Zabtarewar ƙasa

A fannin ilmin kasa da kuma nazarin injiniyoyin ƙasa, zabtarewar ƙasa babbar haɗarin ne a  ƙasa  wurare da yawa a duniya. Ana la'akari da su wani tsari na almubazzaranci, wanda aka fi sani da su shine tarkace kwarara, faifan tuddai, da faɗuwar dutse .  Waɗannan abubuwan na iya faruwa a cikin shekaru masu yawa na motsi mai raɗaɗi amma mai ƙarfi, ko kuma a cikin wasu ƴan lokuta masu ɓarna. Akwai abubuwa da yawa da suka shafi tsarin ilimin ƙasa waɗanda ke da alaƙa kai tsaye da abubuwan da suka faru na zaizayar ƙasa. Babban abin da ya shafi zabtarewar ƙasa shine ƙarfin dutse. Ƙarfin dutse ana bayyana shi ta hanyar danniya/matsala dangantaka, matsa lamba mai ƙarfi, da matsa lamba .  Ƙarfafa, manyan duwatsu masu yawa ba su da yuwuwar shiga cikin zamewar dutse ko zabtarewar ƙasa fiye da raƙuman duwatsu masu ƙarancin yawa waɗanda za a iya cika su da ruwa cikin sauƙi. A Utah matakin ruwan karkashin kasa yana ci gaba da jujjuyawa, yana mai da yankin ya zama mai saukin kamuwa da zaftarewar kasa.  Yayin da ruwa ya cika ƙasa, yana sa ta yi laushi kuma ta yi nauyi, damuwa/dangin dangantakar da duwatsu ke fuskanta suna ƙaruwa sosai. Ƙarfin dutsen ana iya bayyana shi ta hanyar Mohr Circle, da ambulaf ɗin gazawarsa . Da zarar an sami yanayin da zai sanya dutse akan ambulan da ya gaza, zai  iya fuskantar nakasu.

Akwai manyan nau'ikan nakasawa guda biyu waɗanda duwatsu suke yi kuma duka suna da alaƙa da zabtarewar ƙasa. Idan dutsen yana da ƙarfi kuma ya sami raunin raunin da ke tattare da ƙananan motsi a cikin dutsen, ƙarfin haɗin gwiwa yana ɗan ɗan kiyayewa, kuma ana iya hana zamewar ɗan lokaci. Koyaya, idan dutsen ya sami gurɓataccen gurɓataccen abu kuma ya karye, zabtarewar ƙasa na iya faruwa da yawa. Damuwa da yanayin damuwa da ke da alaƙa da duwatsu da ambulaf ɗin gazawarsu sun bambanta tsakanin nau'ikan dutsen, amma an yi nazari sosai a cikin dakunan gwaje-gwaje saboda abubuwan da waɗannan bayanan ke da alaƙa suna da mahimmanci a kowane fanni na ilimin ƙasa da ake da Shi.

## Abubuwan zaɓen ƙasa a Utah
Wani bugu na baya-bayan nan da Cibiyar Nazarin Geologic ta Utah ta yi ta ba da rahoton faruwar ayyukan zaizayar ƙasa sama da kimanin 22,000 a duk faɗin jihar a kan yanayin ƙasa na baya-bayan nan.  An sami aukuwar zaftarewar ƙasa da yawa a cikin gundumar Utah a cikin shekaru 25 da suka gabata waɗanda suka haifar da asarar ɗaruruwan miliyoyin daloli na diyya da asarar dukiya. A ƙasa akwai bayanin da ya shafi ƙasuwar Thistle, Utah da zaftarwar ƙasar Cedar, Utah (aiki).

## The Thistle Landslide
Zaftarewar kasa a Thistle, Utah,  a shekarata (1983) ta haifar da asarar sama da dala miliyan 200 da asarar dukiya. Dusar ƙanƙarar ƙanƙara mai ƙarfi, haɗe da dumi, ruwan marmaro ya haifar da zabtarewar ƙasa wanda a ƙarshe ya kai gudu zuwa ƙafa 3.5 a cikin sa'a. Kaurin ya wuce ƙafa 200, faɗinsa ƙafa 1000, kuma tsayin sama da mil ɗaya. Zamewar ta tsaya a ƙarshe lokacin da ta yi karo da wani babban dutse mai yashi a gindin dutsen. Adadin kayan da aka motsa a cikin faifan ya isa ya haifar da dam mai tsayin ƙafa kimanin 200 wanda ya toshe bakin kogin Fork na Sipaniya, kuma ya samar da wani babban tafki inda garin Thistle ya kasance. Hakanan ya hana zirga-zirgar layin dogo tare da rufe manyan manyan hanyoyi guda biyu (US6 da US89). Daga karshe tafkin ya zarce ya bar ragowar garin, wanda har yanzu ana iya gani a cikin kwaruruka.

An tattara samfuran duwatsu da ƙasa waɗanda ke cikin zabtarewar ƙasa Thistle kuma an yi nazari. Babban nau'ikan dutsen su ne dutsen yashi da dutsen farar ƙasa, kuma ƙasar ta ƙunshi kusan hatsin yashi quartz kaɗai da ma'adinan yumbu (illite). Karatuttukan ƙarfin da aka yi a baya akan dutsen yashi mai ƙyalli ya sa a sami sauƙin ganin dalilin da yasa aka jawo zaɓen ƙasa. Gwajin matsawa na Triaxial da aka yi don busassun dutsen yashi na silty yana nuna daidaiton ƙarfin haɗin kai zuwa 18.7 MPa, ma'ana cewa dutsen ba zai karye ba har sai an kai waɗannan yanayin damuwa. Don samfurin rigar, kama da yanayin da ke cikin Thistle, ƙarfin haɗin kai yana raguwa zuwa 15.9 MPa.  Wadannan bayanai sun nuna cewa idan dutsen yashi maras nauyi ya cika, duwatsun sun fi saurin karyewa, wanda hakan ne wata hanya da za ta iya haddasa zabtarewar kasa. Tare da kyawawan kaddarorin dutsen yashi maras nauyi, da kuma ikon ƙasa mai arzikin yumbu don sha ruwa mai yawa, ba abin mamaki ba ne cewa Kogin Fork na Sipaniya ya fuskanci zabtarewar ƙasa da yawa cikin tarihin yanayin ƙasa. Zaben sarkar ya sake kunnawa sau da yawa tun babban aikinsa a shekarata 1983, kuma zai ci gaba da yin hakan har sai ingantacciyar yanayin zaizayar ƙasa da yanayin yanayi ya haifar.

## Zaftarewar Kasa ta Cedar Hills

A cikin Afrilun shekarar 2005, zaftarewar ƙasa ta faru a Cedar Hills, Utah. Yankin zaizayar ƙasa ta ƙarshe ta motsa a cikin shwky 1983, tare da haɗin gwiwa tare da lokacin sanyi iri ɗaya da dumi, yanayin bazara wanda ya haifar da zamewar Thistle. Zaftarewar kasa wani bangare ne na babban, hadadden zaizayar kasa mai hade da Manning Canyon Shale. Zaizayar kasa mai aiki tana da kusan ƙafa 375 tsayi da faɗin ƙafa 150. Nau'in dutsen da ƙasa da ke da alaƙa da wannan taron sune yumbu da laka mai wadataccen shale . Ƙarfafa Properties hade da rigar vs. bushe shale sun yi kama da na rigar vs. bushe sandstone. Lokacin da shale yana kusa da saman ƙasa inda abun cikin ruwa ke jujjuyawa, yakan shiga cikin ƙasa mai arziƙin yumbu inda ƙarin danshi yana rage ƙarfin dutsen kuma yana ƙara yuwuwar faruwar zaɓen ƙasa.  Ana yin gwajin matsawa na Triaxial akan busassun shale ya nuna gazawar danniya mai tasiri sama da 15MPa.  Zaftarwar kasa ta Cedar Hills ba ta yi tsanani kamar zamewar Thistle ba saboda gangaren tudun ba ta kai tsayin daka ba, wanda ke haifar da karancin damuwa. Hakanan, shale yana ƙoƙarin samun ƙarfin matsawa fiye da dutsen yashi, don haka nauyin nauyi bai yi tasiri sosai akan shale ba. An yi sa'a ga mazauna Cedar Hills, nunin ya tsaya a yanzu, kuma da fatan za a ci gaba da kasancewa a tsaye, ko da yake shaidar ilimin ƙasa ta nuna cewa hakan ba zai yiwu ba.

An dauki matakan kiyayewa bayan zamewar shekarata 2005 don rage damuwa a kan tudu, ciki har da gina bango mai riƙewa don rage tasirin damuwa na tsaye (sigma 1), da magudanar tsakuwa don taimakawa wajen cire ruwa daga tudu don taimakawa duwatsu su kula da haɗin kai. ƙarfi. Waɗannan matakan ba su da tasiri, saboda faifan ya motsa sau uku tun a Shekarar 2005, wanda a ƙarshe ya lalata gidajen da ke kusa da hoton.

## Manazarta

## Hanyoyin haɗi na waje

* http://geology.utah.gov/survenotes/geosights/thistle.htm
* https://web.archive.org/web/20101103144603/http://geology.utah.gov/utahgeo/hazards/landslide/cedarhills0405/index.htm
* http://www.imwa.info/docs/imwa_2005/IMWA2005_072_Li.pdf