Trong ITnh vuc tham do dien, phuang phap do dien trd thudng dupe dung de ve lai ban do cau true dien cua be mat trai dat.. The phuang trinh 7 vao 6 dan den phuang trinh vi phan tung phan
Trang 1DAI HOC QUOC GIA HA NOI
TRlTonVG DAI HOC KHOA HOC TlT NHIEN
Trang 2I Bao cao torn tat
a Ten de tai: Xay dung he do dien trd dat da cue (Ma so: QT-07-19)
b Chu tri de tai: Tran VTnh Thang
c Cac can bp tham gia:
ThS Giang Kien Trung ThS Nguyen Ngpc Dinh ThS Nguyen Anh Due
d Muc tieu va npi dung nghien curu
Nghien ciiu cac phuong phap do dien trd dat trong tham do dia vat ly, cac giai phap ky thuat va qua d6 che tao thiet hi do dien trd dat da circ c6 su dung may tinh lam cong cu do dac va xu ly so Heu Vdi muc tieu la cai tien
va nang cao kha nang cua phep do, rut ngan thai gian va cong siic do dac khi trien khai thirc te
e Cac ket qua dat duoc
Khoa hpc:
Tiep can va nam bat duac phuang phap do dac trong ITnh virc dia dien, qua do c6 duac cac giai phap cai tien nang cao hieu qua cua phuong phap Phuc vu dao tao va nghien cuu trien khai thirc cac he do vat ly
01 bai bao gui dang len tap chi DHQG Ha Npi Thirc tien:
- Xay dung thanh cong he do dien trd dat da cue vdi cau true phan bo, bao gom: 01 bp xu ly tap trung va 08 bp phan phan bo chiia cac dien cue dupe dieu khien tir xa, phan mem nhung va phan mem do dac ca ban tren may tinh vdi cac lira chpn hnh boat
f Tinh hinh kinh phi cua de tai
T6ng kinh phi: 20.000.000 ddng
Trong do: Vat tu: 5.190.000 d
Thong tin: 1.578.500 d Thue khoan chuyen mon: 11.631.500 d Quan ly phi, dien nude: 1.600.000 d KHOA QUAN LY CHU TRI DE TAI
(Ky va ghi ro ho ten) (Ky va ghi ro ho ten)
PGS TS Nguyen The Binh Tran VInh Thang
TRU^OTVG DAI HOC KHOA HOC TlT NHIEN
^:/ ^ M^
rtOf* T C / J - ^ - UiHijMOAljWk
Trang 3n Report
a Project: Multi-electrode Earth Resistivity measurement (Code: 07-19)
QT-b Coordinator: Tran Vinh Thang
c Co-operators: MSc Giang Kien Trung
MSc Nguyen Ngoc Dinh MSc Nguyen Anh Due
d Objectives and scientific contents
Methology research of the Earth resistivity measurement, design and build a distributed resistivity measurement system by using computer and microcontroller for measuring and data processing Objective of the research
to develop a new measurement system, which has high performance, saving acquisition time
- 01 paper submits to VNU's journal of Science
- Building sucessfuly a new distributed Earth Resistivity Measurement system included: 01 Central Data Acquisition Unit, 08 distributed electrode with remote control Firmware and software for basical data acquisition
f Budget
Total: 20.000.000 VND
where: Material: 5.190.000 VND
Scientific information: 1.578.500 VND Employments: 11.631.500 VND
Official fee: 1.600.000 VND
Trang 4MUC LUC
• •
Ldi md dau 5
1 Co sd phuang phap do dien trd trai dat 5
2 Thiet ke tong qUan 8
3 Xay dung he do dien trd da cue ban tap trung 11
4 Ket qua va danh gia 16
Ketluan 20 Tai lieu tham khao 21
Trang 5Loi md* dau
Trong ITnh vuc tham do dien, phuang phap do dien trd thudng dupe
dung de ve lai ban do cau true dien cua be mat trai dat Dieu nay nham xac
dinh cau true va/hoac tinh chat vat ly cua cac vat lieu tren be mat trai dat
Trong phuang phap nay, dong dien di vao long dat thong qua cac dien cue
va dien the do dupe thong qua cac dien cue khac
Thiet bi do theo phuang phap nay ca ban bao gom mot nguon phat va
mot may thu Nguon phat cung cap mot dong dien c6 tan so thap (<lHz) dat
vao cac dien cue dong Cong suat ciia nguon phat tiiy thupc vao phuang
phap do Trong hau bet cac trudng hop tiiy vao each bo tri dien cue nhu
Schlumberger, Wenner can cong suat thap va nguon nuoi cd the la pin ha\'
Accu Bp thu cd the la mot Von-met dan gian hay phuc tap nhu mot he do
CO ghep noi vdi may tinh nham nang cao hieu qua cua phep do vdi kha nang
luu trir va xu ly tin hieu so
y f r \
Ve nguyen tac, thiet bi do dac dudng nhu kha dan gian, chi can 4 dien
cue la ta cd the khao sat dupe be mat trai dat, Tuy nhien, trong thuc te, neu
vdi mot he do dan gian, cong viee thuc dja se trd nen rat kho khan do can trd
bdi thai gian va cong sue tien hanh Chinh vi vay, he do da circ ra ddi va
hien nay cd rat nhieu san pham da dupe thuong mai hda nhu cac san pham
SARIS (Scintrex Ltd, Canada), RESECS/RESITOMO (DNT GmbH,
Germany) vdi 960 dien cue, SYSCAL Switch-48 (IRIS Instruments, France)
vdi 48 dien cue Vdi cac che dp do da dang, kha nang phan tich manh boi
may tinh gan kem luon trong he Cac he do c6 cau triic kieu tap chung va dat
tien
Muc dich ciia nghien ciru trong de tai nay nham thiet ke va che tao
mot he do da cue cd cau true ban tap trung, su dung cap it spi, cd kha nang
ung dung trong khao sat thuc te trong dieu kien Viet nam, phuc vu thuc tap
va nghien cuu cho sinh vien nganh Vat ly Dja cau
9
L Co-sd phuong phap do dien trd dat [1]
Phuang phap dien trd DC su dung nguon soay chieu AC c6 tan so rat
thSp lam ngudn tin hieu cho viee xac dinh phan bo dien trd Nhu vay, thanh
phSn tu trudng c6 thi bd qua va ta cd phuang trinh Maxwell:
A X £ - 0, ( 1 )
Trong do E la vector dien trudng e,^ la hang so dien moi cua chan
khong, q la mat dp dien tich
Trang 6Ky thuat dia dien nham dua ra dupe ban do 3D ve tinh chat vat ly cua
trai dat Do do, phuang trinh tren ap dung trong he tpa dp khong gian x, y, z
Mac du phuang trinh chi ap dung cho dong mot chieu lien tuc, nhung cd the
ap dung cho tin hieu AC d tan so rat thap bdi sir anh hudng cua dong cam
ung CO the bo qua Truang tmh dien c6 the mo ta theo gradient ciia dien the
0 day, I la cap tai mot nguon diem, thuc te no chinh la dong phat qua
dien cue The phuang trinh (7) vao (6) dan den phuang trinh vi phan tung
phan cho dien the trong mdi trudng 3D bat dong nhSt, dang hudng tao bdi
mot nguon diem la:
-'i^.[cT{x,y,z)VU{x,y.z) = j^5{x-xJ5{y-yJS{z-zJ (8)
Vdi moi trudng dong nhat va dang hudng, dien trudng gay gdi mot
nguon diem cd the dupe giai bang each tich phan phuang trinh lien tuc (4)
theo the tich va ap dung dinh ly phan ky Gauss dan d8n tich phan mat cua
mat dp dong j The j tir (5) va tich phan theo mat cau vdi ban kinh r thu
duac:
Tir do de dang cd dupe:
Trang 7t/(r) = - ^ ( 1 0 )
Anr
Phuang trinh (10) mo ta the tao bdi mot nguon diem trong khong
^ \ f t y '
gian dong nhat tai mot diem each nguon mot khoang r Tren thuc te, phep do
dien trd vdi cac dien cue duac thuc hien tren be mat trai dat trong trudne
hop do phuang trinh (8) dugc tich phan tren nua mat cau thu dugc:
Ip U{r)
2nr (11)
Ve ly thuyet, nguon diem can cd mot diem tuang irng dat tai vo cue
de cd dong qua mdi trudng Viee xac dinh dien trd be mat can biet them su
phan bd ciia the Su dung hai dien cue dat tai A va B (hinh 1) \a ap dung
phuang trinh 11, the tai mot diem tuy y M la:
Hinh 1: Su' phan bo ciia cac dudng dong va the vdi hai dien cue tai be
mat cua mot ban cau done nhat
Trang 8De do hieu dien the phai can den hai dien cue Ve mat ly thuyet, hai
cue c§p dong A va B cd tha diing luon dS do Xhk tuomg ung Tuy nhien, dien
trd chuyen tiep giira cac dien cue va b6 mat se anh hudng den phep do Do
vay, can diing them mot cap cue nira de do dien the, va nhin chung, phuang
phap do dien trd DC thudng diing bdn dien cue Hieu dien the giua hai diem
M v a N l a At/ la:
LTZ r, r, r^ r^ A
trong do, r3 la khoang each giira N va A, va r4 la khoang each giua N
va B Do vay, K la he so dac trung cho khoang each giira cac dien cue va gpi
la he sd hinh hoc Tir dd ta thu duac:
'^ = ^ ^ ( 1 4 ) Vdi trai dat khong dong nhat, phuang trinh tren se cho cac gia trj bien
ddi theo sir sap xep ciia cac dien cue tren be mat Cac gia tri thu dupe tir
r y r
phuang trinh (14) cho mot mat dat khong dong nhat dupe xem nhu la gia tri
bieu kien p^
2 Thiet ke tong quan
Nhin chung, cac dien cue A, B, M va N cd the dat tiiy y, Tuy nhien, mot
SO sir sap xep cac dien cue dac biet thudng dupe diing nhu tren hinh 2, tuang
ling la cac he sd hinh hpc K
Mot trong nhung tham sd quan trpng ciia phuang phap do dien trd nay la
dp sau tham dd (Schlumberger, 1932), cac khao sat ciia Muskat, Evinger,
1941 cho thay dong xuyen sau chi phuc thupc vao khoang each giua hai cue
A va B, trong khi dp sau tham dd dupe xac djnh bdi tham so hinh hpc cua
ca bdn dien cue Viee phan tich ve dp sau tham dd cung nhu la xu sd lieu la
rat phuc tap va khong phai la van de can giai quyet ciia de tai nay
Thiet bi do dien trd DC ve ca ban la mot thiet bi cd gia thanh thap, cac bp
phan ca ban bao gom:
y y f
Mot nguon dong, trudng hap dan gian la mot nguon Pin dupe ndi
vdi mot chuyen mach dimg de dao chieu cue
Mot ampe ke do dong tiem xudng long dat
Mot Von ke do tin hieu the
04 thanh kim loai ddng vai trd cac dien cue
04 day ndi de noi cac dien cue vdi nguon va thiet bi do
nhu anh minh hoa tren hinh 3
Trang 9Hinh 2: Sir sap xep cac dien cue hay diing trong phuang phap do dien trd
DC va cac he sd hinh hpc tuang ling
Trang 10Hinh 3: Thiet bi do dien trd dat ca ban diing 4 dien cue (Coruh, 1988)
Bang each diing 4 dien cue tren, viee thu thap sd lieu kha dan gian va chiing ta cd the hoan toan thu dupe cac hinh anh 2D va 3D ciia be mat trai dat.Tren thuc te, viee di chuyen cac dien cue va thiet bi do khong thich hop cho viee khao sat mot dien tich rpng
He do da cue ra ddi nham giai quyet bai toan tren, va rat nhieu tac gia da nghien cihi va che tao he do tiiy theo dieu kien su dung va chi phi khac nhau [2-9], ve CO ban he cd cau tao nhu tren hinh 4:
Cctcle C u n c + SA-tcfirp j-v.s Mjitccfe,
lectfooe-c 1
Hinh 4: So dd minh hoa he do da cue (Griffiths, Barker, 1993)
0
Trang 11Mot he da cue ca ban theo ki^n tnic tap trung gdm mot cap nhieu loi \ a
mot he chuyen mach, sd lupng cue cang Idn thi kich thudc phan ciing cang
Idn va dd lai la mot ban che Ngay nay, su phat tri^n ciia ky thuat dien tu va
vi dien tu cho phep chiing ta che tao dupe nhiing he do hien dai ban ddng
thai lam he thong minh ban nhd phan mem Dij lieu do dupe chuyen vao
may tinh va dupe xu ly, luu trir ngay tren thuc dia
Muc tieu de tai nay nham thiet ke va che tao mot he do dien trd dat da
cue theo kien tnic ban tap trung, tire la he cd cac bd phan chuyen mach nam
tai cac dien cue, dieu nay cho phep giam ket cau chi diing cap it spi (so vdi
kien tnic tap trung), chi phi thap (so vdi he cd kien tnic phan bd - thiet bj do
nam tai mdi dien cue)
3 Xay dung he dq dien trd da cue ban tap trung
Tren dieu kien cho phep, chiing tdi da thuc hien viee xay dung he do dien
trd dat da cue vdi cau tnic nhu tren hinh 5:
PC
Accu 12V
CTR DAQ
Hinh 5: So dd cau tnic he do da cue
He bao gom cac bp phan cau thanh sau:
+ PC: may tinh'PC hoac Laptop
+ CTR-DAQ: bo thu thap sd lieu va dieu khien
+ EU#n: Bd dieu khien dien cue thu n (Electrode Unit)
+ DC-DC: bp chuyen ddi nguon dien
+ Accu: nguon dien mot chieu 12-24V
+ En : Dien cue sd n
3.1 Bo ddi nguon DC-DC
Vdi dac thii cua phep do dupe thuc hien tai hien trudng rpng, dja hinh
phuc tap va khong cd nguon dien ludi, ddng thdi nguon kich ddng can phai
dam bao cd dien the cao mdi dap ung dupe yeu cau do vdi khoang each sau
va xa Trong nhieu san pham thuong mai, nguon nay la mot may phat dien
chay bang xang dau Tu}' nhien, muc dich ciia thiet bi trong de tai nay la chi
Trang 12ap dung trong pham vi nhd kich thudc va trpng lupng nho tien mang \ac
trong dieu kien thuc tap, do dd, ngudn kich na\ dupe ch^ tao theo ky thuat
bien ddi dien DC-DC diing ngudn nudi la accu 12V hoac 24V
Hinh 6: So dd khdi bd ddi ngudn DC-DC
Bp tao tin hieu PWM diing IC TL494 cd chuc nang dieu che dp rpng
xung PWM va dieu khien MOSFET cong suat d tan sd khoang 150KHz
MOSFET ddng vai trd cua chuyen mach cong suat dieu khien bien the xung,
ldi ra ciia bien the xung se dupe chinh luu va Ipc de cd dupe dien ap trung
/ •> r y
binh bien ddi trong khoang tir 50V den 350V Mach phan hoi dua tin hieu
cua dien ap ra trd ve bp tao xung PWM de on dinh dien ap mong mudn
Mach dieu khien PWM dupe ket bdi vdi bp CTR-DAQ cd tac dung dat
gia trj ciia the ldi ra Qua bp nay, bp chuyen ngudn cd the boat dong nhu mot
ngudn the on ap dieu chinh dupe, ddng thdi cho phep chuyen chi'rc nang
thanh ngudn ddng
Dien ap ra lai dupe dua vao mot ra-le de dao chieu ngudn dien khi ap
dung do d che dp phan cue cam ling
y -i F
3.2 Bo dieu khien va thu nhan so lieu CTR-DAQ
Vdi vai trd quan trpng la dieu khien toan bd he thong, do dien ap va dong
y t r ^
dien tren cac dien cue Bp dieu khien va thu nhan sd lieu CTR-DAQ can
dam nhan cac chuc nang sau:
Ket ndi vdi may tinh Laptop de nhan lenh va truyen dii lieu do dupe
ve may tinh
Dieu khien xap xep cua cac dien cue tiiy theo mode do
Dieu khien gia tri dien ap cao ap dat len cac dien cue, tuang ling la
ddng can do
12
Trang 13Doc du lieu tu bo chuyin d6i tin hieu ADC I6-24bit mane thona tin
ve ddng va the tuong ung vdi cac niit cue
De dam nhan cac chuc nang dd, bd diSu khien va thu nhan du lieu duac thiet ke bao gdm cac khdi chuc nang nhu so dd hinh 7
, 1 ,
ADC 16-24bits
X3
11 X4 '' n X5 +24 X6 GND X7
A X8
B
out
Hinh 7: So do khoi bp dieu khien va thu nhan dir lieu CTR-DAQ
DSPie4013 la bp dieu khien tin hieu sd ciia Microchip dupe diins lam CPU dieu khien toan bp khdi CTR-DAQ Chip vi dieu khien nay c6 nhan DSP 17xl7bit, 24kB bp nhd chuong trinh 2k RAM vdi bus du lieu 16 bit va chay d toe dp xap xi 29MIPS, nhd dd, bd dieu khien cd the boat ddng vdi toe
dp cao, thuc hien nhieu phep tinh phuc tap, dac biet cd the boat ddng doc lap theo chuong trinh da cai san ma khong can may tinh ngoai khi di da ngoai
Vi dieu khien cd chuc nang ket ndi may tinh qua bp RS232-USB converter dieu khien cac ro-le chuyen mach de bao dam cac che dp do ddng the dieu
13
Trang 14khien bd ngudn va mode do DC, phan cue IP ddng thdi dieu khien mach
chuyen ddi tuong tu thanh sd ADC de dpc tin hieu cua dien ap
Mach chuyen ddi tuong tu sd ADC diing AD7705 ciia Analog Device \ di
dp phan giai 16bit Dien ap tham chieu 2.5V danh gia dp chinh xac cua tin
hieu do dupe diing MAX872 ciia Maxim vdi dp chinh xac 0.2% va dp troi
theo nhiet dp thap 40ppm/^C Dai dien ap vao cd the chpn bang phan mem tir
±10mV den ±2.5V do ben trong chip ADC nay da chua bd khuyech dai lap
y I y
trinh dupe PGA dieu dd khien mach do trd nen linh boat vdi nhieu dai do
khac nhau Khi do d che dp do ddng, ddng dien dupe do bang each do the
tren mot dien trd Shunt 0.1 ohm vdi dp chinh xac 0.1%
Khdi dieu khien cac dien cue dupe thuc hien qua mang cdng nghiep
RS485 chi dung 2 dudng day cap xoan AB cho phep ket ndi tdi 31 dien cue
each nhau tdi 1200m max Viee dieu khien duac thuc hien bang mav tinh
laptop ket ndi cdng USB qua bd chuyen ddi true tiep USB-RS485
Cac ldi vao ra ciia modul CTR-DAQ bao gom 2 cdng ket noi USB vdi
may tinh, mot cdng ndi vdi bp doi ngudn va mot cong gom 8 dudng da>
XI-X8 ndi tdi cac bd dieu khien dien cue EU#n
3.3 Bd dieu khien cac dien cue EU#n
Bd dieu khien cac dien cue EU//n cd nhiem vu chpn ket ndi hoac khong
ket ndi dien cue En vdi cac dudng tin hieu XI-X4 va dupe cung cap nguon
dien +24V tir bd CTR-DAQ, mdi dien cue la mot nut mang RS485 nhan tin
hieu di^u khien va phat tin hieu TEST OK cho may tinh de dam bao da nhan
va thuc hien lenh thanh cdng So do khdi ciia bp nay nhu tren hinh 8
5V Regulator
XI
VI X2 V2 X3
II X4
12
14