Hwaro hwedzidziso uye kushandiswa kweVLF Method muGeophysics
Pendauluan
Nzira yeVLF (Very Low Frequency) inzira yemagetsi inoshandisa mafungu eredhiyo akaderera (anenge 15–30 kHz) kuona kusiyana kwesimba remagetsi riri pasi pevhu. Kusiyana nenzira yekudzivirira geoelectric inoda kupinza magetsi kuburikidza nemaelectrodes muvhu, nzira yeVLF inowanzo shanda nekuti inoshandisa mafungu kubva kumaVLF radio transmitters aripo (kazhinji ekutaurirana kwemauto kana kufamba). Nehunhu uhwu, VLF inzira inoshanda, inokurumidza, uye isingadhuri yekutanga ongororo dzezvinangwa zvakasiyana-siyana zvegeological, kunyanya zvivakwa zvinofambisa mhepo zvakaita senzvimbo dzisina kunaka, kupwanyika kwemvura, sulfide mineralization, uye nzira dzegeological. pasi pevhu.
Chinyorwa chino chinokurukura hwaro hwedzidziso yenzira yeVLF, misimboti yekuyera, nzira dzekududzira, uye mashandisirwo akajairika mumunda wekutsvaga nekugadzira nharaunda.
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Hwaro hwedzidziso dzeVLF Method
1. Pfungwa yemafungu emagetsi uye induction
Zviratidzo zveVLF mafungu emagetsi anosanganisira zvikamu zvemagetsi (E) uye zvemagnetic (H) zvinopararira mumhepo uye zvinobatana nepamusoro peNyika. Kana mafungu aya arova Pasi, rimwe resimba rinopararira semafungu epamusoro uye rimwe rinopinda pasi pevhu. Kana chinhu kana nzvimbo ine simba remagetsi rakakwirira kupfuura dombo rakatenderedza (semuenzaniso, ivhu rakanyorova, nzvimbo dzemvura dzisina simba, sulfide veins), nzvimbo huru yemagetsi inokonzera mafungu emvura mukati memuviri wemagetsi.
Mafungu aya eddy currents anogadzira minda yechipiri, iyo inozobatwa nechishandiso. Nemamwe mashoko, kusarongeka kweVLF kunoitika nekuda kwemusiyano mukupindura pakati pemunda wekutanga kubva kune transmitter nemunda wechipiri unokonzerwa nechimiro chepasi pevhu.
2. Nzvimbo huru inobva: VLF transmitter
Nzira yeVLF inoshandisa maVLF transmitters ane simba guru anotumira chiratidzo chakagadzikana pane imwe frequency. Munzvimbo dzakawanda, nzvimbo dzakawanda dzeVLF dzinogona kugamuchirwa panguva imwe chete, asi vashandisi vanowanzo sarudza maVLF transmitters ane:
- chiratidzo chakasimba uye chakasimba panzvimbo yekuongorora,
- gwara rekutumira rinokwana zvinoenderana nekwakanangana nechinangwa (semuenzaniso, rakatarisa kwakanangana nekwakanangana nepakanga paine dambudziko riri kutsvagwa),
- kuwanda uye mamiriro ekupararira kwembeu zvakakwana.
Nekuti inoshandisa chinhu chekunze, nzira iyi haidi jenareta kana chinotumira tambo mumunda, zvichiita kuti ongororo ishande zvakanaka.
3. Zviyero zvakakosha: kutenderera kwemhepo uye kudzika kwekupinda
Mhinduro yeVLF inokonzerwa zvakanyanya nemagetsi (σ) echinhu chiri mukati. Pfungwa inowanzo shandiswa kufungidzira kuti mafungu anogona "kupindira" kusvika papi iganda (δ), iro riri kudzika uko amplitude yemunda inodzikira kusvika painenge 1/e yehukuru hwayo hwepamusoro. Zvichitaurwa zviri nyore:
– Kupinda kunowedzera kana resistivity yakakwira (conductivity yakaderera).
– Kupinda kwemhepo kunoderera kana conductivity yakakwira, nekuti munda wacho unonyoroveswa nekukurumidza.
Nema frequency eVLF (~kHz), nzira iyi inowanzo shandiswa kudzika kusvika pakati nepakati (makumi emamita, zvichida zvichienderana nemamiriro enzvimbo). Saka, VLF yakakodzera kwazvo pakugadzira mapu ezvivakwa zvisina kudzika zvakaita senzvimbo dzakatyoka nezvikanganiso.
4. Zvikamu zvemunda uye polarization
Mukuita kweVLF, chiyero chekutanga ndechekusiyana kwesimba remagineti (kana kuti kutenderera kwemunda) sekukanganiswa nechimiro chekufambisa. Kana munda wekutanga ukakanganisa kondakita yakareba (semuenzaniso, nzvimbo yekukanganisa), munda wechipiri unogadzirwa nezvinhu zvinokonzera shanduko mu:
– kona yekutsvedza (kona yekutsvedza yenzvimbo),
- zvikamu zvechiratidzo zviri muchikamu (chaicho) uye zvequadrature (zvekufungidzira).
Chikamu chiri muchikamu chine chekuita nemhinduro yemuchina wekufambisa mhepo "yakanaka" uye yakananga, nepo quadrature ichiwanzoenderana nemhedzisiro yechikamu uye hunhu hwemuchina wekufambisa mhepo/ivhu pamwe nemamiriro ejometri nemamiriro ekudzika.
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Nheyo dzekuyera munda
1. Maitiro ekuongorora
Ongororo dzeVLF dzinoitwa nekufamba munzira yekuyera (profile) panguva dzakatarwa (semuenzaniso, 5–20 m). Mushandisi anonongedzera mudziyo kune transmitter yakasarudzwa uye obva anyora maparameter eVLF pachiteshi chimwe nechimwe. Vanyanzvi vanowanzoita mapass akawanda akafanana kuti vagadzire mepu isina kujairika yemativi maviri.
Chinokosha pakugadzira mageometry muVLF ndechekuti: zvinhu zvisingawanzoonekwi zvinoonekwa kana nzira yechinangwa nekwachinongedzera zvikapindirana zvakanaka negwara rekutanga remunda. Zvinangwa zvinofambisa mashoko zvakareba zvakatarisa pedyo nechinhu chinotumira mashoko zvinowanzoburitsa mhinduro dzisina kusimba.
2. Data guru: muchikamu uye quadrature
Zvishandiso zvemazuva ano zveVLF zvinowanzogadzira nzira mbiri huru:
– Muchikamu (% kana madhigirii): mhinduro muchikamu nechikamu chekutanga.
– Quadrature (% kana madhigirii): Mhinduro yemusiyano wechikamu che90°.
Nzira mbiri idzi dzakakosha nekuti:
- Muchikamu chinowanzoonekwa kune maconductor akanaka uye asina kudzika.
- Quadrature inowanzo kuwedzera muma conductor asina simba, ma deeper conductors, kana muma media anokonzera dispersion/phase lag effects.
3. Data processing: Fraser uye Karous-Hjelt filters
Ruzivo rweVLF rusina kugadzirwa runowanzo kuve rwakaoma kuverenga nekuda kwekuchinja kwarwo kudiki kunokonzerwa neruzha. Nzira mbiri dzakakurumbira dzekugadzirisa ndeidzi:
- Fraser Sefa
Kushandura data riri muchikamu kuita chimiro chinonzwisisika nekuratidza shanduko dzegradient. Mhedzisiro yacho inowanzova curve ine peaks inoenderana nenzvimbo dzeconductor.
– Karous–Hjelt Sefa
Inogadzira chikamu che pseudo-section che current density kuti ione nzvimbo uye kudzika kwema conductors. Kunyange zvazvo isiri "inversion" chaiyo seyemazuva ano ERT kana EM, firita iyi inobatsira kududzira nekukurumidza, kunyanya kune marongerwo emutsetse.
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Dudziro yeVLF Anomaly
1. Hunhu hwakawanda hwezvinhu zvisina kunaka zvemutyairi
Makontarakita emutsetse akadai senzvimbo dzekukanganisa anowanzo kukonzera maitiro anotevera:
- kuchinja kwechiratidzo (zero crossing) muchikamu,
- mativi/makombama akaenzana kana asina kuenzana zvichienderana nekudzika uye kudzika,
- mhinduro yequadrature iyo inobatsira kuona kana kusagadzikana kuri kukonzerwa neconductor chaiyo kana kungova mhedzisiro yepamusoro-soro ye topographic/heterogeneity.
Zvikanganiso zvakanyanya zvinowanzoratidza:
– kufambiswa kwemhepo kwakanyanya (semuenzaniso sulfide mineralization kana ivhu rakanyorova),
- kondakita isina kudzika,
- "Kutungamira kwakanaka" kwemutyairi kana tichienzanisa nekutungamira kwemutakuri.
2. Kusajeka uye miganhu
Nzira yeVLF ine miganhu inofanira kunzwisiswa:
- Kuvimba netransmitter: mhando yedata inoenderana nesimba resignal uye kupindirana kwekuparadzira.
– Inonzwa ruzha rwetsika: tambo dzemagetsi, fenzi dzewaya, mapaipi, njanji, nezvimwe zvinhu zvinogona kukonzera kusawirirana kwenhema.
- Kududzira kusiri kwakasiyana: kusarongeka kunogona kukonzerwa nekusanganiswa kwakasiyana-siyana kwekudzika, kutsvedza, uye kufambisa simba.
- Kudzika kushoma: kunowanzo shanda kune zvinangwa zvisina kudzika-pakati; kune zvinangwa zvakadzama dzimwe nzira dzeEM kana geoelectric dzinodiwa.
Saka, VLF yakanaka senzira yekutanga yekuziva kana kugadzira mapping iyo inozosimbiswa nedzimwe nzira dzakadai se2D resistivity/ERT, IP, magnetic, kana drilling.
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Kushandiswa kweVLF Method muGeophysics
1. Kugadzira mepu yenzvimbo dzakakanganisika nedzakatyoka
Kushandiswa kwakajairika kweVLF kuona nzvimbo dzechivakwa dzinofambisa mvura, ivhu, kana shanduko. Semuenzaniso, mukutsvaga kwegeothermal, zvikanganiso uye kupwanyika zvinoshanda senzira dzemvura; VLF inobatsira kukurumidza kuyera nzira idzi pamusoro.
2. Kuongorora pasi pevhu
Mu hydrogeophysics, VLF inoshandiswa kutsvaga:
– kutsemuka kwedombo rakaoma (aquifer yedombo rakaoma),
- kubatana kwe lithologic kunobata mvura,
- nzvimbo ine mvura yakawanda uye inofambisa mvura zvakanyanya.
Nzira iyi inowanzo shandiswa kuona nzvimbo dzinogona kucherwa matsime, kunyanya munzvimbo dzine matombo akachinja kana kuti ane igneous.
3. Kutsvaga zvicherwa
VLF inogona kuona mineralization inokonzera mhepo yakaita semasulfide makuru, graphite, kana mamwe ma alteration zones. Kunyange zvazvo isiri iyo nzira huru yekuongorora reserve, VLF inoshanda kune:
- kurondwa kwetsinga dzinofambisa mweya,
- kuyera mafambiro ezvimiro zvinodzora kuwanikwa kwezvicherwa,
- ongororo yekukurumidza yenzvimbo dzakakura kuti uone zvinangwa zvepamusoro.
4. Geophysics yezvakatipoteredza uye yeinjiniya
Muzvidzidzo zvezvakatipoteredza, VLF inobatsira kuona:
- nzira inodonhera mvura pamadhamu/embankments,
– nzvimbo dzine ivhu rakazara nemvura dzinowanzo kanganiswa nekudengenyeka kwenyika,
- chiratidzo chekusvibiswa kwetsvina yemhepo kana kufambisa kwemhepo kuchisiyana.
VLF inogona kushandiswawo pakutanga kwekuferefeta kwe geotechnical senzira yekukurumidza yekuona kusiyana kwezvinofambiswa nemhepo zviri pedyo nepamusoro.
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Mhedziso
Nzira yeVLF inzira yemagetsi isingashande inoshandisa ma "frequency transmitters" akaderera kuti ione ma "conductive subsurface structures". Hwaro hwayo hwepfungwa hunobva pa "electromagnetic induction": "primary field" inokonzera "current" mu "conductor", zvichikonzera "secondary field" inoyerwa sekuchinja kwe "phase" ne "quadrature". Nekuongororwa kwayo kwe "fast field surveying", mutengo wayo wakaderera, uye kugona kwayo kuratidza ma "linear structures" akadai se "faults" uye "fractures", VLF inobatsira zvikuru pa kuongorora pasi pevhu, kumepu yemaumbirwo ejeologiya, kutsvaga zvicherwa, uye mashandisirwo ezvakatipoteredza. Zvisinei, dudziro yaro haina kujeka uye inonzwa ruzha rwetsika, saka mhedzisiro yeVLF inofanira kubatanidzwa nedzimwe nzira dzegeofizikisi kuti zvisimbiswe.
Kana muchida, ndinogona kuwedzera chikamu chemuenzaniso wekuyerera kweongororo yeVLF kubva pakuronga kusvika pamepu isina kujairika, kana kugadzira chimiro chakakwana chechinyorwa chesainzi chine zvirevo zvakajairwa.
