Bang 1-2. Bang 1-2. Phan loai mire do phong hoa ciia da
52. Dac diem va tinh chat cua timg nhom
1 Du cdng gom cac loai da goc (da me) con tuoi nidi (da macma, da bien chat va da tran tfch gfin ket chiic). Chiing duoc cau thanh bdi su lien ket ket tinh ran chac giua cac
hat khoang vat, sir lien ket nay sinh ra bdi: a). Vat chat gan ket diroc ket tinh d trang thai dung dich nguoi lanh tao thanh, vo co chieu day khoang 10 3f.im d noi tiep xuc cua cac hat, b). Chat gan ket chi lap mot phfin hay toan bo khoang trong giua cac hat. Quy luat bien dang cua da gan giong quy luat bien dang cua vat ran lien tuc. Bien dang dan hoi xay ra d ngay giai doan dau dirdi tac dung cua ngoai luc, bien dang tang len theo su tang len cua tai trong va thdi gian gia tai. Ddi vdi ap lire tuc thdi tin nd phan Ung nhu vat ran dan hoi, gion. Cac da nay khong cd tmh tham nude, tfnh ngam nude rat yeu co the bo qua. Cac loai da cung cd kha nang chiu tai rat tot, d trang thai bao hoa nude do ben chong nen dat > 50kG/cm2, do bdn va do dan hoi rat cao, thirc te khong cd tfnh nen lun va tfnh chiu nude cao. Toe do truydn song dat 2000 ~ 7000m/s. Thfch hop cho moi loai tai trong. Tuy theo nguon goc, dieu kien thanh tao va thanh phan khoang vat ma tfnh chat xay dung khac nhau:
Cac da macma (granit, sienit, diorit, diaba, gabro, foocfiarit, pericfotit, dunit, trachit.
liparit, rionit, andezit, bazan, daxit,...) co tfnh chiu nude cao, kho bi hoa tan; cd cudng do va tfnh on dinh rat ldn; co tfnh dang hudng ve tfnh chat co ly. Nhieu loai cd do rang nhd (n< l%), cudng do chong nen a n = 1000-5000kG/cnr, do ben chong keo a K = (2~4%)an, lie so do be chac (he sd ma sat bieu kien theo Protodiakonop) f > 10.
Cac da bien chat (da hoa, quaczit, pylit, da sung, gonai, xkacno, micmatit, greizen va da phien ket tinh...) co tfnh di hirdng (do cau tao va khe nut), tfnh hoa mem bien ddi d muc do trung binh, de bi phong hoa do tfnh phan phic'n. Chung cd: a n = 750 ~ 1800kG/cnr, a K = (2 ~ 8% )a n vaf> 5 .
Cac da tram tfch thuoc loai da ci'mg (da voi, dolomit,...) cd tfnh hoa tan yeu (theo thanh phan cua nude), cudng do va dd on dinh trung binh. Chung cd: crn = 200 ~ 1500kG/cnr, c K = (4 ~ 10%)a„ va f > 4.
2. Da nifa cidig gom cac loai da ciing da bi bien doi ft nhidu (khe nut phat trien do tac dung phong hoa nhu: da granit, bazan, gnai, phien ket tinh, da cacbonat bi cacsto hoa,...), chiing co cudng do, do on dinh thap tuy theo do nut ne va tfnh tham nirdc ldn.
hoac cac loai da chua he bi phong hoa. Do bdn a n < 50kG/cnr, a k s 0, f = 1,5 ~ 2,0 va k = 10 ~ 20m/ng.d.
Cac cla chua bi phong hoa nhu: phien set, acgilit, macno, bot ket va cat ket co tfnh truong nd, tfnh hoa mem cao va co tfnh di hudng. Chung co a n < 350 ~ 500kG/cnr, a K = (2 ~ 17%)an v a f= 2 ~ 3 .
Cac da tram tfch gan ket nhu: cuoi ket, cat ket, thuy tinh niii lira, cuoi ket chua vdi, dam ket va set ket,... Cudng do va tfnh chat bien dang cua chung tuy thuoc va kidu va loai ximang gan ket. do cung cua manh vun. Loai bdn cao: a n * lOOOkG/cnr va f = 8 ~ 10;
loai bdn vua co: a n ~ 850kG/cm2 va f = 6 ~ 8; loai bdn thap cd tfnh hoa mem cao thi ct„ < 250 ~ 300kG/cnr va f = 2 ~ 3.
Nhin cluing cac loai da ciing dirge sir dung tot cho mgi loai cong trinh va san xuat vat lieu da op hit trang tri co gia tri thirong pham cao. Cac loai da nura ciing dugc dung lam vat lieu xay dung (dap ndn, lam duang,...) va lam ndn kha tot cho cac cong trinh dan dung va cong nghiep, can chii y chong trugt mai doc va chong tham mat nude cho ho chua nudc.
5.2.2. D at phan tan tho (dat loai cat)
Dat co nguon goc tram tich (tan tich, sudn tich, lu tich, bdi tich va phong tich,...) thanh phan pho bien la da khoang (acko, xnauvac, manh vun da khoang), cd khi don khoang (chu yeu trong tang bdi tich: thach anh, mica, olivin, pyroxen, fenspat, ampybon,...), do la cac khoang cd tinh hoa tan thap. Thanh phan hat thirdng khong dong nhat, chiing khac nhau v<§ kich thudc, do trdn nhan tuy theo thanh phan khoang, qua trinh hinh thanh va bien doi cua mdi trudng. Cac hat tiep xiic vdi nhau mot cach don thiuin va hau nhu khong cd lire dinh ket giua cac hat cho nen, do on dinh ciia khoi dat phan tan tho chii yeu la do masat giua cac hat. Dat cd tinh dam chat, dac biet khi o' trang thai tao hoa nudc va dudi tac dung ciia tai trgng dong. Do rdng dat n = 30 ~ 35%, he sd f = 0.5 ~ 1.5 tuy theo cd hat. Chiing cd tinh tham nudc tot, giu nudc kern. Tdc do truydn song dan hdi khoang 800 ~ 1 lOOm/s.
Do bCn chong cat do luc ma sat (lire ma sat phu thuoc vao kfch thudc, do dong ddu, do tron nhan, thanh phan khoang cua hat, vao trang thai am va do chat ket cau cua khoi cat. Dac trung tinh bien dang cua ehung la: tri sd bien dang thu'dng nhd nen dudng cong nen lun doc thoai va nhanh dat trang thai on dinh. Cd the chia ehung thanh hai loai: cuoi soi vt eat.
1. Cuoi soi. Loai nay cd tinh thain nudc rat ldn K = 50 ~ 200m/ng.d. Goc doc tu nhien dat a= 36°~ 45°. Chiing hau nhu khong nen lun khi khong cd lire rung dong. Goc masat trong cp 35°~ 45° va f = 1,0 ~ 1,5. Cuoi soi thirdng dugc dung lam vat lieu xay dimg.
2. Cac loai cat. Gdm cd hat tho d = 2 - 1mm, hat to d = 1 - 0,5mm, hat trung d = 0,5 - 0,25mm, hat nhd d = 0,25 - 0,1mm va hat bui d = 0,1 - 0,01mm. Cac hat pho bien la don khoang, tinh hoa tan rat thap, hau nhu khong cd nirdc lien ket vat ly cho nen, ehung khong cd tinh deo va tinh truong no,...Do on dinh mai doc dat a = 25°~ 35°; goc ma sat trong9 = 5°~ 35° va f = 0,3 ~ 0,8. Chung cd tfnh tham nudc kha tot K = I - 75m/ng.d.
N6n cat bien dang nhieu hay it tuy theo do chat ket cau va loai tai trgng tac dung. Chung tlurdrg dugc dung lam vat lieu xay dung, vat lieu lgc nudc, san xuat thuy tinh,...
5.1.3. D at phan tan min (dat loai set, dat dinh)
D;y la nhom dat cd chua hat phan tan min (hat cd d < 0,002mm trong cat pha la 3 ~ K % , set pha: 10 ~ 30% va set: > 30%), ehung chua nhieu khoang vat set thu sinh dang tam vay rat nhd. Ham lugng hat phan tan min (khoang set) cd tinh ua nudc cho
nen, dat thuong co nirac lien ket vat ly va the hien tinh deo, tinh truang na, tinh co ngot, tinh tan ra va tfnh dmh bam,...Tinh tham nuac rat kern nhung gifr nuac tot. Dat loai set co tmh bien dang (tmh nen lun) lan va dien ra cham chap tuy theo trang thai am cua dat va toe do gia tai; Do ben chong c&t do luc dinh va goc ma sat trong chi phoi. Tdc do truyen song dat 130 ~ 1700m/s. Dac diem cua tirng loai nhu sau:
1. Dat cat pha. Dat co chi so deo: 1 < Id < 7%, tmh deo thap, tmh gifr nuac yeu, do am phan tir Ion nhat W iTLN = 3 ~ 14%, co hien tugng mao dSn va cluing co tmh tham niroc binh thuong la K = 0,5 - 2,0m/ng.d. Dat co lire dinh C = 0,02 - 0,08kG/cm2 va cp = 18°- 25°.
2. Dat set pha. Dat co chi sd deo: 7 < Id < 17%, tinh deo trung binh, tfnh gifr nirdc kha tot, do am phan tir ldn nhat W jrrLN =11- 24%, cd hien tuong mao dfm va tmh tham nudc yeu K = 0,1 m/ng.d. Dat cd C = 0,02- 0,1 kG/cm2 va cp = 14°- 18°.
3. Dat set. Dat cd chi sd deo I d > 17%, tfnh deo cao, the hien hang loat tmh chat ciia he keo khi tac dung vdi nudc. Dat cd tinh giira nudc rat tot, cd W irrLN = 24- 35%, ehung hau nhu khong tham nudc K ^ 0,001 m/ng.d., chieu cao mao dan cd the dat H md = 10 - 12m. Dat cd C = 0,05 - 0,6kG/cnr va cp = 10° - 18° tuy thuoc trang thai am va do chat cua dat.
Dat loai set diroc sir dung rat rong rai trong ddi song va trong ky thuat, dac biet la dat set: san xuat do gom, vat lieu xay clung, d6 gia dung, cong nghiep my pham, san xuat giay,...
5.2.4. Dcit co thanh phan dac biet
Loai dat nay thirdng chua mot luong hiru co nhat djnh (bun, than bun hien dai, bun cat, bun cat pha, biin set pha, bun set va tho nlurdng, xem them muc 2.4 chuong 2). Chat hiru co cd the da, dang va chua bi phan huy lam cho dat cd cac tmh chat va trang thai dac biet. Chiing cd tmh bien dang xiic bien, tri sd bien dang rat ldn va keo dai theo thdi gian. Dat cd kha nang chiu tai rat kem, do ben chong cdt rat thap: C ~ 0 - 0,05kG/cnr, cp = 4 ° ~ 7° va f = 0,3. Chung thuoc loai dat yeu ( R 1C < l,0kG/cnr), khi sir dung ehung lam n&n cong trinh can cd giai phap cai tao hoac gia cd thich hop hoac phai dung giai phap mong sau. Dat cd tfnh tham nudc kem K < 0,01- 0,09m/ng.d., do am rat cao W ln > 50%, he sd rdng e = 1,5-6. Dat thirdng d trang thai deo chay hoac chay nen hau nhu khong lay dugc mSu nguyen dang. Khi sir dung lam vat lieu dat nung, san pham xop nhe va chat lugng kem.
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