Tiebacks
Better Tieback Walls with CHANCE® Helical Tieback Anchors
A pre-engineered tieback system for earth retention supplied by the largest manufacturer of anchors in the world simplifies the challenges for contractors. These tieback anchors are installed by rotating the anchors into the ground with common rotary drilling equipment.
Once the minimum depth is obtained the capacity can be determined by reading the installing torque and correlating it to the holding capacity ratio.
Capacities to 200,000 pounds per anchor are obtainable with this system. Proven on hundreds of applications these cost effective tiebacks can be tested immediately. No concrete to wait for curing! This saves time and money plus improves schedules.
Your local Hubbell Power Systems, Inc. distributor can show you the advantages on specific applications.
Contractors are using the CHANCE tieback anchor system for these reasons:
- Installed anchors can be proof-tested immediately — no waiting for grout to cure
- Install in inclement weather, with conventional drilling equipment. No concrete trucks or grout pumps required
- Predictable holding strength in all soils
The success of the screw anchor tieback system is based on decades of similar use of CHANCE anchors by electric utilities. The proven reliability and engineered predictability of the system’s performance give you tiebacks that are positive, economical and hassle-free.
Typical Construction Applications:
- Building-site preparation
- Roadways
- Retaining walls
- Levees
- Dams
- Revetments
Features
- Predictable results
- Cost-effective method
- Easy to store, reusable
- Pre-engineered system
- Labor-saving, keeps crew small
- Screws into place (not predrilled)
- Site-specific to conditions and loads
- Terminations for various thread bars
- Less equipment than grouted tendons
- Bearing device, not friction dependent
- Extendable with bolted joint connection
Benefits
- Installs in inclement weather
- Installs in limited access areas
- No excavation or spoils to remove
- Immediate proof testing and loading
- Permanent or temporary (removable)
- Labor saving – as few as four on a crew
- Capacity proportional to installing torque
- No concrete trucks or grout pumps needed
- Install with equipment for grouted tendons
Faster Tieback Walls with all the Practical Advantages of Helical Anchors
Immediate pull testing of helical tieback anchors after installation serves as a check on design procedures and eliminates deflection at working loads.
No delays because there is no grout
- Typical production rate of 30 to 40 per day for installing and testing
- No holes to drill
- Cuts labor and equipment costs
- Can save 30% while obtaining high anchor-load capacities
Solves construction problems
- In cohesive soils, no belled and/or long sockets
- In non-cohesive soils, no casings or grouted sockets
- Bearing mode (not friction mode) anchors
- No de-watering for below-water-table applications
Helical Capacity Design Software
HeliCAP® - Helical Capacity Design Software - helps design professionals quickly derive the proper helical tieback anchor for site and load specific data. Contact your local distributor or territory manager about how to get a copy today.
Site-Specific Basics of Screw Anchor Design
- Two typical steps to anchorage design:
- Select helix configuration based on accurate soil characteristics data and tension load.
- Select shaft configuration based on tension load and anticipated installation torque.
- Anchor load capacity equals the sum of all its individual helix bearing capacities. Bearing capacity of each helix equals the product of its projected area and bearing pressure
- Pre-engineered CHANCE screw anchors optimize helix spacing at three times the next lower helix diameter. This assures more predictable torque-to-capacity relationship
- Holding capacity is proportional to installation torque (recommended 10 lbs per ft-lb) Monitor torque while installing to ensure a minimum and not to exceed anchor rating
Helical Tieback
Helical tieback anchors have shafts in five square sizes (1-1/4”, 1-1/2”, 1-3/4”, 2” and 2-1/4”) with helices in configurations of two to four and diameters from 6” to 14”. All components are available hot-dip galvanized per ASTM A 153 after fabrication.
Extensions
Plain and helical extensions are used to reach competent load-bearing soil. Plain extensions range from 37” to 124” long. Helical extensions range from 48” to 124” long with 14”-diameter helices in single, double and triple configurations. Forged integral coupling sockets bolt-up quickly and efficiently transfer installing torque.
Lead Sections
For job-specific combinations, leading sections range from 30” to 124” long in two-, three- or four-helix configurations usually with increasing diameters from the 6”, 8”, 10”, 12” and 14” range.
Anchor System
Anchor terminations fit a threadbar or provide a threaded stud to work with pre- or site-fabricated structural wall connection. Other termination fittings also are available. In some cases, the through-hole at the shaft end may be simply cross-pinned.
Anchor System
1” threadbar adapter for 1-1/2”, 1-3/4”and 2” tieback anchor types
1-1/4” threadbar adapter for 2” and 2-1/4” tieback anchor types
1-3/8” threadbar adapter for 2-1/4” tieback anchor types
Threaded stud socket adapter
Threaded stud socket adapter for 1-1/4” and 1-1/2” tieback anchors
Threaded stud clevis adapter
Threaded stud clevis adapter for 1-3/4” tieback anchors