OVERVIEW
Engineering Earth Retention Systems for Challenging Excavation Conditions
Excavation adjacent to existing buildings, property lines, streets and other structures requires careful consideration of soil pressures, surcharge loads, construction sequencing and the behavior of the surrounding structures.
Anax Engineering provides structural engineering design for excavation support and earth retention systems for building construction, additions, foundation work and other projects requiring temporary or permanent soil retention.
We work with contractors, developers, architects and other design professionals to develop practical earth retention solutions based on excavation depth, site constraints, adjacent structures, soil conditions and the proposed construction sequence.
Critical Conditions That Drive ERS Design
Earth retention design begins with understanding the excavation, surrounding site and the sequence in which the work will actually be constructed. The support system must respond to both structural demands and practical field conditions.
Loads & Site Constraints — Evaluate soil and surcharge pressures, adjacent foundations, property-line limitations, site access and other conditions affecting the retention system.
Support Strategy — Develop an appropriate retention and support approach based on excavation depth, soil conditions, available space and construction requirements.
Construction Sequence — Consider staged excavation, bracing or anchorage installation, temporary load paths and the transition from temporary support to permanent construction.
Typical ERS Applications
Property-Line Excavations
Earth retention where excavation must occur close to property lines or adjacent structures.
Building Additions & New Foundations
Temporary retention for foundations, basements, additions and other below-grade construction.
Excavations Adjacent to Existing Buildings
Systems designed considering existing foundations, surcharge loads and adjacent structural conditions.
Deep Excavations
Earth retention systems requiring staged excavation, internal bracing, tiebacks or other support methods.
Temporary & Permanent Retention
Systems designed for temporary construction conditions or incorporated into the permanent structure.
Complex Urban Sites
Excavation support where limited access, nearby structures, utilities and construction sequencing influence the design.
OUR APPROACH
Developing an ERS Around the Site, Structure & Construction Sequence
Earth retention design begins with understanding the excavation, the surrounding site and the sequence in which the work will actually be constructed.
Anax Engineering reviews available geotechnical information, adjacent structures, proposed foundation construction, excavation geometry and anticipated construction loads before developing the retention concept.
The selected system must resist soil and surcharge pressures while also responding to site access, property-line constraints, adjacent foundations and the practical requirements of excavation and building construction.
01
Review Project Information
Review excavation geometry, geotechnical information, foundation plans, adjacent structures and available site information.
02
Identify Loads & Constraints
Establish soil pressures, surcharge loads, adjacent foundation effects, property-line limitations and other conditions affecting the retention system.
03
Develop the ERS Concept
Select an appropriate retention and support approach based on excavation depth, soil conditions, site access and construction requirements.
04
Analyze & Design
Design the retention system, structural members, bracing or anchorage as applicable, and evaluate critical temporary construction conditions.
05
Coordinate Construction
Develop drawings and details that communicate the required system, support conditions and sequencing to the project team.
EARTH RETENTION SYSTEMS
Selecting the Right System for the Excavation
Earth retention systems must be selected and designed around the specific conditions of the project. Excavation depth, soil and groundwater conditions, adjacent structures, available space, property-line constraints and construction sequencing can all influence the appropriate solution.
Anax Engineering evaluates these conditions together with the proposed foundation and building construction to develop an earth retention concept that is both structurally appropriate and practical to build.
Depending on the project, the system may consist of soldier piles and lagging, sheet piling, internally braced excavation, tieback-supported systems or other project-specific earth retention solutions.
Support requirements may also change as excavation progresses. Temporary conditions, installation tolerances, access for construction equipment and the sequence in which permanent building elements are installed are therefore considered as part of the design.
Common ERS Systems & Components
Sheet Piling
Interlocking sheet pile systems used where excavation geometry, soil conditions or construction constraints make continuous retention advantageous.
Internal Bracing & Rakers
Temporary structural bracing used where external anchorage is not practical or cannot extend beyond the project limits.
Tieback-Supported Systems
Anchored earth retention systems used where subsurface rights, soil conditions and project constraints permit tieback installation.
Underpinning & Adjacent Foundations
Structural support and stabilization solutions where existing foundations are affected by the proposed excavation.
Soldier Pile & Lagging
Steel soldier piles with timber, concrete or other lagging used to retain soil as excavation proceeds.
Temporary Construction Conditions
Evaluation of staged excavation, changing support conditions and temporary load paths during construction.
ADJACENT STRUCTURES & UNDERPINNING
Accounting for Existing Foundations and Surcharge Loads
Excavation near an existing structure requires more than designing the earth retention system itself. Adjacent foundations, building loads, streets, construction equipment and other surcharge loads can significantly influence the pressures acting on the retention system and the behavior of the excavation.
Anax Engineering evaluates available information regarding adjacent structures and foundations together with excavation geometry, soil conditions and anticipated construction loads to determine how these conditions should be incorporated into the ERS design.
Where existing foundations extend into or near the excavation influence zone, additional structural measures may be required. Depending on the project, these may include underpinning, localized foundation support, modified excavation sequencing, supplemental bracing or other means of protecting adjacent construction.
Our objective is to develop a coordinated solution that supports the proposed excavation while recognizing the limitations and sensitivities of the structures surrounding it.
Key Conditions We Evaluate
Adjacent Foundations
Foundation type, depth, geometry and proximity to the proposed excavation.
Building Surcharge Loads
Loads from nearby structures that can increase lateral pressures on the retention system.
Construction Surcharges
Equipment, stored materials and other temporary loads located near the excavation.
Streets & Site Loads
Traffic, pavement and other site-related surcharge conditions where applicable.
Underpinning Requirements
Evaluation of whether adjacent foundations require temporary or permanent support as excavation proceeds.
Excavation Sequencing
Consideration of staged excavation, installation sequence and changing temporary support conditions.
CONSTRUCTION SEQUENCING & TEMPORARY CONDITIONS
Designing for How the System Will Actually Be Built
Earth retention systems often experience their most critical conditions during construction. Excavation depth, brace installation, tieback stressing, temporary access, removal of supports and installation of the permanent structure can all change the way loads are carried through the system.
Anax Engineering considers these temporary conditions as part of the structural design so that the drawings reflect the anticipated sequence of excavation and support. Where the performance of the system depends on a particular construction sequence, those assumptions can be incorporated into the design documents and coordinated with the project team.
Depending on the project, this may include staged excavation requirements, installation elevations for bracing or tiebacks, temporary support of adjacent construction, sequencing of underpinning work, transitions from temporary to permanent support and conditions associated with removal of temporary structural elements.
By considering the construction sequence during design, potential conflicts can be identified earlier and the earth retention system can be developed around both structural requirements and practical field conditions.
Discuss Your Excavation or ERS Project
Planning an excavation, foundation project or building addition that requires earth retention, shoring or underpinning? Anax Engineering can help evaluate site conditions, adjacent structures and construction requirements and develop a practical earth retention solution.