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BS 9295:2020 Guide to the structural design of buried pipes, 2020
- Foreword
- 0 Introduction
- 1 Scope
- 2 Normative references
- 3 Terms, definitions and symbols
- 4 Concepts used in the structural design of buried pipes [Go to Page]
- 4.1 The buried pipe system
- 4.2 Longitudinal and sectional behaviour
- 4.3 Classification of buried pipes
- Figure 1 — Design criteria for pipes laid in open trench
- Table 1 — Pipe classification
- Figure 2 — Rigid and flexible pipe behaviour
- 4.4 Design models
- Figure 3 — Soil pressure changes immediately after pipe burial
- 4.5 Short-term and long-term stiffness characteristics of polymeric pipe materials
- 4.6 Classification of native/embedment soils and trench width
- Figure 4 — Effective trench width, Bd
- 4.7 Key parameters to be specified by the designer
- 4.8 Pipe and design method selection
- Figure 5 — Clauses applicable to the selection and design of pipe
- 5 Classification and calculation of loads [Go to Page]
- 5.1 Introduction
- 5.2 Vehicle surcharge loads
- Figure 6 — Illustration of eccentric surcharge load on pipe
- 5.3 Road and field surcharge loads
- Figure 7 — Loading configurations
- Figure 8 — Example of calculated backfill, road traffic surcharge and combined loadings expressed as a line load on a rigid DN 300 pipe
- Table 2 — Surcharge pressures (kN/m2), Ps, as function of depth of cover to crown, H
- Figure 9 — Surcharge pressure (kN/m2), Ps, due to vehicle wheels
- 5.4 Surcharge pressure due to construction vehicles
- Figure 10 — Surcharge pressure, Ps, due to construction vehicles
- 5.5 Railway loadings
- Figure 11 — Loading configurations for LM 71 and RL railway loading models
- Figure 12 — BS EN 1991-2:2003, load model 71 (α = 1.0) (RU to BS 5400-2� surcharge pressure at depth
- Figure 13 — Rail London (RL to BS 5400-2) surcharge pressures at depth
- Figure 14 — Factor for calculating multi-track railway loadings
- 6 Rigid pipe design [Go to Page]
- Figure 15 — Flowchart for pipe design with rigid pipes
- 6.1 General
- 6.2 Wide and narrow trenches
- Figure 16 — Effect of trench width, Bd, on calculated vertical backfill load on pipe
- Figure 17 — The silo effect
- 6.3 Complete and incomplete projection
- Figure 18 — Complete projection
- Figure 19 — Incomplete projection
- 6.4 Settlement deflection ratio, rsd
- Figure 20 — Settlement deflection ratio
- Table 3 — Guide values of Spangler modulus for native soils, E′3
- 6.5 Projection ratio, ρ
- 6.6 Soil properties
- Table 4 — Values of Kμ and Kμ′ for specific soil types
- 6.7 Bedding factors
- 6.8 Crushing strength adjustments for pressure pipes
- 6.9 Minimum bedding factor and factor of safety
- Table 5 — Rigid pipe embedment
- 6.10 Design loads for rigid pipes
- Table 6 — Design bedding factors for pipes laid in wide trench and embankment conditions with bedding classes B and S and outside diameter greater than or equal to 900 mmA)
- Table 7 — Load coefficients for incomplete projection condition
- 6.11 Supporting strength of rigid pipes
- 6.12 Factors of safety
- Table 8 — Minimum values of Fse and Fsi
- 6.13 Limit state design
- Table 9 — Design factors of actions
- 6.14 Design of egg-shaped pipes
- Figure 21 — Dimensions and bedding distribution cases for egg-shaped pipes
- Table 10 — Bending moment coefficients for egg-shaped pipes
- 6.15 Simplified bedding table for vitrified clay pipes
- Table 11 — Simplified table for the embedment of vitrified clay pipes in wide trench conditions
- 6.16 Simplified bedding table for concrete pipes
- Table 12 — Simplified bedding table for concrete pipes – Strength class 120
- 7 Flexible pipe design [Go to Page]
- 7.1 General
- 7.2 Marston-Spangler method
- Figure 22A — Flowchart for pipe design: GRP pipes
- Figure 23B — Flowchart for pipe design: Steel pipes
- Figure 23C — Flowchart for pipe design: Thermoplastics pipes
- Table 13 — Guide values of Spangler modulus for native soils, E′3
- Table 14 — Semi-rigid and flexible pipe embedment properties
- Table 15 — Flexible pipe embedments
- Figure 23 — Deflection lag factor
- Table 16 — Design values of initial deflection, ∆0/D
- 7.3 Gumbel method
- Figure 24 — Principal deformation modes of the buried pipe ring
- Figure 25 — External loads on the pipe-soil system
- Figure 26 — Components of load on the pipe-soil system
- Table 17 — Msb values A)
- Table 18 — Msn values
- Table 19 — Values of soil support combination factor, Sc
- Table 20 — K values for design
- Table 21 — Design values of initial deflection, δy0
- Table 22 — Values of δy2 for design
- Figure 27 — Linear buckling modes
- Table 23 — Values of ksc for design
- 8 Semi-rigid pipe design [Go to Page]
- 8.1 General
- Figure 28 — Flowchart for design of semi-rigid pipes of ductile iron
- 8.2 Installation conditions
- Table 24 — Semi-rigid pipe embedments
- Table 25 — Semi-rigid and flexible pipe embedment properties
- 8.3 Design pressures for semi-rigid pipes
- Table 26 — Load coefficients for incomplete projection condition
- Figure 29 — Deflection lag factor
- Table 27 — Guide values of Spangler modulus for native soils, E′3
- 8.4 Semi-rigid pipe embedment properties
- 8.5 Design data for semi-rigid pipes
- 8.6 Bedding for ductile iron pipes
- Table 28 — Embedment classes
- 8.7 Simplified bedding table for ductile iron pipes
- Table 29 — Safe depths of cover (m) for ductile iron water pipe with field surcharge
- Table 30 — Safe depths of cover (m) for ductile iron water pipe with main road surcharge
- Table 31 — Safe depths of cover (m) for ductile iron sewer pipe with field surcharge
- Table 32 — Safe depths of cover (m) for ductile iron sewer pipe with main road surcharge
- Annex A (informative) Other design considerations [Go to Page]
- Figure A.1 — Soil loads and stresses produced by surface loads (after Fadum [13])
- Figure A.2 — Uniform surcharge Us /unit area of limited extent in fixed position
- Figure A.3 — Pipe in tunnel, heading or jacked into place
- Figure A.4 — Multiple pipe trenches
- Figure A.5 — Uneven loading of multiple pipes laid in parallel
- Figure A.6 — Circumstances which can result in large lateral loads: Embankment
- Figure A.7 — Schematic of groundwater flotation forces
- Figure A.8 — Pipelines in poor ground
- Figure A.9 — Use of geotextile around pipe embedment
- Figure A.10 — Pipeline on piles
- Table A.1 — Recommended maximum length of rocker pipes
- Figure A.11 — Protection of a shallow pipeline using concrete surround
- Figure A.12 — Protection of shallow pipeline with a slab
- Figure A.13 — Plain and reinforced beddings and surrounds
- Figure A.14 — Pipework under a floor slab
- Figure A.15 — Pipework built in to the wall
- Figure A.16 — Pipework passing through the wall
- Table A.2 — Overview of limit state conditions to be checked for longitudinal effects
- Table A.3 — Compaction fractions for bedding materials
- Table A.4 — Gradings
- Table A.5 — Maximum recommended level of impurity (by mass)
- Table A.6 — Equation errors (percent)
- Bibliography [Go to Page]
