• KHOA HOC CONG NGHE •
GlAl PHAP KHAI THAC NU'O'C BEN V&NG PHUC VU CAP NU'QC SINH HOAT CHO CAC VUNG NUI CAO,
VUNG KHAN HI^M NU'OC TAI TAY NGUYEN
TS. HA HAI DU^ONG, THS. NGUYEN MINH TIEN Vien Nu&c, Tu&i tieu vd Mdi tru&ng - Vifn Khoa hgc Thdy lgi Vi^t Nam Tom t i t : Tdy Nguyen la viing co ngudn nu&c duai ddt rdt doi ddo, v&i trir lupng tinh khodng 3,27 ty m^ vd trir luang dpng khodng 6,75 ty m^/ndm. Tuy nhien, v&i miia kho keo ddi kit hap vM tdc dgng cita hgn hdn vd viec khai thdc nu&c ngdm tir phdt khong theo quy hogch trong nhimg ndm gdn day da khien muc nu&c ngdm & Tdy Nguyen hg thdp, viec cdp nu&c sinh hogt cho ngu&i ddn tgi vitng niii cao ngdy cdng tr& nen kho khdn han. Do vay, viic lua chpn gidi phdp cong nghe trong khai thdc vd bdo ve nu&c du&i ddt Id nhiem vii rdt quan trpng. Bdi bdo ndy trinh bdy kit qud xdy dung mo hinh gieng khoan ngang khai thdc kit hap giing khoan bo cap nhdn tgo nu&c mua tgi Gia Lai vd mo hinh giing khoan khai thdc kit hpp ddp ngdm tgi Ddk Nong phuc vu cdp nu&c sinh hogt ben vieng. Cdc gidi phdp ndy da chirng to dupe hieu qud trong viic khai thdc ben vitng nguon nu&c duai ddt vd cdn duac dp dung rpng rai tgi cdc vung khan hiim nu&c viing Tdy Nguyen.
T u khoa: Nu&c du&i ddt, khai thdc vd bdo vi nu&c du&i ddt, bo cap nhdn tgo. Toy Nguyin Abstract: The Central Highlands is an area having abundance of groundwater, with a static reserve of about 3.27 billion m^ and a dynamic reserve of about 5.6 billion m3 /year. However, due to the long dry season with the impact of drought and uncontrolled groundwater extraction in recent years, the groundwater level in the Central Highlands has decreased and the supply of domestic water for people in high mountains has becomes more difficult. Therefore, the selection of technological solutions in the exploitation and protection of groundwater is a very important task.
This paper presents the development of a model of horizontal drilling wells accompanied with a rainfall -based artificial recharge wells in Gia Lai province and the model of exploitation wells and a underground dams in Dak Nong province for domestic water supply. These technological solutions have proven the effectiveness in sustainable ground waterextraction and should be widely applied in water scarcity areas in the Central Highlands.
Keywords: Groundwater extraction, groundwater protection, artificial recharge, Central Highland Vietnam
1. DAT VAN DE hieu biet khdng t h i u dao, khai th^c nude dudi Ddi vdi ngudn nude dudi dat, tiira nang dit tran lan thiiu k i i m soat da lam cho nude tijr ngudn nude dudi dit d Tay Nguyen dae trung ting tren thoat xudng ting ben dudi, lam cho bdi hai gia tri la trft lugng dgng ty nhien (luu ting tren can kiet. Thdng ke dua ra t u nam 1998 lugng ddng ngam) va trft lugng tmh tu nhien. cho thiy: tdng tru lugng nude dudi d i t (d trang Hai ngudn n^y hmh thanh nen tiem nang trft thai tmh, khdng cd su tae ddng b i t thudng cua lugng khai thac cua nude dudi dat, trong dd trft mdi trudng ty nhien) tai Dak Lak la 120,9 ty m^
lugng tinh ty nhien (3,27 ty mVnam) chiim g i n Hien nay, con sd nay da thip hon rat nhiiu, chi mdt nfta trft lugng dgng tu nhien (6,75 ty edn khoang 1/3 so vdi nam 1988. myc nude ra^/nam). Nhu vay, tiem nang nude dudi d i t ngim tut giam trung binh tft 3 den 5m, ed nai 7 vung Tay Nguyen la kha lon. Tuy nhiSn, do sy d i n 8m. Qua dieu tra, khao sat, do suy giam
48 TAP CHf TAI NGUYEN NUOC S6 1 -2020
• KHOA HOC CONG NGHE • mue nude dudi dit, mdt sd vung nhu vung Dak
Lik, Krdng Pik, Ea Kar, Cu Kuin, nam 2004 ed thi khai thae tdi da 0,4 - 0,6 trieu mVngay thi nay chi edn chua din 300.000mVngay va nhiiu noi cdn d dudi mftc 250.000raVngay.
Rd rang, tiim imng ngudn nude d Tay Nguyen khdng phai la thi6u, nhung do lugng mua phan bd khdng ddng deu tren lanh thd va hien tugng khai thac nude dudi dat thieu kiera soat, khien mye nude dudi dat ngay eang suy giam va mua khd d Tay Nguyen thudng xuyen bi han han de dga. Do dd, cae bien phap, giai phap phu hgp luu gift nude trong raua mua de bd cap cho nude dudi dat su dyng cho mua khd la rat can thiet va can dugc ap dung de dam bao
khai thac nude dudi dat radt each ben vftng.
Nghign cuu nay trinh bay de xuat cac giai phap khai thac ket hgp bao ve ngudn nude dudi dit tai hai tinh Gia Lai (thi digm cap nude cho Trudng tiiu hgc Nguyen Du) va Dak Ndng (Thi diem cap nude cho 01 thdn R'But).
2. GIOI THIEU VE VUNG NGHIEN CUtJ 2.1. Vung khan hi§m nude
Theo Quyit dinh sd 264/QD-TTg cua Thft tudng Chinh phu ngay 02/3/1015 phe duyet
"Chuong trinh dieu tra, tim kiem ngudn nude dudi dat de cung cap nude sinh hoat d cae vung nui cao, vung khan hiem nude", tinh Gia Lai va tinh Dak Ndng cd tat ca 18 vimg khan hiem nhu sau (Hinh 1, Hinh 2).
Hinh 1. Vung khan hiim nu&c tinh Gia Lai Hinh 2. Vimg khan hiim nu&c tinh Ddk Nong Theo ket qua dieu tra khao sat thuc dia, can
cu theo nhu can dung nude, hien trang cap nude va dac diem dia hinh, dia chat thuy van, vung thi diim duge lua chgn tai 2 tinh Dak Ndng va Gia Lai duge lua chgn nhu sau:
(i) Dak Ndng: thdn R'But, xa Quang Son, huyen Dak Giong
(ii) Gia Lai: Trudng tieu hgc Nguyen Du, xa labang, huyen Chu Prdng
2.2. Danh gia dieu kien dia hinh, Idp phu va tang chita nwfre
2.2.1. Xa labang
c i u true trft nude: CSu tnic trung Chu Prdng c i u true nay cd di|n phan bd hiu het huyen
ly Chu Prdng va xa ia Bang - huyen Chu Prdng.
Day la cau tnic cd do day Idn, do cao tuySt ddi day cau tnic la 290 ra, ndng nhat nara d do eao 470 m, tao thanh mgt vung trung voi do chenh cao khoang 200 m vdi dien tich khoang 254,4 km^. Nen cau tnic dugc tao nen bdi cac thanh tao xam nhap axit va trung tinh thudc phftc he Bing Giang - Qui Son (PZ3 bg-qs).
Ddi nut ne cd kha nang chua nude cua cau tnic nay ed be day trung binh khoang 65 m, da bazan nftt ne Id hong cd he sd tru S =:; 0,12.
Toan bg cau tnic nay dugc bao bgc bdi khdi da magma ran chae, ed kha nang ehe chan nude, khdng cd diit gay cit qua.
TAP CHf TAI NGUYEN NUOC S6 1 -2020 49
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/fiw/i 3. 5dn i^o dia chdt thity vdn khu vuc xd labang, huyin Chu Prong, tinh Gia Lai can eu vao mat eit dia chat theo tuyen A-B,
Idp Bazan phong hda va phong hda dd dang d phia tren cd chieu day tuong ddi mdng, dao ddng trong khoang tft 25 den 50m, trung binh day 40m. Ldp Bazan phong hda chia thanh nhieu ldp vdi chieu day khae nhau. Ldp tren cung la ldp set xam raau nau lan ket vdn laterit vdi ehieu day khoang 5 den 10m. Tiep theo la ldp Bazan phong hda thanh thanh set nau dd, phan bd d do sau trung binh tu 20 den 25m. Xen kep gifta hai ldp nay la Bazan raau xam tro, hoac da Bazan Id hdng, dae sit niit ne it den trung binh, kha nang ehfta nude tft ngheo din trung binh.
2.2.2.Xa Qudng San
Cac thanh tao bazan d Quang Son dugc hinh thanh vao hai thdi ky, thudng dugc ggi la bazan
tre p(qp) va bazan ed fi(n2-q). Thanh phin ddi chfta nude gdra phan tren la bazan phong hda thanhset bdt nau dd day tu 10 den 50m, phin dudi la bazan Id hdng xen cac bazankhdi nut ne, bazan dang bgt, tuf, tro va dam ket nui lua, chieu day thay ddi tu vai chuc met d phin ria den 150m d phin trung tara.
Nude dudi dat trong phun trao bazan cd do khoang hoa thay ddi tu 0,03 den 0,5 g/l, thudng gap tft 0,2 den 0,3 g/l. Loai hinh hoa hge chii yeu la bicacbonat natri, bicacbonat natri-magie, bicaebonat magie - natri. Mue nude thay ddi theo mua vdi bien do dao ddng tft 0,3 dSn 5,7 m, trong do mye nude dang cao nhat vao cudi mua mua (thang IX, X) va ha sau nhat vao cudi mua khd (thang IV, V). Thdi gian "lech pha" tu 1,5 den 3 thang.
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Hinh 4. Bdn do dia chdt thity vdn khu virc xd Qudng Scm, huyen Ddk Giong, tinh Ddk Nong Doi voi tang chira nuac khe nirt Jura CSu
tnic nay phan bo xung quanh bon Snar. Dfa da cau thanh cau true nay chit yeu la cac thanh tao
tu5i J2 thuoc he tSng La Nga. Dien tich phan b6 tren mat cua cau tnic nay khong lon, khoang vai tram m^. Cac thanh tao nim a phia tay bSc - 50 TAP CHfTAl NGUYEN NirOCSC 1-2020
• KHOA HOC CONG NGHE • ddng nam cua vung nghien cuu, cd xu hudng
keo len gdc phia ddng dien tich nghien cftu, Id thanh dien nhd vdi cac canh thoai 5-100. Mat cat cua cac he ting la cae thanh tao luc dia mau dd gdm cat kit, hot kit, set ket va da sftng, nftt ne trung binh. Ting J2 nay ed be day trung binh khoang 150m, ddi niit ne trong cau tnic ed be day khoang 45m, he sd tru nude cfta eat ket, bdt ket, set ket nut ne. Tang chfta nude nay duge danh gia la ngheo nude.
Tdng lugng mua trung binh trong 3 nam quan trie (2016-2018) la 1829mra trong dd lugng mua hieu qua chiem den 80% (khoang 1480mm). Nhu vay, can thiit phai cd giai phap thu trft ngudn nude nay de tang kha imng khai thae trong mfta khd tai vung nghien cftu.
Hinh 5. Luang mua hieu qud duac quan trdc trong 03 ndm (2016-2018) 3. CONG c y VA PHirONG PHAP NGHIEN c u t !
3.L Cdc bien phap bo sung nhan tao nir^c dudi dat
Nhin ehung, ed rat nhieu cdng nghe ve bd sung nhan tao dugc ap dung rdng rai tren the gidi, va thinh hanh nhat la eac hd chfta ngam.
Tuong ty nhu su bien ddi ve dia chat thuy van, cdng nghe bd sung nhan tao cung bien ehuyen rat nhanh ehdng. Cae ky thuat bd sung nhan tao cd the dugc phan loai nhu sau:
(i) Ky thuat bo sung nhan t^o true tiep tir be mat: nhu xay dung be chua, hd ehua, he thing kenh, ranh de true tiep lay nude mat bd sung cho nude ngam.
(ii) Ky thuat bo sung nhan tao true tiep dudi be mat: nhu gieng khoan bd cap, gieng va hd dao bd cap nude ngam.
(iii) Ky thuat bd sung nhan tao true tiep ket hgp: la ky thuat ket hgp ciia ky thuat (i) va (ii) nhu kit hgp hd chua nude va gieng khoan bd cap.
(iv) Ky thuf t BSNT gian tiip: thay ddi ting chfta nude.
Ddi vdi tat ea eac phuong phap bd simg nhan tao, chat lugng nude bd cap la mdi quan tam chinh. Nude sach ehi duge bd cap vao tang nude ngam ma khdng can lgc va qua trinh oxy hda la qua trinh nude tham tu nhien qua vung bao hda
3.2. Tieu chi lira chgn giai phap bo sung nhan tao
Can eft tren tinh hinh thye te ve do ddc dja hmh, dieu kien dia chat thuy van, dieu kien tang chfta nude va muc do day du cua lugng raua, giai phap bd sung nhan tao cho vi tri thi diem tai Gia Lai va Dak Ndng nhu sau;
(i) Gia Lai: Bd sung nhan tao trye tiep dudi be mat: Sft dung gieng khoan bd cap do do ddc dia hinh khu vyc rat nhd, bd cap cho tang Bazan phong hda dd dang;
(ii) Dak Nong: Bd sung nhan tao gian tiip:
Sft dyng dap ngam nang cao myc nude ngara va ngan nude that thoat ra sdng/sudi do do ddc dia hinh nhd, dat da gan ket tdt va tang chfta nude khdng ap.
4. KET QUA VA THAO LUAN 4.L Giai phap khai thac, bao v§ nirdc dudi dat tai Gia Lai
Gieng khoan ngang khai thdc ket hpp Id khoan bo cap nhdn tgo nu&c mua
(i) H^ thong thu gom v^ bo cap nude mua Nude mua thu gom tft mai hai nha dien tich 400 m bang he thdng mang thu va dng thu dudng kinh 90 rara. Nude mua tft dng thu dua vao giao thong hao cd kich thudc dai 4 m, rdng 2 m va sau 2 m, trong hd dao dd day cudi, sdi, cat lgc.
Trong giao thdng hao cd 2 giing khoan phan bd each nhau 2 ra duge ky hieu la MDCl, MDC2. Hai giing khoan MDCl va MDC2 dua nude mua vao tang chua nude ndng d do sau din 37 m. Lo khoan MDC3 la Id khoan quan trie rayc nude ngim. Cac lo khoan MDCl, MDC2 la Id khoan hip thu se dugc kit ciu phin thoat nude sudt chiiu dai thanh Id khoan, trong
TAP CHI TAI NGUYEN Nl/Oc SO 1-2020 51
dd phan ddi dien vdi ldp phong hda dat dd dugc chdng dng lgc de chdng sap Id, phan da ciing nftt ne de thanh Id khoan lam dng lgc ty nhien.
Nhu vay Id khoan ed chieu dai thoat nude la 37 m lam nhiem vu dua nude mua tu be lgc vao tang chua nude.
Kha nang hap thu eua mdt Id khoan tuy thugc vao thanh phin thach hgc, mftc do nftt ne eua dat da trong mat cat dia chat. De tinh toan he thdng thu gom nude mua dua vao tang chfta nude d day chung tdi sft dung gia tri q = 2,0 1/phut /m.
Mdi Id khoan cd chieu dai 37 ra, cd thi hip thu dugc mgt lugng nude la 2,0 l/phut /m * 30m - 60 1/phut = 3600 Vgid = 3,6 mVgid. Hai Id khoan hap thu se thu dugc: 3,6*2^7,2 ra^/gid nghia la ed kha nang thu gom lugng nude mua lon nhat trong ngay va trong thang.
'- - " - n - - I — ; 4:!f|o I 111
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Hinh 6. Sa do bo tri mat bdng mo hinh tgi Gia Lai
Hinh 7. Bi chira bo cap nuac mua Chgn thdng sd may bom
Dung tieh dam bao nhu cau dftng nude cho
tdng sd hgc sinh trong trudng hgc la ISmVngay.
Chgn thdng sd may bom nhu sau:
Be Idng The tich phin ling:
W = Q*t (m^)
Trong dd, Q: luu lugng tinh toan (ra^/h) t: thdi gian luu nude trong bi ling(h). Chpn t = l , 3 h
W= 1,9*2-3,8 (m^) chgnW=4 (m^) Chgn chiSu cao phan lang Hl= 1,4 m ChiSu cao dng tnmg tam lay bang 0,94 chieu cao phan lang
Htt=0,94*l,4-l,32(ra) Bi Ipc
DiSn tich be mat loc:
Q
F - >'(m^)
Trong dd,Q: luu lugng vao bS lgc Q=l,9 (m^) v: van tdc loc. Chon van tde loc v^ 0,6 (m/h)
— = 3 2 F = o,56 • (m^)
Chpn kich thuac dai rong ciia be loc axb = 3 xl(m)
Chieu day lop loc:
- Chieu day lap cat: 0,4 (m) - ChiSu day lop than cui: 0,2 (m) - ChiSu day lop soi: 0,25(m) - Be chira
Nhu ciu nuoc 15m%gay chon kich thuoc bS chira nuac kich thuoc nhu sau:
a x b x h = 3 x 3 x 1,6 (m).
(ii) Hf th6ng khai thac
Khoan 4 tia gilng ngang de tang hiSu suit liy nuac ciia gi6ng: gijng khoan ngang duong kinh D60, 6ng loc la 6ng PVC D60 due 16 DIO; chiSu dai giSng ngang khoang tir 10-20m
(iii) HS thdng phiin phoi
Nude duac bam len tir giing dao khoan tia ngang vao he thong be ISng, hh loc va hk chua sau do phan phoi den diem Idy nuoc sach cua nha truang.
4.2. Danh gia liru limng co the khai thac Xac dinh dugc mirc d6 chira nuac thanh tao dia chat phun trao bazan nut ne - 16 h6ng khu
52 TAP CHf T A I N G U Y C N NLTCIC SO 1 2020
• KHOA HOC CONG NGHE • vuc nghien cuu. Tai lieu thu thap trong qua trinh
hut nude thi nghiem day du, ed do chinh xac cao. Phuang phap va thdi lugng do (luu lugng, muc nude, nhiet do) va phuong phap chinh li tai lieu hut nude thi nghiem theo "Quy pham hut
nude thi nghiem trong dieu tra dia chat thuy van". Tai lieu du tin cay de tinh toan thdng sd dia chit thuy van eo ban gdm. He sd din nude Kra(ra^/ng); He sd thira K(m/ng); he sd nha nude \i, he sd truyen dan mye nude ay.
Bang 1. Tdng hop ket qua hiit nirde thi nghifm va khai thae thu gieng dao Trudng TH Nguyen Du
Lo^i thi nghiem Bam thi nghiem
h, (m) 16,10
Q (I/s) 2,0
Ha (m) 21,00
S (m) 4,9
Bom khai thac thir h,
(m) 16,10
Q (l/s) 2,20
Ha (m) 22,00
S (m) 5,90
„
Nuac 26,0
Khong khi 30,0 Gieng dao trudng TH Nguyen Du nude dudi
dat tdn tai va van ddng chu yeu trong ddi phong hoa bazan.
Be day tang ehfta nude: be day tang chfta nude dugc xac dinh tft muc nude tmh den day cfta gieng dao. Tai gieng dao nay chung tdi xac dinh be day tang chfta nude H = 13,9m (tu 16,lmdin30, Om).
De bao dam tang ehua nude khdng bi can kiet, thao khd trong qua trinh khai thae, tri sd ha thap myc nude trong gieng dao (Skt) phai thda nam dieu kien Skt < Sep < Vi H
Scp= 13,9m: 2 = 6,95m;
Bang 2. Ket qua trir luong
Skt < 6,95m.
Tinh trft lugng theo phuang phap thuy lyc la phuong phap ndi suy luu lugng khai thac tft kit qua hftt nude thi nghiem khai thae thft tai gieng dao.
Qns=qxSk,
Trong dd: q la luu lugng don vi, (q = 0,45 l/s.m)
Ski la do ha thap myc nude khai thac:
Chgn Skt^ de an toan trong qua trinh khai thac, lya chon Skt ^ 5,0m.
Thay cac gia tri q, Skt vao edng thftc QKT=q*Sk,
theo phuong phap thuy luc So hieu
Trucmg TH Nguyen Du
D6 sau gifag (m)
30,0 Be day
TCN 13,9
Muc nuoc tinh 16,10
Skt{m) 5
q (1/sra) 0.45
Luu luang khai thac (QKT) l/s
2,25
m^/ngay 194.4 Tuy nhien, cdng tac hut thi nghiem tai gieng
dao tiin hanh vdi mdt lan ha thap mftc nude, ehua du diiu kien de xac dinh phuang trinh quan he gifta luu lugng (Q) va myc nude ha thip (S). Do vay, ndi suy luu lugng khai thae cua giing dao theo cdng thue QKT ^ q*Ski chi la tuong ddi.
4.3. Giai phap khai thac, bao ve nwdc dudi dit tai Dak Nong
Giing khoan khai thdc kit hpp dap ngdm
Mue tieu cap nude cua md hinh thi diera la dam bao cap nude sinh hoat cho phan edn lai cua bon vdi 115 hd gia dinh vdi 538 ngudi va radt trudng mau giao vdi 80 hgc sinh theo tieu chuan cap nude sinh boat vung ndng thdn, dam bao yeu cau cap nude la 80 lit/ngudi/ngay ddi vdi hg gia dinh va 30lit/ngudi/ngay doi vdi trudng hgc va ca quan. Nhu vay tdng nhu ciu dung nude cua bon R'But la 45,44 m^/ngay
(i) He thong dap ngam
TAP CHI TAI NGUYEN NL/OC S6 1-2020 53
Vj tri tuyen dap ngam ed vT do: 12°
9'20.08"Bie, kinh do: 107°52'47.24"Ddng (Hinh 4.8). Tuyin dap ngara: duge bd tri tren dudng ddng mftc tai cao trinh +774m; Do sau dap: Sau 10m tuong ung vdi tang chfta nude Bazan dae xit mau xam xanh, xen kep Bazan Id hdng mau xam den ed do nftt ne tft trung binh den manh.
Vi tri tuyen dap thda man mdt sd cac van de bao gdm:
- Nam trong luu vyc ddng ngam;
- Hudng ddng ngam that thoat ra diem xuat Id
- Kha thi trong viec chan nude dudi dat that thoat ra diem xuat Id cung nhu cd kha nang lam dang rayc nude tai Id khoan khai thac;
-Vi tri thi cdng thude Bon R'But va xa Quang Son quan ly, khdng ein phuang an den bu;
Dara bao tinh khoa hge la lam cham ddng chay, dang myc ngam cho Id khoan khai thae.
can eft tren tinh tham cua dat da tang ehfta nude, dap ngSm dugc xSy dyng di chdng thit thoat nude ngam ra sdng, sudi. Dap ngam dugc xay dung bang vat lieu set (bentonite) tren tuyin dap dai 36m tai vi tri trudc diem xuat Id dia chit thuy van tai bon R'But va dugc thi cdng bang phuong phap khoan phyt set. Vi tri thi cdng dugc dugc xac dinh nhara chan ddng ehay thit thoat ra diera xuat lg. (Hinh 8)
Hinh 8. Mat bdng tong thi mo hinh
Hinh 9. Mat cat dia chdt tgi vi tri mo hinh Qua cdng tac khao sat dia chat, tai vj tri 16 khoan khai thac cua rad hmh, mat eat dia chit dugc chia thanh 3 ldp, ldp tren eung la ldp Bazan phong hda triet de thanh set bdt mau nau ket cau bd rdi, ldp thu 2 la ldp Bazan dac sit, dd man xam den, xam tro, eau tao khdi va ldp thft 3 la ldp Bazan dac sit, it Id hong da xara xanh cd cSu tao khdi (Hmh 9).
Cong tdc khoanphy.t
- Khoan phut tao man nham tang cudng ehdng tham, lam giam ap luc tham giam gradient tham va vi tri ra cfta ddng thim.
Khoang each gifta cac hang khoan, lo khoan va hudng cua Id khoan: di xae dinh duge khoang each giua cac hang khoan, 16 khoan va hudng cua chftng cin thda man hai dieu kien:
+ v i tmh lien tuc cua man chin: khdng c6 khoang gian doan eua man chin di cd kha mng phat sinh ddng tham cue bg;
+ Ve do chat kbit: do tham nude phai ha xudng den luu lugng tham don vi nhd ban hoac bang cho phep.
Khoang each gifta cdc Id khoan va gifta cac hang khoan phai dam bao tinh lien tuc cua man chan, duge ehinh xac hda khi cd kit qua khoan phyt thi nghiem va phut kiem tra).
Hudng eua Id khoan: phy thudc vao diiu kien dia chit, dae trung la hudng khe nut cfta da nin. Dae diim dia chit tai vi tri diim Id la cac ddi phong hoa cua da magma va cae ldp pha tan
54 TAP CHf T A I N G U Y E N Nl/OC Sl3 1 -2020
• KHOA HOC CONG NGHE • tich nen huong cua Id khoan chgn la thang dung
(90 do so vdi phuang nam ngang) Chieu sdu cdc ho khoan ph^t
Chieu sau cae hd khoan phut dugc xac dinh tren cac co sd sau:
- Dieu kien dia chit, dia chit thuy van.
- Can eft theo do sau mye nude tmh va dieu kien dia chit di xae dinh chieu sau cac hd khoan phyt tao man ehdng tham. Vi tri Id khoan khai thac cua md hinh, myc nude tinh H^27,2m (Cao do mat dit = -t-794,75m), vi tri tuyen dap ngam khoan phyt dugc thi cdng tai each vi tri Id khoan khai thae cfta md hinh la 180m va tai vi tri cd cao dg +774,0ra. Do vay, chieu sau cac hd khoan phut tai hang I tft 8,0-^10,0ra va chieu sau cac hd khoan phut tai hang II tu 10,0-Hl2,0ra (tinh tu eao trinh +764,0m cua day dap va +774,0m eua mat dat tu nhien). Trung binh do sau eua Id khoan phut la 10m.
thim vdi ap suat cao de tao pheu lan eua vat lieu tham la 3m. Do vay mdi Id khoan phyt each nhau dra.
De dara bao 2.5 met be day eua man ehdng thim, lya chgn tuyin khoan phyt dugc bd tri 2 hang so le de dam bao tga thanh tuyen dap ngam ngan dong ehay nen khoang each tft tim true I din tim true II cua hang Id khoan la 4ra, cac lo khoan each nhau 6ra, tdng tuyen dap dai 36m (Hmh 11).
Hinh 10. Chieu sdu cdc 16 khoan phut tgi vi tri mo hinh
Chieu ddy mdn khoan phut
Chieu day man chdng tham B so bg cd the xac dinh theo cdng thftc sau:
B = H/J (m)
Trong dd: H: cdt nude tac dung Idn nhat, tinh bang met
H,d=764-774-10m
J: Gradien eho phep cua man phyt, ddi vdi man xi mang set cd thi liy J < tu 3 din 4.
Can cu kit qua tinh toan theo cdng thftc tren: chiiu day yeu cau cua man chdng tham la 2.5m.
Sft dung may nen khi bom nen vat lieu ehdng
Hinh 11. Sadd bo tri hdng khoan phut Vdt lieuph^t
Ddi vdi dieu kien dia chat tai khu vuc nghien cuu, vat lieu phyt cho tang da nay la Xi mang (XM) va Set (S), thyc hien theo tieu chuan tieu ehuin TCVN 8644-2011.
Vua dn dinh dugc che tao bang each pha vat lieu set vao vfta xi mang, phai dugc sft dung khi phut xi mang-set nham myc dich ehdng tham.
Vfta dugc ehe tao nhu sau: trdn xi mang va nude den mftc do huyen phu (tdi thieu la 5 phut), sau do do dat set tinh va (phy gia ddng eung nhanh khi phut trong khu vue cd nude van ddng trong doan phut) theo ty le vao va trdn tiep den khi dung dich hoan toan d dang huyen phu (tdi thiiu la 10 phut).
Vfta dn dinh dugc che tao bang each pha vat heu xi mang vao vat lieu vdi ty le bing 10- 20%. Ty le xi mang liy bing 15%; set 85%).
Hodn thien tuyin dap ngdm
Tuyen dap ngara dugc xay dung bing vat lieu set (bentonite) cd tdng chiiu dai 36ra vdi chieu sau trung binh lOra va dugc khoan tdi
TAP CHf TAI NGUYEN NU(3C 56 1 -2020 55
tang Bazan dac xit, da mau xam den da tao thanh tuyin dap ngSm cd kha nang chan ddng ngim thit thoat ra raach Id. Qua quan trac vao raua khd 2018, muc nude tinh cua Id khoan khai thac cd chiiu sau la 27.2m, sau khi thi cdng tuyin dap ngim, myc nude tmh tai Id khoan khai thac duge quan trac cd dao dgng tang len tft 05-lm (chiiu myc nude tmh Id khoan khai thae dao dgng tft 26,2-26,7ra). Nhu vay cd the danh gia, tuyen dap ngap ngam dam bao dugc yeu eiu khdng chi la giam that thoat ddng ngSm ma cdn cd kha nang dang myc nude cho Id khoan khai thac. Tuy nhien, de dam bao hieu qua nhu mong mudn, dac biet trong dieu kien
bien ddi khi hau va thien tai bit thudng, can tiep tuc quan trae trong ca miia khd lin mfta mua trong tuong lai.
4.4. Danh gia liru Ivgng cd the Ichai thac Phuang phap va thdi lugng do (luu lugng, mye nude, nhiet do) va phuang phap ehinh ii tai lieu hftt nude thi nghiSm theo "Quy pham hut nude thi nghiem trong dieu tra dia chat thuy van". Tai lieu dft tin eay de tinh toan thdng sd dia chSt thuy van co ban gdm. He sd din nude Km(m^/ng); He sd tham K(m/ng);
he sd nha nude \i, he sd truyen dan myc nude. Kit qua hut nude thi nghiem dugc the hien tai Bang 3.
Bang 3. Tdng hop ket qua hut nude thi nghiem v^ vkhai thac thu Id khoan Bon R*But Loai thi nghiem
Bom thi nghiem h,
(m) 27,05
Q (l/s) 2,20
Ha (m) 40,17
S (m) 13,12
Bom khai thac thir h,
(m) 27,05
Q (Vs) 2,30
Ha (m) 42,29
S (m) 15,24
Nuoc 26
Khdng khi
25 Trong di8u kien khi hau eua vung nghien ciiu
mdt nam chia lara 2 mfta ro ret, mfta mua tu thang 4 din thang 10, mfta khd tft thang 11 nam trudc din thang 3 nam sau. Lugng mua trung binh nhiiu nam la 1.900mm den 2.000mm.
Theo tai lieu quan trac nude dudi dat trong vung Dak Ndng eho thay lugng nude hao hyt trong
Bang 4. Tri so ha thap muc nude tai gieng khoan
mfta khd duge bu dap hoan toan vao cudi mua mua. Vi vay, chgn "t" khai thae bang 6 thang (180 ngay); t = 180 ngay.
Tri sd ha thap muc nude tai gieng khoan Bon R'but tucmg ftng lim lugng khai thae 235 ra /ngay dugc tinh toan va ghi d Bang 4.
Chieu sau (mj 120
Muc nuoc tinh (m) 27.05
Be day TCN (H)m 53.75
Scp = H/2 (m) 26.88
I) (m7nR)
235 km (mVng)
11880 0
2.903 a (m7n|.)
135 t (nsay)
180 Kri (m)
234
tg
m
0.065 Ln (Rd/ro)
8 Sk, imi
23.77 HB (m)
50.82 Tu ket qua tinh toan ghi d tren cho thay: tri
sd ha thap myc nude trong Id khoan vao cudi raua kho dau mua mua hang nam Skt = 23,77m la hoan toan thda man dieu kien Skt< Sep
<26.80m
Nhu vay, luu lugng khai thae eua gieng khoan ed thi khai thac vdi luu lugng 235 m^/ngay, rauc nude ha thap Skt sau 6 thang cudi raua khd diu miia mua 23,77ra, rauc nude ddng khai thae tuong ung 50,82m.
56 TAP CHfTAl NGUYEN N U ^ C S6 1-2020
• K H O A H O C C O N G N G H E •
5. KET LUAN
Ngay nay, vdi su tiin bd eua khoa hgc ky thuat, nhieu md hinh edng ngh8 vfta giup nang cao hieu qua khai thac nude, vfta bao ve ngudn tai nguyen nude da dugc ap dyng va mang lai ket qua rat tdt. Qua nghien ciiu, cac rad hinh thu gom nude mua, thu gom nude raat sau dd tich chua, bd cap vao cac tang chfta nude de sft dung vao mua khd da dugc ap dyng thanh cdng ca tren the gidi va Viet Nam. Vdi dieu kien dia hinh, dia chat thuy van va dac diem tang chua nude, md hinh nay dugc ap dyng tai xa labang, huyen Chu Prong, tinh Gia Lai. Ben canh dd, xay dyng dap ngam de thay ddi ket cau tang tru nude cung la mdt bien phap kha thi. Cdng nghe nay hoan toan cd the ap dung de dam bao cap nude sinh hoat va khai thac tai nguyen mdt each ben vimg tai xa Quang Son, huyen Dak Giong, tinh Dak Ndng.
Ket qua xay dung 2 md hinh thi diem tai Dak Ndng va Gia Lai ap dung cdng nghe khai thac ket hgp vdi bao ve nude dudi dat budc dau da dem lai hieu qua tdt, dap iing du kha nang cap nude sinh hoat ben vftng cho ngudi dan. Cu the, rad hinh tai Dak Ndng cho phep khai thac vdi luu lugng dat 235m^/ngay dap ung dugc nhu cau sft dyng cua 115 hd dan va tai Gia Lai la 194,4 m"'/ngay dap ftng du nhu cSu nude hang ngay cho 868 hgc sinh.
Theo Quyit dinh sd 264/QD-TTg "Phe duyet Chuang trinh diiu tra tim kiem ngudn nude dudi d i t d i cung cap nude sinh hoat cho cac vung nui cao, vimg khan hiera nude" cua Thft tudng Chinh phu ban hanh ngay 02/3/2015, tiep theo dy an 1 va 2, du an 3 "Xay dyng thi diira he thdng c i p nude tai cac vung nui cao, vung khan h i i m nude dae trung" se dugc triin khai va k i t qua nghien cuu nay se la can cu cho viec
thuc hien tiip dy an do. Cac rad hinh dugc thi diem ap dyng trong khudn khd nghien ciiu nay da chiing duge hieu qua cap nude cho vung khan hiim nude va cd the ap dung cho cac xa khan hiim nude tuong ty vung Tay Nguyen.
TAI LIEU THAM KHAO CGWB (Central Ground Water Board), 2007. Manual on Artificial Recharge of Ground Water.Teehmcal Series-M, No. 3. Ministry of Water Resources, Government of India, pp. 215.
Bui Minh T h i va nnk, 2000.Nu&c du&i ddt khu vuc Tdy Nguyen. Cue dia chat va khoang san Viet Nam. Sd 6 PhamNgft Lao, Ha Ngi.
Doan Van Canh, 2005. Nghiin cuu xdy dimg ca sa khoa hpc vd di xudt cdc gidi phdp bdo ve vd su dung hap ly tdi nguyin nu&c viing Tdy Nguyen.Bao eao tdng ket De tai nghien cftu trgng diem eip Nha nude KC.08.05 giai doan 2000-2005. Trung tam thdng tin KHKT Qudc gia. Ha Ngi, 2005. 260 trang
Doan Van Canh, 20lO.Nghiin cieu ca s& khoa hpc vd xdy dung cdc gidi phdp luu giir nuac mua vdo long ddt phuc vu chong hgn vd bdo ve tdi nguyin nuac du&i ddt vitng Tdy Nguyen. Dai hgc Md - Dia chit. Ha Ndi...
Ngu&i phdn bien: PGS.TS Nguyen Quang Trung Phdn bien xong: 12/2019
TAP CHfTAl NGUYEN Nl/CfC S6 1-2020 57