تعيين منحني عملكرد روسازي با استفاده از مطالعه موردي

Determining Pavement Performance Diagram Using Case Study

به منظور آگاهي از شرايط روسازي در طول سال‌هاي متمادي براي قطعه‌هاي متفاوت شبكه راه، ضروري است نرخ تغيير كيفيت روسازي در اثر عواملي همچون عبور ترافيك، شرايط جوي، نوع روسازي و ضخامت آن، بر اساس شاخص‌هاي بيان كننده وضعيت روسازي تخمين زده شود. مطالعات زيادي در كشورهاي توسعه يافته انجام شده است كه نتايج آن‌ها معمولاً به صورت منحني‌هاي عملكرد ارائه مي‌شود. در اين منحني‌ها تغييرات شاخص بيان‌كننده وضعيت روسازي راه در اثر گذشت زمان رسم مي‌شود. منحني عملكرد به طور قابل توجهي به تصميم گيرندگان برنامه‌هاي تعمير و نگهداري راه‌ها جهت كاهش هزينه‌ها با تعيين زمان صحيح انجام عمليات تعمير و نگهداري، عمر باقي‌مانده روسازي و در نهايت بهبود كيفيت روسازي شبكه را‌ه‌ها كمك خواهد كرد. در اين مقاله اطلاعات خرابي به صورت چشمي از چند قطعه راه داراي شرايط مشابه در شهر تهران و سبزوار جمع‌آوري شد. آنگاه كيفيت روسازي آسفالتي بر اساس اطلاعات جمع‌آوري شده و با محاسبه شاخص وضعيت روسازي براي اين دو شهر، تعيين شد. در نهايت منحني عملكرد كه نشان‌دهنده تغييرات كيفيت روسازي راه در طول عمر آن بود، با بكارگيري چندين تابع برازش متداول ترسيم شد. منحني چندجمله‌اي درجه يك براي منحني عملكرد شهر تهران و شهر سبزوار بر اساس دو پارامتر مجموع مربعات باقي‌مانده اصلاح شده و مجذور متوسط مربعات خطا، مناسب تشخيص داده شد. نتايج نشان مي‌دهد اگر حداقل سطح مطلوب شاخص وضعيت روسازي برابر 40 فرض شود، عمر مفيد روسازي‌هاي منطقه يك تهران و سبزوار به ترتيب 7/6 و 11/5 سال خواهد بود.

To determine the future condition of pavements in a pavement network, the deterioration rate of pavement condition should be estimated with accordance to traffic volume, environmental condition, pavement type and its thickness. The pavement condition index (PCI) can be used to estimate the pavement condition. PCI is a practical index widely used in Pavement Management System (PMS) and ranges between 0 to 100. The severity and quantity of pavement disteresses increase as it gets older. As the result of it, PCI decrease by the pavement age increase. PCI can be predicted in future by applying different models. These models consist of deterministic and probalistic models. Deterministic models yields a single value of future pavement condition while the probalistic ones yields a probability for any value of the future pavement condition. Empirical, mechanistic and imperical mechanistic models can be used for pavement condition calculation. Among them empirical models are more practical because of its simpilisity in development and application. In this paper, empirical deterministic model is used to predict the future pavement condition. A lot of research has been done on this subject in the developed country and its result is presented by performance diagrams. In such diagrams, pavement condition changes within the years are shown. Performance diagrams can significantly contribute to the road authorities to reduce their costs by right time selection for maintenance and rehabilitation actions, remaining life determination and pavement condition improvement in the road network. In this paper, type, severity and quantity of distresses is collected by visual inspection in Tehran NO.1 district and Sabzevar city. There are up to 5 years old pavements in Tehran district NO.1 which are all rehabilitated pavements. In contrast, Sabzevar’s mainly initial pavements reaches the age 15 years and consequently more deteriorated condition with lower PCI. The least PCI for Tehran NO.1 district is 61 percent and for Sabzevar city is 11 percent. Pavement condition index as an indicator of pavement condition is then calculated according to the collected data and Performance diagram, which is the pavement condition change during pavement life, is interpolated using different typical functions including exponentioal, linear and multi polynomial equations up to 3th order on. 1th order polynomial diagrams is best descriptive diagrams for Tehran and Sabzevar which are selected based on Adjusted R square and Root mean square error parameters. All the plotting performance diagram, Adjusted R Square and Root Mean Square Error calculation is done by SPSS. Adjusted R square equal to 1 and Root Mean Square Error of 0 are the ideal conditions which means the interpolated diagram passes through the scattered points. To obtain more precise estimation of scattered data both parameters should be considered as it is done in this paper. The results indicate that if the minimum desirable level of pavement condition index is assumed 40, then the useful life of the pavement in the Tehran NO.1 district and Sabzevar city will be 7.6 and 11.5 years.