ارزیابی پارامترهای توزیع اندازه ذرات و منافذ یک خاک درشت بافت با استفاده از پرتونگاری مقطعی اشعه ایکس (cbct scan)

علم پردازش تصویر، از علوم پرکاربرد در فنون مهندسی می‌باشد و از دیرباز مطالعات و تحقیقات گسترده‌ای در این زمینه صورت گرفته و پیشرفت‌های فراوانی حاصل شده‌است. سرعت پایین و مخرب بودن روش‌های رایج قبلی اهمیت استفاده از تکنیک پردازش تصویر در محاسبه منافذ و توزیع اندازه ذرات را دوچندان می‌کند. در این تحقیق شش نمونه خاک دست‌خورده و شش نمونه دست‌نخورده درشت بافت (sandy) نمونه‌برداری شد. با استفاده از نمونه‌های دست‌خورده منحنی دانه‌بندی و تخلخل کل با روش‌های معمول آزمایشگاهی اندازه‌گیری شد. از نمونه‌های دست‌نخورده هم تصاویر سی‌بی سی‌تی اسکن در آزمایشگاه عکس‌برداری تهیه شد و پس از پردازش تصاویر ویژگی‌های دانه‌بندی، تخلخل کل، تخلخل غیرمفید و مفید این نمونه‌ها تعیین شد. صحت‌سنجی نتایج ویژگی‌های تخمین زده شده با روش پردازش تصاویر سی‌بی سی‌تی اسکن نسبت به داده‌های به دست‌آمده از روش‌های آزمایشگاهی، با پارامترهای آماری مورد ارزیابی قرارگرفت. ضریب همبستگی پیرسون بین داده آزمایشگاهی و داده‌های اخذ شده از پردازش تصاویر سی‌بی سی‌تی اسکن 0.98 می‌باشد. نتایج ارزیابی صحت نشان داد (1.082، 1.229، 1.108 و 2.334 به ترتیب برای میانگین قدرمطلق انحرافات، میانگین مربعات خطا، ریشه میانگین مربعات خطا، میانگین درصد خطای مطلق) که استفاده از تصاویر cbctscan و تکنیک پردازش تصویر با دقت قابل قبولی می‌تواند ویژگی‌های هندسی خاک‌های درشت بافت را تخمین بزند. همچنین نتایج نشان دادند که بهترین روش آستانه‌گذاری تصاویر برای پردازش تصاویر در نرم افزار imagej روشostu intermodes تعیین شد.

Assessing parameters of distribution particle size and pores of a coarse textured soils using CBCT scan image processing

Introduction: CT scan was first invented by Hounsfield in the twentieth century in 1972. But it was soon used in engineering, agriculture, biology, physics, chemistry, etc. Recently, with advances in computed tomography at the global level, the use of different generations of Xrays on a micrometer scale to study some of the different phenomena in soil science has begun. Due to the lack of geotechnical and soil mechanics studies in many engineering projects, CT scan image processing method can be used as a suitable method for extracting soil particle size and other soil characteristics. The main purpose of this study: a) The use of CBCTscan in soil science for the first time in Iran. B) Comparing the ability of CBCTscan in terms of quality of results with conventional methods. C) Identify the best filter and binary method (threshold). Another goal of this research is to acquaint more researchers with the application of computed tomography (CTscan) technology in soil science studies.Material and Methods: The sampling area for this study was located in DiwandarehSaqez axis in Kurdistan province, where six disturbed and undisturbed soil samples were collected in a sandy area (12 samples in total). In disturbed samples, particle size distribution was measured by ASTM D421 method, and the porosity of the samples was measured directly using the fuzzy equations in soil mechanics. In a radiology laboratory, threedimensional images of intact soil samples were taken using a Planmeca Promax 3D CBCT CT scanner. In this study, ImageJ software was used to process CBCTscan images. With this software, the percentage of phases, number of particles and particle size can be calculated. One of the most important steps in image processing is generating binary images. A total of 17 global thresholding methods have been proposed for generating binary images in ImageJ software. In this study, 15 standard methods for generating binary images were examined and the best method was selected. The total pore volume and soil particle size distribution of each sample calculated by quantifying Xray images were compared with the total pore volume and soil particle size distribution obtained in the soil science laboratory and performance of the CT scan method evaluated by statistical parameters including The results of the accuracy evaluation for the correlation coefficient, mean absolute value of deviations, mean square error, root mean square error, and mean absolute error percentage.Results and discussion: The most significant point in image processing is the image thresholding method. In this study, due to the nature of CBCTscan images, global thresholding was preferred. From the results of image processing, it can be understood that the results of binary images with Otsu and Intermodes methods are in complete agreement with the laboratory sample. The average of total porosity of the processing image slides is 44.03%, which is approximately consistent with the calculated 45/6% for the laboratory sample. Also, the average of ineffective porosity of the samples is about 6.53%. Therefore, it can be said that the effective porosity of the samples is about 37.5%. The results of the accuracy evaluation for the correlation coefficient, mean absolute value of deviations, mean square error, root mean square error, and mean absolute error percentage were 0.98, 1.082, 1.229, 1.108 and 2.334 respectively, indicating that the use of CBCTscan images and image processing technique can identify and evaluate the geometric properties of granular soils with acceptable accuracy. The advantages of the computed tomography method of the soil are: (1) Obtaining information from the threedimensional structure of the soil with appropriate accuracy in a short time, (2) Nondestructiveness of this method, and (3) Accurate separation into soil phases in different energy radiations.Conclusion: Using the processes defined by the authors for image processing, this technique is well able to determine some engineering features such as particle size distribution, total porosity, effective porosity and ineffective porosity. Also, the best thresholding method for binary images and processing in ImageJ is the Ostu and Intermodes method. The accuracy of the device used in this research is 0.2 mm, in other words, spaces or grains smaller than this value cannot be identified; For this reason, in the present study, the term coarsetextured soils, which means gravel to coarsegrained sand, has been emphasized. The results of evaluating the statistical parameters testify to the accuracy and ability of this method.