Phát triển hệ chương trình xử lý, phân tích tài liệu phân cực kích thích ở việt nam

MUC LUC

Trang
MODAU

4

ChUOng 1: TONG QUAN VE CAC PHl/ONG PHAP PHAN ClTC KICH
THICH DONG MOT CHIEU
1.1

13

Vai net ve lich su phat trien ctia phuong phap ph^n cue kich
thich

J3

1.2

Coche ciia hien tucmg phan cue kich thich

1.3

Cac phuong phap phan cue kich thich thuong dung

\j
21

1.3.1 Mot so he cue do cabdn

21

1.3.2 Mot vai phuangphap do sdu PCKT thong dung

24

1.4

Diem qua m6t vai phuofng phap do s^u dien tro vi phan da
duac de xuat cai tien

30

1.4.1 Phuofng phap do sdu dien chung

30

1.4.2 Phuang phap do sdu khdu trittrudng

33

1.4.3 Phuang phap do sdu dien doi xitng ludng cue hap nhdt

35

1.4.4 Mot so nhdn xet ve edc phuang phap do sdu dien tra vi phan
da duae de xudt edi tien
1.5

38

Cac ton tai chinh trong ap dung phuofng phap phan cue kich
thich dong mot chieu o Viet Nam

K^luan

42
45

Chuang 2: NHUNG DE XUAT U6\ TRONG PHUONG PHAP DO SAU
PHAN

c u e KICH THICH

47

2.1

Dat va'nde

4-7

2.2

G\6\ thieu cac thong so PCKT mdi

48

2.3

Ca sof de xuat cac phuang phap do sau PCKT cai tien

50


2.3.1 Ca sd de xudt phuang phap do sdu PCKT doi xung cai tien

50

2.3.2 Ca sd de xudt phuang phap do sdu PCKT luang cue cai tien...

51

2.4

52

Gioi thieu cac he cue do sau phan cue kich thich cai tien

2.4.1 He cue do sdu PCKT doi xicng edi tien

52

2.4.1.1 Mo td he cue do sdu PCKT doi xicng edi tien KM-01

52

2.4.1.2 Qui trinh do dgc ngodi thue dia

55

2.4.2 He cue do sdu PCKT luang cue edi tien

56

2.4.2.1 Mo td he cue do sdu PCKT ludng cue true edi tien KM-02....

57

2.4.2.2 Mo td he cue do sdu PCKT ludng cue xieh dao edi tien

58

2.4.2.3 Qui trinh do dge ngodi thue dia

60

2.4.3. Mot so nhdn xet

61

Ket lutin

64

Chuofng 3: HUCiNG PHAT TRIEN MC*I VE X U L Y , PHAN TICH TAI
LIEU DO SAU PHAN c u e KICH THICH
3.1

Dat van de

3.2

Cac phep bien doi mdi - mot hudfng phat trien \t xu ly, phan

65
65

tieh tai litn do sau PCKT

67

3.2.1 Phuang phap do sdu PCKT doi xicng

67

3.2.2 Phuang phap do sdu PCKT luang cue

70

3.3

75

Tmh cac thong so PCKT mdi tren mo hinh ly thuyet

3.3.1 Tinh cac dudng cong do sdu dien tra va do sdu phdn cue tren
mdi trudng 3 lap
3.3.1.1

Casdly

thuyet

3.3.1.2

Cac kit qud tinh todn

75
75
78

3.3.2 Kiem ehicng tinh dung dan vd tinh uu viet eua edc phep bien
doi mdi tren mdi trudng 3 Idp
3.3.2.1

Doi vdi phuang phap do sdu PCKT doi xicng

81
81


3.3.2.2

Doi vdi phuang phap do sdu PCKT ludng cue

84

3.3.3 Mot so nhdn xet ve tinh chat ca bdn vd khd ndng eua ede
thong sdmdi trong khdo sat mdi trudng dia chat

3.4

86

Kiem chutig tinh dung d^n va tinh uu viet ciia cac phep bien

87

d6i mdi tren moi trucmg thuc td'.
3.4.1 Doi vdi phuang phap do sdu doi xicng PCKT

88

3.4.2 Doi vdi phuang phap do sdu PCKT ludng cue

90

3.5

Cong thiic bien doi Petrovski cai tien

96

3.6

Gidi thieu ve he chuang trinh xir ly, phan tich

98
98

3.6.1 Ngon ngUMatlab
3.6.2 He chuang trinh xu ly, phdn tieh

100

Ket luan

101

Chuang 4: CAC KET QUA THlTNGHIEM

103

4.1.

N6i dung ap dung thir nghiem thuc te eua cac d6 xuat mdi

103

4.2.

Ket qua ap dung cac di xuat mdi de khai thac tai lieu do sau
PCKT doi xiing da c6

104

4.2.1 Dae diem dia chat vd tinh chat vat ly cua tuyen 20

104

4.2.2 Ket qud xu ly, phdn tich tai lieu do sdu PCKT doi xung

105

4.2.2.1. Ket qud theo tai lieu do sdu PCKT doi xicng thong thudng

105

4.2.2.2 Ket qud dp dung ede de xudt mdi dekhai thde tai lieu

108

4.3.

112

Ket qua ap dung phuang phap do sau PCKT luang cue cai tien

4.3.1 Dae diem dia chat vd tinh chat vat ly cua tuyen Sll

112

4.3.2 Ket qud xic ly, phdn tich tai lieu

112

Ket luan

118

Ket luan va kien nghi

121

Tai lieu tham khao

125
4


MODAU

1. Tinh can thiet cua de tai:
Cac phuang phap Dja Vat ly la nhung cOng cu manh dung de nghien
cun trai dat. Chung lien tuc duge bo sung, hoan thien va phat trien. Trong to
hop phuang phap Dia Vat ly tham do, cac phuang phap Phan cue kich thich
(PCKT) chiem mot vi tri quan trong va hien nay vSn la mot trong nhiing
phuang phap Dia Vat ly tham do thong dung nhat.
So vdi phan Ian phuang phap Dia Vat ly khac, phuang phap PCKT eo
nhiJng uu diem nhu: chu tiinh ky thuat do dac tuang doi dan gian va khong
doi hoi may mdc thiet bi qua phiic tap, tinh vi; xit ly so lieu nhanh chong bang
tay hay tren may tinh vdi chi phi thap nhung kha nang giai quyet da dang,
hieu qua kinh t6' cao. Do do, phuang phap PCKT da dugc ap dung of nhieu
nude tren the gidi va ngay ca a nude ta, thudng chiem mot ty le kha cao trong
khoi lugng tham do dien ndi chung, no ngay cang dugc su dung pho bien
trong cong tac tham do Dia Vat ly.
Sau nhi6u nam lien tuc phat trien, ngay nay phuang phap PCKT da trdf
thanh mot trong phuang phap chii dao de nghien euru dia chat c6 hieu qua kinh
te va khoa hoc cao. Cac phuang phap PCKT cho phep xac dinh su thay doi
dien tra suat va do phan cue theo chi6u sau cua v6 trai dat, dugc sir dung rong

rai d^ ve ban do dia chat, nghien ciiu cau true, tim kiem cac khoang san c6 ich
cQng nhu trong dia chat cong trinh va dia chat thuy van....
Nhiem vu chii yen ciia phuang phap PCKT la chi ra dugc vi tri tuang
d6i cua cac doi tugng dia chat can tim. Trong nhimg dieu kien thuan Igi cd the
xac dinh b6 day cac I6p dat da cau thanh lat cat dia-dien, hinh dang, kich
thude, chieu sau the nam cua cac doi tugng nghien cuu trong pham vi sai so
cho phep cua phuang phap.


Nhu chung ta da biet, of nude ta tir trudc den nay, cac tham so truyen
thong da va dang dugc sir dung pho bien trong viec xir ly, phan tich tai lieu
PCKT la do phan cue bieu kien % va dien trd sua't bieu kien A • Co nhieu
each khac nhau: tinh toan cac dudng cong 7^ va p^ d6'i vdi moi trudng phan
Idp, dong nhat, song phing ngang tren may vi tinh bang phuang phap lua
chon de xay dung cac ban chuan; tinh 7^ -- f(ABl2) true tiep tii dudng cong
p^ = f{ABI2)\ chuyen cac gia mat cat thanh cac mat cat ban dinh lugng; su
dung cac tham so thuc nghiem S, va Z^ (vdi 5,1a thdi gian ma tai do cd do
phan cue giam di mot nua, Z^ = 0,75 . 5^ . % ) ; do phan cue bieu kien tuang
dd'i A^ va do phan cue bieu kien tong hgp Al, toe do suy giam the phan cue
Vpc

Tuy nhien, phai cong nhan rang vi th6ng tin con ngheo nan va phuang
phap xir ly, phan tich cdn han ehe nen ket qua thu dugc con chua dap ling
dugc ydu cau mong muon. Cd the diem qua mot vai nguyen nhan ciia tinh
trang tren la do:
+ Chi do true tiep dugc tiing loai dudng cong ling vdi m6t loai \\t cue
nen chi phan anh dugc mot dac trung nao do ciia moi trudng nghien ciiu.
+ Cac cong thiic chuyen doi giua cac dudng cong nham thu dugc nhieu
loai thong tin cho den nay vSn chua thuc su cd hieu qua, doi khi cdn lam cho
"meo" thong tin va khdng on dinh.

+ Cac phuang phap s6 dung de xu ly, phan tich tuy da dugc nang cao
khi ap dung nhung thanh tuu mdi hien dai cua Toan hoc va Tin hoc, nhung
van cdn nhieu han che do tinh khong on dinh va da tri cua bai toan ngugc. Doi
khi vSn chi luan giai mot each dinh tinh va chi sir dung dau hieu diem gSy
hoac diem udn ciia dudng cong de du bao hoac cdn sir dung qui luat bien doi
ciia dudng cong dien trd de gan cho cac Idp dia - dien cac gia tri do phan cue
bieu kien do dugc bang thiet bi do tuang duang vdi dudng cong dien trd.


Chinh vi vay ma d6i khi cdn nh^m Ian khi du bao cac di thudng trien
vong khoang san, lien ket di thudng cdn chua dat y6u cau mong muon.
Lam th6' nao de khac phuc tinh trang nay, nham nang cao do tin cay, tao
dieu kien md rong pham vi ap dung ciia phuang phap PCKT trong ditu kien
dia-di6n phiie tap?. Do chinh la mot muc tieu kha hap dan da I6i cudn su dau
tu suy nghi ciia kha nhi6u nha khoa hoc trdn the gidi va trong nude trong
nhieu nam qua.
Cd the ndi rang cho den nay hau nhu tat ca cac tac gia deu tap trung sure
lue cua minh theo hai hudng chinh sau:
• Cai tien cac he thiet bi do (may mdc, he cue do, phuang phap do ngoai
thuc dia...) de cd the do true tiep dugc cac thong tin can thiet ngoai thuc dia.
• Tim ra cac cong thiic de tinh chuyen doi giiia cac loai dudng cong nham
tang lugng thong tin phuc vu cho cong tac xir ly, phan tich.
Tuy vay, cac he thiet bi cdn phiic tap ca ve he cue do ISn cac phep do;
c6ng thiic bi6n doi giua cac dudng cong cdn phai tinh qua phep dao ham
khong on dinh. Mac du cd nhi6u cd gang nhung cho den nay, dieu ba't hgp ly
neu tren vSn chua dugc hoan toan giai quyet.
Chung toi cho rang cd the giai quyet tirng phan hoac triet de nhiing van
di ca ban cdn ton tai neu tren m6t each thiet thuc (tuy theo muc dich va doi
tugng nghien ciiu) bang each ket hgp ca hudng de xuat cac thong sd PCKT
mdi cd nhiing uu diem han (nhu do phan giai cao han, tong hgp thdng tin

han...) vdi viec cai tien cac he thiet bi do, tim ra cac edng thiic bien doi thong
tin chinh xac han. Cd nhu vay mdi mong tang them nhieu thong tin khac loai
thu dugc tuf moi trudng thuc te, nham lam phong phii han cac thong tin, tang
do chinh xac phuc vu cho cong tac xu ly, phan tich dat hieu qua nhat.
De thuc hien dugc y tudng nay, trong pham vi de tai luan an, vdi mong
mudn gdp phan khac phuc nhiing ton tai tren, chiing toi da nghien ciiu de xua't
cac thong sd PCKT mdi (dac bi6t la thong sd PCKT Petrovski 7 ) de xir ly.


phan tich tai li6u PCKT hieu qua han. Tur cac ket qua do thu duge bang mot
loai he cue thdng thudng nao dd ta vSn cd dugc thong tin tin cay cua cac loai
dudng cong khac thong qua cac phep bien doi dai sd dan gian. Tat ca cac
thong tin nay da dugc khai thac triet de trong he chuang trinh tu dong xir ly,
phan tich tong hgp, ma nd dugc viet bang ngon ngu cap cao MATLAB nhu
mot san pham phan mtm vdi cac chiic nang hoan toan tien ich, dd sir dung,
gan giii vdi thuc te. Giai phap nay khong chi da dugc chiing minh bang mo
hinh ly thuyet, ma cdn da dugc kiem nghiem tren moi trudng thuc te vdi cac
he cue do va cac phep do mdi ma tac gia da dt xuat, dac biet cdn dugc ap
dung de khai thac cac tai lieu thuc te cu ciia phuang phap do sau PCKT thong
thudng, lam md rong va nang cao tinh hieu qua kha nang ap dung thuc te cua
phuang phap. Day la mot van d6 hap dan, hoan toan mdi can thiet phai lam,
dd Cling chinh la hudng suy nghi nghien ciiu va ket qua dat dugc cua tac gia
trong thdi gian qua.

2. Muc tieu va cac nhiem vu cua luan an:
• Muc tieu:
Hoan thien he chuang trinh xir ly, phan tich tai lieu PCKT tren ca sd
de xua't thong sd PCKT mdi 7^; thiet lap cac phep bien doi dai sd dan gian, ap
dung de tinh toan khai thac, bo sung them cac thong tin cd ich doi vdi tai lieu
PCKT da cd tCf trude den nay, cung nhu ap dung cho cac tai lieu mdi thu dugc

bang cac phuang phap cai tien nham nang cao do chinh xac cua phuang phap.
•

Cac nhiem vu:
1. Tim hieu, phan tich tong hgp nhiing ket qua nghien ciiu cua cac tac

gia trudc. Dua ra va xay dung ca sd ly thuyet ciia thong sd PCKT Petrovski


8

2. Dua tren nguyen ly chong cha't dien trudng, dua ra cac cong thiic
bi6'n d6i giiia cac dudng cong PCKT sao cho khac phuc dugc cac nhugc diem
ca ban ve tinh khong on dinh cdn tdn tai tii trudc den nay.
3. Chiing minh tinh diing dan cua cac phep bien doi dd tren mo hinh ly
thuyet va kiem nghiem tren moi trudng thuc te.
4. xay dung cac thuat toan xir ly, phan tich qua cac phep bien doi dai
sd neu tren va thiet lap he chuang trinh tu dong tuang ling bang ngon ngii
MATLAB.
5. Cai tien cac he cue do va quy trinh do nham thu dugc thong tin dSu
vao phu hgp de xir ly.
6. Tien hanh thir nghiem ap dung phuang phap mdi trong thuc te, ciing
nhu khai thac cac tai lieu da cd de cd ket luan \t tinh hieu qua cua cac de xuat
theo hudng phat trien xir ly, phan tich mdi.

3, Cac ket qua mdi:
1. Lan dau tien de xuat va sir dung thong sd PCKT Petrovski /j^ mdi ed
do phan giai cao, xay dung dugc ca sd ly thuyet va chiing minh dugc cac uu
diem cua chiing so vdi cac tham sd truyen thong p^, rj^ ,
2. Dua ra dugc cac phep bien doi mdi gifla cac dudng cong do sau

PCKT. Da chiing minh dugc tinh diing dan ciia cac phep bien doi dd tren mo
hinh ly thuyet va moi trudng thuc te. Day ciing chinh la mot phan thuat toan
xir ly, phan tich tai lidu PCKT theo hudng mdi de xuat nay.
3. Vdi thuat toan da thiet lap, xay dung dugc he chuang trinh tu dong
bang ngon ngir MATLAB nhu mot san pham phSn mem vdi cac chiic nang
hoan toan tien ich, d6 sir dung, giao dien va dd hoa tot, gan giii vdi thuc te.
4. Cai tien cac he cue do va quy trinh do hgp ly nham giam thieu cac
phep do, khdng lam phiic tap quy trinh thuc dia ma ta vSn cd dugc dii thong
tin can thiet.


5. Ket qua do, xir ly va phan tich tai lieu theo phuang phap mdi, eQng
nhu ap dung khai thac cac tai lieu p^, 7^ thuc te da cd de cd dugc 7^ vdi do
phan giai cao, chieu sau nghien ciiu Idn da chiing minh hieu qua dia chat ciia
de xua't mdi ap dung trong thuc te.

4, Y nghla khoa hoc va thiic te:
•

Y nghia khoa hoc:
1. Thong sd PCKT Petrovski 7^ dugc xac lap va khai thac cd ca sd khoa

hoc, lam tang dang ke lugng thong tin hiiu ich. Chiing cd do phan giai cao nen
phan anh sat thuc han hieu ling PCKT cua cac doi tugng nghien ciiu; tang do
phan giai doi vdi cac di thudng yeu.
2. Phep bien doi thong tin da dt xua't va sir dung chi qua cac phep tinh
dai sd dan gian, khdng phai thuc hien qua cac phep tinh dao ham cd tinh
khong on dinh, nen chiing da khac phuc dugc cac nhugc diem cdn ton tai
trudc day. Cac phep bien doi nay cd do tin cay va khoa hoc cao. Phat trien he
thong chuang trinh xir ly, phan tich tai lieu PCKT tren ca sd cd lua chon thong

tin dang tin cay nhung mang tinh tong hgp han.
3. De xua't cai tien he cue do va qui trinh do hgp ly, thuan tien, cd tinh
kha thi trong thuc te.
•

Y nghla thuc te:
\. Hudng xir ly, phan tich tai lieu PCKT mdi thong qua cac phep bien

d6i da de xua't lam ro han va tang dd tin cay ciia cac ket qua du bao dia chat vi
lam phong phii them nhieu thong tin bo ich. Trong trudng hgp thuan Igi cd the
dung kd't qua du bao de theo doi, phat hien cac ddi tugng can tim.
2. Md rong va nang cao kha nang ap dung ciia phuang phap PCKT,
chang nhiing ddi vdi cac phuang an do mdi, ma cdn khai thac bo sung them
dugc cac thong tin cd ich khac giiip cho cong tac xir ly, phan tich tai lieu


10

PCKT eua cac phuang phap cii da cd trudc day. Trong trudng hgp cd the cdn
giiip cho viec kiem tra, phat hien cac ddi tugng can tim ddi vdi cac phuang an
cii da dugc thuc hien.
3. Kha nang thir nghiem va ap dung vao san xuat la hien thuc.

5. Cac luan diem mdi chii yeu cua luan an
1. Tir cac ket qua do thu dugc bang m6t loai he cue thong thudng nao
dd ta vSn cd dugc thong tin tin cay cua cac loai dudng cong tuang ling vdi cac
he cue khac thong qua cac phep bien doi dai sd dan gian khong phai tinh dao
ham, nen da md rdng va nang cao cd hieu qua kha nang ap dung thuc te cua
phuang phap.
2. Y nghia cua viec de xuat thong sd PCKT mdi Petrovski 7^, ed do

phan giai cao va mang tinh tong hgp. Phat trien he chuang trinh tu dong xir ly,
phan tich tai lieu PCKT bang ngon ngii MATLAB, theo hudng khai thac thong
sd PCKT Petrovski ^^va cac phep bien ddi da de xuat, nham xir ly, phan tich
tai lieu PCKT hieu qua han.

6. Bd cue cua luan an
Ngoai phan md dau, phan ket luan va kien nghi, danh muc cac tai lieu
tham khao, ngi dung luan an dugc trinh bay trong 4 chuang.
Chuorng 1: Tong quan ve phuang phap do sdu phdn cue kich thich
ddng mot chieu,
Trong chuang nay chiing tdi trinh bay vai net ve lich sir phat trien ciia
phuang phap phan cue kich thich (PCKT); ca che cua hien tugng PCKT;
nhiing net tong quan hien trang eua cac phuang phap do sau dien vi phan tren
the gidi va trong nude cd lien quan den de tai, danh gia uu diem va nhugc


11

diem ciia cac phuang phap nay; cac tdn tai chinh trong ap dung phuang phap
phan cue kich thich ddng mot chieu d Viet Nam.
Chuang 2: Nhiing de xudt moi trong phuang phap do sdu PCKT
Trong chuang nay chiing tdi trinh bay wt cac tham sd PCKT truyen
thong; gidi thieu cac thong sd PCKT mdi; ca sd dt xuat va gidi thieu ve cac
ht cue, qui trinh do sau PCKT cai tien.
Chuang 3: Hu&ng phat trien m&i ve xvt ly, phdn tich tdi lieu do sdu
phdn cue kich thich.
Trong chuang nay chung toi trinh bay v6 ca sd ly thuyet cua cac phep
bien doi mdi - mot hudng phat trien ve xii ly, phan tich tai lieu PCKT; tinh
toan va kiem chiing tinh diing dan, tinh uu viet ciia cac phep bien doi mdi tren
md hinh ly thuyet 3 Idp va moi trudng thuc te, tii dd cd mot sd nhan xet \t

tinh cha't ca ban va kha nang eua cac thong sd mdi trong khao sat moi trudng
dia cha't; gidi thieu cong thiic bien ddi Petrovski cai tien; gidi thieu \t he
chuang trinh xir ly, phan tich lap bang ngon ngii MATLAB.
Chuang 4: Mot so ket qud thu: nghiem
Trong chuang nay chung toi trinh bay mot sd net chinh ve dac diem eua
viing nghien eiiu thir nghiem; cac ket qua xir ly, phan tich tai lieu theo hudng
mdi ddi vdi cac tai lieu thuc te, tii dd nit ra ket luan ve hieu qua ap dung thuc
te ciia cac de xuat mdi.

7. Ldi cam on
Ban luan an nay dugc hoan thanh tai Bg mon Dia Vat ly, Khoa Vat ly,
Trudng Dai hoc Khoa hoc Tu nhien - Dai hoc Qudc gia Ha Noi, dudi su
hudng dan khoa hoc cua PGS.TSKH. Tang Mudi, PGS.TS. Le Viet Du
Khuang.
Trudc het, tdi xin bay td Idng biet an sau sac ddi vdi cac thay true tiep
hudng dan khoa hoc - PGS.TSKH. Tang Mudi va PGS.TS. Le Viet Du Khuang


12

- vl su tan tinh chi bao, giiip dd tdi trong qua trinh thuc hien va hoan thanh
luan an.
Trong thdi gian hoe tap va nghien ciiu, de hoan thanh ban luan an nay,
tdi cdn nhan dugc su giiip da ciia Bd mdn Dia Vat ly, Khoa Vat ly. Tac gia da
nhan dugc nhCrng y kien ddng gdp quy bau va sau sac ciia: GS.TSKH. Ngd
Van Buu, GS.TSKH. Lam Quang Thiep, GS.TSKH. Pham Nang Vu, GS.TS.
Bui Cong Que', PGS.TSKH. Mai Thanh Tan, GS.TS. Nguyen Trong Nga,
PGS.TS. Nguyen Nggc Thiiy, TS. Nguyen Tai Thinh, TS. Nguyen Nggc Loan,
TS. Doan Van Tuyen... va nhieu nha khoa hoc khac. Ngoai ra, tac gia cdn
nhan dugc su giup da nhiet tinh, cd hieu qua ciia TS. Nguyen Tai Thinh va

cac can bg Doan Dia Vat ly mat dat thudc Lien doan Vat ly-Dia chat trong
qua trinh thu thap tai lieu va do dac thir nghiem tren thuc te. Tac gia xin chan
thanh cam an sau sdc de'n cac dan vi va ca nhan ndi tren.
Nhan dip nay, tdi xin cam an su quan tam, dong vien, iing ho va tao
dieu kien thuan Igi eua GS.TSKH. Nguyen Van Mau cung tap th^ lanh dao
trudng Dai hoc Khoa hoc Tu nhien - DHQGHN; xin cam on GS.TS. Mai
Trong Nhuan ve su giiip dd chan thanh ddi vdi tdi trong qua trinh thuc hien,
hoan thanh luan an va thu dugc ke't qua tot dep.


13

Chircmg 1

T6NG

QUAN VE CAC PHl/ONG PHAP

PHAN Cl/C KICH THICH DONG MOT CHIEU

1,1

VAX NET VE LICH SlT PHAT TRIEN CUA PHl/ONG PHAP PHAN CUC
KICH THICH
Nam 1912 nha Dia Vat ly ngudi Phap K. Schlumberger de ra y tudng sir

dung hien tugng phan cue kich thich vao dieu tra nghien ciiu dia cha't - khoang
san. Cho den nay, sau mot khoang thdi gian khong dai so vdi thdi gian ra ddi
cua cac phuang phap Dia Vat ly khac, phuang phap phan cue kich thich
(PCKT) da dugc hinh thanh va nhanh ehdng dugc ap dung rong rai tren the'

gidi va nude ta trong dieu tra dia cha't tim kiem va tham dd khoang san.
•

0 Lien X6 (cQ) viec nghien ciiu hien tugng phan cue kich thich cua da't

da va quang ciing nhu nghien ciiu phuang phap va che' tao thiet bi ghi chinh
xac the' phan cue kich thich dugc nhieu nha khoa hoc va to chiic Dia Vat ly
quan tam, thu dugc nhiing ket qua dang ke ca ve ly thuye't va thuc nghiem.
Trudc khi ra ddi tram do phan cue kich thich kieu VP-59, phuang phap
do sau PCKT duge ddng dao cac nha Dia Vat ly, Dia chat ap dung va thir
nghiem bang cac may do dien the thong thudng nhu EP-1, ESK-1 cd lap them
bg phan phu de dieu chinh thdi gian phat ddng qua dat va thdi gian ghi cac tin
hieu tren nhieu viing khac nhau da khang dinh tinh uu viet cua phuang phap
ddi vdi quang xam tan ma cac phuang phap Dia Vat ly khac it cd hieu qua.
Tijr khi ra ddi tram tham dd dien VP-59 do VITR, VNHIGEOPHYSIKA va
MPZ nghien ciiu che tao, tiep sau la cac tram hoan thien han nhu: VP.62, VP0.62 va VPP-67..., phuang phap do sau PCKT da dugc ap dung pho bien trong


14

cong tac tim kie'm va tham dd khoang san d Lien Xd. Cung vdi su ra ddi cac
tram do PCKT tren mat dat, VITR va MPZ da nghien ciiu che tao cac tram do
phan cue trong 16 khoan kieu VPS-63 va san xuat hang loat vao nam 1964.
Den nay da md rong kha nang ap dung cua phuang phap d ca tren mat dat va
dudi mat dat. Dd la cac may do PCKT bang ddng mot chieu.
Vao nam 1972, Lien Xd da che tao tram do PCKT bang ddng xoay
chieu INFA2-VP de do pha phan cue trong gidi han tan sd tii 0,3 den 78 HZ.
Tiep sau dd la che tao tram VP-F vao nam 1975. Tii dd da tao ra dieu kien ap
dung rdng rai phuang phap phan cue xoay chieu trong tim kiem va tham dd
khoang san.

Su ra ddi va phat tri^n eua cac thiet bi do PCKT ndi tren da tao dieu
kien di sau nghien ciiu ban cha't cua hien tugng phan cue kich thich, xay dung
ca sd ly thuyet cua phuang phap tren ca sd tong hgp cac thanh qua nghien ciiu
ap dung cua nhieu nha Dia Vat ly d Lien Xd va nude ngoai, cac phuang phap
do PCKT d thuc dia va phuang phap tinh toan xir ly ke't qua. Mot trong sd cac
cong trinh tong hgp neu tren phai ke de'n la cdng trinh cua Comarov V.A [70],
[71].
Tii dd del nay, ciing vdi su ap dung ky thuat dien tir va tin hoc, phuang
phap do sau PCKT khong ngiing dugc md rdng pham vi ling dung, do cd su
cai tien ve may do va phuang phap tinh toan. Trong sd cac phuang phap tham
dd, phuang phap do sau PCKT dugc coi la phuang phap chii yeu de phat hien
va theo ddi cac than quang xam tan. Dang chii y la ngoai cac tham sd do phan
cue bieu kien 7^ va dien trd suat bieu kien p^ da sir dung them tham so td'c
dd suy giam he sd phan cue kieh thich theo thdi gian tinh bang [%/ms] do ddi
tugng sulfur - vang gay ra [66] cd gia tri han han so vdi da vay quanh.
•

6 cac nude XHCN Ddng Au (cu) nhu Hungary, Tiep Khac, CHDC

Diic, Nam Tu, Ba Lan

, phuang phap do sau PCKT dugc ap dung pho bien

va cd hieu qua trong dieu tra dia chat, tim kiem va tham dd khoang san cua


15

•

tiing nude. Viec ap dung phuang phap do sau PCKT d cac nude nay di theo
hudng thuc dung han nen cd su hgp tac vdi cac nude tu ban nhu Canada,
My.... nham che tao may do gon nhe, ghi sd va tu ddng tinh toan ke't qua ngay
tii nhiing nam 1980. Rieng d Hunggary, Vien Dia Vat ly ELLGI (Budapet) luc
dd da che' tao may do phan cue cd kha nang do 11 gia tri he so phan cue sau
khi ngat ddng phat tao thuan Igi cho cac nghien ciiu dac trung suy giam ciia
the PCKT theo thdi gian. Cac nghien ciiu ciia cac nha Dia Vat ly Hunggary
nham phan biet quang va da vay quanh dua tren cac tinh toan hang sd thdi
gian r^ = f{t) va ty sd bien do 2 thanh phan chinh gay nen the phan cue kieh
thich la Wi va W2. Chiing da dat dugc nhiing ket qua nhat dinh va dugc cdng
bd trong cac tuyen tap cdng trinh nghien ciiu hang nam eua Vien.
Cac may do phan cue do cac nude XHCN Ddng Au (cii) dugc xem nhu
la mot tien bg ky thuat trong he thong XHCN liic ba'y gid nhu may DIAPIR
E+T cua Hunggary, may IPOR cua Tiep Khac

Dd la cac may do true tiep

cac ket qua 7^ va p^ bang dong ho chi thi kim hoac hien sd.
• O Trung Qudc, phuang phap do sau PCKT ciing duge phat trien gan
nhu dong thdi vdi qua trinh phat trien d Lien Xd (cii). Do cd su cai tien may
do dien the' kieu UJ-18 thanh may do kieu DDJ-I, nen phuang phap do sau
PCKT duge ap dung rdng rai va pho bien trong tim kiem va tham dd khoang
san d Trung Qudc. May do DDJ-I la may xach tay, ed do ben ca hoc cao, nen
da tao thuan Igi cho viec md rdng pham vi ap dung cua phuang phap do sau
PCKT. Hien nay Trung Qudc da che tao cac thiet bi do phan cue cd vi xir ly
nhu DFJ-5 dat trinh do trung binh tien tien.
• O cac nude tu ban phuang Tay, phuang phap PCKT dugc nghien ciiu,
thir nghiem va ap dung rat sdm. Tu" nhiing nam 1950, cac cdng ty tu nhan nhu
Newmont Mining Co., Me Phar Geophysics Ltd., Sharp Instrument... da ap
dung cd ke't qua phuang phap do sau PCKT trong tim kiem khoang san. Cac

may do phan cue bang ddng xung va xung doi chieu cd chu ky da dugc che


16

tao d My va Canada (Cdng ty Scintrex, Mc Phar Intrument, Phoenix
Geophysics, Huntec, Crone Geophysics). Cac tap doan md Idn nhat da hoan
thanh cac xir ly khoa hgc va ap dung rdng rai phuang phap do sau PCKT d
nhieu nude tren the gidi. 6 Canada, My, Irland, Perue, Ao, Nam Tu, Phan lan,
Iran, Tho Nhi Ky va cac nude khac, nhd phuang phap do sau PCKT da phat
hien md da kim, ddng, kim loai quy hiem cd quy md Idn.
Ngay nay cac may do PCKT da dugc cac nude phuang Tay hoan thien
va che' tao cd do chinh xac cao va ed nhieu tinh nang khac nhau nhu IPR-12
cua Canada, GPR-12 cua My, SYSCAL-R2 ciia Phap. Nhd dd da nang cao
hieu qua va pham vi ap dung ciia phuang phap do sau PCKT.
• 6 Viet Nam, tii nhiing nam 1970 phuang phap do sau PCKT dugc dua
vao thir nghiem tren ddi tugng Pyrit d viing md Giap Lai (VTnh Phu) va ddng
Sinh Quyen (Lao Cai) khi ta nhap dugc tram VP-62 cua Lien Xd. Sau dd
phuang phap dugc trien khai thir nghiem tren cac ddi tugng khac nhu ddng Ta
Khoa (San La), chi kem Chg Dien (Bae Thai), mangan (Bac Thai) va mot sd
viing md khac. Ke't qua cho tha'y phuang phap da td ra cd nhieu hieu qua trong
viec tim kie'm, phat hien cac than quang ndi tren, dac biet la quang xam tan
ma trude dd rat khd phat hien nd bang phuang phap dien trd va dien trudng tu
nhien. Viec phat hien di thudng phan cue ma sau dd dugc cdng trinh khoan
sau tim ra than quang pyrit so 12 d Giap Lai da khang dinh vai trd chii yeu cua
phuang phap do sau PCKT trong tim kiem quang pyrit d Viet Nam.
Trong khoang 10 nam trd lai day, phuang phap do sau PCKT dugc md
rdng cho nhieu loai khoang san, dac biet la khoang san cd ty le khoang vat
dan dien dien tir thap nhu molipden (Sapa - Lao Cai), thiec (Quy Hgp - Nghe
An), apatit (Lao Cai), thach anh - sulfur chiia vang d Cao Ram (Hoa Binh), d

Na Pac (Lang San), d Cam Tam (Thanh Hoa).., vang-antimon d Ta Sdi ( Nghe
An), Nam San - Na Pac (Hoa Binh), antimoan d Khe Chim - Ddng Md (Quang


17

Ninh). Phuang phap do sau PCKT da duge md rdng ap dung de xac dinh do
tong khoang hoa cua nude dudi dat viing ddng bang Nam Bd.
Cac may do PCKT pho bie'n d nude ta hien nay van la cac tram VP - 62
va VP - 062, DDJ-I, DIAPIR E+T, DGJ-1 cai tien cua Trung Qudc. Nam 1989
ta nhap dugc tram do phan cue xoay chieu VP-O eua Lien Xd (cii). Gan day ta
da nhap duge may do phan cue SYSCAL-R2 eua Phap. Vdi tinh hinh thiet bi
nhu vay, d Viet Nam cho de'n nay mdi chi ap dung do PCKT bang ddng mot
chieu hoac xung doi chieu la chii yeu.
Cd the ndi rang phuang phap do sau PCKT d nude ta dugc ap dung
mudn han nhieu so vdi cac nude phat trien tren the' gidi, song lai dugc phat
trien manh me trong cdng tac dieu tra, tim kiem va tham dd khoang san.
Trong tim kiem phat hien hau he't cac khoang san ma to hgp khoang vat tao
quang cd khoang vat dan dien dien tir thi phuang phap do sau PCKT deu cd
mat va dugc ap dung de tim kiem phat hien chiing. Ciing do hieu qua cua
phuang phap ma ty trong dau tu cho phuang phap nay kha Idn, khong nhiing d
Viet Nam ma cdn tren the' gidi. Theo cac tai lieu thd'ng ke ty le chi phi cho
cdng tac Dia Vat ly tim kiem va tham dd khoang san tren the' gidi tii nam
1958 de'n 1970 cho thay ty le chi phi cho phuang phap do sau PCKT chiem tdi
han 50% vao nam 1970 da chiing td vai trd chii dao cua phuang phap nay
trong td hgp cac phuang phap tim kie'm tham dd khoang san [71].

1.2

CO CHE CUA HIEN Tl/ONG PHAN Cl/C KICH THICH

Cho de'n nay, chua cd cdng trinh nao nghien ciiu hoan chinh ve hien
tugng PCKT, cac ket qua nghien ciiu [71], [80], [81], [82] chii yeu bang thuc
nghiem d6u cho rang ca che hien tugng PCKT la cac qua trinh ly hoa phiic tap
xay ra d ranh gidi tiep xiic giiia khoang vat ran vdi dung dich dien phan choan
trong Id hong cua da khi cd ddng dien chay qua. Hien tugng PCKT cd the khai
quat gdm 3 dang chinh sau:


18

- Do su bie'n dang dien kep d ranh gidi 2 pha ran va Idng cua dat da lien
ke't d trang thai chuyen ddng nhiet. Khi dd trudng dien nguyen sinh lam dinh
hudng md men Idp dien kep, Idp dien kep bi bien dang khdi vi tri can bang,
tao thanh trudng dien thii cap Epc^^*(t). Trudng thii ca'p nay hinh thanh tiic thdi
va ciing tat di nhanh va chi ton tai tdi 2-3 giay say khi ngat ddng phat.
- Do dien phan va phan ling oxy hoa khir xay ra d be mat khoang vat
dan dien dien tir va mdi trudng dan dien ion. Khi cd ddng dien chay qua quang
dan dien dien tii, theo hudng ddng dien chay tdi thi hien tugng dien phan tao
thanh khi H^, hudng ngugc lai thi tao thanh khi CL", O", tir dd tao nen cac pin
yeu td. Ddng thdi do san pham dien phan d hai phia vat quang ciing xay ra
phan ling dxy hda khir lam xuat hien cac dien tich trai dau. Ket qua tao thanh
trudng dien phan cue thii cap Epc*-*(t). So vdi trudng Idp kep, trudng do dxy
hoa khir xay ra eham han va tdn tai ciing lau han, thudng keo dai tdi 7-8 giay
sau khi ngat ddng phat.
- Do phan cue ndng do: Trong Id h6ng eua dat da, cd dung dich dien
phan, do su ha'p thu ciia set tao nen cac vimg cd ndng do khac nhau. Khi cd
trudng dien ben ngoai lam cac ion chuyen ddng, lam mat can bamg trang thai
ban dau tao nen trudng thii ca'p Epe*^*(t). Trudng dien nay xay ra cham va tdn
tai tdi vai chuc giay sau khi ngat ddng phat.

Nhu vay, the' PCKT chi tdn tai chii yeu trong mot khoang thdi gian nha't
dinh sau khi ngat ddng phat. Ne'u dung thiet bi do the PCKT trong khoang thdi
gian thich hgp ay, ta se nhan dugc the PCKT.
Do phan cue bieu kien la ty sd hieu dien the' phan cue AUpc{t) do d thdi
die'm t sau khi ngat ddng phat va hieu dien the AL'' do duge d thdi diem chua
ngat ddng phat (tinh theo ty le %) khi cting dieu kien thu phat:
%=

Af/pc(t)
Bil^lOO%
^ ^ — °

(1.1)


19

7^(0 la ham ciia thdi gian, cd quy luat suy giam tuang tu nhu the' phan cue
AUpc(t), Ham //^(t) dugc ggi la ham dd phan cue bieu kien cua mdi trudng.
•

D6 thi bi^u dien dd phan cue bieu kie'n 7^ (/) theo kich thudc he cue r dugc ggi
la dudng cong do sau phan cue [15].
Bai toan phan bd the' eua ngudn dien ddng khong ddi cudng do I tren
mat nira mdi trudng phan Idp, ddng nha't, song phang ngang da dugc nhieu tac
gia quan tam va giai hoan chinh. Theo Vanhian [68J khi phat ddng khong ddi
I bdi ngudn diem dat tren mat mdi trudng nira khdng gian ddng nhat vd han,
dien trd suat p, dien the' tai diem each ngudn mot khoang r dugc tinh theo
cdng thiic:

U(r)

(1.2)

l7tr

Khi phat ddng khdng ddi / bdi hai dien cue AB dat tren mat mdi trudng
nira khdng gian ddng nha't vd han, dien trd suat p, hieu dien the' giiia hai dien
cue thu MN dugc tinh theo cdng thiic:

At/ =

VI vay:

P.=K

trong dd:

K=

Ip(
ITT

\

1

1

AM

AN

BM

1^
BN

AU
(1.3)
l7t

(1.4)
AM

AN

BM

BN,

dugc ggi la he sd he cue do, phu thudc vao each bd tri he cue do va kich thudc
giiia cac dien cue.
Ddi vdi mdi trudng bat ddng nha't, cac dien trd suat that ciia mdi trudng
khdng the tinh theo cdng thiic dan gian (1.2) nhu trong trudng hgp mdi trudng
ddng nha't. Khi ay, dai lugng p{r) thay doi theo kich thudc r giiia ngudn phat


20

va diem do, dugc tinh theo (1.3), cd thii nguyen dien trd suat phan anh thong
tin chung ve cau tnic va tinh cha't dien cua mdi trudng, ddng thdi phu thudc
vao each bd tri he cue do. Ham p^ (r) dugc ggi la ham dien trd suat bieu kien
ciia mdi trudng. Do thi bieu dien dien trd suat bieu kien Pi^{r) theo kich thudc
he cue r dugc ggi la dudng cong do sau dien trd [15], [75].
Do phan cue bieu kie'n cd mdi quan he vdi dien trd sua't bieu kien cua
mdi trudng phan cue va khdng phan cue. That vay, khi mdi trudng phan cue,
trudng dien ciia chiing bieu dien bang bieu thiic:
E = E,+E^^

(1.5)

do dd hieu dien the' do dugc la:
At/ = A[/o+At/^,

(1.6)

d day EQ , AUQ va Ep^, AC/^^ tuong ling la dien trudng va hieu dien the' do dugc
khi mdi trudng khdng phan cue va mdi trudng cd phan cue.
Tii bieu thiic tinh do phan cue bieu kie'n (1.1), ta cd:
AUpc

AU-AUf,

Chia ca tu: so va mau sd cho dong phat / va nhan vdi he sd he cac K ta
c6:
_

'Ik ~

Pl-Pk
Pi

(1-8)

d day PI va p^ la dien trd suat bieu kie'n ciia mdi trudng khi d trang thai phan
cue va khdng phan cue, tuang ling vdi cac tham sd dien trd suat la p] va p. cd
quan he:


21

vdi / la chi so cua md hinh mdi trudng.
Cdng thiic (1.8) cho phep tinh dudng cong J]^ ly thuyet khi cd cac tham
•

sd cua md hinh mdi trudng.
Hai tham so p^, rj^ la cac tham sd truyen thd'ng da va dang dugc sir
dung pho bie'n trong phuang phap do sau PCKT de dieu tra dia chat, tim kiem
khoang san d Viet Nam tii trudc tdi nay.

1.3

CAC PHl/ONG PHAP PHAN ClTC KICH THICH THl/C)NG DUNG

Khi phat ddng khdng doi tii cac dien cue dat tren mat mdi trudng, thong
tin ve mdi trudng dia dien se phan anh qua phan bd trudng dien tai moi diem
eua mdi trudng. De thu nhan cac thong tin ed ich nay, trong phuang phap do
sau PCKT, ngudi ta phai bd tri cac dien cue phat va dien cue thu mot each
thich hgp tren mat mdi trudng, mdi each bd tri dd tao nen mot he cue do.

Phuang phap do sau PCKT bang ddng khdng ddi la phuang phap the hien
nguyen ly do sau hinh hgc: cang tang kieh thudc giiia cac dien cue phat va cac
dien cue thu thi do sau nghien ciiu cang tang. Phu thudc ddi tugng va nhiem
vu khao sat ma ngudi ta sir dung each bd tri he cue thich hgp de' thu nhan dugc
sd lieu tot nha't ve mdi trudng, do dd cac phuang phap do sau PCKT cd the
duge phan loai theo he cue do.

1.3.1 Mot sd he cue do ca ban:
Ngudi ta phan loai he cue do dua vao each bd tri cac dien cue va kich
thudc giiia cac dien cue phat va thu (ggi la kieh thudc he cue). Cac loai he cue
do khac nhau dugc sir dung phu thudc vao dac diem mdi trudng va dieu kien
do dac, trong dd hai nhdm he cue do ca ban thudng dimg nhat la he cue do 4
cue ddi xiing va he cue do ludng cue.

13.1.1 He cue do bdn cue doi xitng:


22

He cue do 4 cue ddi xiing gdm bdn dien cue tie'p da't phan bd ddi xiing
vdi nhau qua tam do sau, trong dd ddng dien / duge phat qua hai dien cue phat
A, B d ngoai, hieu dien the AU dugc do giiia hai dien cue thu M, N d trong.
Cac dien cue phat va thu dugc bd tri thang hang, ddi xiing vdi nhau qua tam
O, tam nay dugc qui udc la diem do eua he cue (Hinh 1.1).
A

M

\|/

\|/

O

N

•

B
N|/

N1^

+1

-I

Hinh 1.1: He cue do 4 cue ddi xiing

He so ciia he cue do dugc tinh theo cdng thiic:
^^ . .

TTAM.AN

MN
trong dd:

^s ~

AB

^

la kich thudc he cue.

- Trong trudng hgp khoang each MN «

AB, he cue do 4 cue ddi xiing

dugc ggi la he cue Schlumberger, duge sir dung pho bien trong thue te tham
dd dien d nude ta. He sd he cue Schlumberger duge tinh bdi cdng thiic:
^^^'^

=^
MN

(1-11)
^

^

Khi mot cue phat dat ra't xa cac cue thu ( 5 -^ oo), he cue do trd thanh he
cue nira Schlumberger.
- Trong trudng hgp khoang each AM=MN=L/3, vdi L = Z s thi he cue
do 4 cue ddi xiing trd thanh he cue Wenner. He so he cue Wenner dugc tinh
bdi cdng thiic:


23

K(r) = -;rAB

3

(1.12)

1.3.1.2 He cue do luang cue:
He cue do luang cue gdm hai dien cue phat AB va hai dien cue thu MN,
vdi khoang each AB va MN deu rat nhd so vdi kieh thudc he cue r = 0 0 ,
trong dd hai diem O, O tuang ling la tam hai dien cue phat va hai dien cue thu
(Hinh 1.2). Ddng dien / dugc phat qua hai dien cue AB, hieu dien the' AU dugc
do giixa hai dien cue MN.
M

N

Hinh 1.2: He cue do ludng cue,
He cue nay thudng duge sir dung hiru hieu trong phuang phap do mat
cat dien de nghien ciiu sau, nham khac phuc khd khan trong viec bd tri he cue
phat ddng AB vdi kich thudc he cue Idn ciia he cue do 4 cue dd'i xiing; hoac
dugc sir dung trong trudng hgp tim kiem phat hien bat ddng nhat ngang, trong
tim kie'm quang md.
- Khi MN l O O ta ggi la he ludng cue phuang vi. He sd he cue do nay
dugc tinh theo cdng thiic:


24

'~^MN,sm0

^^'^^^

Khi 6 = 90^, he cue do nay duge ggi la he ludng cue xieh dao.
- Khi MN // 0 0 ' ta ggi la he ludng cue xuyen tam. He sd he cue do nay
dugc tinh theo cdng thiic:

'' 'JBMN,COS0

^^'^^"^

Khi 0 = 0^, he cue do nay dugc ggi la he ludng cue true.
1.3.2 Mot vai phuang phap do sau PCKT thong dung
1.3.2.1 Phuang phap do sdu doi xAngphdn cue kich thich
• He cue do 4 cue dd'i xiing Schlumberger chinh la he cue do ciia phuang
phap do sau PCKT dd'i xiing . Phuang phap do sau PCKT ddi xiing td ra thich
hgp de phat hien va du bao hinh dang cac ddi khoang hoa va than quang thau
kinh cd xu hudng nam ngang va dia hinh tren mat khdng qua phiic tap [64].
Tuy thudc vao dieu kien dia cha't - khoang san cu the cua viing va dac diem
ciia ddi tugng nghien ciiu ma lua chon cac bang he sd he cue do sau thich hgp
da quy dinh trong quy pham ky thuat tham dd dien PCKT bang ddng khdng
ddi. Trong trudng hgp can thiet ed the dan day them cac kich thudc he cue
nham phan anh rd han dd'i tugng nghien ciiu [7].
Ket qua do dac ngoai thuc dia la cac dudng cong p^ = f{AB/2)Yk
7]^ = f(AB/2) de phan tich dinh lugng va lap mat cat dia - dien eua lat cat.
• Giai thich dinh lugng tai lieu do sau PCKT ddi xiing cd nghia la phan
tich dinh lugng ddng thdi cac dudng cong 7^, A •
Viec phan tich dinh lugng cac dudng cong do sau PCKT ciing da dugc
nhieu nha Dia vat ly nghien ciiu va xay dung ban chuan (palet) de phan tich
cac dudng cong do sau 77^ cd dang 2 hoac 3 Idp.


25

Ddi vdi mdi trudng nhieu Idp, cac nha Dia vat ly Lien Xd (cii) gdm
Vanhian L.L, Morozova E.M. va Logienxuna L.V. [69] da de nghi phuang
phap tinh toan cac dudng cong rj^ tren may tinh dien tir theo each tinh toan
dudng cong p^ cua Vanhian L.L. tii nam 1961.
Hien nay, d Nga va My..., ngudi ta da de nghi tinh toan cac dudng cong
7^ va p^ dd'i vdi mdi trudng phan Idp, ddng nha't, song phang ngang tren
may vi tinh bang phuang phap lua chon. Ket qua tinh toan se dugc chinh xac
han bang each sir dung cac thong tin tien nghiem cd dugc tii mat cat thuc te'
va ddng thdi han che' dugc anh hudng eua nguyen ly tuang duang.
Viec xir ly cac dudng cong rj^ cd the tien hanh theo cac each sau:
> Cach thii nha't:
Cd th^ tinh rj^ =f{ABI2)

true tiep tir dudng cong p^ =f{AB/2)

theo

cdng thiic (1.8).
Vdi each tinh toan nay, ta cd the xir ly dinh lugng cac dudng cong do
sau PCKT dd'i xiing va lap duge mat cat dia-dien theo hai tham so chinh la do
phan cue 7^ va dien trd sua't p^. Lien ket cac Idp cd dac trung ciia di thudng
quang, cho phep ta du bao duge hinh dang ciia than quang cd trong lat cat dia
chat [2].
> Cach thii hai:
Dudng cong 7^ =f(AB/2)

dugc xa'p xi theo cdng thiic cua Pispareva

N.A. khi mdi trudng phan Idp, ddng nhat song phang ngang, it phan di ve dien

trd suat [71]:
N

N

- % =T.uX/=i

dday: (p, ={\ + H./if

1=1

^{l + Z.f

vdi

Z-

=H./L

trong dd: H- la chieu sau de'n mai Idp thii /; L = OA = AB/2

(1.15)