Technical Manual

Inc.

p 178

APPENDIX 2F

MODEL SPECIFICATIONS

Chapter 2

Helical Foundation Systems

6.2.4 Shaft Coupling Hardware: The lead and extension shaft sections are coupled with two

(2) bolts and nuts per coupled shaft section. The coupling hardware consists of 0.750-

inch standard hex bolts conforming to SAE J429 Grade 8 and jam nuts. The bolts and

nuts are mechanically galvanized in accordance with ASTM B695.

6.2.5 Thread Rod Adapter: Thread rod adaptor HA175TRA is suitable for use with the

HS175 shaft. Thread rod adapter finishes are either plain steel or hot-dip galvanized

in accordance with ASTM A123. Adapter shaft coupling hardware is mechanically

galvanized in accordance with ASTM B695.

DESIGN AND PERFORMANCE REQUIREMENTS

7.1 Helical soil nails shall be designed to support the specified load(s) as shown on the project

Plans. The overall length, helix configuration and minimum torsional resistance of a helical soil

nail shall be such that the required geotechnical capacity is developed by the helix plate(s) in an

appropriate bearing stratum.

7.2 All structural steel soil nail components shall be designed within the limits provided by the

American Institute of Steel Construction (AISC) Specification for Structural Steel Buildings

(AISC-360). Either Allowable Stress Design (ASD) or Load and Resistance Factor Design (LRFD)

are acceptable methods of analysis. Product testing in accordance with ICC-ES Acceptance

Criteria 358 may also be considered as an acceptable means of establishing system capacities.

7.3 Design of helical soil nail structures for excavation support, earth retention, slope stabilization,

or other applications shall consider the following (at a minimum):

7.3.1 Global and internal stability of the system

7.3.2 Surcharge loads from adjacent structures or other loading that will be present during

and/or after construction.

7.3.3 Helical soil nail torque correlated bearing capacity (bond strength) & load transfer

7.3.4 Structural capacity of individual helical soil nail components

7.3.5 Construction sequencing

7.3.6 Drainage conditions

7.3.7 Serviceability

7.4 The design of helical soil nail walls shall be in accordance with the FHWA Geotechnical

Engineering Circular No. 7, “Soil Nail Walls”.

7.5 Except where noted otherwise on the project Plans, all helical soil nails shall be installed to

provide an ultimate torque-correlated capacity based on an ASD or LRFD analysis. For ASD, a

minimum factor of safety of 2 for internal stability of the wall and slope stability at the elevation

of the toe of the wall shall be used for temporary or permanent applications. Lower factors of

safety may be considered if approved by the Owner. When an LRFD analysis is required, the

Owner shall provide applicable soil nail design information including but not limited to; factored

loads, resistance factors and/or the required ultimate soil nail capacity. Factors of safety (ASD)

or resistance factors (LRFD) may require modification to meet specific deflection criteria stated

on the Plans or drawings.