17253

17253

تخمين پارامترهاي مقاومت برشي خاك با استفاده از نتايج (GPR) رادار نفوذي زمين

كارشناسي ارشد

ژئوتكنيك

اسفند 1395

دكتر شريعتمداري

عمران

روش‌هاي مختلفي براي اندازه گيري و تخمين زاويه اصطكاك داخلي و چسبندگي خاك به عنوان اصلي‌ترين پارامترهاي مقاومت برشي وجود دارد كه از متداولترين آنها مي توان آزمايش برش مستقيم را نام برد. در اين پژوهش به كاربرد استفاده از دستگاه رادار نفوذ زمين به عنوان يكي از تجهيزات ارزيابي غيرمخرب كه كاربرد آن در علوم مختلف در حال گسترش است در تخمين پارامترهاي مقاومت برشي پرداخته شده است. با توجه به اينكه قسمتي از مصالح مورد استفاده در اين آزمايش، مصالح درشت‌دانه مي‌باشند، در نتيجه اين تحقيق از آزمايش برش مستقيم بزرگ مقياس (30×30) بهره جسته‌است. در اين پژوهش به مقايسه نتايج آزمايش‌هاي ژئوتكنيكي و رادار نفوذي زمين پرداخته شده است. با برداشت داده‌ها توسط دستگاه‌ رادار نفوذي زمين و مقايسه نتايج آن‌ با نتايج آزمايش‌هاي ژئوتكنيكي متداول همانند آزمايش تراكم و آزمايش برش مستقيم بزرگ مقياس، دقت و هم‌چنين فاكتورهاي موثر در مسائل اقتصادي هر دو روش، مورد مقايسه قرار گرفتند. هم‌چنين مزايا و معايب هر دو روش جداگانه ارائه شده¬اند.نتايج نشان داده‌اند كه پارامترهاي مقاومت برشي خاك با استفاده از نتايج آزمايش رادار نفوذي زمين قابل محاسبه‌اند همچنين در مطالعات آتي نيز مي‌توان محدوده وسيع‌تري از تراكم‌هاي مختلف را جهت بررسي مورد مطالعه قرار داد.

1396/03/02

1/1/1900 12:00:00 AM

Shear strength parameters are one of the most important parameters in geotechnics. One of the common ways to compute the shear strength and cohesion of soil, is to use geotechnical experiments such as direct shear test.According to the geophysical sciences developments in all fields specially in civil engineering and by considering studies on Ground Penetrating Radar and the results of geotechnical characteristics -such as dry unit weight, soil moisture content, fine percentage, plastic limit, liquid limit etc- assessing soil shear strength parameters -friction angle and cohesion- are considered as an innovative in Ground Penetrating Radar tests because of limited studies on this topic. Ground Penetrating Radar tests are known as a common test in pathway and transportation engineering. In this research soil shear strength parameters of base materials are studied to calculate the shear strength parameters of soil which is an inseparable part of geotechnical sciences. Because some of the material used in this test is performed by granular soil materials, consequently this research has used large scale direct shear test. Preciously, according to the former studies, the parameters that affect the dielectric value of soil are considered as variables to remove the possible errors of these parameters. In this study 30 samples were made with different moisture content, clay content and compression. Ground Penetrating Radar test calculate the round-trip time of the wave along the soil sample thickness. By the means of geophysics equations, dielectric value of soil sample are calculated.By the latter view, this research compares geotechnical test results and Ground Penetrating Radar test results. Moreover, the Ground Penetrating Radar data and results, precision and economic issues of the test were compared with the general geotechnical test results -proctor compaction test and large scale direct shear test-. Advantages and disadvantages of both methods will be presented as well. The results of this study showed that the shear strength parameters of soil can be calculated by Ground Penetrating Radar test results. Also we observed a qualitative and logical process between Ground Penetrating Radar test data and the proctor compaction test data -the dielectric value increases by increasing the relative density percentage-, By considering dry unit weight -that shows relative density percentage- as an interface parameter, we could present a new model to calculate friction angel by dielectric value and relative density percentage in granular soil. Any specific logical and qualitative differences on cohesion section couldnot be seen because the material which was selected from base layer- granular soil –However; adding 5% kaolinite did not seem to be enough soil to show the plastic behavior, so we couldn’t analyze and estimate cohesion of soil samples with Ground Penetrating Radar test in the correct order. Above all, it has been suggested that in future studies switching the materials to fine materials in order to have cohesion in soil samples-creating samples with high percentage of clay content-, calculating more different relative density of soil, performing more experiments such as Standard Penetration Test& Cone Penetration Test and trying to expand the moisture content of soil can be considered as well.