پهنه‌بندی خطر فرونشست زمین در دشت جوین با استفاده از مدل تحلیل شبکه ای_ فازی

فرونشست پدیده ای مورفولوژیکی است که تحت تاثیر حرکت فرورو زمین پدید می آید. علت رخداد این پدیده ممکن است متاثر از عوامل طبیعی و انسانی باشد. برداشت بی رویه از آب های زیرزمینی و وجود نشانه های فرونشست زمین در دشت جوین، ضرورت نیاز به پهنه بندی فرونشست در این دشت را نشان می دهد. هدف تحقیق حاضر بررسی مناطق مستعد پدیده فرونشست بوده که برای این منظور از مدل تحلیل شبکه ای- فازی استفاده شده است. لایه های اطلاعاتی شامل لیتولوژی، خاک، بارش، سطح پیزومتری، ارتفاع، تکتونیک، تراکم چاه ها، کاربری اراضی، شیب، ژئومورفولوژی، آبراهه، پوشش گیاهی به عنوان معیارهای موثر مورد استفاده قرار گرفتند. سپس مقایسات زوجی معیارها انجام و وزن اختصاص یافته در نرم افزار super decesion به شکل معیارهای اصلی و زیرمعیارها وزن دهی شدند. لایه های مربوط به هر کدام از عوامل با استفاده از نرم افزار gis در محیط arc map آماده سازی گردید. سپس تلفیق وزنی در محیطgis انجام گرفت و در انتها لایه نهایی به صورت تابع خطی طیف بندی گردید. در این مرحله نقشه fuzzy & anp فرونشست به صورت کلاس بندی برای نشان دادن ویژگی های مناطق بحرانی فرونشست استخراج شد و اولویت بندی مناطق مختلف از نظر استعداد برای وقوع پدیده فرونشست بدست آمد. از این مقدار در نقشه anp حدود 56 درصد و در نقشه فازی به صورت فرض صفر و یک، قسمت مرکزی دشت جوین با خطر زیاد تا خیلی زیاد به حساب می آید. بر این اساس با توجه شرایط منطقه هر دو نقشه به واقعیت نزدیک است. تراکم بالای چاه های عمیق و نیمه عمیق و افت بالای آب های زیرزمینی به دلیل برداشت بی رویه این محدوده(خطر زیاد تا خیلی زیاد) جزو مناطق با استعداد بالای فرونشست مشخص شد، همچنین وجود شکاف های بوجود آمده و نشست چاه ها در همین محدوده ها تا حدودی صحت سنجی مدل را با داده های زمینی نشان می دهد. از نتایج حاصل از محاسبات انجام شده توسط روش های مذکور، می توان به عنوان تخمین اولیه مقدار فرونشست در محل مورد مطالعه استفاده کرد.

zoning the risk of land subsidence in joveyn plain using a fuzzy network analysis model

introductiontoday, the phenomenon of land subsidence is one of the most important geomorphologic hazards on a global scale, causing a great deal of damage to urban and rural construction, construction and civil engineering. give par (2012) explores the use of neuro-fuzzy inference system to map the risk of land subsidence in south korea’s south korean region. for this, the combination of geographic information systems and fuzzy inference system has been used. five main factors affecting subsidence including depth, distance from fault, gradient, geology, land use, were used to prepare the map. the results indicate the correctness of the method used to compile the suppression risk map. in this study, the causes of subsidence in the joveyn plain were investigated using the network-fuzzy analysis model. field studies and the observation of cracks and cracks created in rural buildings and agricultural land in the plain made it possible to study the possibility of land subsidence in the joveyn plain in the present study.matherials & methodsthe sources used in this research were based on studies and statistical surveys, geological maps and field operations. in order to study the causes of land subsidence in joveyn plain, information layers including lithology, soil, precipitation, piezometric surface, altitude,tectonics, wells density,land use,slope, geomorphology, waterway, vegetation were used as effective criteria. arc gis software was used to create these basic maps in the gis.in this research, network analysis and fuzzy modeling models have been used to study the status of factors affecting subsidence. the fuzzy network analysis process is derived from the integration of the fuzzy hierarchy process analysis process and the matrix of interactions between criteria.discussion of resultsin joveyn plain, 1957 wells allowed to operate with a mean discharge of 17 liters per second are pumping water. the faults in the catchment area are diverse in importance and role in the area’s morphology. it is also possible to see the main faults (miami, with the east-west trend) to the possible underlying faults. the main drainage of joveyn plain is the calshoor joveyn river, which runs from west to east. quaternary alluvium has the largest share in the joveyn basin. as far as the northern and southern parts of the plain are concerned, the diameter of the alluvial particles is reduced and the sediments form in fine form. so, in the central part and within the main drainage of the basin, sediments are reduced to size of silt and clay. in the context of vegetation cover, the study area covers the cover of arable land, pastures, gardens and bayer. the elevation survey shows that there is the lowest elevation in the central plain area of ​​the aquifer area. evidence of subsidence is also found on this altitude. in the case of the slope of the tilt range, the tilt range is 5-0 the lowest tilt in the region. this slope provides an important role in collecting groundwater resources and forms an aquifer. in the area of ​​ joveyn plain, in terms of land use, the central part of the plain has been allocated to agricultural use, which has caused the deep and semi-deep wells to be excavated in this area. according to the last 10 years (2007-2013), the meteorological stations of the region, the average rainfall of the last 10 years in the study area is 180 mm, which leads to a decrease in the trend and its effects on underground aquifers are evident. final weight and prioritization of each of the following criteria were extracted and based on the weight of each of them, the final weight of the main index indicators is obtained (table 1).table (1): final weight of criteria and sub criteria hydrologyenvironmentalphysicalcriterion0/6927740/0872830/219942weightvegetationpezumeter levelwells densityriverrainslopefaultaltitude levelssoil type  geomorphologylithology landuseunder the criteria 0/28197210/5011030/0978250/3259960/01851710/085214/00/0773040/146648/00/1523330/1515970/171725weight under normalized the   0/1953420/692770/3471510/067770/2257410/0134860/0074370/0067470/0322540/0335040/0355410/037769the final weight in the anp’s map it is critical that 1046 square kilometers of the studied basin area, located in the central aquifer area, is shown in red. since the study area of ​​the basins is considered, the high risk area shows a small percentage of the extent of the basin, but a significant percentage of the plains and aquifers is considered as a high-risk area . according to the fuzzy map, the subsidence range is located in the central part of the plain with bright color. as you can see, the middle part of the joveyn plain is among the high-talent areas of the subsidence, largely adapted to the drainage map of the groundwater and the field observations of the region and signs of subsidence, such as turks, and the proposed model verifies maps to a large extent the reality of the region is showing. the high density of deep and semi-deep wells and the high drop in groundwater due to over-harvesting as well as other factors have led to subsidence in these ranges.conclusionsin joveyn plain, 1957 deep and semi-deep wells were drilled, which was drilled at an average of 0.96 sq. km from joveyn plain. based on field surveys and the observation of the cracks created and consistent with the maps drawn in this area, anp-fuzzy is a model with high abilities in the area of ​​subsidence zoning. the density of wells throughout the center of the plain, especially around the railway, is based on the danger zone of this area. medium and low subsidence classes, including the southern mountain range, around calshoor and the end of the plain in the west. because of the low water level in the southern margin, the well is less drilled, resulting in subsidence with lower risk. at the end of the plain (west), we see the level of the ballast water level as a result of low risk submergence.