Refraction Intro
-
Upload
ezadin-baban -
Category
Documents
-
view
26 -
download
5
description
Transcript of Refraction Intro
-
Seismic Refraction
-
Some uses of seismic refractionMapping bedrock topography Determining the depth of gravel, sand or clay deposits Delineating perched water tables Determining the depth to the water table Detecting subsurface caverns Estimating rippability Detecting shallow faults and fracture zones Detecting large boulders
-
ACTIVE STANDARD: D5777-00(2006) Standard Guide for Using the Seismic Refraction Method for Subsurface Investigation $42.90 for PDF Developed by Subcommittee: D18.01 See Related Work by this Subcommittee Adoptions: Book of Standards Volume: 04.09 1. Scope This guide covers the equipment, field procedures, and interpretation methods for the assessment of subsurface conditions using the seismic refraction method. Seismic refraction measurements as described in this guide are applicable in mapping subsurface conditions for various uses including geologic, geotechnical, hydrologic, environmental, mineral exploration, petroleum exploration, and archaeological investigations. The seismic refraction method is used to map geologic conditions including depth to bedrock, or to water table, stratigraphy, lithology, structure, and fractures or all of these. The calculated seismic wave velocity is related to mechanical material properties. Therefore, characterization of the material (type of rock, degree of weathering, and rippability) is made on the basis of seismic velocity and other geologic information.
-
Refraction Lay Out
-
Seismic RefractionAdvantagesSimple layoutLow manpower requirementsLimited Equipment RequirementsRapid data reduction and analysis (computer not needed)Easy interpretation
-
Seismic RefractionDisadvantagesRelatively large energy input requiredRelatively long layout (10 times depth)Limited number of model layersLimited velocity differencesLimited interface geometry (assume smooth)
-
Rippability versus seismic velocity. (Caterpillar. Handbook of Ripping, 8 th Edition)
-
Chart1
2.1428571429
4.2857142857
6.4285714286
8.5714285714
10.7142857143
12.8571428571
15
17.1428571429
19.2857142857
21.4285714286
23.5714285714
25.7142857143
27.8571428571
30
32.1428571429
34.2857142857
36.4285714286
38.5714285714
40.7142857143
42.8571428571
45
47.1428571429
49.2857142857
0.00
Meters
miliseconds
Direct Wave
Sheet1
DistanceArival Time in ms
mDirectRefracted
00.00
32.140.0021428571
64.29
96.4315.58213.58
128.5716.242.666666666713.5733333333
1510.7116.913.333333333313.5766666667
1812.8617.58413.5813.5766666667
2115.0018.244.666666666713.5733333333
2417.1418.915.333333333313.5766666667
2719.2919.586
3021.4320.246.6666666667
3323.5720.917.3333333333
3625.7121.588
3927.8622.248.6666666667
4230.0022.919.3333333333
4532.1423.5810
4834.2924.2410.6666666667
5136.4324.9111.3333333333
5438.5725.5812
5740.7126.2412.6666666667
6042.8626.9113.3333333333
6345.0027.5814
6647.1428.2414.6666666667
6949.2928.9115.3333333333
Sheet1
meters
miliseconds
Direct and Refracted Waves
Sheet2
0.00
Meters
miliseconds
Direct Wave
Sheet3
-
Simple Plot
DistanceTimeDTime R0030683212163418243624323830404036484242564448644654724860805066885272965478104568411258
Chart1
030
832
1634
2436
3238
4040
4842
5644
6446
7248
8050
8852
9654
10456
11258
Distance (meters)
Time (miliseconds)
Sheet1
DistanceTimeDTime R
0030
6832
121634
182436
243238
304040
364842
425644
486446
547248
608050
668852
729654
7810456
8411258
Sheet1
Distance (meters)
Time (miliseconds)
Sheet2
Sheet3
-
Chart2
00
2.14285714293
4.28571428576
6.428571428615.58
8.571428571416.24
10.714285714316.91
12.857142857117.58
1518.24
17.142857142918.91
19.285714285719.57667
21.428571428620.2433366667
23.571428571420.9100033333
25.714285714321.57667
27.857142857122.2433366667
3022.9100033333
32.142857142923.57667
34.285714285724.2433366667
36.428571428624.9100033333
38.571428571425.57667
40.714285714326.2433366667
42.857142857126.9100033333
4527.57667
47.142857142928.2433366667
49.285714285728.9100033333
meters
miliseconds
Direct and Refracted Waves
Sheet1
DistanceArival Time in ms
mDirectRefracted
00.00
32.140.0021428571
64.29
96.4315.58213.58
128.5716.242.666666666713.5733333333
1510.7116.913.333333333313.5766666667
1812.8617.58413.5813.5766666667
2115.0018.244.666666666713.5733333333
2417.1418.915.333333333313.5766666667
2719.2919.586
3021.4320.246.6666666667
3323.5720.917.3333333333
3625.7121.588
3927.8622.248.6666666667
4230.0022.919.3333333333
4532.1423.5810
4834.2924.2410.6666666667
5136.4324.9111.3333333333
5438.5725.5812
5740.7126.2412.6666666667
6042.8626.9113.3333333333
6345.0027.5814
6647.1428.2414.6666666667
6949.2928.9115.3333333333
Sheet1
meters
miliseconds
Direct and Refracted Waves
Sheet2
0.00
Meters
miliseconds
Direct Wave
Sheet3
-
Two Equations for Simple Refraction
These two equations should give the same answer. It should be less than half the crossover distance.
-
Steps in solving for depth1Determine the velocities of both layers in meters per second or feet per second2Determine the crossover distance3Determine the time intercept for V24Determine the depth to layer 2 usingBoth refraction equations (internal check)
-
Up DipDown Dip
-
Dipping Bed Equations