KHOA HOC VA CONG NGH| MO _ ^ ^
NGHIEN c u t ; XAC D|NH MOT SO
THONG SO SONG DONG DAT CO THC XU^T HI€N or KHU VUC XAY DUNG TAU DIEN NGAM HA NOI
GS.TS. GOSPODARIKOV ALEXANDR Dai hge Quoc gia nguyen liiu, khoang san va Mo-LB Nga NCS. NGUviN CHl T H A N H -Trw&ng D^i hge M6-Dja chit D^i hge Quoc gia nguyen liiu, khoang san va Mo-LB Nga
W k a Ndi dang trong giai doan phat triln mgnh
^ H I ve kinh td, xa hgi. Nhiing he thing cong ' -1 " trinh ngam d l dap ung dugc cie nhu cau
v l giao thdng, van tai, d p thoat nude,... trong khu vyc la rit c i n thilt. Dac biet, he thing tau dien ngam tai Ha Ngi da va dang dugc xay dyng, phat ' trien d l dap ung duge eac yeu eau v l ddi sing va
chinh tri cua Ha Npi.
Do dieu kidn dja ehit kha phue tap, cac dudng
! him trong he thing tau didn ngam d Ha Ngi chu ylu nim nong va trong vung dit ylu. Ha Ndi Igi nam trong vung dugc danh gia la ed kha nang chju tac dpng cua ddng dit nen vide danh gia anh hud'ng cua song ddng dit tdi su on dinh cua cae cdng trinh nglm trong hd thong tau didn nglm tai H i Ngi la hit sue d n thidt. Dilu nay se dam bao eho vide thilt k l , thi cdng va trong qua trinh hogt ddng cua eac dudng ham trong he thdng tau dien nglm Ha Npi dap ung duge cac yeu to vd an toan, kT t i u i t va kinh t l .
1. Co* so-1;^ thuylt
Song ddng d i t la mpt trong nhung ylu td thien tai xay den bit ngd' v i khd dy doan cung nhu tinh toin nhat hidn nay. Tuy theo cac dac tinh eua sdng ddng dat (cuo'ng dp eOa song, khoang each tu tam clian cua sdng den khu vuc giy anh hud'ng dang xet, tinh chat cua mdi trud'ng truyin sdng...) ma cac tac hai cua sdng din cac cdng trinh se cd dp pha huy la nhd hay lan.
2.1. Cac loai song dgng dat hign nay Nhu Chung ta da bilt, sdng ddng dit la nhO'ng dgng sdng nang lugng hinh thinh va lan truyin bai sy va chan cua cae lap dja ting khi xay ra ddng dit.
Sdng dgng dit cd nhilu dgng vdi nhieu each lan tmyen khac nhau. Trong dd, co t h l phan ra hai nhdm lan: sdng khoi (body wave) v i song b l mgt (surfare wave). Sdng khoi cd t h l lan tmydn trong eic tang dit
phia sau, edn sdng b l mat chi cd thl lan tmyen a Idp dit phia tren cua vo qua dit.
2 . 1 1 Sdng khoi
Khi dpng dit xay ra, sdng khoi di chuyin xuyen qua cac lap dit va truyen len mat dit. Sdng khli co t i n so cao han va van tde lan truydn tu t i m chin nhanh han sdng bd mat. Cd hai dang sdng khoi chinh [2]: Sdng P (P Waves); Sdng S (S Waves).
a. Song P (P Waves). P la vidt tat cua "primary"
CO nghTa la sdng sa d p . Day l i sdng dja chan cd van t i c nhanh nhlt, vi t h l nd dugc ghi nhgn sdm nhlt khi cd ddng dit xay ra. Sdng P cd t h l di chuyin qua cac ldp da ran va cae Idp vat chit long trong vd qua dit, nhu Idp mac ma, nudc bien hay nudc nglm. Sdng P tmydn theo phuang dgc, tuang tu nhu sdng am thanh. Sdng P con duge ggi l i sdng nen (compression waves) vi t i c dung dly va keo ldn Idp dit da. Hudng lan tmydn cua sdng P dae trung cho hudng phan tan nang lugng dja chin.
Si*-
H. 1. Hinh dang ctja sdng P [2]
H.2. Hinh dang cua sdng S [2]
b. Song S (S Waves). S la Viet tit cua
"secondary" cd nghTa la sdng thu d p . Van toe lan truyen cua song S nhd han song P, do do song S
CdNG NGHIEP MO, SO 4 - 2 0 1 6
KHOA HOC VA CfiNG NGHE MO dugc ghi nhin sau sdng P, v i vi thd dugc gpi la
sdng thu d p . Sdng S chi ed the lan truyin trong ldp da rin m i khdng t h l di chuyen qua eae Idp vat chit Idng. Chinh tfnh chat nay cua sdng S giup cac nha dja chin khang djnh ldp vo qua dat ed chu'a mac ma. Sdng 8 tmyln theo phuang ngang, tue la vudng goe vai phuang tmyln nang lugng dia chin (eung la phuang P) cua song.
2.12. Sdng bi mat
Dang sdng nay cd tan so thap han sdng khli, ehi di ehuyln trong Idp dit phia tren sat mgt dit.
Mae du dang song nay "din" sau sdng khli, nhung hlu nhu sdng b l mat mdi la nguydn nhan ehinh giy ra phi hoai nha eua trong cac trgn dpng dit.
Khi t i m chin d dd siu Idn, thi cuo'ng do sdng eung nhu nguy ca phi hogi do song nay gay ra mai giam bdt.
a. Sdng Love (Love Waves)
Day la dang sdng diu tidn eiJa sdng bd mat, duge dat ten theo nha toan hpc ngudi Anh A.E.H. Love, l i ngudi diu tidn dd xuit md hinh toan hge cho kilu
song nay vao nam 1911. Sdng Love lan t r u i ^ j phuang ngang va cd t i c dp nhanh nhlt trom sdng be mat, Sdng Love la nguydn nhan c t i Q ^ nen chuyen dgng ngang cOa be mgt vd q u M f i ^
dang cOa sdng Love [:
dang cua song Rayieigh
Bang 1. Tham 'jv nghien cOv [2]
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b. Song Rayieigh (Rayieigh Waves) Day ia dang thu hai cua sdng b l mat, dugc dat theo ten eua Lord Rayieigh, ngudi da dung cdng
thuc toin hpc tidn doin sy t i n tai ci^a dang s ^ nay vio nam 1885. Song Rayieigh cugn trdn,^
theo mat dit, tuang ty nhu sdng nudc cugnj^
CdNG NGHIEP MO, Sfi 4 - 2 0 1 6
KHOA HOC VA CfiNG NGHl MO I m#t'bien. VI the, mat d i t bi di chuyen Idn xuong, I qua lai theo phuang tmyen cua sdng nay. Phan [. ldn su rung lac cam nhan dugc trong cae tran
dgng dat la ti> sdng Rayieigh, vai cudng do Id'n han t i t c i c i e dang sdng dja chin khic.
Trdng cac loai sdng d\a chin k l tren, cd t h l thay doi vdi cac h# thong cdng trinh tren be mat thi logi sdng CO tad dpng chO ylu la logi song b l mat (song Love va sdng Rayieigh), cdn doi vdi he thong cic cdng trinh ngam d- Ha Npi (hiu hit cac cdng trinh ngam nam ndng) thl hai loai sdng P va dgc bidt l i sdng S se la hai logi song giy tie dpng lan nhit.
2.2. D$c tfnh ddng dit tai khu vwc Hd Ngi Nhu da bilt, dd nguy hilm dpng dit bao gom 2 tham s6 ehinh: 1) Vung nguon phat sinh dpng dat vdi eac thdng so dae trung cua nd nhu dp nghieng do thi lap lai, Chan eip cyc dai, dd siu tmng binh cua ^ n g dat va toe dp xay ra ddng dit. 2) Phuang trinh tat dan dao dpng nen theo khoang each. Dya vao cac nghign cuu v i tinh toin, tie gia tong hgp dugc mpt so du lidu vd d p dd nguy hilm v l dpng dit a Ha Ngi ndi ridng v i Vidt Nam ndi chung: cie vOng ngudn phat sinh ddng d i t mgnh cCing cic k i t qua xac dinh dd nghidng do thj lap Igi, Mmax. toe dp xay ra ddng d i t va dd s i u tmng binh dugc trinh biy trdn Bang 1.
Vdi gia thilt tam chin cua trgn ddng dit tdi Ha N6i khoang 50 km, cae edng trinh ngam thude hg thing tau dign nglm H i Ngi dugc xiy dyng d dp sau khoang 20 m, d p dd ddng dat dugc liy bang M=6,5 riehter d l dam bao an toan vdi cac thdng s6 cua mdi trudng dit da ma sdng tmyln qua (Bang 2).
Bang 2. Cdc thuoc tinh cOa mdi trwdng truyen 3 ddt cdngtrinh r
H.S. Bdn dd vung ngudn phdt sinh d&ng^ dat manh d khu vwc Viet Nam [2]
06 t h l thay rang, tgi Ha Ndi cd t h l chju anh hudng CLia sdng ddng dit thupc vung nguin Sdng Hong - Sdng Chay vdi cac dae tinh cua ddng dit cap chin M=5,4 va ehilu s i u tmng binh H=20 m.
2.3. Tfnh todn cac tham s6, d$c tinh cua song dpng ^it tai khu vi/rc dat cac cdng trinh tdu diin n^am Hd Npi
Bdng 3. Xdc dmh van tdc sdng truyen trong cdc mdi trwdng tuxmg wng [4]
ldng ddng dat lan truyen tnsng moi iiLTwiiy ^u Llll duae tinh theo eic cong thuc sau day[1],[3]:
C = IK+K= I E.(1-v) \
^ V p ^p.(1+v).(1-2vv 408.(1-0,35)
1,803.(1-0,35).(1-2.0,35) = 596,34 m/s.
(1)
(2) 408
^2.1,803.(1 + 0,35)
Trong dd: Cp - Van t i c sdng dpc (sdng P); Cs - Van CfiNG NGHIEP MO, 30 4-2016
KHOA HOC VA CONG NGH| MO toe cua song ngang (song S); E - Modun dan hol
cua moi tru-ong truyen song, MPa; p - Ty trong cua vat li§u moi tnrong truyen s6ng, kg/m'; v - He so Possion cua moi truo-ng truy§n song.
Gia toe dinh cua song dong dat du'oc tinh toan va lu'a chon [4]:
ag={0,2.g). (3) Hhu da biSt, trong cac loai song dong dat thl
song dpng dat lo?i S co tac dung manh nhat va chu yeu d§n cac cong trinh nam trong pham vi anh huong cua dia chan. Bo qua tac dung cua song P, ta tinh du'oc v§n t6c song hieu dung cua sdng S la [3], [4]:
C,e=(k/0.8*C,)=(283.24*0.8)=226.6 m/s. (4) Trong do: ks - He so anh hud'ng boi chi§u sau dat cong trinh, vol H=15 m, co k,=0.8;
Van t6c dinh ma song S g§y ra la:
VJ=(0.8*0.2*102/100)=0.ie32m/s. _ (5) TO day, cd the tinh duwc do bien d?ng cat cue dai theo phuong ngang cua cong trinh theo cdng thuc:
T ™ > = ^ ^ = ^ ^ ^ ! ^ - H ' 0 = 0 ' 0 7 2 % . (6)
™"' CsE 226,6 3. Ket qua nghiin cii'u
Tu cac ket qua nghien cuu va tinh toan if tren, CO thS thay rang Ha Noi nSm trong vung co the chju anh hu'O'ng cua dgng dit. Vd'i cac thong s6 nhu van toe song khoi so cap Cp=596.34 m/s, van tdc song ngang thii d p C,=283.34 (m/s), van toe song ngang thu cap hieu dung Cs,=226.6 m/s, van tdc dinh Vs=0.163 (m/s). Do dac dilm cua Ha Ngi la thu dd CLia dat nuo'c, ia trung tim chinh tri va van hoa cua ca nudc, noi tap trung dan cu vd'i mat dp rat Idn, cac cdng trinh nglm tai khu vuc Ha Ngi hlu hit deu nim nong, gin mat d i t nen day la nhCrng cdng trinh cd khi nang chiu anh hu'dng cua sdng dgng d i t rit cao va se rat nguy hiem nlu khong tinh toan chinh xac cac anh hudng nay.
Chmh vl vgy, viec dinh gia va du'a ra cac tinh chit cua sdng dpng d i t cd the xult hien tai khu vuc Ha Ndi la rit can thilt de tu dd cd the van dung cac phu'ong phap tinh toan, thilt k l cho cac cong trinh tai khu vuc Ha Npi va cac cdng trinh nglm x9y dung tgi Ha Ndl. Mpt so phudng phap tinh toan anh hu'dng va kit ciu cho cdng trinh nglm da dudC tac gia dua ra trong tai lieu [2].
4. K i t luan
Hien nay, cd rat nhieu 1^ thuylt de danh gia va tinh toan cac tac ddng cua dja chin tdi su on dinh cua cac cdng trinh ngam (Phuong phap giai tlch cua Wang, Pienzen va nnk, phuong phap HRM, phuong phap sd,...). Tuy nhien, du la cac phudng phap khac nhau t h l nao thl cac thong so co ban
cua sdng ddng d i t gay ra bo'l^dja chan cDng i sir dung lam oac thong so dau vao cho vli quylt c4c bai toan ndl tren. Trdng khudn khd r bao nay, tac gia da sO' dung cac kit qui do danh gia ve khi nang dja chin cd t h l co tai' Ha Ndi, ket hop vol oac ket qua khao sat cua khu vyc Ha Npi d l nghien dru vi tfnh mdt s6 cac thdng so co' biin nhlt cua sdng 6 cd t h l anh hudng tdi khu vyc Hi Ngi, tO' dd iam ngupn dO lipu cho cac nha nghiSn cCru, t va thi cdng cic cong trinh noi chung, coi ngam ndi rieng tgl khu vuc Ha Ndl nham dj an toan va kT thult, kinh te cho cac cdng trinh
TAI LIEU THANI KHAO 1. Do Ngpc Anh, 2014, Lu|n an tien sT. sS 2014ISAL0042, INSA de Lyon.
2. Gospodaiikov Alexandr, Nguyen C h i ; (2016). Nghien cilu, trinh bay mgt s6 phudnj;
tinh toan anh huong cua sdng ddng dit din jE dinh CLia cong trinh nglm tai Ha nOl'. Tuyen ti cdng trinh khoa hge ky niem 50 nam thanh l_
mdn Xay dung Cdng tnnh ngam va Md. Nha xuli Khoa hge Tu nhien va Cong nghd. Ha Ngi. 2016.1
3. KyrysoB, BapraHOB. "BeaonaCHOCib c B03flyuiHoro eo^eiiCTBHn luiaccoBbix E MSAaTBnbCTBO, MocKsa, 2008.
4. Youssef M.A. Hashasha, Jeffrey J. Hooka, I Schmidtb, John l-Chlang Yao. "Seismic i analysis of underground stnjctures". Tunnelld Underground Space Technology, USA, 2001, '
Ngu'di bien tap: V6 Trong HCing Tip khoa: sdng dgng dit, van toe sdn^'^
nglm, tham so song, d p dd dgng d i t Ngay n h | n bai: 26 thing 10 nam 2 0 t | Ngay duySt dang b^i: 12 thing 7 i l M
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CONG NGHIEP MO, SO 4 - 2 0 1 6
