ASTM D5777-2000(2006) Standard Guide for Using the Seismic Refraction Method for Subsurface Investigation《地下勘探用震波折射法的标准导则》.pdf

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1、Designation: D 5777 00 (Reapproved 2006)Standard Guide forUsing the Seismic Refraction Method for SubsurfaceInvestigation1This standard is issued under the fixed designation D 5777; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t

2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 Purpose and ApplicationThis guide covers the equip-ment, field procedures, and interpretation methods for

3、theassessment of subsurface conditions using the seismic refrac-tion method. Seismic refraction measurements as described inthis guide are applicable in mapping subsurface conditions forvarious uses including geologic, geotechnical, hydrologic,environmental (1), mineral exploration, petroleum explor

4、ation,and archaeological investigations. The seismic refractionmethod is used to map geologic conditions including depth tobedrock, or to water table, stratigraphy, lithology, structure,and fractures or all of these. The calculated seismic wavevelocity is related to mechanical material properties. T

5、herefore,characterization of the material (type of rock, degree ofweathering, and rippability) is made on the basis of seismicvelocity and other geologic information.1.2 Limitations:1.2.1 This guide provides an overview of the seismicrefraction method using compressional (P) waves. It does notaddres

6、s the details of the seismic refraction theory, fieldprocedures, or interpretation of the data. Numerous referencesare included for that purpose and are considered an essentialpart of this guide. It is recommended that the user of theseismic refraction method be familiar with the relevant mate-rial

7、in this guide and the references cited in the text and withappropriate ASTM standards cited in 2.1.1.2.2 This guide is limited to the commonly used approachto seismic refraction measurements made on land. The seismicrefraction method can be adapted for a number of special uses,on land, within a bore

8、hole and on water. However, a discussionof these other adaptations of seismic refraction measurementsis not included in this guide.1.2.3 There are certain cases in which shear waves need tobe measured to satisfy project requirements. The measurementof seismic shear waves is a subset of seismic refra

9、ction. Thisguide is not intended to include this topic and focuses only onP wave measurements.1.2.4 The approaches suggested in this guide for the seismicrefraction method are commonly used, widely accepted, andproven; however, other approaches or modifications to theseismic refraction method that a

10、re technically sound may besubstituted.1.2.5 Technical limitations and interferences of the seismicrefraction method are discussed in D 420, D 653, D 2845,D 4428, D 5088, D 5730, D 5753, D 6235, and D 6429.1.3 Precautions:1.3.1 It is the responsibility of the user of this guide tofollow any precauti

11、ons within the equipment manufacturersrecommendations, establish appropriate health and safety prac-tices, and consider the safety and regulatory implications whenexplosives are used.1.3.2 If the method is applied at sites with hazardousmaterials, operations, or equipment, it is the responsibility o

12、fthe user of this guide to establish appropriate safety and healthpractices and determine the applicability of any regulationsprior to use.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to

13、 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.5 This guide offers an organized collection of informationor a series of options and does not recommend a specificcourse of action. This document cannot replace education ore

14、xperience and should be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicable in allcircumstances. This guide is not intended to represent or1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcomm

15、ittee D18.01 on Surface and SubsurfaceCharacterization.Current edition approved July 1, 2006. Published August 2006. Originallyapproved in 1995. Last previous edition approved in 2000 as D 5777 00.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Un

16、ited States.replace the standard of care by which the adequacy of a givenprofessional service must be judged, nor should this documentbe applied without consideration of a projects many uniqueaspects. The word “Standard” in the title of this guide meansonly that the document has been approved throug

17、h the ASTMconsensus process.2. Referenced Documents2.1 ASTM Standards:2D 420 Guide to Site Characterization for Engineering De-sign and Construction PurposesD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 2845 Test Method for Laboratory Determination of PulseVelocities and Ultrasonic

18、Elastic Constants of RockD 4428/D 4428M Test Methods for Crosshole Seismic Test-ingD 5088 Practices for Decontamination of Field EquipmentUsed at Waste SitesD 5608 Practices for Decontamination of Field EquipmentUsed at Low Level Radioactive Waste SitesD 5730 Guide for Site Characterization for Envi

19、ronmentalPurposes With Emphasis on Soil, Rock, the Vadose Zoneand Ground WaterD 5753 Guide for Planning and Conducting Borehole Geo-physical LoggingD 6235 Practice for Expedited Site Characterization ofVadose Zone and Ground Water Contamination at Hazard-ous Waste Contaminated SitesD 6429 Guide for

20、Selecting Surface Geophysical Methods3. Terminology3.1 Definitions:3.1.1 The majority of the technical terms used in this guideare defined in Refs (2) and (3).3Also see Terminology D 653.4. Summary of Guide4.1 Summary of the MethodMeasurements of the traveltime of a compressional (P) wave from a sei

21、smic source to ageophone(s) are made from the land surface and are used tointerpret subsurface conditions and materials. This travel time,along with distance between the source and geophone(s), isinterpreted to yield the depth to refractors refractors (refractinglayers). The calculated seismic veloc

22、ities of the layers are usedto characterize some of the properties of natural or man-mademan subsurface materials.4.2 Complementary DataGeologic and water table dataobtained from borehole logs, geologic maps, data from out-crops or other complementary surface and borehole geophysi-cal methods may be

23、 necessary to properly interpret subsurfaceconditions from seismic refraction data.5. Significance and Use5.1 Concepts:5.1.1 This guide summarizes the equipment, field proce-dures, and interpretation methods used for the determination ofthe depth, thickness and the seismic velocity of subsurface soi

24、land rock or engineered materials, using the seismic refractionmethod.5.1.2 Measurement of subsurface conditions by the seismicrefraction method requires a seismic energy source, triggercable (or radio link), geophones, geophone cable, and aseismograph (see Fig. 1).5.1.3 The geophone(s) and the seis

25、mic source must beplaced in firm contact with the soil or rock. The geophones areusually located in a line, sometimes referred to as a geophonespread. The seismic source may be a sledge hammer, amechanical device that strikes the ground, or some other typeof impulse source. Explosives are used for d

26、eeper refractors orspecial conditions that require greater energy. Geophonesconvert the ground vibrations into an electrical signal. Thiselectrical signal is recorded and processed by the seismograph.The travel time of the seismic wave (from the source to thegeophone) is determined from the seismic

27、wave form. Fig. 2shows a seismograph record using a single geophone. Fig. 3shows a seismograph record using twelve geophones.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information,

28、refer to the standards Document Summary page onthe ASTM website.3The boldface numbers given in parentheses refer to a list of references at theend of the text.FIG. 1 Field Layout of a Twelve-Channel Seismograph Showing the Path of Direct and Refracted Seismic Waves in a Two-Layer Soil/Rock System (a

29、c= Critical Angle)D 5777 00 (2006)25.1.4 The seismic energy source generates elastic waves thattravel through the soil or rock from the source. When theseismic wave reaches the interface between two materials ofdifferent seismic velocities, the waves are refracted accordingto Snells Law (4, 8). When

30、 the angle of incidence equals thecritical angle at the interface, the refracted wave moves alongthe interface between two materials, transmitting energy backto the surface (Fig. 1). This interface is referred to as arefractor.5.1.5 A number of elastic waves are produced by a seismicenergy source. B

31、ecause the compressional P-wave has thehighest seismic velocity, it is the first wave to arrive at eachgeophone (see Fig. 2 and Fig. 3).5.1.6 The P-wave velocity Vpis dependent upon the bulkmodulus, the shear modulus and the density in the followingmanner (4):Vp5 =K 1 4/3!/r (1)where:Vp= compression

32、al wave velocity,K = bulk modulus, = shear modulus, andr = density.5.1.7 The arrival of energy from the seismic source at eachgeophone is recorded by the seismograph (Fig. 3). The traveltime (the time it takes for the seismic P-wave to travel from theseismic energy source to the geophone(s) is deter

33、mined fromeach waveform. The unit of time is usually milliseconds (1 ms= 0.001 s).5.1.8 The travel times are plotted against the distancebetween the source and the geophone to make a time distanceplot. Fig. 4 shows the source and geophone layout and theresulting idealized time distance plot for a ho

34、rizontal two-layered earth.5.1.9 The travel time of the seismic wave between theseismic energy source and a geophone(s) is a function of thedistance between them, the depth to the refractor and theseismic velocities of the materials through which the wavepasses.5.1.10 The depth to a refractor is cal

35、culated using the sourceto geophone geometry (spacing and elevation), determining theapparent seismic velocities (which are the reciprocals of theslopes of the plotted lines in the time distance plot), and theNOTEArrow marks arrival of first compressional wave.FIG. 2 A Typical Seismic Waveform from

36、a Single GeophoneFIG. 3 Twelve-Channel Analog Seismograph Record ShowingGood First Breaks Produced by an Explosive Sound Source (9)FIG. 4 (a) Seismic Raypaths and (b) Time-Distance Plot for aTwo-Layer Earth With Parallel Boundaries (9)D 5777 00 (2006)3intercept time or crossover distances on the tim

37、e distance plot(see Fig. 4). Intercept time and crossover distance-depthformulas have been derived in the literature (6-8). Thesederivations are straightforward inasmuch as the travel time ofthe seismic wave is measured, the velocity in each layer iscalculated from the time-distance plot, and the ra

38、ypath geom-etry is known. These interpretation formulas are based on thefollowing assumptions: (1) the boundaries between layers areplanes that are either horizontal or dipping at a constant angle,(2) there is no land-surface relief, (3) each layer is homoge-neous and isotropic, (4) the seismic velo

39、city of the layersincreases with depth, and (5) intermediate layers must be ofsufficient velocity contrast, thickness and lateral extent to bedetected. Reference (9) provides an excellent summary of theseequations for two and three layer cases. The formulas for atwo-layered case (see Fig. 4) are giv

40、en below.5.1.10.1 Intercept-time formula:z 5ti2V2V1=V2!22 V1!2(2)where:z = depth to refractor two,ti= intercept time,V2= seismic velocity in layer two, andV1= seismic velocity in layer one.5.1.10.2 Crossover distance formula:z 5xc2V22 V1V21 V1(3)where:z, V2and V1are as defined above and xc= crossove

41、r distance.5.1.11 Three to four layers are usually the most that can beresolved by seismic refraction measurements. Fig. 5 shows thesource and geophone layout and the resulting time distance plotfor an idealized three-layer case.5.1.12 The refraction method is used to define the depth toor profile o

42、f the top of one or more refractors, or both, forexample, depth to water table or bedrock.5.1.13 The source of energy is usually located at or neareach end of the geophone spread; a refraction measurement ismade in each direction. These are referred to as forward andreverse measurements, sometimes i

43、ncorrectly called reciprocalmeasurements, from which separate time distance plots aremade. Fig. 6 shows the source and geophone layout and theresulting time distance plot for a dipping refractor. The velocityobtained for the refractor from either of these two measure-ments alone is the apparent velo

44、city of the refractor. Bothmeasurements are necessary to resolve the true seismic veloc-ity and the dip of layers (9) unless other data are available thatindicate a horizontal layered earth. These two apparent velocitymeasurements and the intercept time or crossover distance areused to calculate the

45、 true velocity, depth and dip of therefractor. Note that only two depths of the planar refractor areobtained using this approach (see Fig. 7). Depth to the refractoris obtained under each geophone by using a more sophisticateddata collection and interpretation approach.5.1.14 Most refraction surveys

46、 for geologic, engineering,hydrologic and environmental applications are carried out todetermine depths of refractors that are less than 100 m (about300 ft). However, with sufficient energy, refraction measure-ments can be made to depths of 300 m (1000 ft) and more (6).5.2 Parameter Measured and Rep

47、resentative Values:5.2.1 The seismic refraction method provides the velocity ofcompressional P-waves in subsurface materials. Although theP-wave velocity is a good indicator of the type of soil or rock,it is not a unique indicator. Table 1 shows that each type ofsediment or rock has a wide range of

48、seismic velocities, andmany of these ranges overlap. While the seismic refractiontechnique measures the seismic velocity of seismic waves inFIG. 5 (a) Seismic Raypaths and (b) Time-Distance Plot for aThree-Layer Model With Parallel Boundaries (9)FIG. 6 (a) Seismic Raypaths and (b) Time-Distance Plot

49、 for aTwo-Layer Model With A Dipping Boundary (9)D 5777 00 (2006)4earth materials, it is the interpreter who, based on knowledge ofthe local conditions and other data, must interpret the seismicrefraction data and arrive at a geologically feasible solution.5.2.2 P-wave velocities are generally greater for:5.2.2.1 Denser rocks than lighter rocks;5.2.2.2 Older rocks than younger rocks;5.2.2.3 Igneous rocks than sedimentary rocks;5.2.2.4 Solid rocks than rocks with cracks or fractures;5.2.2.5 Unweathered rocks than weathered rocks;5.2.2.6 Consolidated sediments than