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Proposed Specifications for LRFD Soil-Nailing Design and Construction (2011)

Chapter: Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls

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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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Suggested Citation:"Appendix A - Proposed LRFD Design Specifications for Soil Nail Walls." National Academies of Sciences, Engineering, and Medicine. 2011. Proposed Specifications for LRFD Soil-Nailing Design and Construction. Washington, DC: The National Academies Press. doi: 10.17226/13327.
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A-1 Revisions to SECTION 11 AASHTO LRFD Bridge Design Specifications TABLE OF CONTENTS 11.1 SCOPE ..................................................................................................................... ................. A-2 11.2 DEFINITIONS ............................................................................................................... ........... A-2 11.3 NOTATION .................................................................................................................. ............ A-2 11.3.1 General ................................................................................................................ ............ A-2 11.5 LIMIT AND RESISTANCE FACTORS .................................................................................. A-5 11.5.2 Service Limit States ................................................................................................... ..... A-5 11.5.4 Resistance Requirement ................................................................................................. . A -5 11.5.6 Resistance Factors ..................................................................................................... ...... A-5 11.12 SOIL NAIL WALLS .......................................................................................................... ....... A-7 11.12.1 General Considerations ................................................................................................. .. A-7 11.12.2 Loading ................................................................................................................ ........... A-8 11.12.3 Movement and Stability at the Service Limit State ......................................................... A-8 11.12.3.1 Abutm ents ............................................................................................................ A-8 11.12.3.2 Displacements ...................................................................................................... A- 9 11.12.3.3 Overall Stability ................................................................................................. A-11 11.12.3.4 Seismic Effects on Global Stability .................................................................... A-11 11.12.4 Stability at Strengt h Limit States: Safety Against Soil Failure ..................................... A-12 11.12.4.1 Sliding .............................................................................................................. .. A-12 11.12.4.2 Basal Heave ........................................................................................................ A-13 11.12.5 Stability at Strength Lim it States: Safety Against Structural Failure ............................ A-13 11.12.5.1 General .............................................................................................................. . A -13 11.12.5.2 Nail Pullout Resistance ...................................................................................... A-13 11.12.5.3 Nom inal Bond Resistance .................................................................................. A-14 11.12.5.4 Lim it State for Soil Nail in Tension ................................................................... A-16 11.12.6 Strength Limit States: Limit States for the Facing of Soil Nail Walls .......................... A-16 11.12.6.1 General .............................................................................................................. . A -16 11.12.6.2 Flexural Lim it State ............................................................................................ A-17 11.12.6.3 Punching-Shear Resistance in Facing................................................................. A-20 11.12.6.4 Headed-Stud in Tension ..................................................................................... A-23 11.12.7 Drainage ............................................................................................................... ......... A-24 11.12.8 Corrosion Protection ................................................................................................... .. A-24 REFERENCES ..................................................................................................................... .................... A-25 A P P E N D I X A Proposed LRFD Design Specifications for Soil Nail Walls

11.1 SCOPE C11.1 This section provides requirements for design of abut me nts and walls. Conventional retaining walls, non- gravity cantilevered walls, anchored walls, mechanically stabilized earth (MSE) walls, prefabricated m odular walls, and soil nail walls are considered. 11.2 DEFINITIONS Soil Na il Wall s – A soil-retaining system that deri ves lateral resistance from a regular pattern of soil nails. S oil nails are sub-horizontal closely spaced steel bars (spacing in each direction of approximately 5 FT or with a tributary area of generally no mo re than 36 sq FT), th at are mo st co mmonly installed in a predrilled hole and subsequently encased in grout. Other installation me thods, in cluding self-drilling nails, exist. Soil nails are mo st commonly in stalled as passiv e elements whereby no post-tensioning is applied. Soil nails are connected with a facing, which is a structurally continuous reinforced shotcrete or concrete layer covering the soil nails. 11.3 NOTATION 11.3.1 General A E = Effective cross-sectional area of threaded anchors (or bolts) (C11.12.6) A H = Cross-sectional area of the connector head (IN 2 ) (11.12.6) a hm = Cross-sectional area (per unit width) of mesh reinforcem ent in the wall facing, in the horizontal direction, at midspan between soil nails (I N 2 /FT) (11.12.6) a hn = Cross-sectional area (per unit width) of mesh reinforcem ent in the wall facing, in the horizontal direction, at soil nail heads (IN 2 /FT) (11.12.6) A HH = Total cross-sectional area of additional reinforcement (i.e., waler bars) in wall facing, in the horizontal direction and around soil nail heads (IN 2 ) (C11.12.6) A S = Cross-sectional area of headed-stud shaft (IN2) (11.12.6) A t = Nail bar cross-sectional area (I N 2 ) (11.12.5) A VH = Total cross-sectional area of additional reinforcement (rebar) in wall facing, in the vertical direction and around soil nail heads (IN 2 ) (C11.12.6) a vm = Cross-sectional area (per unit width) of mesh reinforcement in the wall facing, in the vertical direction, at soil nail heads (IN 2 /FT) (11.12.6) a vn = Cross-sectional area (per unit width) of mesh reinforcement in the wall facing, in the vertical direction, at soil nail heads (IN 2 /FT) (11.12.6) C = Coefficient used for the estimation of the soil nail wall displacement (FT) (11.12.3) Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-2

A-3 C F = Factor that considers non-uniform soil pressures behind a soil nail wall facing and is used in the esti mati on of nom inal resistances at the soil nail head (DIM) (11.12.6) C P = Factor that accounts for soil contribution to support and is used in the estimation of nominal resistances at the soil nail head (DIM) (11.12.6) D C = Effective, equivalent diam eter of the potential slip conical failure in the facing around soil nail heads (FT) (11.12.6) D DE F = Horizontal distance behind soil nail wall where ground defor ma tion can be significant (FT) (11.12.3) D DH = Average diameter of soil nail drill-hole (IN) (11.12.5) D E = Effective diameter of the core of a threaded anchor (IN) (C11.12.6) D H = Diam eter of the head of a soil nail head connector (i.e., headed-stud) (IN) (11.12.6) D S = Diameter of the shaft of a soil nail head connector (i.e., headed-stud) (IN) (11.12.6) f c = Concrete com pressive no mi nal resistance (PSI) (11.12.6) f y = Yield tensile nominal resistance of soil nail bar (KSI) (11.12.5) f y- f = Yield tensile nominal resistance of reinforcement in facing (KSI) (11.12.6) f y- hs = Yield tensile no mi nal resistance of headed-stud in facing (KSI) (11.12.5) h = Thickness of facing (IN) (11.12.6) H = Wall height (FT) (11.12.3) h C = Effective depth of potential conical slip surface form ing in facing around soil nail head (FT) (11.12.6) h f = Thickness of permanent facing (IN) (11.12.6) ht = Thickness of temporary facing (IN) (11.12.6) KA = Active earth pressure coefficient of soils behind soil nail wall (DIM) (C11.12.6) L = Soil nail length (FT) (11.12.6) LBP = Bearing plate side dimension (FT) (11.12.6) LP = Pullout length extending behind slip surface (FT) (11.12.5) LS = Length of headed-stud (FT) (11.12.6) mhm = Horizontal flexural resistance (moment per unit length) mid-span between soil nails (KIP-IN/FT) (11.12.6) mhn = Horizontal flexural resistance (moment per unit length) at soil nail head (KIP-IN/FT) (11.12.6) mvm = Vertical flexural resistance (moment per unit length) mid-span between soil nails (KIP-IN/FT) (11.12.6) mvn = Vertical flexural resistance (moment per unit length) at soil nail head (KIP-IN/FT) (11.12.6) NH = Number of headed-studs in soil nail head connection (DIM) (11.12.6) nt = Number of threads per unit length in threaded anchor (i.e., bolt) (IN) (C11.12.6) qU = Nominal bond resistance of soil nails (KSI) (11.12.5) RFF = Nominal resistance for flexure in facing (KIP) (11.12.6) RFH = Nominal resistance for tension of headed-studs located in facing (KIP) (11.12.6) RFP = Nominal resistance for punching-shear in facing (KIP) (11.12.6) RPO = Nominal pullout resistance of soil nails (KIP) (11.12.5) rPO = Nominal pullout resistance per unit length of soil nails (KIP/FT) (11.12.5) RT = Nominal resistance of a soil nail bar in tension (KIP) (11.12.5) SH = Horizontal spacing of soil nails (FT) (C11.12.6; 11.12.6) SHS = Spacing of headed-studs (FT) (11.12.6) Smax = Maximum spacing of soil nails (FT) (C11.12.6) SV = Vertical spacing of soil nails (FT) (C11.12.6; 11.12.6) tH = Head thickness of headed-studs (FT) (11.12.6) Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

T ma x = Maximum load in a soil nail (KIP) (11.12.6, 11.12.6) T o = Maxim um load in the head of a soil nail (KIP) (11.12.6) t P = Thickness of bearing plate (FT) (11.12.6) V F = Punching-shear force acting through facing, around soil nail head (KIP) (11.12.6) α = Angle of batter of soil nail wall (DEG) (11.12.3) = Backslope angle (DEG) (11.12.1) δ h = Horizontal displacement at the top of a soil nail wall (FT) (11.12.3) δ v = Vertical displacem ent at the top of a soil nail wall (FT) (11.12.3) φ FF = Resistance factor for flexure in facing (DIM) (11.12.6) φ FH = Resistance factor for facing headed-stud in tension (DIM) (11.12.6) φ FP = Resistance factor for punching-shear in facing (DIM) (11.12.6) φ PO = Resistance factor for nail pullout (DIM) (11.12.5) φ T = Resistance factor for nail bar in tension (DIM) (11.12.5) γ s = Unit weight of soil (KCF) (C11.12.6) ρ ij = Reinforcement ratio in “i” direction (vertical or horizontal) and location “j” (at nail head “n,” or midspan “m ” in-between soil nails) (PERCENT) (C11.12.6) ρ ma x = Maximu m reinforcem ent ratio in facing (PERCENT) (11.12.6) ρ mi n = Minim um reinforcem ent ratio in facing (PERCENT) (11.12.6) Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-4

A-5 11.5 LIMIT AND RESISTANCE FACTORS 11.5.2 Service Limit States Deflections of soil nail walls shall be limited to the ranges presented in Section 11.12.4. 11.5.4 Resistance Requirement Abut me nts …… 11.10, 11.11, or 11.1 2 C11.5.2 In general, soil nail walls with concrete/shotcrete facing or with precast panels are mo re rigid than MSE walls with welded wire or geosynthetic facing . C11.5. 4 11.10, 11.11, and 11.1 2 ….., and soil nail walls, respectively 11.5.6 Resistance Factors The limit states shall be as specified in Article 1.3.2. Wall-specific provisions are contained in this article. Walls shall be proportioned so that the factored resistance is not less than the effects of the factored loads specified in Section 3. C11.5.6 Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

Table 11.5.6-1 Resistance Factors Limit State Resistanc e Condition Resistance Factor Value Sliding All φ τ 0.90 Soil Failure Basal Heave ALL φ b 0.70 Slope does not support a structure φ s 0.75 (1) Slope supports a structure φ s 0.65 (2) (3) Overall Stability NA Seismic φ s 0.90 (4) Mild steel bars – Grades 60 and 75 (ASTM A 615) φ T 0.56 Static High-resistance – Grade 150 (ASTM A 722) φ T 0.50 Mild steel bars – Grades 60 and 75 (ASTM A 615) φ T 0.74 Nail in Tension Seismic High-resistance – Grade 150 (ASTM A 722) φ T 0.67 Facing Flexure Temporary and final facing reinforced shotcrete or concrete φ FF 0.67 Facing Punching-Shear Temporary and final facing reinforced shotcrete or concrete φ FP 0.67 A307 Steel Bolt (ASTM A 307) φ FH 0.50 Facing Headed-Stud Tensile A325 Steel Bolt (ASTM A 325) φ FH 0.59 Sand φ PO 0.47 (5) Clay φ PO 0.51 (5) Weathered Rock φ PO 0.45 (5) Structural Pullout Soil/Rock Type All φ PO 0.49 (5) Notes: (1) Also when geotechnical parameters are well-defined. (2) Also when geotechnical parameters are based on lim ited information. (3) For temporary SNWs, use φs = 0.75. (4) Per current practice but subject to m odifications. A value φ s = 1.00 ma y be acceptable, as long as perm anent deform ations are calculated (see Anderson et al., 2008) and are found not to be excessive. Currently, there is no di fferentiation for temporary structures under seismic loading; th erefore, use φ s = 1.00. (5) From reliability-based calibration. Values shown correspond to a load factor γ = 1.00. Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-6

A-7 11.12 SOIL NAIL WALLS 11.12.1 General Considerations C11.12.1 Soil nail walls mo st commonly consist of: (a) a soil nail (i.e., steel bar) that is placed in a pre-drilled hole, then grouted along its entire length in the hole; (b) connectors in the soil nail head; and (c) a structurally continuous reinforced concrete or shotcrete cover (facing) connecting all nail heads. Figure 11.2.1-1a shows a cross-section of a typical soil nail wall and main com ponents. Horizontal nail spacing, S H , is typically the sa me as vertical nail spacing, S V , and can be between 4 and 6.5 FT, and mo st comm only 5 FT. Soil nail spacing ma y be m odified to accomm odate the presence of existing underground st ructures or utilities behind the wall. Soil nail spacing in horizontal and vertical direction mu st be such th at each nail has an in fluence area S H × Sv 40 FT 2 . Soil nail walls are top-down construction structures that are particularly well suited for ground conditions that require vertical or near-vertical cuts. Favorable ground conditions ma ke soil nailing technically feasible and cost effective, com pared with other techniques, when: • the soil in which the excavation is advanced is able to stand unsu p ported in vertical or nearly vertical, 3- to 6-FT high cuts for one to two days; • all soil nails are above the groundwater table; and • the long-term integrity of the soil nails can be maintained through corrosion protection. Subsurface conditions that are generally well suited for soil nails applications include stiff to hard fine - grained soils, dense to very dense granular soils with som e cohesion (apparent cohesion due to ce me ntation), weathered rock without weakness planes, and other competent soils with a wide gradation (i.e., glacial tills). Examples of unfavorable soil types and ground conditions include dry, loose, poorly graded cohesionless soil, soils with hi gh groundwater, soils with cobbles and boulders, soft to very soft fine-grained soils, organic soil, highly corrosive soil (e.g., cinder, slag), weathered rock with weakness planes, karstic ground, loess, and soils that generally have a liquidity index 0.2. Corrosion protection is provi ded by grouting, epoxy coating, galvanized coating, or encapsulation [not shown in Figure 11.12.1-1(a)]. See Section 11.12.8 “Corrosion Protection” for references to consider corrosion protection in the design. Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

Figure 11.12.1-1 Soil Nail Wall : (a) Typical Section, (b) Nail Head and Facing Details 11.12.2 Loading C11.12.2 The provisions of Article 11.5 shall apply. When a soil nail wall is part of a bridge abut me nt, the effect on the soil nail wall due to shrinkage and temperature from the bridge deck shall be evaluated fro m structure analysis. 11.12.3 Movement and Stability at the Service Limit State 11.2.3.1 Abutments The provisions of Articles 10.6.2.4, 10.6.2.5, 10.7.2.3 th rough 10.7.2.5, 10.8.2.2 through 10.8.2.4, and 11.5.2 shall apply as applicable. SEE DETAIL SV 15° (TYP) SOIL NAIL (TYP) PERMANENT FACING H L TEMPORARY FACING DRAINAGE SYSTEM NAIL HEAD GEOCOMPOSITE STRIP DRAIN STEEL BAR GROUT BEARING PLATE WELDED WIRE MESH REINFORCEMENT PERMANENT FACING (e.g., CAST-IN-PLACE REINFORCED CONCRETE) TEMPORARY FACING (SHOTCRETE) HEADED STUD WASHERS VERTICAL BEARING BARS WALER BARS Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-8

A-9 11.12.3. 2 D isplacements The considerations of Article 11.6.2.2 shall be considered. A soil nail wall shall be designed so as the m ove me nts of the wall rem ain within tolerable ranges. C11.12.3.2 In addition to the considerations of article 11.6.2.2 , the effects of the m ove me nt of a soil nail wall on adjacent structures shall be considered in the design. Empirical data indicate that for soil nail walls with: (a) nail-lengt h ratios, L/H, b etween 0.7 and 1.0; (b) negligible surcharge lo ads; and (c) adequate safet y margins achieved for overall stability, the ma xi mu m long-ter m horizontal and vertical displacements at the top of the wall, δ h and δ v , respectively, can be estim ated as follows (Byrne et al., 1998): H H h h ×= (C11.12.3-1 ) h v ≈ (C11.12.3-2 ) where: ( δ h /H) = ratio presented in Table 11.12.3.2-1 (DIM) H = wall height (FT) Ground deform ation considered to be o f significance can occur within a horizontal distance, D DE F , which can be estim ated as follows: ) tan (1 C H D DEF − = (C11.12.3-3 ) where: α = batter angle of wall (DEG) C = coefficient presented in Table 11.12.3.2-1 (DIM) For soil nail walls resisting relatively large load s (e.g., walls being part of bridges abutments), mo re advanced me thods (e.g., finite elem ent meth od) ma y be required to produce a mo re precise estimation of the wall deform ation . Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

Table 11.12.3.2-1 Values of ( δ h /H) and C as Functions of Soil Conditions Variabl e Weathered Rock and Stiff Soil Sandy Soil Fine-Grained Soil ( δ h /H ) 1/1,000 1/500 1/333 C 0.8 1.25 1.5 SOIL NAIL (TYP) V h H DDEF EXISTING STRUCTURE L DEFORMED PATTERN INITIAL CONFIGURATION Modified after Byrne et al. (1998) Figure 11.12.3.2-1 Deformation of Soil Nail Walls DEFOR MA TION PATTERN IS EX AG GER A TED Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-10

A-11 11.12.3. 3 O verall Stability The provisions of Article 11.6.2.3 shall apply. The evaluation of overall stability of soil nail walls shall be perform ed using acceptable me thods that consider all reinforcement elements of a soil nail and loads. Global stability analyses ma y be necessary for intermediate excavation conditions. The potential slip surfaces to be considered in overall stability ma y or ma y not intersect soil nails (Figure 11.12.3.3-1). For the case of slip surfaces intersecting soil nails, the nominal resistance of soil nails shall be adequately considered in analy ses. For soil nail walls with complex geom etry (e.g., mu ltiple-tiered walls) involving composed failure surfaces, the provisions of Article 11.10.4.3 shall apply. C11.12.3.3 Overall stability of soil nail walls is commonly evaluated usi ng two-dimensional limit-equilibrium- based me thods, in which the contribution of nails is accounted for in equilibrium equations. Stability analyses of soil nail walls are commonly perform ed using computer program s specifically developed for the design of soil nail walls. Other com puter program s developed for general slope stability analysis can also be used, if various reinforcem ent bars developing pullout resistance can be considered by the software. 11.12.3.4 Seismic Effects on Global Stability The pseudo-static met hod shall be routinely used for the seismic stability analysis of soil nail walls. The provisions of Article 11.6.5 shall apply to consider the effect of seismic loads on the global stability of soil nail walls. In general, the vertical seis mi c coefficient is disregarded in global stability analysis. For flexible structures such as soil nail walls, it is reasonable to use horizontal seis mi c coefficients that are a function of the expected seismically induced wall displacem ent. The following expressions can be used to estimate the horizontal seismic coefficient as a function of the tolerable seismically induced wall lateral m ove me nt , d , in inches before any wall/sliding bl oc k takes place (Kavazanjian et al., 1997; Elias et al., 2001): 0.25 m m h d A A 0.74 k = (C11.12.3.4-1 ) where: k h = horizontal seismic coefficient (DIM) SOIL RESISTANCE FAILURE SURFACE (a) SOIL RESISTANCE NAIL RESISTANCE FAILURE SURFACE (b) Fi g ure 11.12.3.3-1 Limit States in Soil Nail Walls—Overall Stabilit y : (a) Slip Surface not Intersectin g Nails; (b) Slip Surface Intersecting Nails Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

Am = normalized horizontal acceleration (DIM) d = seismically induced wall lateral movement (INCH) The value of Am is a function of the normalized peak ground acceleration coefficient, A, which is defined in Appendix 11A, Seismic Design of Abutments and Gravity Retaining Structures. Equation C11.12.3.4-1 should be used only for 1 ≤ d ≤ 8 IN, with more typical values of d between 2 and 4 IN The selection of smaller tolerable seismically induced deformation results in larger seismic coefficients, which results in larger nail lengths. Elias et al. (2001) recommend that Equation C11.12.3.4-1 should not be used when: • the peak ground acceleration coefficient, A, is ≥ 0.3 • the wall has a complex geometry (i.e., the distribution of mass and/or stiffness is abrupt), and • the wall height is greater than approximately 45 FT. If the seismically induced displacement is not available, it is acceptable, in general, to select a seismic coefficient for soil nail walls between: mmh A0.67toA0.5k = (C11.12.3.4-2) 11.12.4 Stability at Strength Limit States: Safety Against Soil Failure Soil nail walls shall be proportioned to satisfy sliding and bearing criteria normally associated with gravity structures as shown in Figure 11.12.4-1. SOIL RESISTANCE (SLIDING AT BASE) (a) SOIL RESISTANCE (b) SOFT COHESIVE SOIL Figure 11.12.4-1 Soil Limit States: (a) Sliding Stability; (b) Basal Heave 11.12.4.1 Sliding C11.12.4.1 Soil nail walls shall resist sliding along the base of the retained system in response to lateral earth pressures behind the soil nails. Sliding is a feasible but uncommon limit state for soil nail walls and is considered here for consistency with other retaining systems. Sliding may become a Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-12

A-13 The general princi ples referred to in Article 10.6.3.4 shall apply. mo re realistic lim it state when the bl ock of soil resisted b y a soil nail wall is underlain by a weak soil layer. In this case, th e critical slip surface ma y be oriented along the weak soil layer. 11.12.4.2 Basal Heave C11.12.4.2 The bearing resistance shall be evaluated if the soil nail wall is constructed in or over soft fi ne-grained soils. The bearing resistance shall be evaluated as a service limit state, based on equilibrium, not defor ma tions. When soft cohesive soils exist at the base of a soil nail wall, the potential for basal heave at the base of th e excavation should be evaluated. If th e lo ads generated due to the excavation are excessive for the existing soft soil conditions, the bottom of the excavation may heave and possibly cause a basal heave failure. SNWs ma y be mo re susceptible to basal heave th an ot her retaining system s (e.g., anchored walls) because the facing o f soil nail walls is not or seldom em bedded in th e underlying soil. 11.12.5 Stability at Strength Limit States: Safety Against Structural Failure 11.12.5.1 General The structural limit states to consider for soil nail walls include soil nail pullout and soil nail in tension, as illustrated schematically in Figure 11.12.5.1-1. TENSILE RESISTANCE (b) SLIP SURFACE PULLOUT RESISTANCE(a) Figure 11.12.5.1-1 Structural Limit States: (a) Pullout; (b) Nail in Tension 11.12.5.2 Nail Pullout Resistance C11.12.5.2 The nom inal pullout resistance (per unit length) of soil nails, r PO , can be expressed as: 12 ×= DH U PO D q r (11.12.5.2-1) where: q U = nom inal bond resistance (KSI) D DH = average diameter of drill-hole (IN) The pullout resistance, R PO (KIP), is computed as: P PO L r R PO = (11.12.5.2-2) It shall be verified that: The no mi nal pullout resistance is also referred to as nom inal load transfer rate, with units KIP/FT. A uniform distribution of resistance along th e pullout length behind the slip surface, L P , is assu me d. Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

max PO T R PO ≥φ where: R PO = nom inal pullout resistance (KIP) φ PO = resistance factor for soil nail pullout (DIM) T ma x = maximum tensile load in a soil nail (KIP). 11.12.5.3 Nominal Bond Resistance C11.12.5.3 Table 11.12.5.3-1 provides presum ptive values of the nominal bond resistance for soil nails installed in soil or rock. The nominal bond resistance is in general a function of the soil/rock type, soil nail installation method, and soil/rock condition, as seen in Table 11.12.5.3-1. Verification load tests (and possibly proof load tests) can provide information to assess nominal values of the soil nail bond resistance. See details on soil nail load testing in Appendix B, Proposed LRFD Construction Specifications for Soil Nail Walls; Byrne et al. (1998); and Lazarte et al. (2003). Proof load tests shall be conducted on at least 5 percent of all production soil nails and up to a load of 150 percent of test design loads. Design loads are derived from presumptive nominal pullout resistances and test bonded lengths. Verification load tests should be conducted on a project-specific basis and up to a load of 200 percent of the test load. Pullout nominal resistance values of soil nails can be estimated as the maximum load obtained from verification tests (i.e., 200 percent of the design load) times the pullout resistance contained in Table 11.5.6-1. The nominal bond resistance of drilled and grouted soil nails is affected by various factors, including: • Conditions of the ground around soil nails, nam ely: – soil type; – soil characteristics; – magnitude of overburden. • Conditions at time of soil nail installation, nam ely: – drilling met hod (e.g., rotary drilled, driven casing, etc.); – drill-hole cleaning procedure ; – grout injection method (e.g., under gravity or with a nom inal, low pressure); – grouting procedure (e.g., tremie met hod); and – grout characteristics (e.g., grout workability and com pressive strength). Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-14

A-15 Table 11.12.5.3-1 Presumptive Nominal Bond Resistance for Soil Nails in Soil and Rock Material Soil Nail Installion Method Soil/Rock Type No mi nal Bond No mi nal Resistance, q u (psi) Rock Rotary Drilling Marl/limestone Phyllite Chalk Dolo mi te (soft) Dolom ite (fissured) Sandstone (weathered) Shale (weathered) Schist (weathered) Basalt Slate/hard shale 45 - 58 15 - 45 75 - 90 60 - 90 90 - 145 30 - 45 15 - 22 15 - 25 75 - 90 45 - 60 Rotary Drilling Sand/gravel Silty sand Silt Piedm ont residual Fine Colluvium 15 - 26 15 - 22 9 - 11 6 - 17 11 - 22 Driven Casing Sand/gravel low overburden high overburden Dense Moraine Colluvium 28 - 35 40 - 62 55 - 70 15 - 26 Cohesionless Soils Auger Silty sand fill Silty fine sand Silty clayey sand 3 - 6 8 - 13 9 - 20 Rotary Drilling Silty clay 5 - 7 Driven Casing Clayey silt 13 - 20 Fine-Grained Soils Auger Loess Soft clay Stiff clay Stiff clayey silt Calcareous sandy clay 4 - 11 3 - 4 6 - 9 6 - 15 13 - 20 Modified after Elias and Juran (1991). Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

11.12.5.4 Limit State for Soil Nail in Tension C11.12.5.4 The limit state for a soil nail in tension shall be verified as follows: max T T T R ≥φ (11.12.5.4-1) where: φ T = resistance factor for soil nail in tension (DIM) R T = nom inal tensile resistance of a soil nail (KIP) T ma x = maxim um load in soil nail (KIP) The nom inal tensile resistance of a soil nail shall be com puted as: y t T f A R = (11.12.5.4-2) where: A t = cross-sectional area of a soil nail bar (IN 2 ) f y = nom inal yield resistance of soil nail bar (KSI) The contribution of the grout to the nom inal resistance in tension shall be disregarded. T ma x is estimated from global stability analyses perform ed with computer programs. 11.12.6 Strength Limit States: Limit States for the Facing of Soil Nail Walls 11.12.6.1 General C11.12.6.1 The limit states of th e facing of a soil nail wall that shall be considered include: (a) flexure; (b) punching - shear; and (c) headed-stud in tension. These limit states are shown schematically in Figure 11.12.6.1-1(a) and (c). The limit states for flexure and punching-shear in the facing shall be considered separately for the tem porary and the perm anent facing. The limit state for tension in th e headed-stud shall be considered only in perm anent facings . Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-16

A-17 Figure 11.12.6.1-1 Limit States in Soil Nail Wall Facings: (a) Typical Section; (b) Flexure; (c) Punching-Shear in Temporary Facing; (d) Punching-Shear in Permanent Facing; and (e) Headed-Stud in Tension 11.12.6.2 Flexural Limit State C11.12.6.2 For the limit state of flexure in the facing, it shall be verified that: o FF FF T R ≥φ (11.12.6.2-1) 45° TO FLEXURE LIMIT STATE mV CONICAL SURFACE COMPOSITE CONICAL SURFACEREINFORCEMENT VERTICAL MOMENT, mV BEARING PLATE HEADED STUD WWM (ADDITIONAL REINFORCEMENT NOT SHOWN) (TEMPORARY FACING) PUNCHING- SHEAR LIMIT STATE (PERMANENT FACING) WWM OR BAR (b) (c) (d) RFP RFP RFH BREAKAGE STUD IN TENSION LIMIT STATE (PERMANENT FACING) PUNCHING- SHEAR LIMIT STATE (e) (a) Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

where: φ FF = resistance factor for flexure in the facing (DIM) R FF = nom inal tensile resistance for flexure in the facing (KIP) T o = maxim um tensile load at soil nail head (at facing) (KIP) R FF can be estimated using the following expression: [ ] [ ] ( ) ( ) ×+ ×+ ×××= h[ft] S /ft 2 in hn a a h[ft] S /ft 2 in vm a a of greater ks i y f F C 3. 8 R hn vn kip FF H S V V S H (11.12.6.2-2) where: C F = f actor that considers non-uniform soil pressures behind a soil nail wall facing and is used in the estimation of nom inal resistances at the soil nail head (DIM) h = thickness of facing (IN) that can take the values h t or h f . a vn = Cross-sectional area (per unit width) of mesh reinforcement in the wall facing, in the vertical direction, at soil nail heads (IN 2 /FT) a vm = Cross-sectional area (per unit width) of mesh reinforcement in the wall facing, in the vertical direction, at soil nail heads (IN 2 /FT) a hn = Cross-sectional area (per unit width) of mesh reinforcement in the wall facing, in the horizontal direction, at soil nail heads (I N 2 /FT) a hm = Cross-sectional area (per unit width) of mesh reinforcement in the wall facing, in the horizontal direction, at mi dspan between soil nails (IN 2 /FT) f y- f = Yield tensile nominal resistance of reinforcem ent in facing (KSI) The cross-sectional areas of reinforcement per unit width in the vertical or horizontal direction and around and in-between nails are shown schematically in Figure The nail head tensile force may be estimated b ased on th e equations below (Clouterre, 1991) that were developed for working conditions: [ ] max T 3) max (S 0.057 0.6 max T o T ≤− + = (C11.12.6.2-1 ) where: T ma x = maximum nail load (KIP) S ma x = maxim um s oil nail spacing (i.e., greater of S V and S H ) (FT) The ma xi mu m nail load under working conditions typically varies from T o = 0.60 K A γ H S V S H to 0.70 K A γ s H S V S H (Byrne et al., 1998), where K A is the active earth pressure coefficient, γ s is the unit weight of the soil behind the wall, H is th e wall height, and S V and S H are the nail vertical and horizontal spacing, respectively . The nom inal resistance for flexure in th e facing depends on th e soil pressures m obilized b ehind the facing, horizontal and vertical soil nail spacing, soil conditions, and facing stiffness. To account for non - uni form soil pressure distri but ions and other conditions, C F is used (Byrne et al., 1998). Table C11.12.6.2-1 presents values of CF for typical facing thickness. For all permanent facings and “thick” (i.e., h t 8 IN) temporary facings, the soil pressure is assumed to be relatively uniform. Reinforcem ent can be welded wire me sh (WWM) or concrete reinforcem ent bars. If (vertical) bars are used behind the nail heads, the total reinforcement area per unit length in the vertical direction can be calculated as: H VH vm vn S A a a + = (C11.12.6.2-1 ) where: A VH = Total cross-sectional area of additional reinforcement (rebar) in wall facing, in the Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-18

A-19 11.12.7.2-2. The nom enclature for the reinforcem ent areas per unit width is presented in Tab le 11 .12.3.2-2: vertical direction and around soil nail heads (I N 2 ) Similar concepts can be applied if additional horizontal rebar (i.e., waler bars) is used in this direction. The total reinforcement area per unit length in the horizontal direction can then be calculated as: a hn = a hm + V HH S A (C11.12.6.2-2) A HH = Total cross-sectional area of additional reinforcem ent (i.e., waler bars) in wall facing, in the horizontal direction and around soil nail heads (IN 2 ) Table 11.12.6.2-1 Factor C F Type of Wall Nom inal Facing Thickness, h t or h f (IN) Factor C F 4 2.0 6 1.5 Tem porary 8 1.0 Permanent All 1.0 Table 11.12.6.2-2 Nomenclature for Facing Reinforcement Area per Unit Width Direction Location Cross-Sectional Area of Reinforcement per Unit Width Nail head (1) a vn = a VM + H VH S A Vertical Mid-span a vm Nail head (2) a hn = a hm + V HH S A Horizontal Mid-span a hm Notes: (1) At the nail head, th e total cross-sectional area (per unit length) of reinforcement is the sum of th e welded-wire me sh area, a vm , and the area of additional vertical bars, A VH , divided by th e horizontal spacing, S h . (2) At the nail head, th e total area is the sum of the area of the welded- wire me sh, a hm , and the area of additional horizontal bars (i.e., waler bars, A HH ) divided by S v . Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

S V Wale r Bar (T YP ) WW M (Tempora ry Facing ) Re ba r Me sh or WW M (Fin al Fa ci ng ) A A Section A- A Waler Ba r d f = 0. 5 h f h f = final facing thickness d t = 0.5 h t Total Cross S ectional Area (p e r u n i t l e n g t h ) V e r t i c a l Mid-s p an between na ils: a vm At na il he ad : a vn = a vm + A VH S H Ve rtica l Re bar At Na il Head Vertical Re ba r At Na il He ad h t = tempo rary facing th ickn es s A VH A HH S H H o r i z o n t a l Mid-span between nails: a hm At nail head: a hn = a hm + A HH S V Figure 11.12.6.2-2 Geometry Used in Flexural Limit State The mi nim um and ma xim um am ount of steel reinforcem ent to be placed in the facing, ρ mi n and ρ ma x , respectively, shall be as follows: f - y ' mi n f f 0.24 [% ] c = (11.12.6.2-3) + = f - y f - y ' max f 90 90 f f 0.05 [% ] c (11.12.6.2-4) where: f c = concrete co mp ressive no mi nal resistance (PSI) f y- f = reinforcement tensile yield nominal resistance (KSI) The reinforcement ratio, ρ , shall be calculated as: 100 h 0.5 a ij = (C11.12.6.2-3 ) where: a ij = ratio of cross-sectional area of reinforcem ent per unit width (in “i” direction and “j” location) (PERCENT) The direction “i” can be vertical or horizontal; the location “j ” can be at the nail head or mi d-span, giving rise to th e four possi ble cross-sectional areas noted in Figure 11.12.6.2-2 . In addition to the mi nim um and ma xim um ratios indicated in this section, the ratios a vn /a vm or a hn /a hm should be limited to values less than 2.5. 11.12.6.3 Punching-Shear Resistance in Facing C11.12.6.3 For th e limit state of punching-shear in the facing, it shall be verified that: The limit state for punching-shear may involve the form ation of a localized, conical slip surface around the nail head. The slip surface ma y extend behind th e Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-20

A-21 o FP FP T R ≥φ (11.12.6.3-1) where: φ FP = resistance factor for punching-shear in the facing (DIM) R FP = nom inal resistance for punching-shear in facing (KIP) The factored soil nail tensile force from punching - shear failure shall be calculated as: F P FP V C R = (11.12.6.3-2) where: V F = nom inal punching-shear resistance acting through the facing section (KIP) C P = correction factor that accounts for the contribution of the support resistance of the soil (DIM) The nominal punching-shear resistance shall be calculated as : C c ' c F 'h D f V 0.58 = (11.12.6.3-3) where: D’ C = effective diameter of conical failure surface at the center of section (i.e., an average cylindrical failure surface is considered) (FT) h C = effective depth of conical surface (FT), as discussed below. bearing plate or headed studs and may p unch through the facing thickness at an inclination of about 45 degrees and form two punching limit states (Figure 11.12.6.3-1). The size of th e conical slip surface depends on the facing thickness and the type of the nail-faci ng connection (i.e., bearing-pl ate or headed-studs). Generally, the contribution from the soil support is ignored and C P = 1.0. If the soil reaction is considered, C P can assum e value s up to 1.15. These equations shall be separately used for tem porary and perm anent facing. The ma ximum and average diam eters of th e slip surface ( D C and D’ C on Figure 11.12.6.3-1), as well as the effective depth of th e slip surface ( h C ) shall be selected separately for temporary and permanent facings. For temporary facing, only th e di me nsions of the b earing plate and facing th ickness shall be considered. For perm anent facings, the dimensions of headed-studs and bearing plate, and the facing thickness shall be considered. Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY WALER BAR (TYP) CONICAL SLIP SURFACE DDH IDEALIZED SOIL REACTION DC D 'C LBP COMPOSITE CONICAL SURFACE IDEALIZED SOIL PRESSURETO DHD CD ' CD (a) BEARING-PLATE CONNECTION (vertical view) (b) HEADED-STUD CONNECTION SHS 45° (TYP) (TYP) 45° V F 2 V F 2 T o V F /2 V F /2 h t h t /2 h t h t /2 (Horizontal Cross Sections) Modified after Byrne et al. (1998) Figure 11.12.6.3-1 Punching-Shear Limit States A-22

A-23 The effective diam eter of the slip surfaces mu st be considered as follows: Tem porary facing D’ C = L BP + h t h C = h t where: L BP = bearing plate length (FT) h t = tem porary facing thickness (FT) Perm anent facing D’ C = minimu m of ( S HS + h C , or 2 h C ) h C = L S – t h + t P where: S HS = headed-stud spacing (FT) L S = headed-stud length (FT) t H = headed-stud head thickness (FT) t P = bearing plate thickness (FT) 11.12.6.4 Headed-Stud in Tension C11.12.6.4 For the limit state of facing headed-stud in tension, it shall be verified that: o FH FH T R ≥φ (11.12.6.4-1) where: φ FH = resistance factor for headed-stud in tension (DIM) R FH = nom inal tensile resistance of headed-stud (KIP) R FH is com puted as: y-hs S H FH f A N R = (11.12.6.4-2) where: N H = num ber of headed-studs in the connection (usually 4) (DIM) A S = cross-sectional area of th e headed-stud shaft (I N 2 ) f y-hs = yield tensile nom inal resistance of headed- stud in facing (KSI) To provide sufficient anchorage, the length of the headed-studs shall extend beyond the mi d-section of the facing, while maintaining 2 IN minimum cover. When th readed bolts are used in lieu of headed- stud connectors, the effective cross-sectional area of the b olts mu st be em ployed in the equations above. The effective cross-sectional area, A E , of threaded anchors is com puted as follows: 2 0.9743 4 − = t E E n D A (C11.12.6.4-1 ) where: D E = effective diameter of the bolt core n t = num ber of threads per unit length Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY

In addition, the limit state for compression of th e concrete behind the head of the headed-stud shall be established by assuring th at the following geom etric constraints are met (ACI, 1998): A H ≥ 2.5 A S (11.12.6.4-3) t H ≥ 0.5 ( D H – D S ) (11.12.6.4-4) where (see Figure 11.12.6.4-1): A H = cross-sectional area of the stud head t H = head thickness D H = diam eter of the stud head D S = diam eter of the headed-stud shaft D H L S t H DS Figure 11.12.6.4-1 Geometry of a Headed-Stud 11.12.7 Drainage C11.12.7 Drainage Surface water runoff and groundwater shall be controlled both during and after construction of the soil nail wall. If appropriate perform ance cannot be achieved, th e effect of th e groundwater table shall be considered in the analysis. Perm anent surface and groundwater controls ma y consist of a combination of the following features: p er ma nent surface water controls, geocomposite drain strips, shallow drains (weep-holes), toe drain, and drain pipes. Geocom posite drain strips are routinely p laced in vertical strips against the excavation face along the entire dept h of the wall. The lower end of the strips typically discharges into a pipe drain that runs along the base of the wall or through weep holes at the botto m of the wall. 11.12.8 Corrosion Protection C11.12.8 For all perm anent soil nail walls and, in some cases, for temporary walls, the soil corrosion potential shall be evaluated and considered part of the design. See Appendix B, Proposed LRFD Construction Specifications for Soil Nail Walls. A full discussion on corrosion of metallic com ponents and a met hodology that assists in selecting the appropriate level of corrosion protection of soil nail walls is presented in Lazarte et al. (2003). Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY A-24

A-25 REFERENCES American Concrete Institute (ACI) (1998) “Code Requiremen ts for Nuclear Safety-Related Concrete Structures (ACI 349-97) and commentary,” ACI 349R-97, ACI Co mmittee 349, American Concrete Institute, Farmington Hills, MI, p. 129. Byrne, R.J., Cotton, D., Porterfield, J., Wolschlag, C., and Ueblacker, G. (1998). “Manual for Design and Construction Monitoring of Soil Nail Walls,” FHWA-SA-96-69R, Federal Highway Administration, Washington, D.C. Clouterre (1991). “Recommendations 1991” (Trans.: Soil Nailing Recommendations 1991), English Translation, Presses de l’Ecole Nationale des Ponts et Chaussées, Paris, France. Elias, V., Christopher, B.R., and Berg, R. (2001). “Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines,” Federal Highway Administration, FHWA-NHI-00-043, Washington, D.C., 394 pp. Kavazanjian, E., Jr., Matasovi , N., Hadj-Ham ou, T., and Sabatini, P.J. (1997). “Design Guidance: Geotechnical Earthquake Engineering for Highways, Volum e I, Design Principles,” Geotechnical Engineering Circular No. 3, FHWA-SA-97-076, Federal Highway Administration, Washington, D.C. Lazarte, C.A., V. Elias, R.D. Espinoza, and P.J. Sabatini (2003). “Soil Nail Walls,” Geotechnical Engineering Circular No. 7, FHWA0-IF-03-017, Federal Highway Administration, Washington, D.C., 305p. Section 11 - Abutments, Piers and Walls PROPOSED SPECIFICATIONS PROPOSED COMMENTARY Elias, V., and Juran, I. (1991). “Soil Nailing for Stabilization of Highway Slopes and Excavations,” FHWA-RD-89- 198, Federal Highway Administration, Washington, D.C. Clouterre

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Proposed Specifications for LRFD Soil-Nailing Design and Construction Get This Book
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TRB's National Cooperative Highway Research Program (NCHRP) Report 701: Proposed Specifications for LRFD Soil-Nailing Design and Construction contains proposed specifications for the design and construction of soil-nailed retaining structures.

The American Association of State Highway and Transportation Officials (AASHTO) Standard Bridge Specifications, the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications, and the AASHTO LRFD Bridge Construction Specifications do not include guidance for soil-nailed structures.

In the absence of AASHTO LRFD specifications, some state departments of transportation will not use soil-nailed retaining structures. Given the potential advantages of soil-nailed structures, there was a need to develop proposed standard design and construction specifications for soil-nailed structures for incorporation into the AASHTO LRFD Bridge Design and Construction Specifications.

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