Geotechnical Engineering

 👉Casagrande apparatus: used to determine liquid limit.

👉 Oedometer is used to find the consolidation characteristic of soil.

👉 Hydrometer is used to determine grain size distribution

👉 Plate load test is used to determine safe bearing capacity of soil.

👉Pycnometer method is the laboratory method for determining specific gravity as well as water content of soil sample

👉Permeameter is used to find hydraulic conductivity and permeability of soil sample.

👉Core cutter is a field method to compute bulk density of soil.

👉 Increasing order of their grain size:

         Montmorillonite < Illite < Kaolinite

👉Sequence of plasticity index

    Montmorillonite > Illite > Kaolinite

👉 Relative compaction: Degree of compaction achieved as a percentage of the laboratory compaction

       Relative compaction = dry density in field/ maximum dry density from the proctor test 

👉Relative density can be zero but relative compaction can never be zero.

👉with increase in temperature, viscosity decreases and permeability increases.

                     k ∝ Unit weight/ Viscosity

👉Effective stress increases, void ratio decreases and permeability decreases.

 👉Organic matter has the tendency to move towards flow channel and choke them, thus reduces permeability

👉 Entrapped air decreases the permeability of soil.

 

Engineering Hydrology

 👉 A flow duration curve is a plot of discharge against the percentage of time the flow was equaled or 

exceeded. This curve is also known as discharge frequency curve.  

👉Line joining points of equal rainfall depth is called isohyet.

👉 Isopleths are line on a map through points having equal depth of evapotranspiration.

👉                    Name                       Isopleth of (i.e line joining places of equal)

                        Isotherm                                           Temperature

                         Isobar                                               Pressure

                 

                         Isobath                                             Depth in sea

 

                        Isochrone                                        Travel time from a common centre

                       Isohaline                                              Salinity

                        Isohyets                                                 Rainfall

                        Isonif                                                Snowfall amount

                       Isoryme                                                Frost

                        Isohels                                                Sunshine

👉  Bowen's ratio is defined as the ratio of Sensible heat transfer from water surface to air (Ha) to Heat energy used up in evaporation (He)

👉               Property                                  Measuring Instrument

                  Evapotranspiration                          Lysimeter

                Capillary Potential                            Tensiometer

                Transpiration                                    Phytometer

                 Evaporation                                     Atmometer

                Hydraulic Conductivity                     Permeameter

                Infiltration Capacity                          Infiltrometer

                                                                           Rainfall Simulator

              Humidity                                             Hygrometer

              Relative Humidity                              Psychrometer

              Wind Speed                                        Anemometer

 👉 Ratio of total channel length to the discharge area is called drainage density. 

👉         Hyetograph:  Rainfall intensity versus time 

   

               Mass Curve: Cumulative rainfall versus time

               Hydrograph: A hydrograph is a graph showing the rate of flow versus time past a specific point in a river, channel, or conduit carrying flow

Target GATE & ESE 2022 (Building Materials)

 👉Fine grinding leads to high early strength.

👉 The finer the cement the higher is the rate of hydration which results in early development of strength.

👉Decreasing the lime cement increases the proportion of C2S (Belite) and reduces that of C3S (Alite) and hence leads to slow setting low heat cement.

👉Burning at higher temperature increases the proportion of Alite (C3S) in cement and hence leads to high early strength.

👉Increasing the quantity of gypsum retards setting of cement.

👉Before testing setting time of cement, test for consistency (Normal Consistency) is done to know the water required for preparation of standard paste of normal consistency. Amount of water (0.85 times water used in consistency) is used for preparation of cement paste in setting time test.

👉Low heat cement has a high percentage of dicalcium silicate (C2S) and low percentage of tricalcium silicate (C3S)

👉High early strength portland cement has high percentage of C3S and lower percentage of C2S

👉Specific gravity of cement (G = 3.14) is determined by Le Chatelier's Flask.

                                                                 Le Chatelier's Flask

👉For checking the soundness( Soundness test is done on cement to determine the expansion of cement due to the presence of free lime and magnesia in the cement) of cement Autoclave test is done.

    

👉The fineness of cement is determined by Blaine's Air Permeability apparatus.

👉Superplasticizers increases the workability by dispersion of cement particles. It can remove air bubbles . It can also be used to retard setting.

👉Blast furnace slag cement is more resistant to sulphate attack and is specified for marine work or pipe carrying water containing chemicals or sewage.

👉  Different Phase of cement                          Temperature ( in Degree Celsius)

      Formation of C3S                                                               > 1250 

   

       Formation of C2S                                                               900-1200

      Formation of C3A and C4AF                                              Cooling Stage

      Decarbonation of CaCO3                                                     < 900

👉LSF(Lime saturation factor) is a used quality parameter to limit the amount of free lime (CaO)

👉LSF is used a quality parameter to limit the Unsoundness of the cement.         

👉 Crystal Structure of different phases

             C3S ------------------  Irregular Structures, several polymorphs.

         

             C2S--------------------Rounded structures, several polymorphs

             C3A ------------------Cubic in pure form

             C4AF-----------------Series of solid solutions

👉 The decreasing order of heat of hydration of pure cement compounds are:

                 C3A > C3S > C4AF > C2S

Geomatics Engineering

 👉Actual Distance = (Measured Distance/Nominal length of chain) x Actual length of chain

👉Offsets are lateral measurements made w.r.t main survey line which may be oblique or perpendicular in nature.

👉In aerial photogrametery the photographs are taken at proper interval to provide generally 60% longitudinal overlap and 30 % side overlap.

👉The tape corrections used in Surveying

• Correction for Standardization (+ or -)
• Correction for Slope (Always negative)
• Correction of Pull (+ or -)
• Correction for Temperature (+ or -)
• Correction for Sag (Always negative)
• Normal Tension 
• Correction for Misalignment (Always negative)

👉 Tape correction for standardization (Csd):

                            Csd = (l'-l)/l x L

where, l = nominal length of tape
          l’ = actual length of tape

          L = measured length

          Csd = Correction for standardization

 👉 Correction for Slope (Cs):

        

Where,

                    D = horizontal equivalent
                    L = slope distance
            

                        

     Where,          h = difference in elevations of the end points

                           Cs = correction due to slope

 

👉 Correction for Pull (Cp):

The correction of pull is computed as

Where,
P = pull applied during measurement.
Po = Standard pull
L = Measured length
A = Cross- sectional area of the tape
E = Young’s modulus of material of tape

👉Correction for Temperature (Ct):

The correction for temperature is computed as

Ct = α (Tm - To) L

where,
α = coefficient of linear expansion
Tm = Mean temperature of the tape
To  = Standard temperature

👉 Sag Correction (Csg):

• A tape is supported at two ends, it takes the shape of a CATENARY. 
• The correction for sag should be applied as the horizontal chord Length is always shorter than the curved length

Where,
W = Weight of tape per unit length.
P = Applied pull.
l1 = length of the tape suspended between the supports.

The above equation can also be written in the form of total weight of tape

where,
W = total weight of tape between the supports

👉 Normal Tension:

The normal tension is a tension at which the effects of pull and sag are neutralized.

     

👉Correction for Misalignment (Cm):

•  If L1 = L2 then Cm = d² / L (Negative)

👉Optical square is used to establish two points at right angle. The principle used is double reflection.

👉Method commonly used in Reconnaissance surveying for measurement of horizontal distance are PACING, PASSOMETER, PEDOMETER, ODOMETER,MEASURING WHEEL, SPEEDOMETER,PERAMBULATOR.

👉Equation of cubic parabola  = X^3/6RL

👉Shift in Transition Curve = L^2/24R

Environmental Engineering

 👉Typical range of Hydraulic Conductivity are as follows:

   Soil classification of an aquifer      Hydraulic Conductivity (m/day)          Drainage Characteristics 

         Gravel                                            100-1000                                                Pervious

          Sand                                               1-10                                                      Pervious

         Silt                                                  0.1-0.01                                                 Slightly Pervious

        Clay                                                 10^-5 to 10^-6                                      Impervious

👉 Components of Water Demand:

     Domestic Demand     :         135 lpcd (litre per capita per day)

    Public Demand           :         20 lpcd

  Industrial Demand        :         50 lpcd

  Commercial Demand   :         20 lpcd

       Fire Demand           :          15 lpcd

      Loss and waste         :          50 lpcd 

       Total =  270 lpcd

👉Fire Fighting Water Demand

👉 Fire Fighting Water Demand Empirical Formulae:

• Buston's Formula
• Kuichling's Formula
• Freeman's Formula
• National Board of Fire Underwriter's Formula

       

👉 Population Forecasting Methods:

• Arithmetic Increase Method
•  Geometric Increase Method
•  Incremental Increase Method
•  Logistic Curve Method
•  Growth Composition Analysis Method
•  Master Plan Method
•  Decreasing Rate of Growth Method
•  Simple Graphical Method
•  Comparative Graphical Method
•  Ratio Method

Solid Mechanics

 👉Plane having principal stress has no tangential stress.

👉Mutually perpendicular planes are 180 degree apart in Mohr circle and have numerically equal value of shear stress.

👉Maximum shear stress = radius of Mohr's circle

👉         Theory of Failure                                               Also Known as  

       Maximum principal stress theory             Rankine theory, Lame's theory, Maximum stress theory

        Maximum principal strain theory                             St. Venant theory

           Maximum shear stress theory                   Tresca theory, Guest theory, Columb theory

          Maximum strain energy theory                              Beltrami Haigh theory

      Maximum shear strain energy theory                 Distortion energy theory, Von-Mises theory

👉 Bending Equation 

                                  M/I = σ/y  = E/R

where, M = Bending Moment

           σ  = Bending stress

           I =  Moment of inertia

          y = Distance of the fibre from Neutral axis

         R = Radius of curvature

         E = young's modulus of elasticity

👉 Torsion Equation:

                      T/Ip = τ/r = τmax/R  = N.θ/l

👉 Strain energy per unit volume = 1/2 x shear stress x shear strain

👉 Strain energy in torsion = 1/2 x T x θ

👉  For Brittle materials, Normal stress theory gives best result

👉 For ductile material maximum shear stress theory is applicable.

                                                                Happy Learning

Design of Steel Structure

 👉 Steel's modulus of elasticity is about 3 times that of Aluminium.

👉 Coefficient of thermal expansion for aluminium is about twice that for steel.

👉 Aluminium requires less maintenance than steel as steel prone to rusting

👉Strength to unit weight ratio of aluminium is higher than that for steel.

👉As per IS 800-1984 Cl 9.1.3 members subjected to heavy impact and fatigue shall not be designed on basis of plasticity theory, as it makes full use of materials strength beyond elastic limit.

👉 Truss carries axial load and that can cause shortening.

👉Beam carries force by bending.

👉Column resist force as axial load which can cause buckling of column.

👉Shaft carries force by twisting.

👉According to IS 800-1984 Following are the limits for slenderness ratios

• For compression member carrying dead and super imposed loads =180
• For members carrying compressive loads due to wind or seismic forces only =250
• For members carrying tension but in which the reversal of stress occurs due to wind and seismic forces = 350

👉Permissible axial tensile strength = 0.60 fy

👉Permissible shear stress = 0.45 fy

👉Permissible bearing stress = 0.75 fy

👉Permissible stress in slab base = 185 MPa for all steels

👉Allowable maximum average shear stress = 0.40 fy.

                                                            HAPPY LEARNING

Engineering Hydrology

 👉The hydrological budget equation is:

                          P-R-E-T-G = △S

Where, P = total precipitation

             R = Net runoff = R2-R1 = surface runoff flow- surface runoff inflow

            E = Total evaporation

            T = total Transpiration

          G = Net ground water flow

         △S = Total storage increase

 👉 Hydrological cycle is the cycle in which water is transported from the oceans to the atmosphere as vapours, from the atmosphere to the land as precipitation and back from land to oceans as runoff.   

👉Drizzle:  A fine sprinkle of numerous water droplets of size less than 0.5 mm and intensity less than 1 mm/h

Rain: The precipitation of liquid water with drops of sizes larger than 0.5 mm 

Hail: It is showery precipitation in the form of irregular pellets or lumps of ice of size more than 5 mm.

👉 Average rainfall over a catchment area can be estimated as

1. Arithmetic mean method: 

• every rain gauge station is given equal weightage regardless of its location.
• Rainfall is almost uniformly distributed over the whole catchment area which rarely occurs in nature.
• method is fast but does not give accurate results.

2. Theissen polygon method: 

• In this method weightage to the various rainfall datas based on area close to the rain gauge station 
• Method is fast when once the weights are known
• It does not take care of the variability in rainfall due to elevation difference(topographical influence are not take care of)
• New polygon is required to be drawn when due to addition or deletion of raingauges to the network, weight of each station changes.

3. Isohyetal method :

• This is most accurate method
• It utilizes all relevant data's and properly interpret them.
• method is slow and laborious

4. Normal ratio method: 

• It is used to estimate missing rainfall data.