Rushewar gadar Schoharie Creek

Schoharie Creek Bridge wata gada ce ta Jihar New York (I-90) a kan Schoharie Creek kusa da Fort Hunter da Kogin Mohawk a Jihar Nework . Ginin yana zaune kusa da tarihin Schoharie Crossing . A ranar 5 ga Afrilu, 1987, ya rushe saboda guguwar gada a tushe bayan ruwan sama mai rikodin. Rushewar ta kashe mutane goma. An kammala gadar da aka maye gurbin kuma an buɗe ta gaba ɗaya ga zirga-zirga a ranar 21 ga Mayu, 1988.

Rashin nasarar Schoharie Creek Bridge ya haifar da ci gaba a cikin ƙirar gada da hanyoyin dubawa a cikin New York da bayan.

 Tsarin gada da gini 

An amince da zane na karshe don gadar a watan Janairun 1952 ta Ma'aikatar Sufuri ta Jihar New York (a baya Ma'abiyar Ayyukan Jama'a ta Jihar Nueva York). Zane ya bayyana ƙetare mai ƙafa 540 (160  wanda ya ƙunshi ƙetare guda biyar da aka goyi bayan kawai tare da tsawon ƙafa 100 (30.5 , ƙafa 110 (33.5 , mita 120 (36.6 , ƙafa 110, da ƙafa 100 (33.5. An goyi bayan gadar tare da bangarorin tashar jiragen ruwa tare da matakai a kowane ƙarshen. An gina bangarorin tashar jiragen ruwa da ginshiƙai biyu da aka ɗan ƙuƙwalwa tare da katako. An gyara ginshiƙan a wurin a cikin wani matattarar da aka ƙarfafa da aka sanya a kan wani wuri mai zurfi, mai ƙarfafawa. Za a kare kafafu da aka shimfiɗa tare da busassun layin riprap.

Tsarin ya kunshi manyan katako guda biyu tare da katako na bene. Kashi na gadar gadar (7.9 inci (200  kauri) an yi shi da igiyoyin ƙarfe.

Ginin ya fara ne a ranar 11 ga Fabrairu, 1953, ta hanyar B. Perini da Sons, Inc.

 Hidima 
An buɗe gadar a wani ɓangare a lokacin rani na shekara ta 1954 kafin a kammala gini. Schoharie Creek Bridge (NY 1020940, lambar gano gada ta Jihar New York), ya fara cikakken aiki tun daga watan Oktoba 1954.

A cikin bazara da rani na shekara ta 1955, matattarar tashar jirgin ruwa ta fara nuna raguwa a tsaye daga 0.12 zuwa 0.20 in (3 zuwa 5 , sakamakon matsin lamba a cikin matattarar kankare. Kusan shekara guda bayan haka, a ranar 16 ga Oktoba, 1955, ambaliyar ruwa ta lalata gadar. A shekara ta 1957, an kara karfafawa ga kowane ɗayan matakai huɗu.

 Rushewa 
A safiyar Afrilu 5, 1987, a lokacin ambaliyar ruwa mai yawa, gadar Schoharie Creek ta rushe. Rugujewar dusar ƙanƙara tare da ruwan sama wanda ya kai   in) ya haifar da ambaliyar ruwa mai kimanin shekaru 50 a kan rafin.

Jirgin ruwa na uku shine na farko da ya rushe, wanda ya haifar da rushewar sassan uku da hudu. Minti casa'in bayan haka tashar jirgi biyu kuma ta fadi biyu. Sa'o'i biyu bayan haka tashar jirgin ruwa daya kuma ya sauya daya. Binciken Hukumar Tsaro ta Kasa ya ba da shawarar cewa tashar jiragen ruwa ta biyu ta rushe saboda rushewar tashar jiragen kasa ta uku da kuma bangarorin biyu na iya toshe kogin, sake juyawa da kara saurin kwararar ruwa zuwa tashar jiragen sama ta biyu.

Kwanaki shida bayan haka,  mi (5  sama, babban ɓangaren Mill Point Bridge ya rushe. An rufe gadar tun lokacin ambaliyar a matsayin kariya, tunda binciken ya nuna cewa tushe ya lalace.

 Wadanda suka mutu 
A lokacin rushewar, mota daya da tractor-semitrailer daya suna kan gadar. Kafin a iya toshe hanyar, wasu motoci uku sun shiga cikin rata. A cikin makonni uku masu zuwa, an gano gawarwaki tara daga kogi. An gano gawar wanda aka kashe na 10 daga Kogin Mohawk a watan Yulin 1989.

 Binciken gazawar 
Shaidu sun lura cewa tashar jirgin ruwa ta uku daga yammacin (mafi uku) ta kasa da farko. Hotunan da aka dauka a ranar taron sun nuna cewa hanci na uku ya fadi dangane da wutsiyarsa, wanda ya kasance a cikin matsayi. Ginin kankare guda ɗaya a hanci na tashar jirgin ruwa uku ya rasa goyon baya, wanda ya sa wannan shafi ya yi tsalle kuma bangarorin biyu da ke goyan bayan tashar jirgin sama ta uku su fada cikin kogin da ya kumbura. Bayan ɗan gajeren lokaci, shaidu sun kalli yayin da tashar jiragen ruwa ta biyu daga yammacin yamma ta gaza. Wata ƙungiyar labarai ta yanar gizo ta rubuta wannan taron a kan tef na bidiyo. Bidiyo ya nuna saukowa kwatsam da bala'i a ƙarshen tashar jirgi ta biyu. Wannan ya sa tsayin daka nan da nan a yammacin tashar jiragen ruwa biyu ya fada cikin rafin.

Saboda babban bayanin wannan bala'i da asarar rai, Hukumar Tsaro ta Kasa ta fara bincike nan da nan bayan gazawar. Hukumar Kula da Harkokin Kasuwanci ta Jihar New York ta hayar da wata kungiya da ta kunshi ma'aikata daga Wiss, Janney, Elstner Associates, Inc., da Mueser Rutledge Consulting Engineers don jagorantar binciken a madadin su. Masu nutsewa sun fara cire ƙarfe daga kogin bayan matakan ruwa sun ragu. Gina akwatin gawa a kusa da wasu sassan shafin ya ba da damar cire ruwa. Bincike ya nuna gagarumin lalacewar yankin na rafin da ya faru kafin gazawar kuma mai yiwuwa ƙarin ƙura saboda yanayin toshewar gadar da ta fada cikin rafin bayan gazawar. Hanci na tashar jiragen ruwa uku ya shimfiɗa a cikin babban rami mai kama da doki. Rashin nasarar da aka lura na ƙarshen (wutsiya) na tashar jiragen ruwa biyu ya kara rikice-rikice ga binciken da ya haifar. 

Don nazarin abubuwan da suka haifar da gazawar, ƙungiyar injiniya mai bincike ta ba da umarnin nazarin samfurin jiki a dakin gwaje-gwaje na hydraulics a Jami'ar Jihar Colorado. Misali na ruwa na jiki na filin kwararar yanki wanda aka gina a sikelin da ba a karkatar da shi ba na 1:50 ta amfani da ruwa mai tsabta da yashi ya ba da damar lura da ci gaban gazawar. Schoharie Creek yana yin kusan digiri 120 zuwa hagu yana kallon ƙasa zuwa wurin gadar. Ma'auni na filin kwarara da ke kusantar samfurin gada ya nuna cewa matsakaicin saurin ya dace da wurin tashar jiragen ruwa uku, tashar jiragen sama tare da zurfin ruwa mafi kusa da waje na karkata. Nazarin samfurin ya nuna a sarari cewa da zarar fuskar da ke cikin tashar jirgin ruwa guda uku da aka shimfiɗa a cikin kwararar, ya haifar da babban vortex na doki wanda ya kara dabara a cikin gida a kusa da hanci. Gudun ruwa na biyu yana faruwa ne lokacin da kogi ke gudana a kusa da karkata. Gudun saurin gudu, wanda ke da ƙarfin ƙarfi, yana tsayayya da karkatawar kogin kuma yana motsawa zuwa bankin waje. Tun da yake wannan kwararar ta wanzu kusa da saman ruwa, tana haifar da kwararar kusa da gado don motsawa zuwa cikin karkata. A sakamakon haka, kwararar kusa da gadon kogin a budewar gadar tana da kusurwa dangane da daidaitawar tashar jiragen ruwa 3. Wannan ya haifar da wani bangare na saurin kusa da gadon rafi yana motsawa daga tashar 3 zuwa tashar 2. Misali na biyu na jiki wanda aka gina a sikelin 1:15 tare da kusurwar da ta dace na hari dangane da axis na tashar 3 ya ba da damar cikakken nazarin abubuwan da suka faru game da tsarin tsafta.
Binciken ya kammala cewa gadar ta rushe saboda babban hadari a karkashin tashar jirgin ruwa ta uku. Sakamakon daga binciken samfurin ruwa na jiki ya nuna cewa da zarar hanci mai laushi na shimfida tushe ya fallasa ga kwararar, wani tsananin vortex mai tsananin hawan doki ya fitar da kayan gado daga hanci na wannan tashar. Da zarar zurfin ƙuƙwalwa a hanci na tashar ya wuce zurfin shimfida tushe, an fara lalatawa. Saboda kusurwar harin da aka kirkira ta hanyar gudana ta biyu, tsaftacewar ta fi shafar ɓangaren hannun dama na tashar jiragen ruwa yayin da kayan gado da aka rushe suka kwashe zuwa ƙasa. Tare da kowane ci gaba na lalacewa, wanda ya ci gaba daga hanci na tashar zuwa wutsiya, ɓangaren sama na matattarar ya sami karuwar tashin hankali. Shaida daga binciken bayan taron na shafin da aka cire ruwa ya nuna cewa rushewar tashar jirgin ruwa uku ya kasance mai yawa, sama da kashi 50 cikin dari na tsawonsa, lokacin da matattarar ta kasa kwatsam. Wannan ya ba da damar hanci na tashar jiragen ruwa uku ya sauka cikin rami. Tsarin gada mai sauƙi ba shi da ikon tsayayya da sakamakon nauyin gefe a kan ginshiƙi mara tallafi, wanda ke haifar da rushewar kwatsam, bala'i da ci gaba na ɓarkewar ɓangarorin biyu da ke goyan bayan tashar 3.

Tsarin asali na gadar ya ƙayyade watsi a maimakon ginshiƙan ƙarfe da aka shigar yayin gini don daidaita wurin gini a matakai 2 da 3. Wannan zai kare waɗancan matakai daga ƙura, amma ba a yi ba. Tushen tashar jirgin ruwa yana kan ƙasa mai lalacewa, wanda ya ƙunshi yadudduka na dutse, yashi da yashi, an haɗa su da ninkawa da kuma karkata har zuwa. Wannan ya ba da damar ruwan ambaliyar ruwa mai saurin gudu don shiga cikin yanayin da ke ɗauke da shi. Yankin da ya rage a kusa da tushe bai cika da dutse ba, amma a maimakon haka an cika shi da ƙasa mai lalacewa kuma an rufe shi da busassun riprap. An ƙaddara kariya, dubawa, da kulawa da rashin isasshen.

Binciken ya nuna cewa tsarin tsaftacewa a ƙarƙashin matakai ya fara jim kadan bayan an gina gadar. A lokacin rushewar, ƙarshen tashar jirgin ruwa ta 3 ya fada cikin rami mai zurfi kusan  . Masu bincike sun kiyasta cewa kimanin ƙafa 25 zuwa 30 (7.5 zuwa 9  na tashar jirgin ruwa ya lalace.

Wani abu da ya ba da gudummawa ga gazawar shine nauyin riprap da aka yi am da shi a cikin ginin. Bayanan ƙirar ya kira riprap tare da kashi 50 cikin 100 na duwatsu masu nauyi  da    ), kuma sauran tsakanin 0.44 da 1.3  lbf). Masu bincike sun gano cewa ya kamata a ƙayyade nauyin riprap mai nauyi na 4.4 zuwa 6.7  lbf).

Sauran la'akari game da dalilin rushewar sun haɗa da ƙirar ginin, ingancin kayan aiki da gini, da dubawa da kulawa. Bincike ya gano cewa waɗannan abubuwan ba su ba da gudummawa ga rushewar ba.

Sa'o'i goma sha biyu kafin gadar Schoharie Creek ta rushe saboda ruwan sama mai yawa, ruwan da ya faru ta hanyar Blenheim-Gilboa Pumped Storage Power Project   sama ya kai tarihi. Don magance yawan nauyi, madatsar ruwan ta saki ruwa a cikin Schoharie Creek bisa ga yawan da yake shiga tafkin daga sama, yana ƙarawa ga nauyin a cikin rafin.

 Manazarta 

Rukuni:Shafuka masu fassarorin da ba'a duba ba