advanced drainage system - Polypipe

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General Structural Design 3.2 Ridgidrain Advanced Drainage System Figure 3.2.4 Surcharge Pressure P s due to vehicle wheels 100 90 80 70 60 50 40 30 Main Roads 20 Light Roads P S , kN/m 2 10 9 8 7 Fields 6 5 4 3 2 Inclusive of relevant impact factors 1 0.5 .6 .7 .8 .9 1 2 Reference (BS EN 1295-1) Cover Depth, m 3 4 5 6 7 8 9 10 54
General Structural Design 3.2 It should be noted that the advice and guide values provided by this manual and BS EN 1295, for the various design parameters, is generally conservative. These values are provided to facilitate design, where precise details of types of soil and installation conditions are not available. The choice of design assumptions is left to the judgement of the engineer. 3.2.2 Prediction of buckling resistance The buckling resistance of buried, flexible non-pressure pipelines is a combination of the pipes inherent buckling resistance and support afforded by the pipe surround. The critical buckling pressure of a buried pipe is substantially greater than that for unrestrained pipes subject to external loading. BS EN 1295-1:1995, recommends buckling calculations be performed to ensure that a sufficient factor of safety exists when the critical buckling pressure is compared against actual buckling pressure. It should be noted that when performing the following calculation with a weak native soil, the resultant factor of safety may fall just below the recommended value of 2.0. In <strong>Polypipe</strong>’s experience, buckling has not been a critical mode of failure where pipe deflections are less than 15%. A buckling check with a factor of safety just below the recommended minimum, despite a predicted level of deformation within the appropriate performance limit, may be attributed to how the buckling calculations use short and long-term pipe modulus. Stiffness (commonly also known as Young’s modulus) may be defined as: E = σ /ε Where: E = Young’s Modulus (kN/m 2 ) σ = Stress (kN/m 2 ) ε = Strain (dimensionless) NOTE: In this instance strain relates to the amount of pipe deflection. This equation shows that, if stress is constant and strain (deflection) increases, then a material’s modulus must therefore decrease. This empirical relationship holds true for laboratory-based creep testing of the pipe - where the pipe deflection (strain) is not limited or restrained. Therefore as deflection of the pipe increases over time, it’s modulus apparently decreases - leading to a lower long term stiffness value. If making a similar assumption for pipes installed in the ground, where the imposed load (stress) is assumed to be constant after backfilling. If a pipe continues to deflect (an increase in strain) over time, according to the above empirical relationship the pipe modulus must therefore decrease. However research has shown that exhumed pipes do not decrease in stiffness but in fact have a post-installation stiffness equal to, or actually higher, than that when it was manufactured. Passive earth pressures generated in the side-fill restrict deformation of a pipe buried in the ground. Once installed, any significant increase in pipe deformation requires the pipe and soil structure to creep or deform, or a change in the imposed loading to occur. The stiffness of the backfill surrounding the pipe (vastly superior to that of the pipe itself) plays the most significant part in this pipe/soil <strong>system</strong>. Buckling check with soil support: 1 Factor of Safety, Fs = ≥ 2.0 (Pe/Pcrl)+[(Ps+Pv)/Pcrs] Where: Pcr* = 0.6(EI/D 3 ) 0.33 .(E’) 0.67 *The long and short term values of the pipe modulus (E) are used to calculate (Pcrl and Pcrs respectively) the critical pressure for buckling of flexible pipes. Where the depth of cover is less than 1.5m, an addition check is performed to mimic the temporary case of adjacent excavations. Buckling check without soil support: Pcrs Factor of Safety, Fs = ≥ 1.5 (Pe+Pv) Where: Pcrs* = 24 x EI/D 3 [*The short term value of pipe modulus (E) is used to calculate Pcrs] 55
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Uniclass G581 C1/SfB (52.3) October
Page 3 and 4: Contents Company Introduction 3 Str
Page 5 and 6: CONTACTS Polypipe Civils Division P
Page 7 and 8: Ridgidrain introduction 1.1 Ridgidr
Page 9 and 10: BBA BRITISH BOARD OF Ridgidrain AGR
Page 11 and 12: Ridgidrain Pipe Dimensions 1.2 90°
Page 13 and 14: Ridgidrain Pipe Dimensions 1.2 90°
Page 15 and 16: Pipe detail specifications Ridgidra
Page 17 and 18: Ridgidrain Pipe Design Properties 1
Page 19 and 20: Ridgidrain Installation 1.5 Standar
Page 21 and 22: Ridgidrain Installation 1.5 Midi-gu
Page 23 and 24: Ridgidrain Installation 1.5 Special
Page 25 and 26: Ridgidrain Model Specification Clau
Page 27 and 28: Ridgisewer and Polysewer Introducti
Page 29 and 30: BBA BRITISH BOARD OF AGRÉMENT CERT
Page 31 and 32: Polysewer Pipe Dimensions 2.2 45°
Page 33 and 34: Ridgisewer Pipe Dimensions 2.2 Plai
Page 35 and 36: Ridgisewer Pipe Dimensions 2.2 90°
Page 37 and 38: Ridgisewer Pipe Dimensions 2.2 11.2
Page 39 and 40: Ridgisewer Pipe Dimensions 2.2 Rock
Page 41 and 42: Ridgisewer Pipe Specification 2.3 S
Page 43 and 44: 1ess than 1.2m Road Construction St
Page 45 and 46: Ridgisewer Installation 2.5 Concret
Page 47 and 48: General Introduction and Cover Dept
Page 49 and 50: General Structural Design 3.2 Metho
Page 51 and 52: General Structural Design 3.2 Figur
Page 53: General Structural Design 3.2 Figur
Page 57 and 58: General Structural Design 3.2 Table
Page 59 and 60: General Hydraulic Design 3.3 Hydrau
Page 61 and 62: 750 500 450 375 150 100 General Hyd
Page 63 and 64: General Properties 3.4 Urban draina
Page 65 and 66: General Properties 3.4 Abrasion Res
Page 67 and 68: General Properties 3.4 Chemical Res
Page 69 and 70: General Site Instructions 3.5 Gener
Page 71 and 72: General Site Instructions 3.5 Joint
Page 73 and 74: General Site Instructions 3.5 Recom
Page 75 and 76: General Maintenance 3.6 Maintenance
Page 77 and 78: FAQ Section 3.8 What special requir
Page 79 and 80: FAQ Section 3.8 Q. How are pre-fabr
Page 81 and 82: FAQ Section 3.8 b) Spigot and socke
Page 83 and 84: References 3.9 British Standards In
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advanced drainage system - Polypipe

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