Civil Tips

What Are The Precautions In Construction Of Tunnels ? For economic safe and quick construction of tunnels, the following precautions should be taken: 1. The shape of the tunnel should be decided according to its purpose. 2. Cross-sectional dimensions of the tunnel should be decided to achieve economy in its construction. 3. Economic calculations for extent of equipment and labour should be made before starting the tunnel construction. 4. The pattern of blasting the material in different locations should be decided for maintaining speed of driving and safety. 5. The sequence of operations must be decided so that proper use of labor and equipment is made. 6. Labour should be well organized to maintain continuous progress of the tunneling operations. 7. Outdated or unsuitable tools should not be used. 8. Care should be taken to see that every operation is completed at scheduled time. 9. The Excavated material should be piled up in a manner suitable to the method of loading being employed. 10. loading and hauling of muck should be carried out efficiently. 11. The sequence and type of lining should be determined in advance to achieve economy. 12. Selection of multipurpose and uniform type of equipment should be made, according to the size and shape of the tunnel.

How To Calculate Quantity Of Materials In Arch ? 1. Semi Circular Arch:Given: Span = 8 ft Height = 4 ft Thickness = 1 ft Breadth = 1ft To calculate the quantity of materials in semi circular arch we need to calculate the volume of arch. Volume of arch = Cross-section of arch x Arch length We know Cross-section area = Thickness of arch x Breadth of arch = T x B From the above image, you can see the thickness and breadth are 1 ft. Cross-section of arch = 1 x 1 = 1 ft² Now Arch length = Circumference of half circle (The arch is semi circular) We know circumference of circle = 2πR Circumference of half circle = 2πR/2 = πR We don’t what is R. So we need to find out the ‘R’. R = Half span + Thickness/2 = 4 +1/2 = 4.5 ft. Arch length = πR =3.14 x 4.5 = 14.13 ft. Quantity of materials in arch = 1 x 14.13 = 14.13 cft. 2. Segmental Arch: Given: Span = 8 ft Height = 2ft Thickness = 1 ft Breadth = 1ft Central angle = 105° Solution: Volume arch = Cross-section of arch x Arch length We know Cross-section area = Thickness of arch x Breadth of arch = T x B Arch length = θπR/180 Now R = (a² + h²)/2h     [a =half span = 8/2 =4] =(4² + 3²)/2 x 3 = 25/6 =4.16 ft. Arch length = (105 x 3.14 x 4.16)/180 = 7.61 Quantity of materials in arch = 1 x 7.61 = 7.61 cft.

What Are The Components Of Road Pavement Structure ? 1. Subgrade The finished and compacted surface of earthwork on which a road pavement rests is called subgrade or formation. The subgrade of a road may be provided on an embankment, in cutting or existing ground level depending upon the topography and the finalized formation level. It consists of well compacted natural soil brought to the required camber and gradient. The thickness and type of pavement structure depend upon the supporting power of the subgrade because the entire load of the pavement, including the load of traffic transmitted through the pavement, is ultimately taken up by the subgrade. 2. Sub-base A layer of granular material provided in between the subgrade and the base course in a road pavement is known as a sub-base. It is provided as an additional layer when the subgrade is of poor quality. It consists of a layer of comparatively cheaper material like burnt clinker, natural gravel, or slag. 3. Base Course A layer of boulders or bricks provided over the subbase or immediately over the subgrade in the absence of sub-base in a road pavement is called base course or soling or foundation course.

What Are The Types Of Bridge Foundation ? 1. Spread Or Open Foundation This type of bridge foundation is suitable for moderate height, to be built on dry ground which is sufficiently firm to support the bridge structure. It is best suited in situations where hard soil is available within 1.5 to 3 m below the bed level of watercourse and when the scouring is minimum. 2. Raft Foundation This type of foundation is suitable for bridge when the bed of the watercourse consists of soft clay and silt and the hard soil is not available within reasonable depth (1.5 to 2.5 m) below the river bed. It is best suited in situations where the allowable bearing capacity of the soil is low or when the bridge loads are heavy. Raft foundation is also suitable when the soil bed has some soft pockets which are compressible and there is possibility of unequal settlement. 3. Grillage Foundation This type of bridge foundation is suitable for heavy and isolated footings of piers where deep foundations are to be avoided. It is best suited where sub-soil conditions are poor. 4. Inverted Arch Foundation This type of bridge foundation is suitable when the depth of excavation for foundation is less. It is best suited where the bearing capacity of the soil is less, especially when the sub-soil has some soft pockets and there is possibility of unequal settlement. 5. Pile Foundation This type of bridge foundation is suitable when the soil is very soft and the hard strata are not available at a reasonable depth below the bed level of the river.