• KHOA HQC CONG NGHE •
TAC DONG DIA C H A T THUY VAN D^N CAC PHiyaNG PHAP KHAI THAC B £ THAN SONG H O N G
GS.TS VC TRpNG H6NG Nguyin Chu tfch Hpi Thuy Igi VietNam Tdm tat: Bai bdo nay se phdn tich ve tdc dong dia chdt thuy van tdi nhimg phuong phdp khai thdc than cua Dong bdng song Hong
Abstract: In this article, impact of subsurface water on coal exploited methods in the Red Delta is considering.
1. DONG B A N G S O N G H 6 N G Dong bang sdng Hdng nam trong vimg ven bidn d phia bac Vi$t Nam [^1].
Trung tam cua viing dong bang sdng Hdng rat bang phdng, phan Idn nam giiia 0,4m va 12m trdn m\rc nudc bidn, vdi 56% ndm dudi 2m.
[2] Khi hau cua lim vuc sdng Hdng nim trong vung nhiet ddi gid mua vdi mua ddng lanh, khd, it mua ya mua he ndng am mua nhidu. Miia mua d ddng bang thudng tir thang 5 ddn thang 10, tap tnmg tdi 85% lugng mua nam. Thang 8 la thang thudng cd lugng mua Idn nhdt dat tir 300 ddn 400mm. Lugng mua thang Idn nhat la 569mm. Trong mua it mua, tu tiiang 11 ddn thang 4, lugng mua chi chidin xap xi 15% lugng mua nam, thang it mua nhat thudng la thang 3, ydi lugng mua tii 15 den 20mm.
Ddng bang sdng Hdng nam trdn hai tang chiia nudc chinh:
TSng chua nudc do tram tich thdi ky holocen rdt day, tu vai met tdi 40m. Chidu sau tdi mat nudc rat khac nhau Idioang 0,5m den 2m trong mua mua, va tCr 2m den 8 trong mua khd, tuy thupc tung vung.
Tdng chtia nudc do tram tich thai ky pleistocen dugc khep kin. Chieu day rat khac nhau, tir khoang 10m, 20m tdi 100m, tang tu ddng bac tdi tay nam.
Kdt luan: viec khai tiiac than d Tliai Binh se gap lugng nudc ngam Idn, bdi myc nudc ngam ndm rat cao gan vdi mat dat, dac bidt trong miia mua.
2. TAG DONG CUA Nl/OC NGAM DEN CONG NGHE KHAI THAC THAN
Theo xu thd khai thac than hien nay trong nudc ciing nhu d mdt sd nudc tidn tidn, thi cd thd tdm tat mpt sd cdng ngh$ sau:
a/ Khai thdc ha: Do lugng than nam rai rac trdn pham vi rpng Idn 2700km2, va d dp sau d
300, 1200 va 3000m. Ndu khai thac tat ca trG lugng, thi didn tich phai dao ra chiem 75% dipn tich ca ddng bang.
b/ Khai thdc kiiu ham Id: day la cdng ngh?
dugc ap dung phd bidn cua nganh than. Tuy nhidn trong vung dat ydu nhu be than sdng Hdng, di^u kien dia chdt, dia chdt thuy van khac vdi vijng md Quang Ninh.
Nhung loai dat d ddng bang sdng Hdng gdm tir trdm tich cita sdng Hdng va bdi tich cua bidn.
Tram tich song gdm nhiing hat phii sa va cat min dugc xdp vao loai dat dinh. Cdn boi tich gdm nhiing hat edt thd cac kich cd do sdng biln va nhung ddng ven bd dem vao. Ddi vdi khu vuc be than sdng hdng, hai loai dat nay cd su dan xen nhau. Dac didm nay dugc thd hidn trdn nhung ndn khoan thdm dd d Ddng Hung gan day. Cd ndn khoan, ciing vdi than, cdn lan ca ldp set cua trim tich sdng. Co ndn khoan cdn lan nhihig hat cat thd ciia su bdi tich bidn. Nhu vay, dJtc didm dja chat trdn cimg mdt tang than ciuig khac nhau, ddn ddn kha ndng chiu tai ciia dat ciing khac nhau. Dd la khd khan cho vi$c bao v^ nhung mai dat cita nhiing tang khai thac.
Nhieu ndn khoan cdn cd nudc chay ra, the hidn tang nudc ngam nSm gan mat dat. Cd ndn cdn khd rao, idy nguydn dugc ndn, chiing td d via dd nudc ngam nam sau. Do su khdc nhau vd muc nudc ngam, ndn danh gia ve luu lugng nudc ngam de hiit idn khi khai thdc ciin^ khd khan.
Do la chua kd cd anh hudng ddn su dn djnh cua dat khi khai thdc ciing nhu sau khi khai thdc.
Dac thii ddi vdi khai thdc hdm Id trong ddt mdm, nhiing chi tidu va nhihig didu kien cdn chu y cu thd, lai khdng the tdch rdi vdi didu kien nudc n^am dpc theo tuyen hdm Id va cdc dac trung ve su dn dinh (hoac cudng dp) cua ddt phai dugc tinh den d ciia Id. Thudng thudng.
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• KHOA HQC CONG NGHE •
ddc bi?t trong ddt dang hgt, ca hai su quan tam cd mdi quan h? qua lai mat thidt vdi nhau.
[3] Ddi vdi j)huang phap dao ham Id trong ddt thi vi?c kidm soat nudc ngam la vd cimg quan trpng. Phuang phap ha thap myc nudc ngdm la pho bien nhdt. Khd khdn d day la tinh thoat nudc lai khac nhau. Vi d\i cat thd, vide hixt nudc thuan lgi, nhung cat min hoac cdc tang set thi khdng thd diing mdy bom Idn dugc, bdi vi?c thodt nudc loai ddt nay rat cham. Neu hiit nhanh, trong dat cdn dp luc nudc rat Idn, se sinh hidn tugng trugt mai. Mai ho mdng vdi cat thd cd the ddc, cdn set min thi mdi rat sodi, didn tich mat bdng khu vuc hiit nudc se rat Idn.
c/ Phuang phdp khi hod than, (synthetic natural gas) SNG de lay khi gas tir than, dimg phdn ling hod hpc, khdng ddt. Theo jihuong phap ndyj cd hai nhugc diem Idn: san xiiat ra khi C02 nhidu qud va phai sii dyng nudc nhidu hon.
d/ Phuang phdp cong ngh$ sach (underground coal gasification) UCG, bang each bam khi O2 yd hoi qua cac lo khoan, tao ra su tu chay cd kidm soat. Chuydn than tir thd cung sang thd khi. Khi Hydrogen, methan, carbon monoxid, va CO2 dugc bom vao lo thii hai dd dua len sir dung.
Hai phuang phap nay nay van phdi bom tidu nudc ngam. Ngoai ra van tao ra lugng khi CO2 Idn, ddng thdi van can mpt lugng nudc Idn, do v|iy khdng phii hgp ydi nudc ta, bdi dong bdng dang bi thidu nudc ve mua khd.
Kdt luan: Phuang phdp khai thdc cd thd nghien ciru la phuang phdp hdm Id, song vifc tidu thoat nude ngam va hau qua gay liin syt vimg Ddng bang sdng Hdng la nhiing rui ro Idn.
3. SV* XAM NHAP CUA NU'6c MAN VAO
T A N G NU^dC NGQT DO KHAI THAC THANTheo,[4] nudc biln cd^ thd xuyen sau vao tdng nudc ngpt dudi ddt, theo cdng thiic:
H=40h, h-la chdnh l$ch muc nudc ngpt trdn muc nudc bidn, H- chieu sau ciia dudng bidn gidi chia tach dudi muc nudc bidn. Nhu vay, khi khdng cd nudc sdng dan vd ddng bdng (miia khd) thi muc nudc m ^ xdm nhap vao trong ddt se ndm ngang myc nudc bidn. Ngugc lai, vd niiia mua, lugng nudc ngpt cung cap cho ddng bang Idn thi nudc man cang xudng sau, anh hudng cdc tdng Holocen va pleistocen. Theo [2]
thi hidn nay d cua sdng ha liru luu vuc sdng Hdng - Thai Binh thi dd man 4 phdn nghin da vao sdu 1km d sdng Ddy, vd 12 km d sdng Kinh
Thay, Lsieh Tray. Ngudn nudc ngpt ciia sdng Hdng cung cdp cho ddng bdng, vd miia khd, cd doan chi cdn 10cm. Vi^c khai thac than sd 1 ^ tyt m\rc nudc ngdm xudng, khidn cho nudc bidn cang xSm nhgp sau vao viing ddng bdng.
Ket luan: khi kl^i thdc ldp tiian ndm dudi ddng bdng sdng Hdng, nhu Tidn Hdi, Dong Hung, se tao ra su xani nhap nudc man vdo tdng nudc ngpt nam dudi dat cang sdu vd cang xa, c6 the tdi hang trdm km.
4. NHAN XET
a. Ddng bdng sdng Hdng da tdn tai hdng nghin nam, va dang tiep tue phat tridn iihd s\r tram tich cua phii sa cua hp thdng sdng Hdng va sdng Thai Biiih, ya sy bdi tich cua edt bidn dpc cdc tinh veil bien, trong do cd bd than sdng Hdng. Neu lay di bd than sdng Hdng, ddng bdng se bi lun sut xudng.
b.Can danh gid phuang phdp khai thac nao Id kha thi. Nen xem xet I^ trij lu^jng than nhu trong quy hoach da ndu la 210 ty tdn, hay chi co thd khai thdc dugc 30 - 40 ty tdn. Nhiing mlu than tham dd lan cat, va va vyn nhieu.
c. Vide khai thac than d ven biln, khien cho cd hai tang chua nudc nggt chinh la Holocen va pleistocen deu hi nhiem man hoan toan. Viing ddng bang se trd thanh m0t vung chdt, bdi nudc man se theo cdc dng mao ddn trong ddt n6i Idn bd mdt. Khdng cht Thai Binh, Nam Dinh, ma cd Hung Ydn, Hd Npi cimg cac tinh Idn cdn ciia thii dd Ha Npi se chiu hau qua nay.
E)d la chua ke nhiing nii ro khdc nhu bao tao ra nhung con sdng Idti ma dinh sdng cao tdi chuc met, hoac gap sdng thdn ngoai khoi, thi nhiing via than da dirge lay di, se la ducmg truydn sdng ngdm vdo ddt lidn, gdy ra sy sup dd bd mdt ddt lidn mOt each bdt ngd khdng thd dy bao dugc.
TAI LIEU THAM K H A O [1] Red river delta master plan. Volume 1, Summary, (VIE/89/034), June 1995.
[2] Bao cao thuydt minh nhiem vu quy hoach tdi nguyen nudc luu vuc sdng Hdng-Thdi Binh, Trung tam quy hoach vd didu tra tdi nguydn nudc qudc gia, Bd Tai nguydn va Mdi tnidng, HdNpi 2016.
[3] Tunnel engineering handbook, John O.Bickel etal, 1996.
[4] Submarine groundwater, Igor S. Zektser et al, 2007.
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