Harbour & Docks Introduction

Get a look at the sourceful and basic details of Harbor Docks Engineering

                                   

As in present condition transportation being carried out by three ways:

1. Roadways  
2. Waterways 
3. Airways 

In this we will focus towards the waterways where we can deal with the aim of understanding about Harbour & Docks Engineering.Waterways transportation is concerned with the conveyance of people and goods in vehicle that float on water.                                   Further waterways can be classified into two types:

1. Oceanic waterway
2. Inland waterways

Firstly the oceanic waterways concerned with conveyance of people and goods primary across the ocean between continents and land                                                     

Secondly the inland waterways consist of water transportation on rivers,lakes and canal within main land

Harbour

As transportation develop in waterways there create need of place  where ship could take in and discharge passenger & cargo such place of refuge called as Harbor.

So in short it is place of refuge of  ship ,cruise and passenger. Harbor  are broadly classified as : 

1. Natural Harbor: Natural formation affording safe discharge facilities.For ships on sea coast in form of creeks and basin Eg: Kandla port,Cochin port,Mumbai port
2. Artificial Harbor: When the natural formation are not available they are being made artificially for refuge purpose.As again during bad weather within a tract or area of water close to shore a novel ship shelter is must  which require good hold for anchorage and such berthing condition constitute the roadstead and such roadstead can be naturally available or artificially created Eg ; Chennai Port
3. Semi natural Harbor : It is protected on sides by contours of land and require man made protection to entrance Eg;Veraval port,Vishakhapatnam Port

Natural Port - Cochin port

Artificial Port - Chennai Port

Seminatural Port - Vizag Port

Roadstead :

It is a place for ship for safety berthing near the banks. They can be naturally available or it is artificially created.

1. Natural Roadstead :A deep navigable channel with a protective natural bank or shoal to seaward is an example of the natural roadstead.
2. Circumscribed Natural Roadstead: A confined area naturally enclosed by island as in creek if available.
3. Artificial Roadstead: These ma be created by constructing the breakwater or wall parallel to coast or curvilinear from the coast also artificial roadstead form by enclosing tract providing good anchorage by projecting solid walls called Jetties from shore. Another method to create confined basin of a small area having narrow entrance and exit.Such Roadstead with loading and unloading conditions used for Fishing vessels.

View of Roadstead

Harbor Classification Based on their Utility:

1. Commercial Harbor : Harbor which is provide with necessary facility for loading and unloading of cargo Eg: Chennai Port
2. Refuge Harbor: Used for the refuge of ship and it is part of commercial harbor Eg: Chennai and Vishakhapatnam Port
3. Military Harbor: Use for accomodating naval ships or vessel and it serves as a supply depot Eg: Mumbai and Cochin Port
4. Fishing Harbor: Having facility for arrival and departure of fishing ships

Harbor Classification based on Location:

1. Ocean harbor
2. River harbor
3. Canal harbor
4. Lake Harbor

Tidal Range: when vessel loaded and unloaded it range not exceed 5.5m. It is important to select site with minimum tide range

Requirement of Good Harbor:

Commercial Harbor:

• It has spacious accommodation
• Enough quay space and facilities for transporting, loading and unloading cargo
• Storage sheds for cargo
• Good and quick repair facilities

Refuge Harbor :

• Ready accessibility
• Safe and commodious anchorage
• Facilities for obtaining supplies and repairs

Fishing Harbor:

It entrance is made broad and fishing craft beam is of 6 to 8m

Size of fishing harbour - 4 to 40 hectares 

Depth - 3 to 5 m

• Harbor should be constantly open for departure and arrival of fishing ships
• Loading and unloading facilities and quick dispatch facilities
• Refrigerated stores with ample storing space for preserving the catch

Accessibility and size of Harbour:

Size of Harbour:

1. It depends on the location of the harbor
2. Harbor entrance should be narrow not to expose the harbors to effect of stormy sea
3. Maximum dimensions up to 600' has been adopted
4. The entrance provided from being affected from worst condition
5. Size of harbor depends on number and size of ships likely to be used at one time.Some ship has size up to 900' to 1000' long and 100' wide

Design of Entrance:

• Regarding entrance width narrow the width better will be the entrance protected
• As even if the breakwater are high enough to protect the harbor waves from outside harbor , set up diminutive waves inside the harbor depending on entrance width

The following empirical formula can be used with limited application is as follows:

                

               h = H{1/2 -0.02４sqrt(D)ｘ(1 + sqrt(l/L)}

• H- Height in feet of unrestricted wave of 1 feet width
• h - reduced height of diminutive wave inside the harbor at distance D' from the mouth and where the harbor is L feet wide 
• This formula is applicable to a distance up to 50 feet from the entrance and where the harbor is well protected 

Width of Entrance to Harbor:

Entrance width should be proportion to size of harbor and ships using it and if to reduce wave height within the harbor the entrance width should not be more than that necessary to provide safe navigation and also to prevent dangerous current.

1. For small Harbor - 90m
2. For medium Harbor - 120 to 150m
3. For large Harbor - 150m to 250m 

Width of entrance channel:

Maneuvering land width - 2B

Ship clearance lane width - B

Bank clearance - depend on side slopes

Also width of entrance channel for single lane traffic

L = 4B+2 (Bank clearance) 

TURNING BASIN

Radius of turning basin equal to 2 times length of largest ship at harbour 

R = 2l

R=Ra

l = length of large ship

Depth of Harbour :

D = D`

D - Draft of largest ship to be accommodated

H - Height of storm waves

• Maximum harbour depth = loaded draft +1.2m when bottom is soft
• Maximum harbour depth = loaded draft + 1.8m when bottom is rock
• Depth of sea can be measured by fathometer or echo sounder 

REFERENCES

1. Railway bridge and Tunnel Engineering by Rangwala
2. Harbour dock and Tunnel Engineering by R.Srinivasan
3. Roads,Railways Bridges and Tunnel Engineering by Ahuja & Birdi