121.%20Site%20Investigation

121.%20Site%20Investigation - Site Investigation Lecture 12...

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Unformatted text preview: Site Investigation Lecture 12 Site Investigation Lecture 12: Site Investigation Page 1 of 38 Lecture 12: Site Investigation Hazard Evaluation Lecture 12: Site Investigation Page 2 of 38 Lecture 12: Site Investigation Erosion Hazards Geohazards Lecture 12: Site Investigation Page 3 of 38 Lecture 12: Site Investigation Human Induced Human Induced Lecture 12: Site Investigation Page 4 of 38 Lecture 12: Site Investigation Human Induced Hazard Assessment Lecture 12: Site Investigation Page 5 of 38 Lecture 12: Site Investigation Determine Acceptable Level of Risk Hazard Assessment Lecture 12: Site Investigation Page 6 of 38 Lecture 12: Site Investigation Site Investigation Evolution of an Engineering Project Lecture 12: Site Investigation Page 7 of 38 Lecture 12: Site Investigation Investigation Components Mission Statement Lecture 12: Site Investigation Page 8 of 38 Lecture 12: Site Investigation Project Planning Project Management Lecture 12: Site Investigation Page 9 of 38 Lecture 12: Site Investigation Map Data ► Two-dimensional ► Scale view Critical Map Scale ► Common Source of Error ► Large Scale 1:250,000 or 1:200 1:250,000 1 inch = 4 miles or 1 inch = 50 feet inch 1 mile 500 feet Lecture 12: Site Investigation Page 10 of 38 Lecture 12: Site Investigation Scale vs. Detail vs. Small Scale = Large Area Limited Detail Medium Scale = Medium Area Moderate Detail Large Scale = Small Area Great Detail Map Orientation Lecture 12: Site Investigation Page 11 of 38 Lecture 12: Site Investigation Finding NORTH Map Location Techniques X-Y Grid Lecture 12: Site Investigation Bearing & Distance Page 12 of 38 Lecture 12: Site Investigation Triangulation 3-Point—2 Angles Survey Geometry Lecture 12: Site Investigation Page 13 of 38 Lecture 12: Site Investigation Property Survey Surveyor’s Chain ► Edmund Gunther developed basic method of surveying – standardized length units ► 1 Gunther’s chain =100 links long ► 66 ft (22 yd) long ► 10 chain = 1 furlong ► 80 chains = 1 statute mile ► 10 square chains = 1 acre ► 1 acre = 1 chain X 1 furlong Lecture 12: Site Investigation Page 14 of 38 Lecture 12: Site Investigation Determine Elevation Step Method Determine Elevation Elevation Angle and Distance Method Lecture 12: Site Investigation Page 15 of 38 Lecture 12: Site Investigation Image Analysis ► Total ► Pattern Dangerous practice Dangerous Biased result Biased Based upon prior experience Based Image Landform – topography Landform Drainage – texture and pattern Drainage Tonal Tonal Vegetation Vegetation Land Use Land Analysis ► Geomorphic ► Landform Applies to areas of uniform geomorphic Applies history and form Analysis Interpretation of terrain forms Interpretation Often uses a set of keys to aid interpretation Often Every Landform has a unique set of features: Every ►topography ►soils ►erosion character ►rock type ►drainage ►history Analysis ► Other Shadows, Reflections, Texture, Land-use, etc. Shadows, Features Lecture 12: Site Investigation Page 16 of 38 Lecture 12: Site Investigation Electromagnetic Spectrum Mid-Day Balance Lecture 12: Site Investigation Page 17 of 38 Lecture 12: Site Investigation Night Radiation Photogrammetry ► Determine three-dimensional data from stereo photography ► Mapping from photographs ► Mission Planning Objective Objective Scale Scale Relief Relief ► Variables Camera Focal Length (f) Camera Film size & type Film Aircraft Position and Altitude Aircraft Lecture 12: Site Investigation Page 18 of 38 Lecture 12: Site Investigation Photo-Geometry ►f = focal length ► H = Height above Datum Scale = f/H ► Assumes true vertical photograph = axis is perpendicular to the datum plain Height Above/Below Datum ► Scale changes with height above/below datum ► ABOVE Scale = f/(H-h1) ► BELOW Scale = f/(H+h2) Lecture 12: Site Investigation Page 19 of 38 Lecture 12: Site Investigation Radial Distortion Impact of Focal Length Lecture 12: Site Investigation Page 20 of 38 Lecture 12: Site Investigation Parallax, P = ao + rb P/f = B/(H - h) h = H - Bf/P Parallax Correction Lecture 12: Site Investigation Page 21 of 38 Lecture 12: Site Investigation Aircraft Attitude ► 4-degrees of FREEDOM FREEDOM Pitch – nose-up/nose-down Pitch Roll – wing low/wing high Roll Crab – rotation around the vertical axis Crab Flight Height (Altitude) – aircraft above/below Flight project altitude (Height above datum) Photogrammetry Lecture 12: Site Investigation Page 22 of 38 Lecture 12: Site Investigation Annotated Stereo-Model Total Image Analysis People, 7 July 2008, pg.98 Lecture 12: Site Investigation Page 23 of 38 Lecture 12: Site Investigation Pattern Analysis Character = f(Land Form) ► Drainage Patterns ► Topographic Texture (fine, medium, coarse) Texture Pattern (dendritic, trellis, angular, radial) Pattern Pattern = f(Land Cover) ► Human Patterns = f(Land Use) ► Tonal Land FORM-Land COVER-Land USE Pattern Analysis Demonstration ► Objective: Investigate potential Investigate groundwater sources for this area ► Dec 27 (winter) ► Band 7 (IR) ► Sun Elevation 28o ► Azimuth 149o Lecture 12: Site Investigation Page 24 of 38 Lecture 12: Site Investigation Factors ► Bedrock Systems ► What does this overlay show? & Drainage ► Why select the Band 7, Winter image? Factors ► Drainage Texture ► What does this show? ► Why be concerned about drainage texture? Lecture 12: Site Investigation Page 25 of 38 Lecture 12: Site Investigation Factors ► Linear ► Define Features ALL linear features to assess geologic structure Factors ► Linear Trend Interpretation ► Define major structural features and boundaries Lecture 12: Site Investigation Page 26 of 38 Lecture 12: Site Investigation Land Cover Assessment ► False Color Image ► 23 April ► Bands 4, 5, 7 ► Sun Elevation = 55o ► Azimuth 124o Factors ► Land Cover/Vegetation ► Why use the April image? ► Why Bands 4, 5, 7? Lecture 12: Site Investigation Page 27 of 38 Lecture 12: Site Investigation Interpretation ► Groundwater source from mountains ► Flow is toward fault block basins ► Vegetative evidence suggests shallow groundwater basin south of Site of Interest Conclusion ► Image analysis shows that groundwater is in a down dropped structural basin ► Spring vegetation shows shallow groundwater Lecture 12: Site Investigation Page 28 of 38 Lecture 12: Site Investigation Geophysical Techniques ► Seismic = f(velocity differences) Refraction Refraction Reflection Reflection ► Electrical = f(resistivity/conductivity) Resistivity Resistivity Conductivity Conductivity Electromagnetic Electromagnetic Induced Polarization Induced Spontaneous Potential Spontaneous Geophysical Techniques ► Magnetics ► Gravity ► Nuclear Natural Gamma Natural Gamma-Gamma Density Gamma Neutron Scatter Neutron ► Microwave (GPR) Lecture 12: Site Investigation Page 29 of 38 Lecture 12: Site Investigation Seismic Refraction Seismic Reflection ► Expensive for environmental and engineering applications on land ► Low cost in marine/lake applications ► “Fish Finder” Lecture 12: Site Investigation Page 30 of 38 Lecture 12: Site Investigation Hydrocarbon Seismic Operations Marine Seismic Reflection Lecture 12: Site Investigation Page 31 of 38 Lecture 12: Site Investigation Interpretation Resistivity Survey Lecture 12: Site Investigation Page 32 of 38 Lecture 12: Site Investigation Resistivity Surveys Electrical Conductivity Survey Lecture 12: Site Investigation Page 33 of 38 Lecture 12: Site Investigation Conductivity Profile North 60 South Apparent Conductivity (mS/m ) 50 40 30 Boat Slip 20 MW-1 10 Gas Line 0 0 50 100 150 200 Private Docks MW-5 Vertical Dipole 250 Horizontal Dipole 300 350 Station Number Use of Gravity Defines areas of lower mass Lecture 12: Site Investigation Page 34 of 38 Lecture 12: Site Investigation Gravity and Land-Form Use of Magnetics Defines areas of increased iron (magnetic) properties Lecture 12: Site Investigation Page 35 of 38 Lecture 12: Site Investigation Magnetics and Land-Form Geophysical Log Response Lecture 12: Site Investigation Page 36 of 38 Lecture 12: Site Investigation Geophysical Log Interpretation Log Correlation Lecture 12: Site Investigation Page 37 of 38 Lecture 12: Site Investigation Cross-Section Construction Break Lecture 12: Site Investigation Page 38 of 38 Lecture 12: Site Investigation ...
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This note was uploaded on 04/16/2011 for the course GEOL 320 taught by Professor Mathewson during the Spring '11 term at Texas A&M.

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