3555

3358

كارشناسي ارشد

آبياري و زهكشي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده كشاورزي

1385

پانزده، 126، [II]ص.: مصور، جدول، نمودار

ص. ع. به فارسي و انگليسي

منوچهر حيدرپور، فرهاد موسوي

اسماعيل لندي، حسين سقائيان نژاد

16/4/86

حسين افضلي مهر، سعيد سلطاني

مهندسي كشاورزي

ID3358

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

AbstractLocal scouring is one of the most important causes of bridge failure Therefore there isan interest in finding reliable ways to control and reduce local scour depth and thereby requisite pier embedment depth Countermeasures for local scour at bridge piers can begrouped in two categories Armoring devices and flow altering devices An acceptedengineering method to deal with pier scour problems is to place riprap material aroundthe pier foundation The scour reduction of riprap has been the topic of scientificinvestigations The effect of riprap on pier groups is not studied by earlier researches The scour hole around group piers is affected by factors which are not valid for singlepier Therefore study in this field is necessary For group piers aligned with the flow reinforcement and sheltering are additional parameters which affect the depth of localscour Furthermore the group effects will alter with changes in pier spacing Thepresent study examines using of riprap for reduction of local scour in pier group Theresults of the experiments were compared with data from present study and earlierstudies on single pier with riprap The models consist of two and three circular shapedpiers in line with diameter of 0 02 m and pier spacing of twice and four times the pierdiameter Four uniform sediments with median diameters d50 2 86 3 67 4 38 and 5 18mm were used as riprap material The riprap layer were installed at the same above andbelow the surface of the streambed The results showed that instability depth in grouppier was lower than single pier because of the sheltering effect The reduction ininstability depth at riprap placed below is found to be as much as 8 33 for biggestriprap and 6 1 for smallest riprap The riprap stability for three piers in line is morethan single pier and two piers The stability number for riprap with median diametersd50 2 86 and 5 18 mm is 3 29 and 2 38 respectively According to the results stabilitynumber increased with increasing pier spacing From the results riprap placed belowthe surface of the streambed has the highest stability riprap stones placed above thesurface of the streambed have the lowest stability and the third ones have the valuebetween previous ripraps The effect of wake vortices formed at the downstream side ofgroup piers was decreased Therefore the cover of riprap layer at downstream of grouppiers was decreased as compared with single pier The reduction in cover of riprap layerwas about 60

منوچهر حيدرپور، فرهاد موسوي

اسماعيل لندي، حسين سقائيان نژاد

حسين افضلي مهر، سعيد سلطاني