिन इस गेज को स्थापित करने वाला पहला देश नॉर्वे था। उस समय नॉर्वे अभी भी स्वीडन से जुड़ा हुआ था, और यह एक अविकसित अर्थव्यवस्था वाला सीमावर्ती क्षेत्र था। जब इंजीनियर कार्ल पिहल ने नॉर्वे की पहली रेलवे बनाने की कोशिश की, तो उन्होंने दो संभावित चौड़ाई पर विचार किया जो पहाड़ी नॉर्वे के लिए उपयुक्त थीं। एक 3 फीट 6 इंच (1067 मिमी) और दूसरी 3 फीट 3 इंच (मीटर गेज, 1000 मिमी) है। उन्होंने स्टीम लोकोमोटिव बनाने वाले स्टीवेंसन परिवार से सलाह मांगी। हालाँकि यह अधिक महंगा होगा, स्टीवेंसन ने सोचा कि थोड़ा चौड़ा गेज पहाड़ों की सुरक्षा में मदद करेगा। इसलिए अंत में, 1067 मिमी नॉर्वेजियन मानक ट्रैक चौड़ाई के रूप में तय हुआ। • 

केप गेज के अलावा, नैरो-गेज रेलवे में केवल मीटर गेज (1000 मिमी) का प्रचलन अपेक्षाकृत अधिक है, मुख्य रूप से दक्षिण-पूर्व एशिया और ब्राजील में। आम तौर पर, मीटर गेज से संकरी रेलवे की वहन क्षमता बहुत कम हो जाएगी। इसलिए, चीनी कारखाने में 762 मिमी की पांच मिनट की गाड़ी जैसे औद्योगिक रेलवे का ही उपयोग किया जाएगा। हालांकि, पांच मिनट की ट्रेन की कम बिछाने की लागत और छोटे मोड़ त्रिज्या के कारण, यह पर्वतीय रेलवे पर उपयोग के लिए भी उपयुक्त है। ब्रॉड गेज रेलवे ट्रैक मानक गेज से अधिक चौड़े गेज को ब्रॉड गेज कहा जाता है। रूसी गेज, इबेरियन गेज और भारतीय गेज तीन विशिष्ट ब्रॉड गेज हैं। रूस के अधिकांश क्षेत्र समतल हैं। जब इंजीनियर पावेल मेलनिकोव ने पहला रेलवे बनाया, तो उन्होंने लोड क्षमता और ड्राइविंग स्थिरता बढ़ाने के लिए मानक गेज से अधिक चौड़े गेज का उपयोग करने की योजना बनाई। इस प्रकार रूसी गेज (1524 मिमी) का जन्म हुआ। रूस के पास मानक गेज बनने के लिए यूरोपीय महाद्वीप के बाकी हिस्सों के साथ गेज को सिंक्रनाइज़ करने के कई अवसर थे। लेकिन यह चिंता थी कि अगर दूसरे देशों की ट्रेनें बेरोकटोक प्रवेश कर गईं तो रूस के भीतरी इलाकों पर आक्रमण हो जाएगा। प्रथम विश्व युद्ध से लेकर द्वितीय विश्व युद्ध और फिर शीत युद्ध तक, यह अंततः एक ऐसी घटना में बदल गया जिसमें पूर्व सोवियत संघ ने सभी ने इस मानक को अपना लिया।

सैन्य कारणों से अपने विनिर्देशों को अपनाने वाले क्षेत्र स्पेन और पुर्तगाल हैं। ये दोनों देश इबेरियन प्रायद्वीप पर हैं, इसलिए इस्तेमाल किए जाने वाले गेज को इबेरियन गेज (1688 मिमी) कहा जाता है। ऐसा कहा जाता है कि इस खुद के विनिर्देश को प्राप्त करने के लिए फ्रांस के आक्रमण को रोकना था। लेकिन अब नव निर्मित स्पेनिश हाई-स्पीड रेल यूरोप में हाई-स्पीड ट्रेनों के आपसी संचालन को सुविधाजनक बनाने के लिए मानक गेज का उपयोग करती है।

भारतीय गेज (1676 मिमी) पूरी तरह से एक और कारण है। ऐसा कहा जाता है कि भारत द्वारा इतनी चौड़ी रेल को अपनाने का कारण यह है कि अगर रेल बहुत संकरी है, तो गाड़ी आसानी से हवा से उड़ जाती है? हम केवल यह कह सकते हैं कि इस चौड़ाई को निर्धारित करने वाला व्यक्ति दूरदर्शी है! लोगों से भरी भारतीय ट्रेनों की स्थिति को देखते हुए, संकरी पटरियाँ अच्छी नहीं हैं। गिट्टी और गिट्टी रहित रेलवे ट्रैक

गिट्टी वाला ट्रैक लकड़ी के स्लीपरों और कुचले हुए पत्थरों से बना पारंपरिक ट्रैक ढांचा है। पारंपरिक गिट्टी वाले ट्रैक में सरल बिछाने और कम समग्र लागत की विशेषताएं होती हैं, लेकिन यह आसानी से ख़राब हो जाता है इसलिए इसे बार-बार रखरखाव की आवश्यकता होती है। साथ ही, ट्रेन की गति सीमित होती है।

गिट्टी रहित ट्रैक उस ट्रैक संरचना को संदर्भित करता है जिसमें ढीले बजरी ट्रैकबेड के बजाय कंक्रीट, डामर मिश्रण और अन्य अभिन्न नींव का उपयोग किया जाता है। स्लीपर खुद कंक्रीट से बने होते हैं, और रोडबेड को बजरी की आवश्यकता नहीं होती है। स्टील की रेल और स्लीपर सीधे कंक्रीट रोडबेड पर बिछाए जाते हैं। गिट्टी रहित ट्रैक आज दुनिया में एक उन्नत ट्रैक तकनीक है, जो रखरखाव को कम कर सकती है, धूल को कम कर सकती है, पर्यावरण को सुंदर बना सकती है और ट्रेनों की गति को 1000 किलोमीटर प्रति घंटे से अधिक बढ़ा सकती है।

Types Of Railways ENG

Types Of Railways

How many types of railway tracks are there in the world? Probably more than you think. Types of railway tracks can be divided from different aspects such as the rail gauge, the construction form, etc.

Railway tracks with different rail gauges          

Rail gauge is the distance between the rails of a railroad track or the wheels of a train. Generally, the types of railway track gauges can be divided into the standard gauge, the narrow gauge, and the broad gauge. The most common gauge is standard gauge 1435mm (4 feet 8 1/2 inches). Gauges narrower than 1435mm are called narrow gauge while wider than 1435mm are called broad gauge.

The standard gauge railway track has a total of 720,000 kilometres in the world. It only accounts for 60% of the world’s railways. The Cape Gauge railways, one kind of narrow gauge tracks, ranks third in the world in terms of utilization. With a total of more than 110,000 kilometres,  cape gauge railway tracks account for approximately 11% of the world’s railways. Besides, there are various gauges such as Indian gauge, Iberian gauge, Russian gauge, metre gauge, etc.

The standard gauge railway track

The standard gauge is 1435mm (4 feet 8 1/2 inches) wide and one of the most historic gauges. There is a story of the standard gauge dates back to the ancient Roman era. The roads at that time were far less paved than they are now, and most of them were made of dirt. Therefore, the carriages ran back and forth gradually left deep wheel marks on the ground. A carriage with the same width as this wheel mark will run very easily, but a carriage with a different width will risk the wheels accidentally falling into the ditch and damage the carriage. Over time, carriages in the same area had become the same track. After Emperor Nishizawa ruled the empire, he issued an edict requiring all of Rome to use the same carriage wheelbase, and even the new paved stone road would leave grooves for wheels to travel! From the historical sites, we can know now that the carriage gauge is 4 feet 9 inches, which is very close to the width of the standard gauge. But does it matter if it is passed down? There are different opinions on this part. The initiator of the standard gauge is George Stephenson. A more romantic view is that he just saw the excavation of a Roman monument, so he decided to set the gauge to this width. But it is more likely that this is just a simple coincidence. The width of the standard gauge is the same as asses of two horses. In the earliest days, the train was a product that replaced the rail-type wagon. Naturally, it would adapt to the existing track width, so this “standard” appeared!

Did everyone follow the 1435mm width from the beginning? The answer is no. The Great Western Railway built by Isambard Brunel uses an invincible wide track of 2140mm. The main purpose is that this design can increase stability and leave room for a larger steam engine. In the mid-nineteenth century, these two specifications also fought a lot in the United Kingdom, and finally won with a standard gauge that is easier to corner and lower in cost. After being recommended by a government research group, the United Kingdom enacted the Track Law in 1845 to force the newly constructed lines to adopt a width of 1435mm to facilitate direct operation between different lines. The final specification war ended with the Great Western Railway’s full conversion to standard gauge in 1892. Beginning in the United Kingdom, the European continent and the United States either hired British engineers to build the first railway in the early days or bought locomotives and trains produced by the United Kingdom. Therefore, the European continent and the United States. After turning over and punching, the standard gauge is the standard.

The narrow-gauge railway track

Gauges narrower than standard gauges are called narrow gauges.

• Cape Gauge

Cape gauge is 1067mm wide, because it is narrower than the standard gauge of 1435mm, so it is a kind of “narrow gauge”. It’s named Cape Gauge because the former Cape Province of South Africa adopted this gauge in 1873. But the first country to install this gauge was Norway. Norway was still attached to Sweden at the time, and it was a border region with an underdeveloped economy. When engineer Carl Pihl tried to build Norway’s first railway, he considered two possible widths that suitable for mountainous Norway. One is 3 feet 6 inches (1067mm)  and the other is 3 feet 3 inches (meter gauge, 1000mm). He asked for advice from the Stevenson family who made the steam locomotive. Although it would be more expensive, Stevenson thought a slightly wider gauge will help the safety of the mountains. So in the end, 1067mm as settled as the Norwegian standard track width.

• Metre Gauge

In addition to cape gauge, only meter gauge (1000mm) in narrow-gauge railways has a relatively high prevalence mainly in Southeast Asia and Brazil. Generally speaking, railways that are narrower than meter gauges will be greatly reduced in terms of carrying capacity. Therefore, only industrial railways like the 762mm five-minute car in a sugar factory will be used. However, due to the low laying cost of the five-minute train and the small turning radius, it is also suitable for use on the mountain railway.

The broad gauge railway track

Gauges wider than standard gauges are called broad gauges. Russian gauge, Iberian gauge and Indian gauge are three typical broad gauges.

Most areas of Russia are flat. When the engineer Pavel Melnikov built the first railway, he planned to use a gauge wider than the standard gauge to increase the load capacity and driving stability. The Russian gauge (1524mm) was thus born. Russia had many opportunities to synchronize the gauge with the rest of the European continent to become the standard gauge. But it was worried that the hinterland of Russia would be invaded if trains from other countries could enter freely. From World War I to World War II to the Cold War, it finally evolved into a phenomenon in which the former Soviet Union all adopted this own standard.

The regions that also adopted their specifications for military reasons are Spain and Portugal. These two countries are on the Iberian Peninsula, so the gauge used is called the Iberian gauge (1688mm). It is said that it was to prevent the invasion of France to get this own specification. But now the newly built Spanish high-speed rail uses standard gauges to facilitate the mutual operation of high-speed trains in Europe.

The Indian gauge (1676mm) is another reason entirely. It is said that the reason why India adopts such a wide rail is that if the rail is too narrow, the carriage is easily blown over by the wind? We can only say that the person who determines this width is farsighted! Looking at the situation of Indian trains that are full of people, narrower rails are not good.

Ballasted and ballastless railway track

The ballasted track is the traditional track structure made of wooden sleepers and crushed stones. The traditional ballasted track has the characteristics of simple laying and low overall cost, but it is easy to deform thus needs frequent maintenance. At the same time, train speed is restricted.

Ballastless track refers to the track structure that uses concrete, asphalt mixture and other integral foundations instead of the loose gravel trackbed. The sleepers themselves are made of concrete, and the roadbed does not need gravel. The steel rails and sleepers are directly laid on the concrete roadbed. Ballastless track is an advanced track technology in the world today, which can reduce maintenance, reduce dust, beautify the environment, and speed up trains to more than