ESSELEN DSI PROGRESS 10 November 2017 Nkosazana Leseka Substation - - PowerPoint PPT Presentation

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ESSELEN DSI PROGRESS 10 November 2017 Nkosazana Leseka Substation - - PowerPoint PPT Presentation

Mar 05, 2024 50 likes •122 views

ESSELEN DSI PROGRESS 10 November 2017 Nkosazana Leseka Substation Engineering (PDE) Geophysical Method Gravity Survey Geophysical investigation involved in a simple method of ascertaining subsurface details from studying them from the

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SLIDE 1

ESSELEN DSI PROGRESS

10 November 2017 Nkosazana Leseka – Substation Engineering (PDE)

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SLIDE 2

Geophysical Method – Gravity Survey

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  • Geophysical investigation involved in a simple method of ascertaining

subsurface details from studying them from the surface

  • Achieved by measuring physical properties of the body and the

interpretation is done via subsurface geology, in this case through:

  • Percussion Drilling – to determine the voids
  • DPSH – to confirm the consistency/lack of
  • Gravity Surveys are normally used during oil and gas investigations

during mine explorations but can be used to determine the existence

  • f karsts in the subsurface
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SLIDE 3

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Science of Gravity Survey

  • Uses natural gravity field of the earth and the density of the earth

material becomes the controlling physical propety

  • Principle:
  • The nature of the distribution of gravity (g) on the earth surface is

analyzed

  • If the gravity pull is more (+) – it means the subsurface body is heavier,

larger and occurs at shallow depth

  • If the gravity pull is less (+) – it means the subsurface body is lighter
  • So in regions where body densities differ from surrounding rocks and

the gravity field deviates

  • This is an indication of inhomogeneous bodies in the subsurface (can be
  • re bodies, oil+gas or IN OUR CASE, A KARST)
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SLIDE 4

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Science of Gravity Survey example…

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SLIDE 5

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Why is not enough to conclude information?

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SLIDE 6
  • The areas identified for drilling are correct, however the karsts can
  • nly be confirmed by drilling
  • Once the drilling has been completed, then the material needs to be

checked for consistency

  • Safety Risk Assesment for the Power Lines:
  • According to the method statement for the drilling, the machine to be

used is 13m absolute height

  • The contractor in areas where there are powerlines should be clear for 13 from

the outer phase of the line case the machine topples over within the vicinity

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Why is not enough to conclude information?

540A

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SLIDE 7

Thank you