Types of Valve

 Check Valve: 

• Also called non-returns valves.
• Automatically prevents reversal of flow.
• Fitted to release air automatically when a pipeline is being filled.
• Also called Reflux valve.

Sluice Valve:

• Used to regulate the flow of water through pipes.
• Used for isolating or scouring.
• It will seal well under high pressures.

Scour Valve:

• Provided to stop the flow of water to remove silt manually
• Also used to release water to eject the silt that might have got collected in the pipe.
• Also called Blow off valve or Drain valve.

Relief Valve or Safety Valve:

• Also known as pressure relief valve or cut-off valve
• This valve is used when the pressure of the water suddenly exceeds the permissible pressure due to water hammer phenomenon, then the valve is opened automatically and the excess pressure is released instantaneously and it will save the pipe line from bursting.

 

Facts about SPT Test and CPT Test

 CPT Test:

•  Cone Penetration Resistance: It is the ratio of total force acting on the cone to the base area of the cone (10 cm^2).
• Sleeve frictional resistance or local side friction is defined as the ratio of force required to push the friction jacket to the surface area of friction jacket.
• Friction ratio is defined as the ratio of sleeve frictional resistance to cone penetration resistance.
• Friction ratio is the important parameter for classifying soil.

    Soil Classification based on friction ratio:

                   Friction Ratio (%)                         Type of soil

                      0-0.50                                        Loose Gravel Fill

                      0.5-2.0                                       Sand or Gravels

                        2-5                                          Clayey sand and silts

                       >5                                             Clay, Peats

Correlation between CPT and SPT:

State of sand                   Relative Density(%)            N-Value           Cone Penetration Resistance(MPa)

  Very Loose                               <15                           <  4                          <2.0

  Loose                                     15-35                         4-10                          2-4

  Medium                                  35-65                        10-30                        4-12

    Dense                                   65-85                         30-50                       12-20

Very Dense                               > 85                          >50                            >20

SPT value related to consistency of clay

   Consistency                         N-Value                      UCS (in kPa)

  Very Soft                                0-2                                <25

    Soft                                       2-4                               25-50

 Medium                                    4-8                              50-100

  Stiff                                          8-15                           100-200

 Very Stiff                                 15-30                           200-400

  Hard                                          >30                              >400

SPT values related to relative density of cohesionless soil

 Relative Density(%)       Compactness             N-value                     Angle of internal friction in degree

  0-15                                  Very Loose              0-4                                 <28

15-35                                      Loose                   4-10                              28-30

35-65                                   Medium                  10-30                             30-36

65-85                                   Dense                      30-50                            36-41

>85                                    Very Dense               >50                                >41

Soil Classification

 Unified Soil classification system:

• This classification was given by Casagrande.
• Soil is divided into 4 groups (Coarse grained soil, fine grained soil,organic soil and peat)
• Prefix and suffix used in USCS
• Soil Type       Prefix                 Soil Subgroup                  Suffix
• Gravel              G                       Well Graded                      W
• Sand                 S                       Poorly Graded                    P
• Clay                C                        Clayey                                C
• Silt                   M                       Silty                                  M
• Organic            O                       If liquid Limit<50%          L(Low Plasticity/compressibility)
• Peat                  Pt                      If Liquid Limit>50%         H (High Plasticity/Compressibility)

American Association of State Highway Transport Official (AASHTO)

• In this classification soil is subdivided into 8 groups namely A-1 to A-7 and A-8 for the Peat or Muck soil.
• Soil is classified on the basis of Group Index(GI)
• GI = 0.2 a + 0.005 ac + 0.01 bd

          Where,   a = p-35 and should not exceed 40 ,         b = p-15 and should not exceed 40 
                        c = L.L- 40 and should not exceed 20,     d = P.I - 10 and should not exceed 20

                        L.L = liquid Limit, P.I = Plasticity Index and p = %  finer

Indian Standard Soil Classification System (ISSCS)

• Extension of USCS
• Intermediate compressibilty is introduced(I)

Soil Type       Prefix                 Soil Subgroup                  Suffix

• Gravel              G                       Well Graded                      W
• Sand                 S                       Poorly Graded                    P
• Clay                C                        Clayey                                C
• Silt                   M                       Silty                                  M
• Organic            O                       If liquid Limit<35%          L(Low compressibility)
• Peat                  Pt                      If Liquid Limit>50%         H (High Compressibility)
•                                                   If 35% <L.L <50 %           I (Intermediate Compressibility)

Classification of Fine Grained Soil 

• Classification is based on plasticity chart
• Equation of A-line :    Ip = 0.73 (L.L -20)

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