بررسي علل تخريب بتن در پوشش كانال هاي آبياري (مطالعه موردي در دشت همدان - بهار)

Study of Failure Factors in Concrete Lining of Irrigation Canals in Hamedan-Bahar Plain.

Concrete is one of the most important construction materials widely using in hydraulic structures, such as lining of irrigation canals. Concrete durability might be decreased due to the environmental or inner factors with physical, chemical or mechanical reactions. Since, the climatologically condition is variable in most part of the country, local studies are needed to evaluate of the weakness and straight of the different concrete component for a given climate. Therefore even thought a large expense is used for lining of irrigation canals, most of these projects have low conveyance and distribution efficiency. This study was conducted for evaluation of failure factors in applied concrete lining in irrigation canals of Hamadan-Bahar plain. The main issue in irrigation canals of the mentioned plain has been destruction of lining, which appeared as cracks and destruction in concrete linings. The main purpose of this research was determination of effective factors for destruction of irrigation canals in four different locations namely, Gondehjin, Bahadorbeig, Abroomand and khooshabe Olia. The data collection were include samples of concrete linings, inflow water in canals and bed soil of lining. Totally, 9 samples of concrete, 12 of water and 78 of bed soil were collected. The samples were tested based on standard methods of ASTM and the results were compared with the primary documentations on design and performance of each irrigation canals as well as Iranian Concrete Code and ACL According to results, the main causes of cracking and destructing of concrete lining of irrigation canals were: (i) the factors that related to concrete preparation (inner factors) such as improper vibration, wormy holes and low compressive strength, (ii) environmental factors such as temperature variation and freezing and thawing.