Nheyo dzekutanga uye kushandiswa kweTDEM Method muGeophysics
Nzira yeTime Domain Electromagnetic (TDEM) inzira inoshandiswa zvakanyanya mukuongorora zvivakwa zvepasi pevhu zvichibva pamusiyano uripo muhunhu hwemagetsi hwezvinhu, kunyanya resistivity (kana inverse, conductivity). TDEM inzira isingapindi, inokurumidza, uye inoshanda kune zvinangwa zvakasiyana-siyana kubva pakutsvaga pasi pevhu kusvika pakutsvaga zvicherwa uye kugadzira mapu etsvina. Chinyorwa chino chinokurukura misimboti yekutanga yeTDEM, zvikamu zvesystem, mashandiro ayo, kududzirwa kwedata, zvakanakira uye zvisingakwanisike, uye mashandisirwo ayo anoshanda mu geophysics.
1. Nhoroondo nepfungwa huru
Mu geophysics, kuramba kwedombo kunokonzerwa nezvinhu zvakawanda, zvakaita sehuwandu hwemvura, munyu, kuyerera kwemvura, rudzi rwemineral, tembiricha, uye mwero wekuchinja. Zvinhu zvine maburi zvakazadzwa nemvura ine munyu zvinowanzo fambisa mvura zvakanyanya (kudzora mvura zvishoma), nepo matombo makuru akaoma anowanzo dzivirira.
Nzira yeTDEM inoshandisa mhinduro yePasi kumunda wemagetsi unochinja-chinja nguva. Kusiyana nenzira yefrequency-domain electromagnetic (FDEM), iyo inoshandisa mafungu e sinusoidal pama frequency chaiwo, TDEM inoshandisa sosi yemagetsi inobatidzwa nekudzima (pulsed kana step-off). Mushure mekunge magetsi adzimwa, simba guru remagineti rinodonha, richigadzira simba remagetsi riri pasi pevhu. Kuora kwesimba iri rinonyorwa panguva dzakatarwa, zvichibvumira ruzivo rwakadzama kuti ruwanikwe kubva pakuchinja kunoita chiratidzo nekufamba kwenguva.
2. Nheyo dzefizikisi dzeTDEM: induction uye eddy currents
Kana magetsi emagetsi achifamba nemuchitenderedzwa chetransmitter, simba guru remagineti rinogadzirwa. Kana magetsi amira nekukurumidza (step-off), simba iri remagineti rinochinja rinogadzira simba remagineti rinokonzerwa nemutemo waFaraday. Nekuda kweizvozvo, magetsi emvura anoumbwa pasi pevhu, ayo anopararira uye anobva aora nekuda kwekusagadzikana kwechinhu ichi.
Hunhu hunokosha hweTDEM hukama hwenguva-hurefu:
– Nguva yekutanga: mhinduro yacho inonyanya kugadzikana nezvikamu zvisina kudzika nekuti mafungu emvura achiri pedyo nepamusoro.
– Nguva yekunonoka: mhinduro inomiririra kudzika kukuru nekuti mafungu emvura "akapararira" pasi uye akaneta.
Muchidimbu, chinhu chinofambisa masaini chinoburitsa kuora kwechiratidzo zvishoma nezvishoma (kuora kwenguva refu), nepo chinhu chinodzivisa masaini chinowanzoratidza kuora nekukurumidza.
3. Zvikamu zvehurongwa uye marongero eongororo
Sisitimu yeTDEM inowanzo kuve ne:
1. Chinotumira: chitubu chemagetsi chinoyerera mapombi emagetsi mu loop/coil.
2. Chinotenderera: tambo yakatambanudzwa pamusoro (inogona kuva sikweya, denderedzwa, kana zvimwe zvinhu).
3. Chinogamuchira: mudziyo wekurekodha voltage inokonzerwa nekufamba kwenguva.
4. Koira yekugamuchira: inogona kuiswa pakati pechitenderedzo (pakati pechitenderedzo) kana yoga (offset loop).
5. Chinotonga uye chinoisa data logger: chinochengetedza voltage decay curve zvichienderana nenguva (transient response).
Magadzirirwo eongororo akakurumbira:
– Chinotenderera chepakati: chinogamuchira chiri pakati pechinotenderera chinotumira mashoko; chakanaka pakunzwika kwe1D uye kupindura kwakagadzikana.
– Kutenderera kwakabatana: mugamuchiri nemutumidziri zvakafanana; zvinoshanda, asi zvinoda kugadziriswa kwemigumisiro yekubatanidza uye mhinduro yekutanga.
– Chinotenderera cheoffset: chinogashira chinoiswa padaro rakati kubva pachinotenderera; chinobatsira pakugadzirisa mativi uye zvinangwa zvakananga.
Kusarudzwa kwehukuru hwechitenderedzwa uye simba remagetsi kunokanganisa kudzika kwekupinda: zvitenderedzwa zvakakura uye mafungu akakwirira anowanzo kuwedzera kugona "kuona" zvakadzama, asi zvinoda mafambiro akawanda.
4. Kuwanikwa kwedata: nguva uye kuderedza ruzha
Data reTDEM rinonyorwa mumahwindo enguva akasiyana, semuenzaniso, kubva kuma microseconds kusvika kuma milliseconds (kana kutopfuura) mushure mekunge magetsi adzimwa. Mahwindo ekutanga anobata mhinduro dzisina kudzika, nepo mahwindo ekupedzisira achibata kudzika kukuru.
Zvinetso zvakajairika mukuyera kweTDEM zvinosanganisira:
– Ruzha rwetsika: tambo dzemagetsi, fenzi, mota, uye zvivakwa zvesimbi.
– Kubatanidza magineti: kubva pazvinhu zvesimbi zviri pedyo nechinhu chinogamuchidza kana chinotumira.
- IP (Induced Polarization) inokonzeresa zvimwe zvinhu zvinogona kugadzirisa chimiro chekuora.
- Kufamba kwezvishandiso uye shanduko yemagetsi: kuyera uye kurongedza zvinodiwa.
Kuti data riwedzere kunaka, kurongedza (kudzokorora kwepulse uye kunyorovesa masaini) kunoshandiswa kuderedza ruzha rwezvinhu zvisina tsarukano. Uyezve, kusarudzwa kwenzvimbo yekuyera uye kurongeka kweloop zvinowanzova zvinhu zvakakosha pakubudirira kweongororo.
5. Kududzira uye kuchinja data
Kubuda kweTDEM kunowanzo kuve kutenderera kwekushushikana kunokonzerwa nekushandiswa kwedata kana nguva. Kuti rigone kutsanangurwa semuenzaniso wepasi pevhu, data racho rinogadziriswa uye rinoshandurwa kuita resistivity profile.
Nzira dzinoshandiswa pakududzira:
– 1D model (sounding): inofunga kuti ine maturikirwo akatwasuka; yakakodzera kuferefeta zviri nyore pamusoro pe stratigraphic, sedimentary basin, kana aquifers.
- Mhando dze2D: dzinoshandiswa pakuvaka zvivako zvirefu zvakaita sezvikanganiso, miganhu yelithological, kana kupinda mukati.
- Mhando dze3D: dzakakosha pazvinangwa zvakaoma, semuenzaniso sulfide ores, masisitimu ekupisa kwepasi, kana nzvimbo dzakasiyana dzemaguta.
Kuchinja kweTDEM kunoedza kutsvaga modhi yekudzivirira inogadzira mhinduro yedzidziso inonyatsoenderana nedata. Nekuti dambudziko racho harisi rega, kurongeka (kudzora kupfava kwemodhi) uye kubatanidzwa nedzimwe ruzivo rwe geology kana geophysical zvinowanzo shandiswa.
6. Zvakanakira uye zvisingakwanisike zveTDEM nzira
Keunggulan
– Inonzwa kune zvinofambisa mhepo: inoshanda zvikuru pakuona nzvimbo dzinofambisa mhepo dzakadai sevhu, mvura ine munyu, sulfide hombe, kana zvinhu zvinosvibisa.
- Kudzika kwakanaka kwekupinda: kunyanya munzvimbo dzinodzivirira uye dzine zvitenderedzwa zvakakura.
- Kugadziriswa kwakakwana kwemativi: kugona kupatsanura zvikamu zvichibva pakuchinja kwe resistivity.
- Inokurumidza: ongororo dzemumunda dzinogona kuitwa zvinobudirira pakuratidza pfungwa dzakawanda.
Miganhu
– Ruzha rwetsika runogona kukanganiswa: nzvimbo dzemumaguta kana pedyo netambo dzemagetsi zvinogona kuoma.
- Kusanzwisisika kwetsananguro: kuramba kwezvakatipoteredza kunokonzerwa nezvinhu zvakawanda; kudzorwa kwenzvimbo kunodiwa.
- Miganhu yekugadziriswa kwemativi ekunzwa kwe1D: kana chimiro chacho chiri che3D zvakanyanya, mamodheru e1D anogona kutsausa.
– Mhedzisiro iri pedyo nepamusoro: zvikamu zvisina kudzika zvinofambisa mvura zvinogona "kuvhara" mhinduro kubva pakadzika.
7. Mashandisirwo makuru eTDEM mu geophysics
7.1 Kuongorora mvura yepasi (hydrogeophysics)
TDEM inozivikanwa zvikuru pakugadzira mamepu:
– ukobvu hwevhu nematombo,
– miganhu yemvura yemugungwa neyemugungwa (semuenzaniso ivhu rinofambisa mvura),
– kupindira kwemvura yegungwa pamhenderekedzo yegungwa (nzvimbo inokonzera mvura nekuda kwemunyu wakawanda),
– kuona nzvimbo yematsime ekugadzira uye kuongorora kugona kwemvura yemugungwa.
Muzvidzidzo zvakawanda, TDEM inoshandiswa pamwe chete neruzivo rwekudhirowa neruzivo rwezve geology kuderedza kusanzwisisika.
7.2 Kutsvaga zvicherwa uye zvinangwa zvekufambisa zvinhu
Madhipoziti makuru esulfide kana mamwe mamineral anowanzo fambisa, zvichiita kuti TDEM ishande kune:
- kuona madhairekita akasiyana (zvinangwa zveore),
- kugadzira mamiriro chaiwo ekuchinja kwemvura inopisa,
- inobatsira kuona zvinhu zvinokosha pakuchera.
Kune zvinangwa zvinofambisa mhepo zvakanyanya uye zvidiki, mafambiro ekunze kana ongororo dzakadzama dzeTDEM (kusanganisira masisitimu emhepo mune dzimwe nzvimbo) dzakakodzera zvakanyanya.
7.3 Kupisa Kwepasi
Munzvimbo dzinopisa zvikuru, chivharo chevhu chinowanzova nemhepo inoyerera zvakanyanya, nepo dziva racho richigona kuramba richidzivirira. TDEM inoshandiswa ku:
- kugadzira chivharo chevhu,
- kugadzira miganhu yesystem uye maumbirwo evanodzora,
- batsira pakusarudza nzvimbo dzekutsvaga matsime.
TDEM inowanzo sanganiswa neMT (magnetotelluric) kuti ifukidze kudzika kwakakura.
7.4 Zvakatipoteredza uye kusvibiswa
Zvinosvibisa zvakanyungudutswa (semuenzaniso, tsvina inodonhedzwa mumarara kana mvura ine munyu) zvinogona kuwedzera simba remhepo muvhu. TDEM inoshandiswa ku:
- kuyera kupararira kwemapundu ekusvibiswa,
- tarisa shanduko mukufambisa kwemhepo nekufamba kwenguva,
- kuferefeta nzvimbo dzinorasirwa marara mumaindasitiri kana kuti dzinobuda mvura.
7.5 Geotechnical uye mainjiniya
Kune zvinodiwa zvezvivakwa, TDEM inogona kubatsira:
- kuyera kudzika kwedombo,
- kuziva nzvimbo dzisina kusimba kana kuti matanda evhu akakora,
- ongororo dzekutanga dzenzira dzemapaipi, migwagwa kana madhamu padanho rakati.
Zvisinei, kune resolution yakadzika kwazvo, dzimwe nzira dzakadai seGPR kana resistivity (ERT) dzinogona kuva imwe yekuwedzera ine ruzivo rwakadzama.
8. Mhedziso
Nzira yeTDEM inzira ine simba yemagetsi yekushandisa electromagnetic response zvichienderana nekusiyana kwe resistivity. Nekushandisa kuora kwe electromagnetic response mushure mekunge transmitter current yadzimwa, TDEM inopa ruzivo rwakadzama runobatsira kune akasiyana mashandisirwo: pasi pevhu, zvicherwa, geothermal, zvakatipoteredza, uye geotechnical. Kubudirira kweongororo yeTDEM kunoenderana nekugadzirwa kweaccount (loop, current, time window), kudzora ruzha, uye kududzira uye inversion zvinofunga nezvemamiriro enzvimbo. Mumazuva ano, TDEM iri kushanda zvakanyanya kana ikabatanidzwa ne drill data nedzimwe nzira dze geophysical, zvichikonzera mhedzisiro yakasimba uye yakavimbika yekuita sarudzo.
Kana muchida, ndinogona kugadzirisa chinyorwa ichi kuti chienderane nemaitiro enyanzvi (nemashoko akanyorwa), kuwedzera mifananidzo yekushanda kweongororo, kana kugadzira muenzaniso weTDEM wekudzidza kwemvura yepasi pevhu/geothermal/minerals.
