gravity displacement, ukudilika nokubhidlika kwezingqumbi — isiZulu

Ukudilika endaweni eyehlelayo kwezimvithi zokukhumuzeka kwezinto zemvelo (bheka i-“erosion”). Kunezindlela nezizathu eziningi zokwenzeka kwalokhu, kodwa izimbangela ezinkulu zalokhu yi-gravity (amandla omhlaba adonsela izinto phansi), ukweqiwa kwesimo sokutsheka (angle of repose) sengqumbi yemvelo, i-loading (umthalo) kanye ne-water saturation (izinga lokumunceka kwamanzi). Ingqumbi yezimvithi – okungenzeka kube yizinto ezihlungiwe, njengezingqumbi zemfucuza yasemayini, noma izinto ezingahlungiwe njengezingqumbi zeqhwa eziqoqanayo zigcine sezakhe intatshana enesimo sokutsheka esibonisa i-angle to the horizontal ethile. Le engela ibizwa nge-angle of repose. Ezintweni zemvelo (njengezimvithi zokukhumuzeka) i-angle of repose ivamise ukuba ngaphansi kuka-35˚. Uma kwenzeka izinhlangothi zengqumbi zitsheke kakhudlwana, ingqumbi iyadilika, okwenza izinhlangothi zigcine sezime esimweni sokutsheka esiphansi, okusho ukuthi ingqumbi ayisatshekile kakhulu. Izinga lokumunceka kwamanzi lento yemvelo nalo lisemqoka kakhulu impela. Qhathanisa ingqumbi yesihlabathi eyakhiwe ngesihlabathi esomile ebhishi nengqumbi yesihlabathi eyakhiwe ngesihlabathi esimanzi – ingqumbi enesihlabathi esomile iyakwazi ukuba nesimo esitsheke kakhulu kunengqumbi enesihlabathi esimanzi. Ingane encane mhlawumbe ingahlala nokuhlala phezu kwengqumbi enesihlabathi esomile, ingabhidliki ingqumbi, kodwa leyo ngane ingayibhidliza ingqumbi eyakhiwe ngesihlabathi esimanzi uma ingazama ukuhlala phezu kwayo. Ingane “iwumthwalo” (“load”), okusho, isisindo engamelana naso ingqumbi yesihlabathi ngaphandle kokubhidlika. Ingane enesisindo esikhudlwana ingayibhidliza ingqumbi yesihlabathi esomile. Uma kuthelwa amanzi phezu kwengqumbi yesihlabathi esomile lokho kungayibhidliza leyo ngqumbi, igcine isiyingqumbi ecishe ibe yisicaba, okubonisa ukuthi ukumunceka kwamanzi kuyinto esemqoka kakhulu ekuzinzeni kwendawo etshekile. Amandla omhlaba okudonsela phansi izinto, ahlala enjalo engaguquki, kodwa uguquko olwenzeka ezingeni lokumunceka kwamanzi, noma uguquko emthwalweni obekwe phezu kwengqumbi, luyayiguqula i-angle of repose yengqumbi, okuholela ekutheni ingqumbi idilike noma ibhidlike ngokushesha. Izinguzunga zamatshe ezigingqikayo, ukugidlika komhlaba kanye nezikhukhula zodaka olugelezayo yizehlakalo ezishaqisayo ezenzeka ngokushesha okukhulu, futhi ezivamise ukudlula nezimpilo zabantu zicekele phansi nempahla ngendlela engeke neze iphinde ibuyiseleke esimweni sayo sangaphambilini. Kule mpilo yethu esiyiphilayo yesimanjemanje ehlelwe ngokwezimo ezithile futhi egxile kwezomnotho, zishaywa indiva izehlakalo eziphindaphindekayo noma ezenzeka ngokulandelana zokudilika kwezinto zemvelo, futhi njalo lokhu kubeka izimpilo zabantu engozini. Isibonelo sokudilika kwezinto zemvelo okudume kakhulu okwadlula nezimpilo zabantu abaningi yinhlekelele yase-Aberfan e-Wales, kwelase-Great Britain, lapho kwabhidlika khona ingqumbi yemfucuza yasemayini ngowe-1966 ngenxa yokungamunceki kahle kwamanzi, okwaholela ekutheni iguguleke imboze isikole esiseduzane lapho kwangcwabeka khona zonke izingane zesikole kanye nothisha ngokushesha okukhulu. INingizimu Afrika nayo inazo ezayo izibonelo zezigameko ezishaqisayo zokudilika komhlaba ezidala umonakalo omkhulu futhi ezivamise ukuthatha imiphefumulo yabantu ezibangelwa yizenzo zabantu. Omunye wemigwaqo edumile emhlabeni jikelele onobuhle bendalo obumangalisayo yi-Chapman’s Peak Drive enqamula eningizimu yenhlonhlo (peninsula) ye-Kapa. Lo mgwaqo wakhiwa ngokuthi kumbiwe futhi kusikwe ingxenye eyehlelayo yenhlonhlo yeKapa futhi ngenxa yalokho-ke kuvamise ukuba nezigameko zokuwa kwezinguzunga zamatshe kuwo wonke lo mzila. Kamuva nje kuchithwe izimali ezinkulu kwenziwa imizamo yokuvimbela amatshe adilikayo ukuze angafinyeleli emgwaqeni, futhi lo mgwaqo uvamise ukuvalwa izinsuku ezimbalwa emva kwezimvula ezinkulu ukuze kugwenywe izinhlekelele nesibhicongo sokulimala noma ukufa kwabantu futhi ukuze kususwe izimvithi eziwele emgwaqeni. Okunye ukudilika kwezinto zemvelo okuhlala kukhona njalo yi-soil creep okuyisigameko sokunyibilika kancane kancane komhlabathi usondela endaweni engatshekile kakhulu, enokutsheka okuphansi okungafinyelela ku-degrees amathathu (3˚). Lena yinqubo eyenzeka ngokwemvelo ngokuphelele, kepha izenzo zabantu nemisebenzi yabo enjengokufunywa kwemfunyo kanye nokukhiqizwa kwezitshalo kungayisheshisa le nqubo futhi lokho kungaholela ekutheni odedangendlale bomhlabathi ovundile bagcine bengasakhiqizi lutho.

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