Technical Overview of Concrete Pipe Design, Installation, Inspection and Construction Pitfalls

Transcription

1 Technical Overview of Concrete Pipe Design, Installation, Inspection and Construction Pitfalls

2 Rinker Materials-Concrete Pipe Division Sarah Matin, P.E. BS Civil Engineering University of Central Florida Technical Promotions Engineer A proud member of the Florida Concrete Pipe Association & American Concrete Pipe Association

3 Concrete Pipe Division One of the Nation s largest and leading manufacturers of concrete pipe and related products. Founded in 1963 and acquired by QUIKRETE in 2017 Comprised of over 40 facilities that serve 30 states Corporate office in Houston, TX. We produce a full range of concrete piping products from Precast box culverts from 3 x2 to spans up to 24 wide Stormceptor a storm water pollution control device

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5 Design Review Concrete Pipe Design Material Properties Soil Requirements Design Specifications Basic Rigid Pipe Design Installation Construction Pitfalls Inspection How to interpret video inspection

6 Going Back to School

7 Design Parameters Its not just a conduit Stress Strain Lateral Forces Pressure Static/Dead Loading Live Loading Elasticity Modulus Elastic/Plastic Deformation Ultimate Force

8 Design Concepts

9 Pipe Design Fundamentals What 2 functions must an underground pipe provide? Conduit Structure

10 Pipe Design Fundamentals A Buried Structure and Conduit o Pipe Properties o Properties of the Soil Surrounding The Pipe Rigid Pipe Design o Active Earth Pressures o Pipe Majority of Strength

11 Pipe Design Fundamentals Rigid Pipe: Pipe is stronger than the backfill Pipe must carry the majority of the load. Strength: Designed to resist stress and transmit the loads on the pipe through the pipe walls to the foundation soil beneath. Flexible Pipe: Pipe is more flexible than backfill Embedment must carry most of the load. Stiffness: Designed to transmit part of the load to the soil at the sides of the pipe and resist deflection.

12 Pipe Design Fundamentals 90% Strength In Pipe Structure Installation Contribution Concrete Pipe Pipe RCP Pipe Contribution 10% Strength In Pipe Structure HDPE Pipe Contribution Installation Plastic Pipe

13 Basic Pipe Design D.01 W B e fe W B L fll FS S Design Method (5 steps): 1. Determination of Earth Load 2. Determination of Live Load 3. Selection of Standard Installation 4. Determination of Bedding Factor 5. Selection of Pipe Strength

14 Dead and Live Load Live load Dead load Pipe

15 Live Load Sources Highway loads Railroad loads Aircraft loads Construction loads Other

16 Dead Load

17 Trench Basics Installation Types: Narrow Trench Jacked/Tunneled Negative Projection Positive Projection 23

18 Trench Basics Installation Types: Narrow Trench Negative Projection (Embankment) Jacked / Tunneled Positive Projection (Embankment) 24 Lots of Help In Situ Help Very Little Help

19 25 Trenching Minimum Trench Widths AASHTO 27 AASHTO 30 Trench width shall be wider than shown if required for adequate compaction. A trench that is too narrow doesn t allow room for compaction. A trench that is too wide doesn t achieve support from the trench walls. When specified trench width is exceeded, engineer shall be notified RCP Plastic Pipe Dia (in) Trench Width (min) Trench Width (min) O.D. + 24" 1.5 x 0.D. + 12"

20 RCP Trench AASHTO Section 27 Trench Width D o / Min Construction Cover Min Cover (special design) Final Backfill D o Springline D i Haunchin g Invert ⅓ D o Bedding 3 6 Minimum Rocky Loosely Placed Bedding Foundation

21 Soil Basics Gradation: Well-graded soil has all sizes of material present from the No. 4 sieve to the No. 200 sieve. Poorly-graded soil may be uniformed-graded or gap-graded. When coarse, open graded (poorly graded) material is placed adjacent to finer materials, the fines may move into the voids in the coarse material because of groundwater flow. This process is known as Migration of Fines. 27

22 Soil Basics Gradation: USCS System Boulders 12 + Cobbles 3 to 12 Gravel Fine Gravel - peas to marbles Course Gravel - grapes to tennis balls Sand Fine Sand - table salt Medium Sand - Virginia Beach Course Sand - ice cream salt Fines Clay - talcum powder (plasticity over a range of moisture contents) (resistance to crushing when air dry) Silt - talcum powder (very little plasticity when moist) (little resistance to crushing when air is dry)

23 Soil Basics Compaction: Water content Type of Soil Compactive effort: Lift thickness, number of roller passes, weight Type of compaction equipment Smooth drum, sheepsfoot, pneumatic tire, vibrating plate, vibratory or static, etc The speed of application Energy Water Content Soil Type Compaction Effort Layer Thickness

24 Soil Basics Compaction: Placing Backfill Materials Heger Pressure Distribution: Dr Frank Heger evaluated SPIDA results and created the Heger Soil Pressure Distribution diagram widely used today. SPIDA research found that embedment materials within 40 degrees of the invert cannot be compacted. Rigid Pipe Standard Installations, Types 1-4, take this lack of compaction into account. Bridging: When backfill is dumped into a trench on either side of a pipe, the angle of repose of the backfill material often exceeds the radius of the pipe wall and begins to bridge or accumulate at the pipe haunches leaving a void between soil and pipe wall. National Clay Pipe Institute Youtube Video

25 Soil Basics Compaction: Some compaction equipment is better suited to different types of soils: Steel wheeled rollers Sheepsfoot rollers Rubber tired rollers Coarse aggregates Cohesive clays or silts Clays to sands

26 Installation Types Lower Strength Loading and Supporting Strengths The four Standard Installations provide an optimum range of soilpipe interaction characteristics. Higher Strength

27 Three-Edge Bearing Test Applied Load Test Specimen The strength test requirement under the threeedge-bearing method shall be either the D-load (test load expressed in pounds-force per linear foot per foot of diameter) to produce a 0.01-in. crack ASTM C497 Supports

28 Bedding Factor D.01 W B e fe Bf W B M M L fll Test FS Ratio between the supporting strength of the pipe in the three-edge-bearing test to the strength of the pipe in the buried condition. S Field The better the installation, the higher the bedding factor o Better Load Distribution o Lower Stress Levels

29 RCP D-Load ASTM C76 Class D-Load Service D-Load Ultimate V 3000 lb/ft/ft 3750 lb/ft/ft D IV 2000 lb/ft/ft 3000 lb/ft/ft III 1350 lb/ft/ft 2000 lb/ft/ft II 1000 lb/ft/ft 1500 lb/ft/ft I 800 lb/ft/ft 1200 lb/ft/ft W E WL - Load F... B. F. D S B.F. = M 1 M 2 The 3EB Test loads the pipe from above, and results in longitudinal cracking in the Tension Zones. 35

30 RCP Proof of Design 48 ASTM C-76 Class III: D 0.01 = 1350 lb/ft/ft D ULT = 2000 lb/ft/ft Total Load Required: D 0.01 = (48 /12)(8 )(1350) = 43,200 lbs. D ULT = (48 /12)(8 )(2000) = 64,000 lbs. Plant Proof of Design ,000 lb F250 14,000 lb African Elephant 53,000 lb CAT

31 Pipe Classifications Pipe Strength for 48 Diameter ASTM C76 Class III Class IV Class V D-0.01 D-Ult ,200# 64,000# D-0.01 D-Ult ,000# 96,000# D-0.01 D-Ult ,000# 120,000# Yield Strength for 0.01 Crack ASTM C 76 Recipe Concrete + Wall Thickness + Steel Reinforcement for Each Size and Strength Class

32 Selection of Pipe Strength

33 Ways to Determine Pipe Strength o Fill height tables o Computer software - PipePac o Plug & chug - Blue book

34 Standard RCP D-Load Strength Classes (ASTM C-76) Class I = 800 lb/ft/ft Class II = 1,000 lb/ft/ft Class III = 1,350 lb/ft/ft Class IV = 2,000 lb/ft/ft Class V = 3,000 lb/ft/ft *Yield Strength for 0.01 crack

35 Example Hand Calculations Given: A 36-inch pipe is to be installed with 6 feet of cover in an embankment. The backfill will be sandy silt, compacted to 90% standard Proctor density. Design for HS 20 Loading. Find: The required pipe strength in terms of inch crack D-load.

36 Selection of Pipe Strength D.01 W B e fe W B L fll FS S W E = Earth Load W L = Live Load B f = Bedding Factor S = Pipe Diameter FS = Safety Factor

37 Earth Loads Prism Load Weight of the Soil directly above the pipe

38 Vertical Arching Factor (VAF) Net Increase to Prism Load (PL)(multiplier) Embankment (We = VAF x PL) o Type 1 = 1.35 o Type 2 = 1.40 o Type 3 = 1.40 o Type 4 = 1.45 Trench o Depends on Soil Type / Strength o Calculated differently (not # < 1.0)

39 D P P P o L L L W VAF 1.4 (Type 3 Installation) W W e e e w H lb / ft3 6' lb/ft VAF (P 1.4 ( lb/ft) L ) lb/ft feet D o(4 - ) 8 D o 3.67'(4 - ) 3.67' 8 6 Depth of cover

40 550

41 B fll B fe

42 ft ft lb D ft lb ft lb D S FS B W B W D fll L fe e / / / /

43 Plan Notes Matter! All Specifications must be followed from FDOT in this case, even if the client is not FDOT.

44 FDOT Specifications

45 Installation Joint Gaps: =5/ =7/8 72 and larger=1 1/3 of pipe circumference out of tolerance

46 Cracks: Greater than 0.01 Longer than 12 Installation

47 Inspection

48 Current Final Inspection Protocol-FDOT

49 How do you Interpret Video Inspection? o Joint Spacing o Staining o Infiltration o Cracking o Active Flow Inspection

50 Inherent Moisture in Pipe Wall exaggerates hairline (<0.01 ) cracks

51 Free of debris ASTM C1840 Inspection and Acceptance of Installed Reinforced Concrete Pipe May 2017 Pipe Inspection Criteria Equipment ability, 0.05 Measure cracks ft/min for observation

52 A few terms Infiltration Spalling Calcium Carbonate Hydration Autogenous Healing Soil/Watermark Staining Rust Colored Staining ASTM C1840 Inspection and Acceptance of Installed Reinforced Concrete Pipe May

53 ASTM C1840 Pipe Evaluation and Acceptable Criteria Cracks shall be evaluated based on crack pattern, length, width and environmental conditions Cracks <0.01 no further investigation Longitudinal cracks </= 0.05 and length up entire length in a non corrosive environment are acceptable Cracks filled with calcium carbonate and not measured > to 0.01 no further investigation (review by a Specialty Engineer for >0.01 ) Cracks in joints <0.01 no further investigation

54 ASTM C1840 Infiltration Defined Level 1 Infiltration: moisture visible on the surface of the pipe wall without any observable active water movement such as drips or water traveling along the surface. Level 2 Infiltration: the slow entry of water identified by visible drips or a constant flow of water traveling along the surface Level 3 Infiltration: a continuous stream of water running into the pipe or spraying through the pipe wall under pressure

55 ASTM C1840 Level 1 Infiltration

56 ASTM C1840 Level 2 Infiltration

57 ASTM C1840 Level 3 Infiltration

58 Construction Protocol

59 Inspection

60 Drainage Manual

61 Drainage Manual

62 So, if the pipe is strong enough to be installed at over 20 feet depth, but is only about 6 feet deep, then why does it sometimes crack?

63 Weight: ~ 25,400 lbs. Min. Vibratory Force: ~ 32,000 lbs. Max. Vibratory Force: ~67,000 lbs.

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66 Poor Installation Issues Poor bedding circumferential cracks Push bells to grade w/bucket impacts Haul routes broken backs / bellies Roadbed subgrade stabilization impact, circumferential and longitudinal cracks Poor gasket / joint assembly joint gaps and leaks

67 Product Durability ASTM C-76, ASTM C1479, ACPA Design Guidelines 100 year Design Life High Risk Environments Fire Hydrostatic Concerns High Fill

68 Installation Large Diameter Installation adjacent to high volume facility

69 Installation Large Diameter Installation at base and within MSE (Mechanically Stabilized Earth) Wall

70 Pipe Design Fundamentals Three Pillars of Buried Infrastructure Design Installation Inspection Installation - Inspection

71 Questions?