Mune mechaniki yevhu zvinotarwa granična nosivost tla uye dozvoljeno opterećenje tla.
Kugona kutakura kwepakati kwevhu ndiko kunosvikwa panguva iyo kuputsika kwevhu kunoitika. Kuputsika kwevhu kunoitika kana mutoro unoiswa nehwaro pavhu ukadarika kusimba raro rekusheara. Muchiitiko ichocho, pasi pemutoro wehwaro P panobuda nzvimbo dzokupikisa kushoma ACD uye BCE – nzvimbo dzekutsvedza muf. 1, dzinobudisa ivhu parutivi uye panguva imwe chete kusimudzwa kwevhu pamusoro pechitsigiro pedyo nechinhu DG ne EF, nepo hwaro pachahwo huchinyura.
Sl. 1. Kutsemuka kweivhu pasi pekuita kwemutoro wenheyo
Simba rekukwenyana kwevhu rinowedzera nekudzika kwehwaro t, nokuti nekuda kwehuremu hwematanho epamusoro mukana wekumanikidzirwa kudivi unoderera. Saka hwaro hwakadzika hunonetsa kukonzera kutsemuka kwevhu, nepo hwaro husina kudzika huchiva nengozi pakutsemuka. Saizvozvowo, mawero akafara anonetsa kukonzera kutsemuka kwevhu, nokuti nzvimbo dzekutsvedza dziri kudzika.
Mutoro unobvumirwa wevhu ndiwo unogona kubvumidzwa kushanda pavhu nenzira yokuti kusatyoka kwevhu kusaitika pasi pemamiriro akaipisisa anogona kuitika. Mutoro unobvumirwa wevhu unotariswa zvichienderana nesimba rekupedzisira rekutakura kwevhu nekushandisa factor yekuchengeteka. Kukura kwefactor yekuchengeteka kunoenderana nezvinhu zvakawanda, pakati pazvo zvinonyanya kukosha kunyatsojeka kwemaitiro emuviri evhu, mukana wekuchinja kwemaitiro ezvinhu ekupikisa kwemukati kwevhu kunyanya cohesion, ukoshi hwayo hunogona kuchinja zvakanyanya pasi pesimba remvura muvhu, pamwe nepesvedzero yezvimwe zvinhu zvinogona kuitika, zvakaita semamiriro emutoro (mukana wemutoro unouya pakarepo uye une simba), kudzika kwekuchengetera hwaro, uye upamhi hwechitsiko chehwaro.
Kukwanisa kutakura kwevhu kunogona kutsanangurwa kubva pakutsemuka kwevhu, kunopa kukwanisa kwekupedzisira kutakura. Nekukwanisa kwekupedzisira kutakura kwevhu kunorehwa huwandu hwemutoro hunokonzera kutsemuka. Pane nzira mbiri dzekutsanangura kukwanisa kwekupedzisira kutakura zvichibva pakutsemuka kwevhu, dzinoti mhinduro yemasvomhu uye mutoro wekuedzwa.
Mhinduro yemasvomhu
Vazhinji vesainzi vakaedza kuwana mhinduro yemasvomhu yekutsanangura kugona kwekupedzisira kwekutakura kwevhu, zvichienderana nekuziva zvinhu zvinokanganisa uye pasi pemafungiro akasiyana emamiriro ekutsemuka. Zvinhu zvinokanganisa ndezvimiro zvepanyama zvevhu, zvinotariswa kuburikidza nemiedzo yemurabhoritari pamasampuli evhu asina kuvhiringidzwa, mamiriro emvura yepasi pevhu, kudzika kwefundation, ukuru nechimiro chenzvimbo iri kutakurwa, pamwe nenzira yekutakura, kureva mutoro wakaenzana kana usina kuenzana, wepakati kana wakatsaukira parutivi. Mafungiro pamusoro pemamiriro ekutsemuka anovakirwa padzidziso yeplastiki uye dzidziso yeelastiki. Zvisinei, nzira dzemazuva ano dzekutsanangura kugona kwekutakura kwevhu dzinovakirwa padzidziso yeplastiki, iyo inosanganiswa nemamwe mafungiro akarerutswa.
Pano tichataura nezvenzira dzinoverengeka dzinozivikanwa dzekuverenga dzinoshandiswa kuona simba rekutakura rekupedzisira, kureva mutoro unobvumirwa wevhu.
Chimiro chaPrandtl-Caquota
Kana tsoka yehwaro AB yakaiswa pakadzika t pasi pechiso chenyika, pakudzika uku pane kudzvanywa kwekubatana nekuda kwemutoro wehwaro uye kudzvanywa kweparutivi p=γt nekuda kwehuremu hwevhu riri pamusoro pehuwandu hwetsoka yehwaro kusvika pachiso chenyika (sl. 2).
Pasi pesimba rakananga rehuremu hwehwaro, panguva yekudarika simba rekutakura rinoibva revhu, panobuda nzvimbo dzakajeka dzokutsvedza AC ne BC, dzinoita kona α = 45° + ϕ/2 nepamusoro pakatakurwa. Nzvimbo idzi dzinotsvedza dzinoumba prism yeivhu inoshanda ABC.
Muf. 2. Mafuremu ekutsvedza ane chimiro chelogarithmic spiral pasi pemutoro wepakati wechitsiko chehwaro maererano na Prandtl-Caquot
Pasi pesimba rekudzvanywa kweprizim reivhu rinoshanda, maprizim eivhu epadivi asingaite ADD1 ne BEE1, ayo anotsvaga kusundidzirwa kumusoro pamusoro pemapfundo ekutsvedza DD1 ne EE1, pakona 45°-ϕ/2 nehorizoni. Pakati pechikamu chekudzvanywa kweivhu chinoshanda neisingashande pane chikamu chekucheka radial ACD kana BCE, umo kana kuenzana kwemuganho kwadarika kutsvedza kunoitika pamusoro pemapfundo akakombama ekutsvedza. Résal akaverenga kuti nzvimbo dzekutsvedza muchikamu chekucheka radial dzine chimiro chelogarithmic spiral ine pole pa A kana B, ine equation r=r0 eπ tg_ϕ_
Pakutsanangura mutoro wemuganhu wevhu, fungidziro dzinotevera dzakaitwa:
- kuti hwaro hwakatsetseka, kureva kuti kukweshera pakati petsoka yehwaro nepasi hakufungidzirwi;
- kuti simba rekucheresa kwevhu pamwe pematanda D1M uye E1N haripo, kureva kuti haritorwi nehanya;
- kuti huremu hwevhu paine pasi pehwaro γ=0, kureva kuti pesvedzero yehuremu hwevhu pasi pechitsiko chehwaro inofuratirwa, munzvimbo yekuenzana kwepurasitiki.
Maitiro aPrandtl-Caquot anoti:
Kukwanisa kwevhu kutakura mutoro wemuganhu kuri
Kana tikaisa:
muganhu wekutakura wevhu rakasungwa ndi qf = γtm + cm1.
Kune zviyero zvakasiyana zvekona yekukweshera kwemukati kwevhu, zviyero zve m uye m1 zvakapiwa mutafura 1.
Tabl. 1. Maitiro emakoefficient m na m__1 pamakona akasiyana ekukweshera kwemukati kwevhu
Mutoro unobvumirwa wevhu ndi qa = pdozv = qf/F apo F iri factor yekuchengeteka. Kuti shandiswe fomura yePrandtl-Caquot, inogamuchirwa F = 4, saka qa = qf/4.
Terzaghi formula
Terzaghi akapa fomura yechikamu-chekufungidzira yekuverenga kugona kutakura kwekupedzisira kwevhu pasi pemutoro wechimiro chebhandi, square uye dhisiki rakatenderera. Akatarisa hwaro hwakavakirirwa pakadzika Df pasi pechiso chenzvimbo, hupamhi B (fig. 3), uye akagamuchira kuti pane kukweshera pakati pehwaro AB nevhu, kunopikisa kusundwa kwevhu parutivi uye kuti nzvimbo dzinotsvedza AB ne BC dzinoumba kona yekukweshera kwemukati nepamusoro pamutoro.
Sl. 3. Kutakura kwekupedzisira kwevhu maererano naTerzaghi
Nekuda kweizvozvo, ivhu riri mukiya revhu ABC, riri pakati pechigadziko AB nemapfundo anotsvedza AC ne BC rinoramba riri muhurongwa hwekuenzana kweelastic uye rinobata sechikamu chechigadziko. Prizma ABC haigoni kusundidzirwa kusvika panguva iyo kumanikidzwa kumativi ayo AC ne BC kusava kwakaenzana nekumanikidzwa kwepasive kwevhu kwemaprizima emativi, zvinoreva kuti kana mamiriro ekupedzisira ekuenzana akapfuura, kumanikidzwa kunobuda kwevhu q kunoshanda pasi pechikona ϕ kune normal yepamusoro inotsvedza, kureva munzira yakatwasuka (muf. 3). Sezvo pasi pekuita kwemutoro kiyi ichifamba yakatwasuka ichidzika, dambudziko rekuenzana muvhu rinoderedzwa pakutsanangura kumanikidzwa kwepasive kwevhu. Zvisinei, sezvo kuverenga chaiko kwekugona kutakura kwevhu nenzira iyi kuri kunetsa, Terzaghi akapa mhinduro yakarerutswa. Fomura yaTerzaghi yekuverenga kugona kwekupedzisira kwevhu _q_f inoti
- Kune nheyo yetsoka yerudzi rwebhande
qf = cNc + γ1 DfNq + 0,5 γ2 BNγ
apo c iri kubatana kwevhu
γ1 huremu hwevhu pamusoro pechigadziko chefoundation
Df kudzika kwekuvambwa pasi pechiso chenzvimbo kusvika pasi penheyo
γ2 huremu hwevhoriyamu yevhu riri pasi pechitsiko chenheyo
B upamhi hwenheyo yetsoka.
Nc, Nq, Nγ ndiwo ma factor ekukwanisa kutakura mutoro, anotsamira pakona yekukweshera kwemukati kwevhu; maitiro anotsanangura kukosha kwechinhu ichi anopiwa nemafomura anotevera:
Nq ndiyo factor inobva kuhuremu hwerukoko rwevhu rweparutivi kusvika pakudzika kwefoundation: Nq = tg2 (45° + ϕ/2) eπ tg_ϕ_
Nc ndicho chinhu chinokonzerwa nekohesheni: Nc = (Nq – 1) ctg_ϕ_
Nγ ndicho chinhu chinobva pachiremba chayo choga chehuremu hwepasi wedge riri pasi petsoka yefoundation, kana kuti pasi pehupamhi hwetsoka AB. Kukosha kwechinhu ichi kunokurudzirwa naBrinch Hansen sekwokufungidzira: Nγ ≈ 1,8 (Nq – 1) tg_ϕ_
Sl. 4. Kugoverwa kwekumanikidzwa kunogamuchirwa nevhu kana hwaro hwacho hwakatakurwa zvakasendama pakati
Nekuda kwekusiyana kudiki kwehuremu hwevhu pahuwandu, kazhinji zvinogamuchirwa γ1= γ2= γ. Maererano neequation iri pamusoro, kukwanisa kutakura kwevhu kunoenderana (muf. 4) ne: kubatana kwevhu rekutangira c, mutoro wevhu pedyo nenheyo _γ1 D_F, uremu hwayo hwevhu riri mupombi inotsvedza inoshanda, ine upamhi B.
Asi apo kugoverwa kwekushushikana kunogamuchirwa nevhu nekuda kwekushanda kwekubatana c uye kudzika kwekudzika Df kwakafanana pahupamhi hwese, kureva kuti, kuri rectangular, zvakadaro kugoverwa kwekushushikana kunogamuchirwa nevhu nekuda kwekukanganisa kwehupamhi B kuri triangular, kureva kuti, kushushikana kukuru kunogamuchirwa pakati penheyo, uye kunoderera kuenda kumicheto apo kunenge kuri zero.
Muf. 5. Dhayagiramu yefactor yekutakura zvichienderana neangero yekukweshera kwemukati kwevhu maererano naTerzaghi
Pamusoro pemakona akasiyana kubva pa0 kusvika ku40°, Terzaghi akagadzira madhayagiramu ezvinhu zvinotakura mutoro (fig. 5). Zvisinei, zvinhu zvinotakura mutoro Nc, Nq uye Nγ (mitsetse yakazara pafig. 5) zvinogona kutorwa chete kana ivhu rakasimba uye rakatsikirirwa zvakanaka. Kana ivhu rakasununguka kana richinyanya kutsikiririka, ipapo zvinofanira kutorwa zvinhu zvinotakura mutoro N’c, N’q uye N’γ (mitsetse yakaputsika pafig. 5), zvinopa 2/3 zviyero zvekupikisa kukweshera. Pamusoro peizvozvo, pachiitiko ichi zvinofanira kutorwa 2/3 zviyero zvekubatana c zvakawanikwa murabhoritari, zvekuti pachiitiko ichocho tine qf = 2/3 cN’c + γ1 DfN’q + 0,5 γ2 BN’γ.
2. Pasi pehwaro hwemhando yeretangirangiri
qf = 2/3 (1+0,3 B/L) cN’c + γ1 DfN’q + 0,5 γ2 BN’γ apo L kureba kwechitsitsinho chenheyo
3. Kune hwaro hwevhu hwemhando yesikweya
qf = 2/3 1,3 cN’c + γ1 DfN’q + 0,4 γ2 BN’γ
4. Panzvimbo yekuvakira hwaro hwakatenderera
qf = 2/3 1,3 cN’c + γ1 DfN’q + 0,6 γ2 rN’γ apo r iri radius yetsoka yevhu.
Pakaverengwa mutoro unobvumirwa wevhu, chinogamuchirwa chinhu chekuchengeteka F: qa = qf/F. Kukosha kwechinhu chekuchengeteka kunobva pa 2 kusvika pa 3 maererano nemamiriro evhu uye mutoro.
Kushandiswa kwemafomura emasvomhu
Kushandiswa kwemafomura emasvomhu ekusarudza mutoro unobvumirwa pavhu kunoda kuziva maitiro egeomechanics evhu, kureva kubatana uye kukweshera kwemukati pakudzika kwenheyo pamwe nehuremu hwevhoriyamu yevhu riri pamusoro nepasi pechitsiko chenheyo. Kana ivhu renheyo riri pasi peyero yemvura yepasi, unofanira kufungawo nezvekusimudzwa nemvura pakusarudza huremu hwevhoriyamu yevhu.
Pamutoro mukuru wevhu uye pazvivako zvikuru, kana kukosha kwakawanikwa kwemutoro unobvumirwa wevhu kuchishandiswa zvizere zvichienderana nemaitiro emasvomhu, kuverengwa kwekugona kutakura mutoro kwevhu kunofanira kuperekedzwa nekuverengwa kwekugadzikana. Kugona kutakura mutoro kwevhu kunogamuchirwa chete kana kuverengwa kwekugadzikana kwakapa kugadzikana kushoma kupfuura kunobvumirwa parudzi irwo rwechivako. Kana kuverengwa kwapa kugadzikana kukuru kupfuura kunobvumirwa, kukosha kwakaverengwa kwemutoro unobvumirwa wevhu kuburikidza nemafomura ekuverenga hakugamuchirwi, asi nzira yekuvandudza nheyo inofanira kuchinjwa kuitira kuti kuwanikwe kugadzikana kushoma, mukati memiganhu yekugadzikana kunobvumirwa kune chimiro chacho chechivako.
Muf. 6. Kudzika kunoshanda kwekuvaka D__f
Mumafomura emasvomhu ekutsvaga huwandu hwekupedzisira hwekutakura mutoro hweivhu, kukweshana kwekunze kwehwaro hakuna kuverengerwa, kunobatsirawo sesimba rinopikisa pakuita kwemutoro, kana hwaro huchibata ivhu zvakasimba kumativi. Kupikisa kwekukweshana kwekunze hakufaniri kuverengerwa, nokuti kukweshana kwechokwadi kwekunze kunongowanikwa pamapango anoroverwa muvhu, nepo pamitsigiro yehwaro kukweshana kwekunze kuri kushoma, sezvo tsigiro idzi dzichiitwa mumakomba akacherwa kare.
Kushandiswa kwemafomura emasvomhu asingatarisi chimiro chehwaro kunopa mhedzisiro iri pedyo zvikuru kune hwaro hwemhando yeribhoni, kureva kana hurefu hwehwaro hwakakura kanopfuura kaviri kupfuura upamhi hwahwo. Nekuedza kwakaonekwa kuti, pamatsoka ehwaro ane chimiro chechikwere kana denderedzwa, kuputsika kunoitika pamutoro unoganhurira uri 10-30% mukuru kupfuura wakaverengwa nemafomura emasvomhu. Matsoka ane chimiro chetriangiro anopa simba rekutakura shoma kupfuura reribhoni, uye simba diki zvikuru rinopiwa netsoka dzemhando yeringi kana dzisina kuzadzwa.
Kudzika kwefundasi Df kunoverengwa sekudzika kunobudirira kwefundasi kubva pasi pechigadziko chefundasi kusvika pasi pefundasi (Muf. 6). Pakuchengetedzwa kuri pasi pezvivakwa zvepasi, kudzika kunobudirira kwefundasi Df kunosiyana nekudzika kwefundasi uye zvakare kubva pamusoro penyika. Muzviitiko zvakadaro, pakuverenga mutoro wemuganhu uye unotenderwa wevhu, Df inofanira kugara ichishandiswa, nokuti pamusoro pevhu rechigadziko chefundasi pane mweya usingapikisani nekusundidzirwa kwevhu parutivi pasi pesimba remutoro wefundasi P.