Ukubala ukuhlala phansi

Ngaphansi komthwalo, yonke inhlabathi, ngaphandle kwedwala eliqinile, iyahlala phansi. Ukucwila kwenzeka ngokujwayelekile ngenxa yezimbangela ezimbili: ukuncipha kwenhlabathi ngenxa yokucindezelwa okungukuthi ukwehla kwevolumu yayo ngenxa yokuxoshwa komoya noma kwamanzi emihosheni yayo kanye nokukhishwa kwenhlabathi eceleni emaphethelweni esisekelo ngenxa yokushelela kwezinhlayiya eziqinile zenhlabathi.

Ukwehla komhlabathi ngenxa yokuminyaniswa kuqukethe ukuguquka okunwebekayo nokwepulasitiki, okubangelwa umthwalo wesisekelo, lapho uma umthwalo ususwa umhlabathi ubuyela ngokwengxenye esimweni sawo sokuqala.

Ukuncipha ngenxa yokucindezelwa eceleni komhlaba kuqukethe kuphela ukuguquka kwepulasitiki, lapho lapho kukhululwa umthwalo umhlaba ungabuyeli esimweni sawo sokuqala. Lokhu kuvame ukuvela ezisekelweni ezincane ezakhiwe ekujuleni okuncane ngaphansi kobuso bomhlaba. Ngokufanayo, ukucindezelwa komhlaba eceleni kwenzeka emhlabathini onomswakama omkhulu futhi onengeli elincane lokungqubuzana kwangaphakathi.

Njengoba umthwalo ovumelekile womhlabathi uthathwa endaweni yokuguquka kwe-elastic-plastic, ukubalwa kokuhlala phansi kwenziwa kuphela ngesisekelo sokuncipha kwe-porosity yomhlabathi ngaphansi komthwalo, kanti ukuhlala phansi ngenxa yokucindezelwa kohlangothi komhlabathi kuyashaywa indiva, okuthathwa njengokungabalulekile.

Ukuhlala phansi ngenxa yokucindezelwa kuncike ekudluleni kwamanzi komhlabathi, ngoba kwenzeka ngenxa yezimbotshana, ezisemhlabathini wemvelo zihlala zigcwele amanzi kancane noma kakhulu. Ngakho-ke, ukuhlala phansi komhlabathi ngaphansi komthwalo empeleni kuyisenzakalo se-hydrodynamic, ngoba inqubo yokuhlala phansi incike ejubaneni lokuxoshwa kwamanzi ezimbotsheni, lapho ukudlulisa kwamanzi komhlabathi kudlala indima enkulu kakhulu.

Izinhlabathi ezingahlangani njengezihlabathi namatshe amancane zinezimbobo ezinkulu, yingakho zingangeni manzi kahle futhi amanzi asezimbotsheni ngaphansi komthwalo wesisekelo akhishwa ngokushesha. Ngakho-ke enhlabathini engahlangani ukuhlala phansi ngaphansi komthwalo wesisekelo kwenzeka ngokushesha, ngokuvamile kuse ngesikhathi sokwakha noma isikhathi esifushane ngemva kwalokho. Ngenxa yalokho ukuhlala phansi kwesisekelo enhlabathini engahlangani akuvamile ukubalwa.

Umhlabathi ohlangene unamaphorosi amancane, ukuvumela kwawo kungaphansi futhi ukuphuma kwamanzi emaphorosini ngaphansi komthwalo wesisekelo kungahlala isikhathi eside kakhulu, kwezinye izibumba ezinohlamvu oluncane ngisho amashumi eminyaka. Ngaphezu kwalokho, njengoba ukuporozeka okuphelele komhlabathi ohlangene kukhulu kakhulu kunokungahlangene, ukucwila komhlabathi ohlangene kukhulu kakhulu.

Enhlabathini ehlangene, lapho izimbotshana zayo zigcwaliswe kancane umoya kanti kancane amanzi, kuqala ukuhlala phansi ngenxa yokucindezelwa komoya ezimbotsheni, kanti okuqukethwe amanzi kuhlala kungashintshi, bese kuba ukuhlala phansi ngenxa yokukhishwa kwamanzi ezimbotsheni. Lapho inhlabathi ilayishwa ngokuma ngenxa yomphumela wesisindo nomthwalo owusizo wesisekelo, zombili lezi zinhlobo zokuhlala phansi ziyavela, kodwa inqubo yesikhathi yokuhlala phansi yehlukile.

Kukhona nezinye izimbangela ezidala ukwehla kwenhlabathi, njengokwehla okungapheli kwezinga lamanzi angaphansi komhlaba, izinguquko zamakhemikhali ekwakhekeni kwenhlabathi kanye nezinye iziphazamiso emhlabathini.

Ucwaningo lokucwila komhlaba luqukethe ukubalwa kwangaphambili kokucwila, okwenziwa ngokusekelwe ekuhlolweni kwelabhorethri kwamasampula omhlaba kanye nokubhekwa kokucwila, okwenziwa ngesikhathi sokwakhiwa kwesakhiwo nesikhathi esithile ngemva kwalokho.

Ukubalwa kokuxegiselwa lapho umthwalo wesisekelo usemkhonweni ophakathi

Ake sicabangele isicathulo sesisekelo esibekwe emhlabathini owakhiwe izendlalelo ezihlukahlukene, isibonelo isendlalelo sesihlabathi H0, noma H1 ngaphansi kwesicathulo, isendlalelo senhlabathi yobumba enobukhulu H2, isendlalelo sobumba obusakhe obunobukhulu H3, ngaphansi kwaso kukhona amatshe amancane acinene anobukhulu obukhulu besendlalelo, nezinga lamanzi angaphansi komhlaba NPV (umf. 1a).

Ukuze kubalwe ukwehla, kudingeka kufakwe umdwebo wengcindezi ngenxa yesisindo sayo inhlabathi (umdwebo ongakwesobunxele ku-fig. 1b) kanye nomdwebo wengcindezi ngenxa yomthwalo owengeziwe ovela esisekelweni (umdwebo ongakwesokudla ku-fig. 1b). Umdwebo wengcindezi ngenxa yesisindo sayo inhlabathi utholwa ngobukhulu bezendlalelo Σ_H_ kanye nezisindo zazo zomthamo γ. Uma isisindo somthamo wesihlabathi singu γ1, wesihlabathi ngaphansi kwamanzi γ’1, wenhlabathi enobumba ngaphansi kwamanzi γ’2, wobumba ngaphansi kwamanzi γ’3, khona-ke izingcindezi zokucindezela emhlabathini ezibangelwa yisisindo sayo inhlabathi zizoba (fig. 1)

γ1 · H’;    γ’1 · H’’;    γ’2 · H2;    γ’3 · H3;

Ishadi lokucindezeleka elibangelwa umthwalo silithola ngokubala kusetshenziswa enye yezindlela ezaziwayo, isibonelo ngeSteinbrenner noma ngeNewmark, ezindaweni ezihlukahlukene ezingaphansi kwesisekelo.

Uma sibeka P njengomthwalo wesisekelo, A indawo yaso yokuncika emhlabathini, γ1 isisindo seyunithi yomhlabathi ekujuleni kwesisekelo t ngaphansi kobuso bomhlabathi, umthwalo othile wesisekelo uthi P/A kanti isisindo somhlabathi kulokho kujula ngu-γ1t. Ukuze kutholakale umthwalo owengeziwe womhlabathi ngenxa yomthwalo wesisekelo, kufanele kususwe ingcindezi yesisindo somhlabathi γ1t emthwalweni wesisekelo P/A, ukuze umthwalo owengeziwe womhlabathi ube

p0 = P/A – γ1t.

Kulelo zinga elifanayo t kusebenzela futhi ingcindezi γ1t ngenxa yesisindo sayo somhlabathi, ngakho kuleli zinga isebenza ingqikithi yengcindezi (P/A – γ1t) + γ1t, lapho ukuqiniswa komhlabathi ngaphansi kwengcindezi γ1t sekwenziwe ngaphambi kokwakhiwa kwento.

Sl. 1. Ukubala ukuhlala phansi lapho isisekelo silayishwa phakathi nendawo

Nokho uma ingxenye eyodwa yesisekelo engenhla konyawo lwesisekelo igcwaliswa ngenhlabathi (sl. 1c), kufanele kubhekwe umthwalo wenhlabathi egcwalisiwe 2_Q_, ukuze kuleso simo umthwalo owengeziwe ube

_P+2_Q/A – γ1t.

Esisekelweni esimise njengomucu A = b x 1,0 m ku 1 m’ yesisekelo.

Ukubalwa kokwehla kwenziwa kuzo zonke izingqimba zenhlabathi ecindezelayo kuze kufike ekujuleni komthelela womthwalo wesisekelo. Phambilini kwakubhekwa njengomkhawulo womthelela womthwalo wesakhiwo ukujula lapho kubusa khona izingcindezi ezinobukhulu obungu ≥ 10% p0. Namuhla kwamukelwa ukuthi lo mkhawulo usekujuleni lapho ingcindezi evela emthwalweni owengeziwe pz ilingana no 20% wengcindezi evela esisindweni senhlabathi uqobo: pz = 0,2 ·γ_Σ_H. Ngezansi kwaleli jula ukwehla akubalwa. Ngokwenye imithetho kunconywa ukubalwa kokwehla kwezingqimba kuze kufike ekujuleni kuka 2_b_ kuya ku 3_b_, lapho u-b kuwububanzi besisekelo. Uma ekugcineni kukhona ungqimba lwetshe eliyizigaxa njengaku-fig. 1a, alucatshangelwa ekubalweni kokwehla, ngoba ukwehla kwalo ngaphansi komthwalo wesisekelo kuncane futhi kwenzeka ngesikhathi sokwakha.

Ekujuleni z ngaphansi kwesole lesisekelo kukhona ingcindezi yokucindezela pg ngenxa yesisindo sayo senhlabathi (sl. 1b), lapho kubhekelwe khona nethonya lokuphakama kokudonswa phezulu. Kule ngcindezi yokuqala yokucindezela kwengezwa ingcindezi pz ngenxa yokusebenza komthwalo wesakhiwo ekujuleni okufanayo. Ngakho-ke, kunoma yiliphi iphuzu M ekujuleni z ngaphansi kwesole lesisekelo kubusa ingcindezi ephelele yokucindezela pn = pg + pz.

Ngaphansi kwesenzo somthwalo owengeziwe, umhlabathi uyahlala futhi uqhame eceleni. Uma ukuguquka eceleni kunganakwa, ngoba kuncane ngokulinganayo, njengoba umthwalo ovumelekile womhlabathi usezoni yokuguquka kwe-elastic-plastic, kungamukelwa ukuthi ukubala kokuhlala kwenziwa ngokusekelwe esivivinyweni sokucindezeleka ku-edometer, kusetshenziswa isampula engaphazamisekanga ekhishwe endaweni yephuzu elibhekiwe emhlabathini, okuthi ngaleso sivivinyo kunqunywe imodyuli yokucindezeleka komhlabathi Ms.

Ngokusekelwe emthethweni kaHooke sithola

Δ_s_ = pz/Ms,

lapho i-Δ_s_ iyisigxobo sokuhlala esiqondile, kuyunithi yobukhulu besendlalelo, pz ingcindezi ekujuleni komhlabathi z ngenxa yomthwalo owengeziwe.

Uma sicabanga ubukhulu besendlalelo obuncane ngokwanele dz, ukuze kuhlonzwe pz no Ms njengabazinze, ukuncipha kokuqala kuzoba

Δ_s dz_ = pz/Ms dz.

Ukwehla okuphelele kongqimba olunobukhulu obungu-H kuzoba

Uma pZ no MS kuhlala kungaguquki ongqimbeni olunobukhulu H, kuzoba

s = pz/Ms · H.

Eqinisweni pz no Ms azihlali zifana kulo ungqimba olunobukhulu H1, kodwa kusetshenziswa inani labo eliphakathi nendawo ephuzwini M.

Imoduli yokucindezelwa komhlabathi Ms inqunywa ngokuhlolwa kwelabhorethri ngesendlalelo ngasinye ngokwehlukile. Kumhlabathi obekade uhlanganiswe ngokujwayelekile, imoduli Ms inqunywa esithombeni sokucindezelwa kokuqala, lapho umthwalo ophelele σ2 = pg + pz; σ1 = pg = Σ_γt,_ umthwalo owengeziwe Δ_σ_ = σ2 – σ1 = (pg + pz) – pg, futhi amanani afanele okucindezelwa okuhlobene angu Δ_h2_/h no Δ_h1_/h, ngakho-ke

Nokho, uma kuyibumba elingaphansi kokucindezelwa kabusha, khona-ke imoduli yokucindezeleka ibalwa kumdwebo wokucindezelwa kwesibili. Kusukela esibonelweni esiku sl. 2 sinakho ngo:

Umfan. 2. Ukunqunywa kwemoduli yokuminyana komhlabathi ngokusekelwe kumdwebo wokucindezeleka okuhlobene

Kusuka kulokhu okungenhla kulandela ukuthi ukuhlala kobumba olungasekatsheki kahle ngaphambili kuzoba kuncane kakhulu kunokuhlala komhlaba ojwayelekile ukuseketshiswa.

Umthelela wokuqina kwesisekelo ekucwileni

Nakuba empeleni zingekho izisekelo eziguquguquka ngokuphelele, lapho ukuhlala phansi kwephuzu elilodwa bekunganciki ekuhlaleni phansi kwephuzu eliseduze, ekubalweni kokuhlala phansi kuhlukaniswa izisekelo eziguquguqukayo kanye nezisekelo eziqinile.

Izisekelo ezinwebekayo, okusho ukuthiwa izinqwaba zamatshe nezindunduma, ngaphansi komthwalo olinganayo zibangela ezindaweni ezithile ukuhlala okuhlukene. Ngakho-ke kulezi zisekelo ukubalwa kokuhlala akwenziwa ebusweni bonke obulayishiwe, kodwa kwenziwa emaphuzwini ahlukene alo: amaphuzu asemakhoneni A, B, C no D amaphuzu aphakathi ezinhlangothini E, F, H no J kanye nephuzu eliphakathi G ebusweni benxande (sl. 3). Ngaphansi komthwalo olinganayo ukuhlala kwamaphuzu B, C no D kuyefana nokuka-A, ukuhlala kwephuzu H kuyefana nokwephuzu E, iphuzu J lifana nephuzu F kumhlabathi onezinto ezifanayo.

Sl. 3. Ukubalwa kokuhlala phansi kwamaphuzu ngamanye endaweni elayishiwe

Ukuze kubalwe ukuncipha ngaphansi kwanoma yiliphi iphuzu G lendawo elayishiwe, i-rectangular ABCD ihlukaniswa yaba ama-rectangle amane amancane futhi ukuncipha kwe G kutholakala njengokuhlanganiswa kokuncipha okubangelwa yilowo nalowo wama-rectangle ahlukanisiwe.

Izisekelo eziqinile azicwile ngendlela efanayo nezinye eziguquguqukayo, ngoba kuzo akunakwenzeka ukucwila kwamaphuzu ngamanye. Ngakho-ke ukucwila kwezisekelo eziqinile kubalwa njengento eyodwa, lapho ngokwezinga lokuqina kubalwa inani eliphakathi lokucwila ngendlela ehlukile, ngoba ukusatshalaliswa kwengcindezi ezansi kwesisekelo kuncike ekuqineni kwesisekelo.

Ezisekelweni eziqinile ezinesimo sesikwele noma unxande omncane, lapho a < 2_b_, kubalwa ukuhlaliswa sG kwendawo emaphakathi G bese kwamukelwa ukuhlaliswa okujwayelekile kwesisekelo s = 3/4 sG. Ezisekelweni eziqinile ezinesimo sonxande olude noma umugqa kubalwa ukuhlaliswa kwendawo yokugcina E, indawo emaphakathi G kanye nendawo M esengxenyeni yebanga phakathi kwazo, ku-eksisi ende yesisekelo, bese kwamukelwa inani eliphakathi.

UVan Hamme ubheka ukuthi ukubalwa okunembile kakhulu kokuhlala phansi kwe-„iphuzu eliyisici P“, elisuka kuma-eksisi aphakathi likude ngo

kusukela ezinhlakeni eziphakathi. NgokukaVan Hamme, ukucwila kwamanye amaphuzu athile esisekelo akuxhomekile endleleni yokusabalalisa kwengcindezi ezansi kwesisekelo. Kulezi zindawo ukucwila kungabalwa ngokucabanga ukuthi ukusabalala kwengcindezi ezansi kwesisekelo kuyalingana. Ekwisekelweni eliqinile, elilayishwe ngomthwalo olinganayo lapho ukusabalala kwengcindezi ezansi kwesisekelo kungalingani futhi kukhula libheke emaphethelweni esisekelo, naphezu kwalokho ukucwila kwesisekelo kulingana nokucwila kwendawo ebonakalayo P. Izingcindezi ekujuleni z ngaphansi kwendawo ebonakalayo P yendawo engunxande enobude a, ububanzi b, elayishwe ngomthwalo olinganayo p0 zingabalwa kusetshenziswa ithebula 1 elenziwe nguJelinek.

Ukucindezeleka σzP ekujuleni z ngaphansi kwephuzu eliyisici P lingu σzP = (σz/p0)·p0, lapho p0 kuwumthwalo owengeziwe wenhlabathi.

Ithebula 1. Amanani σz/p ezingcindezi ezansi kwephuzu eliyisici P ngokwemibandela yobudlelwane bokujula z kuya kububanzi b kanye nobudlelwane bobude a kuya kububanzi b bomthende wesisekelo

Ukubalwa kokuhlala phansi kususelwa ekushintsheni kwe-coefficient ye-porosity yomhlabathi

Uma siqoka ngo e0 i-coefficient ye-porosity yesampula engaphazamisekile ekhishwe ungqimbeni lomhlabathi, kanti ngo ei i-coefficient ye-porosity yesampula efanayo ngemva kokuphothulwa kokuhlanganiswa ku-edometer ngaphansi komthwalo σ1 (sl. 4a), ukuncipha kwevolumu yokuqala yomhlabathi ngaphansi kwesenzo somthwalo Δ_σ_ kuhambisana nokuncipha kwe-porosity, okungukuthi ne-coefficient ye-porosity yomhlabathi

Δ_e_ = e0 – e1

Sl. 4. Ukubalwa kokuhlala phansi kususelwa ekushintsheni kwe-coefficient ye-porosity yomhlabathi

Ivolumu yokuqala yesampula yenhlabathi ingu

Ukuxegiselwa okuthile Δ_s_, okungukuthi, ukuxegiselwa ngeyunithi yomthamo womhlabathi 1+e0 kuyi

Δ_s_ =(e0–e1) / (1+e0)

Ukuhlala kohlaka oluyisisekelo olunogqinsi dz kuhambisana nohl. 4b

Δ_s_ dz=(e0–e1) / (1+e0)  dz

Ukuhlala kongqimba oluwugqinsi H kuzoba

Uma sithi p ukucindezeleka ekujuleni z ngenxa yesisindo senhlabathi uqobo, oluhambisana nomthwalo σ0 ku-edometer, Δp ukucindezeleka okuvela emthwalweni owengeziwe wenhlabathi ngenxa yesakhiwo, okungahambisana nokwenyuka komthwalo Δ_σ_ ku-edometer, p1 ukucindezeleka okuphelele ngaphansi kwesisindo senhlabathi uqobo kanye nomthwalo owengeziwe okuhambisana nomthwalo ophelele σ1 ku-edometer, khona-ke ifomula yangaphambili singayibhala ngale ndlela

Uma sichaza ngo A indawo yediyagramu yokucindezeleka evela emthwalweni owengeziwe womhlabathi, A = Δ_pH_ (indawo enomthunzi ku-sl. 4b), lapho Δ_p_ kungukucindezeleka okuvela emthwalweni owengeziwe maphakathi nongqimba

a=Δ_e_/Δ_p_, ubudlelwano bomahluko we-coefficient ye-porosity kuya engcindezini ehambisanayo yomthwalo owengeziwe Vc = (1+e0)/a, singabeka

okungukuthi s = A/Vc [cm]

Uma inhlabathi yakhiwe ngezendlalelo eziningi, kubalwa ukwehla s kwesendlalelo ngasinye; isamba sokwehla kwezendlalelo ngazinye sinikeza ukwehla okuphelele Σ_s_.