Ukuba kumhlaba odibeneyo sisika isilinda size siyibeke phantsi kwesenzo soxinzelelo oluthe nkqo P (umz. 1), kwisilinda kuya kuvela uxinzelelo olutsha, olo luxinzelelo oluthe nkqo σ kunye noxinzelelo oluthe tye lokucheba. Ukuba uxinzelelo P silunyusa ngokuthe ngcembe, emva kwexesha elithile kuya kuvela iintanda ezithambekileyo kwisilinda, yaye kwangoko emva koko kuya kwenzeka ukuphuka kwesilinda. Ngexesha lokuphuka isilinda sichetywe phantsi kwesenzo soxinzelelo P kwaye ngokuhambelana nomphezulu wokucheba onokumelana okuncinci N-N.
Umz. 1. Isiphumo soxinzelelo kwisakhelo esikhutshwe emhlabeni onodibaniso
Ukuxhathisa komhlaba okunikezwe yisilinda ngokuchasene nesenzo samandla P ngexesha lokophuka kubizwa ngokuba kukuxhathisa kokusikwa komhlaba, yaye i-engile α yokuthambeka komhlaba onokuxhathisa okuncinane xa ithelekiswa ne-horizontal ibizwa ngokuba yi engile yomhlaba wokuxhathisa okuncinane kokusikwa komhlaba.
Ukuchasana nokusika komhlaba odityanisiweyo kubandakanya izakhi ezimbini ezisisiseko: ukukhuhlana kwangaphakathi phakathi kwamasuntswana aqinileyo kunye nokudibana okudibanisa amasuntswana aqinileyo. Amandla okusika omhlaba amkelwa njengalingana noxinzelelo oluphezulu lokusika ngexesha lokuphuka yaye abonakaliswa ngolu lwalamano
τf = c + σ tg_φ_
apho: τf amandla okusika omhlaba [kp/cm2],
c ukuhambelana komhlaba [kp/cm3],
σ uxinzelelo oluqhelekileyo lomhlaba [kp/cm3],
φ ikona yokukhuhlana kwangaphakathi komhlaba.
Ifomula engentla yanikwa ngumFrentshi uCoulomb ngo 1785. ngokwezo nyaka. Ngokwale fomula, kumhlaba onikiweyo ukudityaniswa c kuhlala kungatshintshi yaye kungenziwanga luxinzelelo oluqhelekileyo, logama ukuxhathisa kokungqubana σ tg_ϕ_ kulingana ngokuthe ngqo noxinzelelo σ. Enyanisweni, ukudityaniswa e akusoloko kuhlala kungatshintshi kumhlaba onikiweyo, koko nako kuxhomekeke ngandlel’ ithile kuxinzelelo oluqhelekileyo σ, kuba phantsi kwale ngxinelelo ubukhulu befilimu yamanzi ejikeleze amasuntswana aqinileyo buyancipha yaye ngaloo ndlela ukudityaniswa kuyanda. Ifomula kaCoulomb isebenza kwimihlaba evuzayo, apho phantsi kwesenzo soxinzelelo oluqhelekileyo amanzi aphuma kwiipore ngaphandle kokuxhathisa, nto leyo eyenzeka kumhlaba onograbile nakwomhlaba oyisanti, kodwa ayisiyiyo imeko yomhlaba obophelelekileyo, ongavuzeki kakuhle, ngenxa yoko amanzi asezimbotsheni aphuma nzima aze asale njengamanzi epore axinzelelweyo phantsi kwesenzo somthwalo P.
Iingcinezelo ezisebenzayo nezangaphakathi emhlabeni
Umz. 2. Uxinzelelo olusebenzayo nolungekho mbindini emhlabeni
Ukuba sibeka isampuli yomhlaba ezantsi kwesitya, umzekelo isanti eyomileyo, size siyilayishe ngesisindo esithile, umzekelo amaqhekeza elothe anobunzima W, wonke umthwalo walo bunzima uya kuthwalwa ngamasuntswana aqinileyo omhlaba. Uxinzelelo oluthile phezu komphezulu wesampuli p0 = W/A nge-kp/cm3, apho A ingumhlaba wendawo enqumlayo yesampuli, luya kubangela ukuhlala phantsi kwesampuli, oko kukuthi ukuncipha kwe-porosity yayo, kodwa luya kubangela neenguqu kwezinye iimpawu zomzimba zayo ezifana nokwanda kwamandla okucheba, ukwanda kwemodyuli yokucinezelwa, kunye nezinye. Uxinzelelo olukhoyo kwiindawo zokudibana phakathi kwamasuntswana lubizwa ngokuba luthotho olusebenzayo okanye uxinzelelo phakathi kweenkozo σ’. Xa sele kufezekisiwe ukuhlanganiswa, oko kukuthi xa isampuli iyekile ukuhlala phantsi komthwalo p0, uxinzelelo olusebenzayo lulingana noxinzelelo olupheleleyo oluthile olukhoyo kubunzulu apho umhlaba ujongiwe. Kule meko kubunzulu, phantsi komphezulu wesampuli kumzobo sl. 2 σ’ = W/A + hzγ apho γ bubunzima bomthamo wesampuli.
Noko ke ukuba isampulu esityeni endaweni yokuyithwalisa ngemisesane ekhokelayo siyithwalisa ngamanzi ukuya kubude h, ngeloo ndlela agcwalise zonke ii-pores zesampulu, uxinzelelo lwekholamu yamanzi ngaphezu kwesampulu hγw, apho γw bubunzima bomthamo wamanzi, aluyi kubangela ukuhla kwesampulu nokuncipha kwe-porosity yayo, kwaye aluyi kwandisa amandla ayo okucheba kunye nemodyuli yokucinezeleka. Ngenxa yoko, uxinzelelo lwe-hydrostatic hγw lubizwa ngokuba luxinzelelo olungathathi hlangothi. Uxinzelelo olungathathi hlangothi, olubhalwa ngo u, lusasazwa kwisampulu kuzo zonke iindlela ngamandla alinganayo. Olu xinzelelo aluyi kubangela ukwanda kwamandla okucheba, kuba amanzi ngokwawo akanamandla okucheba.
Ngoko ke, uxinzelelo olusebenzayo σ’ ludluliselwa ngemigangatho yokudibana phakathi kweenxalenye eziqinileyo zomhlaba, logama uxinzelelo olungathathi hlangothi u ludluliselwa ngamanzi akwiipore. Ukuba inxalenye esezantsi yesitya igcwaliswe ngesampuli yomhlaba egcwele amanzi enobunzima bomthamo γz, kwaye ngaphezu komphezulu wesampuli ukuya kwinqanaba N isitya sigcwele ngamanzi anobunzima bomthamo γw, ngoko uxinzelelo olupheleleyo σ kuyo nayiphi na indawo yesampuli luya kuba σ = σ’ + u.
Kunzulu lwe hz, phantsi komphezulu wesampuli, uxinzelelo olusebenzayo luya kuba σ = σ’ - u
apho σ = h γw + h γz
u = (h + hz) γw.
Ngoko ke kuya kuba σ’ = hz γ’
γ’ bubunzima bomthamo bomhlaba ontywiliselweyo emanzini.
Umlinganiselo jikelele wamandla okucheba omhlaba
Ukuba umhlaba odityanisiweyo siwuthwalisa ngomthwalo P, lo mthwalo uya kubangela ukuzinza komhlaba kwaye kuqala phantsi kwawo kuya kukhutshwa umoya kwiipore, ukuze kungekudala kwiipore kuhlale kuphela amanzi. Kuba ngenxa yokungangeni kwamanzi okuncinci komhlaba odityanisiweyo amanzi akanakukhutshwa kwangoko, ahlala njengamanzi axinzelelweyo kwiipore kwaye ekuqaleni athatha wonke umthwalo wangaphandle P. Ngexesha elilandelayo, phantsi kwesenzo somthwalo P, amanzi aqala ukukhutshwa kwiipore kwaye kubakho ukusondela kweziqwenga eziqinileyo, ezithi ngoku zamkele inxalenye yomthwalo P. Emva koko sinayo τf =c + (σ - u) tg_ϕ,_ apho σ luxinzelelo olupheleleyo olusuka kumthwalo P, u luxinzelelo lwamanzi eepore.
Uxinzelelo lwamanzi emingxunyeni lujika ngokuxhomekeke kwizinto ezininzi, ezinje ngexesha lokuhlanganiswa, ukungena kwamanzi emhlabeni, ubukhulu bomthwalo womhlaba njl. Amandla okucheba omhlaba axhomekeke kuxinzelelo lwamanzi emingxunyeni kwaye aphezulu kakhulu xa u=0, xa kusenzeka ukudityaniswa komhlaba.
Umsebenzi wekoloyidi womhlaba
Iindawo zokuxhathisa ngaphakathi komhlaba ukudibana kunye nokukhuhlana zinokwahluka kwaye zixhomekeke kakhulu kubungakanani bamasuntswana aqinileyo omhlaba nakwiimpawu zawo zeplastiki. Ngenjongo yokumisela impembelelo yokudibana ngokunxulumene nokuxhathisa kokukhuhlana kwangaphakathi komhlaba odibeneyo, uSkempton wazisa umxholo womsebenzi we-colloidal womhlaba _K_P, ochazwa ngumyinge wesalathiso seplastiki IP kubungakanani bamasuntswana amancinci kune 0,002 mm nge-% yobunzima besixa sonke. Kule nto kwamkelwa le ndlela ilandelayo (sl. 3):
Sl. 3. Ukusebenza kwekholoidal yomhlaba
Kuba KP < 0,75 ngodongwe olungasebenziyo,
kwi KP = 0,75 – 1,25 ngoodongwe abaqhelekileyo,
kwe Kp > 1,25 yodongwe olusebenzayo.
Njengoko i-KP isanda, impembelelo yokudityana iyanda xa ithelekiswa nokungqubana kwangaphakathi komhlaba odibeneyo.
Ubuthe-ethe bomhlaba
Ukuba kumhlaba odibeneyo sikhupha isilinda enobubanzi 3—3,4 cm nobude ~ 5 cm size siyithwalele umthwalo oqhelekileyo, ngexesha lokuqhekeka kwesilinda siya kufumana amandla oxinzelelo lomhlaba kwisimo esingaphazamisekanga σ__ₙ:
σn = P/A ku-kp/cm2,
apho A ingumqamlezo onqamlezayo wesilinda.
Emva kokugqitywa kovavanyo, isampuli eyaphukileyo siyayisusa size siphinde senze isilinda ngemilinganiselo efanayo, sisebenzisa loo cylinder-mold inye, ngendlela yokuba ukufuma kwayo kuhlale kufana nobo babukho kuvavanyo lwangaphambili. Emva koko, ngokukhawuleza emva kokwenziwa kwalo cilindara exoviweyo, uvavanyo luphindwa ngayo, ukuze kufunyanwe amandla oxinzelelo lomhlaba kwimeko ephazamisekileyo σ__ₚ.
Ubuthathaka (sensitivitet) S__ₜ ngumlinganiselo wamandla oxinzelelo kwimeko engaphazamisekanga xa kuthelekiswa namandla oxinzelelo kwimeko ephazamisekileyo: St = σn/σp,
Ngokomgaqo othile, ubuntununtunu S__ₜ buvavanywa ngolu hlobo lulandelayo:
- kuba S__ₜ = 1 — 2 bubuthathaka obuncinane bodongwe,
- kwi S__ₜ = 2 — 4 kukho uvakalelo oluphakathi lodongwe,
- kwi S__ₜ = 4 — 8 kukho ubuthathaka obukhulu bodongwe,
- kunye ne S__ₜ > 8 ludongwe oluvakalayo kakhulu.
Kwimvelo kwenzeka ukuba ngenxa yesenzo sobuqu, umzekelo ukungcangcazela komhlaba, umhlaba wodongwe ngequbuliso uphulukane namandla awo, aze kamva, xa uphumle, aphinde awufumane. Le mpawu ibizwa ngokuba yi-thixotropy yomhlaba. Iidongwe ezininzi zinempawu ze-thixotropic ukuya kwinqanaba elithile. Zaziwa iimeko zokutyibilika kwamathambeka ezisikiweyo ngenxa yokuphuma kodongwe lwe-thixotropic eNorway, eSweden naseFinland, apho ngovavanyo kwafunyaniswa ukuba kwakungekho tshintsho ekufumeni kodongwe ngexesha lale nkqubo, oko kukuthi, ukufuma kodongwe kwakuhlala kungatshintshanga phambi nasemva kokuphuma.