Civil Engineering tool for Surveying Chain tape:

Civil Engineering tool for Surveying Chain tape:

The chain tape is also referred to as the Günter’s chain. Gunter’s chain, the 300 –year-old measuring instrument by which all survey measurement in the English – speaking countries and much of it elsewhere was done. It has been superseded by the steel tape and electronic equipment. Gunter’s chain is 66 feet long; 80 chain equal to one mile, and 10 square chains equals an acre. The chain is subdivided into 100 links. A rod or perch was 25 links. Each link was a short section of wire connected to the next by a loop. At each end of the chain was a brass handle. The 66 – foot unit is still called a chain and is still in use in property descriptions and in the public land system. The Gunter chain is generally used in taking short and detailed length and breadth of a school farmstead.

Measurement of distance with tapes

Precisions for different methods of measuring distances are given below:-

Pacing (ordinary terrain): 1/50 to 1/100

Taping (ordinary steel tape): 1/1000 to 1/10,000.

Baseline (invar tape): 1/50,000 to 1/1,000,000

Stadia: 1/300 to 1/500

Subtense bar: 1/1000 to 1/7000

Now with technological advances, a technique called Electronic distance measurement or EDM is replacing the use of steel tapes as they are much more precise then steel tapes.

MATERIALS FOR DAMP PROOF COURSE

Damp proof course (DPC) is a barrier of impervious material built into a wall or pier to prevent moisture from moving to any part of the building.

Following are the materials generally used for damp proofing of structures:

1) Flexible Materials:

The materials, which do not crack and deform their shape when subjected to loading, are called Flexible Materials

a) Bitumen Mastic (Mastic Asphalt)

• It consists of asphalt or bitumen mixed with fine sand in hot state to form an impervious mass.
• Due to this consistency it can be spread (when hot) to a depth of 2.5cm to 5cm, which sets on cooling.
• It provides good impervious layer but special care is needed in its laying.
• b) Bitumen Felts (Sheets):
  • It consists of 6mm thick sheet of bitumen prepared in rolls having width equal to that of brick wall.
  c) Hot laid Bitumen:
  This material is used on a bedding of cement concrete or mortar.
  • This should be applied in two layers at the rate of 1.75kg/m2 of the area.
  d) Metal Sheets:
  
  • Metal sheets of Copper, Aluminium, or Lead are used to prevent dampness, but they are costly.
  • Sheets of these materials are used throughout the thickness of the wall.
  • The sheets of Lead are laid over Lime Mortar and not with Cement.
  • Mortar due to the chemical reaction of Cement over the Lead.
  • The sheets of metal should be coated with asphalt.
  • The thickness of the sheets should not be less than 3mm.
  • 
    

  2) Rigid Materials:

  • The materials, which do not resist transverse stresses and cracks when subjected to sever loading, are known as Rigid Materials.
  a) Rich Concrete
  • 1.2cm to 4cm thick layer of Rich Concrete (1:2:4) painted with two coats of hot bitumen is used as horizontal D.P.C.
  • It also prevents the moisture penetration by capillary action.
  • These layers are laid where the damp is not excessive.
  b) Mortar:
  • 2cm thick layer of Rich Cement and Sand Mortar (1:3) is applied on the inner face of external wall.
  • This is a vertical D.P.C.
  • The surface is than painted with two coats of hot bitumen.
  c) Bricks:
  • Over burnt or dense bricks in one or two layers can be used as cheap and effective DPC.
  • They are laid in Rich Cement and Sand Mortar (1:3).
  • Bricks are rarely used as DPC except in cheap houses.
  d) Stones or Slates:
  • Two layers of stone slabs or slates laid in Lime, Cement and Sand Mortar (1:1:6) make a best DPC.
  • They can also be laid in Cement Sand Mortar.
  • It is used where a good quality of stone is easily and cheaply available.
  
  

TYPES OF DEEP FOUNDATION

Deep foundations are required to carry loads from a structure through weak compressible soils or fills on to stronger and less compressible soils or rocks at depth, or for functional reasons. These foundations are those founding too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level. Deep foundations can be used to transfer the loading to a deeper, more competent strata at depth if unsuitable soils are present near the surface.

The types of deep foundations in general use are as follows:

1) Basements

2) Buoyancy rafts (hollow box foundations)

3) Caissons

4) Cylinders

5) Shaft foundations

6) Piles

Basement foundations:

These are hollow substructures designed to provide working or storage space below ground level. The structural design is governed by their functional requirements rather than from considerations of the most efficient method of resisting external earth and hydrostatic pressures. They are constructed in place in open excavations.

Buoyancy rafts (hollow box foundations)

Buoyancy rafts are hollow substructures designed to provide a buoyant or semi-buoyant substructure beneath which the net loading on the soil is reduced to the desired low intensity. Buoyancy rafts can be designed to be sunk as caissons, they can also be constructed in place in open excavations.

Caissons foundations:

Caissons are hollow substructures designed to be constructed on or near the surface and then sunk as a single unit to their required level.

Cylinders:

Cylinders are small single-cell caissons.

Shaft foundations:

Shaft foundations are constructed within deep excavations supported by lining constructed in place and subsequently filled with concrete or other pre-fabricated load-bearing units.

Pile foundations:

Pile foundations are relatively long and slender members constructed by driving preformed units to the desired founding level, or by driving or drilling-in tubes to the required depth – the tubes being filled with concrete before or during withdrawal or by drilling unlined or wholly or partly lined boreholes which are then filled with concrete.

Type of Stones ( Geological Classification )

Type of Stones
Stones used for civil engineering works may be classified in the following three ways:

• Geological
• Physical
• Chemical

Geological Classification

Based on their origin of formation stones are classified into three main groups—Igneous, sedimentary
and metamorphic rocks.

(i)Igneous Rocks: 

These rocks are formed by cooling and solidifying of the rock masses from
their molten magmatic condition of the material of the earth. Generally igneous rocks are strong and
durable. Granite, trap and basalt are the rocks belonging to this category, Granites are formed by slow
cooling of the lava under thick cover on the top. Hence they have crystalline surface. The cooling of
lava at the top surface of earth results into non-crystalline and glassy texture. Trap and basalt belong to
this category.

(ii)Sedimentary Rocks:

Due to weathering action of water, wind and frost existing rocks
disintegrates. The disintegrated material is carried by wind and water; the water being most powerful
medium. Flowing water deposits its suspended materials at some points of obstacles to its flow. These
deposited layers of materials get consolidated under pressure and by heat. Chemical agents also contribute
to the cementing of the deposits. The rocks thus formed are more uniform, fine grained and compact in
their nature. They represent a bedded or stratified structure in general. Sand stones, lime stones, mud
stones etc. belong to this class of rock.

(iii)Metamorphic Rocks:
Previously formed igneous and sedimentary rocks under go changes
due to metamorphic action of pressure and internal heat. For example due to metamorphic action granite
becomes greisses, trap and basalt change to schist and laterite, lime stone changes to marble, sand stone
becomes quartzite and mud stone becomes slate.

elements in Concrete Structural of a building.

Footings:

Footings are pads or strips that support columns and spread their load directly to the soil.

Column:

Columns are vertical members that support loads from the beam or slabs. They may be subjected to axial loads or moments.

Beams:

Long horizontal or inclined members with limited width and height are called beams. Their main function is to transfer loads from the slab to the columns.

Slab:

Slabs are horizontal slab elements in building floors and roof. They may carry gravity loads as well as lateral loads. The depth of the slab is usually very small relatively to its length and width.

Frames:

Frames are structural members that consists of combination of slab, beams and columns.

Walls:

Walls are vertical plate elements resisting gravity as well as lateral loads e.g retaining walls, basement walls. etc