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Optimal dimensions of pennsylvania highway drainage inlet PDF

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Lehigh University Lehigh Preserve Fritz Laboratory Reports Civil and Environmental Engineering 1978 Optimal dimensions of pennsylvania highway drainage inlet gratings, April 1978 A. W. Brune A. W. Spear K. C. Loush Follow this and additional works at: htp://preserve.lehigh.edu/engr-civil-environmental-fritz-lab- reports Recommended Citation Brune, A. W.; Spear, A. W.; and Loush, K. C., "Optimal dimensions of pennsylvania highway drainage inlet gratings, April 1978" (1978). Fritz Laboratory Reports. Paper 486. htp://preserve.lehigh.edu/engr-civil-environmental-fritz-lab-reports/486 Tis Technical Report is brought to you for free and open access by the Civil and Environmental Engineering at Lehigh Preserve. It has been accepted for inclusion in Fritz Laboratory Reports by an authorized administrator of Lehigh Preserve. For more information, please contact 6 COMMONWEALTH OF PENNSYLVANIA Department of Transportation Bureau .of Materials, Testing and Research Leo D. Sandvig - Director Wade L. Gramling - Research Engineer Charles J. Churilla - Research Coordinator PennDOT Research Project 74-2 Optimal Dimensions of Inlet Gratings OPTIMAL DIMENSIONS OF PENNSYLVANIA HIGHWAY DRAINAGE INLET GRATINGS by Arthur W. Brune Andrew D. Spear Kenneth C. Loush This report was prepared in cooperation with the Pennsylvania Department of Transportation and the Federal Highway Administration The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy ,of the data presented herein. The contents do not necessarily reflect the official views o.r policies of the Pennsylvania Department of Transportation or of the Federal Highway Administration. This report does not constitute a·standard, specification, or regulation. Lehigh University Office of Research Bethlehem, Pennsylvania April 1978 Fritz Engineering Laboratory Report No. 401.2 Technical ~eport Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. FWHA-PA-RP-74-2 4. Ti tie and Subti tl e 5. Report Date OPTJMAL DJMENS IONS OF PENNSYLVANIA HIGHWAY April 1978 DRAINAGE INLET GRATINGS 6. Performing Organization Code ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~8.Pe~ormin9 Organi%~ion Report No. 7. Author' $) Arthur W Brune, Andrew D Spear, Kenneth C Loush FEL 401.2 9. Performing OrganizQtion'Name and Address 10. Work Unit No. (TRAIS) Fritz Engineering Laboratory 13 11. Contract or Grant No. Lehigh University . PA-RP-74-2 Bethlehem, FA 18015 13. Type of Report and Period Covered I1-2. -Sp-ons-'or~ing-Ag~en-cy-No-m.-an-d' A-dd-res-s --------------...._....---... Final Report Pennsylvania Department of Tr'ansportation Harrisburg, PA 17120 14. Sponsoring Agency Code 15. S4Pplemen-tary Notes Prepared in cooperation with the U S Department of Transportation, Federal Highway Administration 16. Abstract The results of testing an experimental model are presented about the optimal dimensions of gratings on drainage. inlets that are installed in triangular chan- nels, both grassed and paved, along highways. Each channel was on a grade of either 0.5%, 2%, or 4%. Each grating was a half-scale model of the prototype. The capacity of each grating was obtained by actual m~asurement. The width of each grating, 36 in. for the' prototype in a paved channel and. 48 in. in a grassed channel, was held con- stant throughout the tests whereas the length of grating 'ranged from 18 in. to 48 in. The tests showed that, with an increase in length of the inlet, the capacity increased; the increase depends also upon the grade of the channel, the swale slope, and the back slope. In a grassed channel equal side slopes carry more water than unequal side slopes; both at slopes of 6:1 are superior to both at 12:1; and a flat grade enables more water to enter a grating than a steep grade. A good modulus of th~ capacity of an inlet is that flow rate of which 98% enters into the inlet and 2% bypasses the inlet. 17. Key Words 18. Oi stri bution Statement Capacity of inlets, ,channels, drainage, No restrictions. This document is design capacity, efficiency, grat~ngs, available to the public through the . highway drainage, inlets, model tests, .National Technical Information Service, models, runoff, water Springfield, VA 22161. 19. 'Securi ty Clossif. (or thi s repart) 20. Security Classif. (of this page) 21- No. of Pages 22. Price Unclassified Unclassified 102 Form DOT F 1700.7 (8-72) Reproducti on of comp Ieted page authori zed ABSTRACT The results of an investigation on an experimental model are presented about the optimal dimensions of gratings on highway drainage inlets that are installed in channels along highways in Pennsylvania. The channel considered was triangular in shape with swale slopes rang- ing from 48:1 to 12:1 for the paved channel and from 12:1 to 6:1 for the grassed channel and with back slopes ranging from 3:~ to 1/8:1 for the paved channel and from 6:1 to 1/2:1 for the grassed channel. The grade of the channel was either 0.5%, 2%, or 4%. Each model grating was built to half of the scale of the prototype. Through model laws other prototype-model relationships were established. The capacity of each grating was obtained by actual measurement. The width of each grating, 36 -in. for the prototype in a paved channel and 48 in. in a grassed channel, was held constant throughout the tests whereas the length of grating ranged from 18 in to 48 in. The tests showed that, with an increase in -length of the inlet, the capacity of the-inlet increased; the increase depends also upon the grade of the channel, the swale slope, and the back slope. Additionally, in a grassed channel equal side slopes carry more water than unequal side slopes, that both at slopes of 6~1 are superior to both at 12:1, and that a flat grade enables mor~ water to enter a grating than a steep grade. A good modulus of the capacity of an inlet is that flow rate of which 98% enters into the inlet and 2% bypasses the inlet. ii TABLE OF CONTENTS ABSTRACT ii TABLE OF CONTENTS iii LIST OF TABLES v LIST OF FIGURES vi 1. INTRODlJCTION 1 1.1 PROBI.ID-f STATEMENT 1 1.2 BACKGROtJ~m 2 1.3 OBJECTIVES 3 2. MODEL LAWS 5 2.1 GE1-lERAL REMARKS 5 2.2 HYDRAULIC SIMILIT1JDE 6 2.2.1 Geometric Aimilitude 6 2.2.2 Kinematic Similitude 7 2.2.3 Dynamic Similitude 7 2,3 DIMENSIONLESS ~rrmrnERS 8 2.4 FROUDE MODEL LAW 9 2.5 MANNING MODEL T.AW 10 2.h CONCLUDING REMARKS 14 3. MODEL ROlTGHNESS 15 3• 1 GENERAL REMARKS 15 3.2 FINDING AN APPROPRIArE ARTIFICIAL SURFA~E 15 3.2.1 "Astroturf" 16 3.2.2 Test Procedure 16 3.2.3 Results and Conclusions 17 4 • EXPEF.I'MENTAL INVESTIGATION 18 4.1 LABORATORY EQUIPMENT 18 4.1.1 General Requirements of the Model 18 4.1.2 Apparatus 19 4.1.3 Model Construction 23 4 •2 THE DRAINAGE INLET 26 4.2.1 The Drainage, Inlet in Grassed Channels 26 4.2.2 The Drainage Inlet in Paved Channels 31 iii 4.3 PROCEDURE 34 4.3.1 Flow Measurements 34 4.3.2 Depth and Width Measurements 36 4.3.3 Technique 38 5. RESULTS 40 5.1 INTRODUCTION 40 5.2 INLt;T TIl GRASSED CHANNEL WITH MILD SLOPES 41 5.3 INLET IN GRASSED CHANNEL WITH STEEP SLOPES 42 5 .4 NOMINAL CAPACI'I"f OF GRATINGS IN GRASSED CHANNELS 60 5.5 rnLET m PAVED CHANNEL ' 64 6. DISCUSSION 69 6.1 REMARKS 69 6.2 rnLET IN GRASSED CHANNEL WITH MILD SLOPES 69 6.3 INLET:rn GRASSED CHANNEL WITH STEEP SLOPES 71 6 .4 NOMINAL CAPACITY OF INLET IN GRASSED CHANNEL 72 6.5 INLET IN PAVED CHANNEL 72 6.6 PHOTOGRAPHS OF FLOW TO AN INLET 74 7 • CONCLUSION 79 7 • 1 mLET m GRASSED CHANNEL WITH MILD SLOPES 79 7 .2 TIlLET IN GRASSED CHANNEL WITH STEEP SLOPES 79 7 .3 NOMINAL CAPACITY OF INLET IN GRASSED CHANNEL 80 7.4 INLET m PAVED CHANNEL 81 7.5 ARRANGEMENT OF GRATING BARS 81 8. RECOMMENDAT'IONS 82 9 • ACKNOWLEDG'El1ENTS 83 10. NOMENCLATURE 84 11. BIBLIOGRAPHY 85 12 • APPENDIX 86 iv LIST OF TABLES Table 2.1 Mddel Scales for Froude and Manning Similitudes 11 3.1 Experimental Results for tlAstroturf" Manning Roughness 17 5.1 Capacity of Prototype Gratings in Grassed Channels, Mild 44 Back Slopes (English Units) 5.2 Specific Capacity of Prototype Gratings in Grassed Channels, 48 Mi.ld Back Slopes (English Units) 5.3 Capacity of Prototype Gratings in Grassed Channels, Steep 52 Back Slopes (~nglish Units) 5.4 Specific Capacity of Prototype Gratings in Grassed Channels, 56 Steep Back Slopes (English Units) 5.5 Nominal Capacity, Q~8' of Gratings in Grassed Channels, Dressed 64 Slopes (English. Units) 5.6 Capacity of Prototype Gratings in Paved Channels (English Units) 65 5.7 Specific Capacity of Prototype Gratings in Paved Channels 66 (English Units) 6.1 Flow in a Paved Channel; Prototype Flow Rate 74 Capacity of Prototype Gratings in Grassed Channels, Mild 88 Back Slopes (S1 Units) A.2 Specific Capacity of Prototype Gratings in Grassed Channels, 89 Mild Back Slopes (SI Units) A.3 Capacity of Prototype Gratings in Grassed Channels, Steep 90 Back Slopes (8I Units) A.4 Specific Capacity of Prototype Gratings in Grassed Channels, 91 Steep Back Slopes (5I 'Units) A.5 Nominal Capacity, Q98' of Gratings in Grassed Channels, Dressed 92 Slopes (8I Units) A.6 Capacity of Prototype Gratings in Paved Channels CSI Units) 93 A., 7 Specific Capacity of Prototype Gratings in Paved Channels 94 (SI Units) v LIST OF FIGURES Figure 2.1 Similitude of Highway Inlet Gratings 6 4.1 Schematic Diagram of Model 20 4.2 Cutaway View of Testing Apparatus 22 4.3 Testing Apparatus 24 4.4 Upstream View of Testing Apparatus 27 4.5 Upstream End of Model Apparatus 27 4.6 Inlet Grating for Grassed Channel with Prototype 29 Dirnens ions 4.7 Installation of Model Grating in Grassed Channel 30 4.8 Inlet Grating for Paved Channel with Prototype Dimensions 32 4.9 Installation of Model Grating in Paved Channel 4.10 Sample Data Sheet-for Flow at Inlet with Dressed Slopes 35 4.11 Device for Measuring Depth and Width of Water 37 5.1a Dr~ssed Slopes Adjacent to Inlet 43 5.1b Inlet with Nondressed Slopes 43 5.2 Capacity vs. Length of Grating, Grassed Channels with Mild 45 Back Slopes; Prototype; 0.5% Grade 5.3 Capacity VB. Length of Grating, Grassed Channels with Mild 46 Back Slopes; Prototype; 2% Grade 5.4 Capacity vs. Length of Grating, Grassed Channels with Mild 47 Back Slopes; Prototype; 4% Grade 5.5 Specific Capacity vs. Length of Grating, Grassed Channels 49 with Mild Back Slopes; Prototype; 0.5% Grade 5.6 Specific Capacity vs. Length of Grating, Grassed Channels 50 with Mild Back Slopes; Prototype; 2% Grade 5.7 Specific Capacity vs. Length of Grating, Grassed Channels with 51 Mild Back Slopes; Prototype;· 4% Grade 5.8 Capacity vs. Length of Grating, Grassed Channels with Steep Back 531 Slopes; Prototype; 0.5% Grade vi Figure 5.9 Capacity VB. Length of Grating, Grassed Channels with Steep 54 Back Slopes; Prototype; 2% Grade 5.10 Capacity VB. Length of Grating, Grassed Channels with Steep 55 Back Slopes; Prototype; 4% Grade 5.11 Specific Capacity VB. Length of Grating, Grassed Channels with 57 Steep Back Slopes; Prototype; 0.5% Grade 5.12 Specific Capa-city vs. Length of Grating, Grassed Channels with 58 Steep Back Slopes; Prototype; 2% Grade 5.13 Specific Capacity vs. Length of Grating, Grassed Channels 59 with Steep Back Slopes; Prototype; 4% Grade 5.14 Efficiency of Inlet Gratings VB. Flow Rate in Grassed Channels 61 with Dressed Slopes; Prototype; 0.5% Grade 5.15 Efficiency of Inlet Gratings VB Flow Rate in Grassed Channels, 62 with Dressed Slopes; Prototype; 2% Grade 5.16 Efficiency of Inlet Gratings vs Flow Rate in Grassed Channels 63 with Dressed Slopes; Prototype; 4% Grade 5.17 Capacity vs. L~ngth of Grating, Fave.d' Ch_a.nnels~ Prototype; 67 Grades of O~5%, 2%, 4% 5.18 Specific Capacity VS~ Length bf Grating, Paved Charinels; 68 Prototype; Grades of O~5%, 2%, 4% 6.1 Flow in a Paved Channel; 0.5·Q( ) 76 max 6.2 Flow in a Paved Channel; 76 Q(max) 6.3 Flow in a Paved Channel; 2 Q 77 (max) 6.4 Flow in a Paved Channel; 77 2.5 Q(max) 6.5 Flow in a Paved Channel; 78 3 Q(" max) vii

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