Ram Jack Helical Piles Proven in Liquefaction Simulation Test
VersaGrade is a licensed certified Ram Jack Installer, and is happy to provide Ram Jack solutions. Ram Jack recently was able to participate in the very first liquefaction simulation test of remedial Ram Jack helical piles ever to take place in the United States. The shake test occurred on April 2, 2019, at the University of California, San Diego and was sponsored by PEER (the Pacific Earthquake Engineering Research Center), which is a consortium of universities along the west coast dedicated to furthering research and testing just like this one.
This liquefaction simulation test follows the credible large-scale shake table test, performed to quantify the seismic response of helical piles in dry sands. That large-scale test, also performed at UCSD, under the observation of Dr. Amy B. Cerato, Ph.D., P.E., demonstrated that helical piles far exceeded expectations during various, sequenced earthquake shaking. With the outstanding outcome of the test results, piles were once again put to the test, only this time in a liquefaction zone.
The Liquefaction Test
In June of 2018, the liquefaction soil box was fitted with a foundation system and block weights, and then shake-tested as a “control” test to measure the impact of liquefaction in a seismic event on a foundation with no support measures in place. The result was over 11 inches of foundation settlement, which would almost surely cause any structure to collapse.
Testing with Ram Jack Helical Piles
In efforts to find a cost-effective solution to mitigate foundation failure in liquefaction zones, Ramin Motamed, Ph.D., P.E., from the University of Nevada, Reno began researching helical piles and quickly learned about Ram Jack foundation solutions. Dr. Motamed invited Ram Jack to participate in the second round of testing, but this time, measurable results were available by implementing four (4) Ram Jack helical piles.
Ram Jack helical piles were precisely installed under the same loaded footing that was used in the controlled test performed in June. The soil conditions and magnitude of the seismic force were also identical. Once the testing was complete, the foundation settlement was quickly evaluated and measured. Typically, the limit of settlement that a building's foundation can take is between one and one and a half inches; however, Ram Jack’s helical piles proved to perform exceptionally well, resulting in less than half an inch of settlement.
Ram Jack Foundation Solutions
The data obtained from the test will aid engineers and code officials in revising building codes utilizing helical piles in seismic areas not only for new construction but for seismic retrofits of existing buildings. The predictable performance of Ram Jack foundation repair solutions are becoming known around the world. Ram Jack has high hopes of being involved in various seismic projects as building codes continue to become stricter in the future. They continue to lead the industry in research on the behavior of helical piles during seismic events and will continue to do so for years to come.
Micropiles are small diameter piles, typically between 3-12 inches, that are used for foundation underpinning and new construction. They can extend up to 200 feet, and provide deep foundation support for a variety of structures.
Micropiles can be useful in areas where space limitations exist or where soil conditions are not practical for the installation of helical piers or piles. They can be used in a variety of difficult soil and ground conditions such as clays, sands, silts, gravels and cobbles—even rocks and boulders.
With their versatility and bonding capability to soils, micropiles are useful in many applications including:
Foundation support in low strength or otherwise unsuitable soils
Stabilizing foundations for tall structures such as towers or wind turbines
Seismic upgrades and retrofitting
What Are Soil Nails?
Soil nails are usually installed on an angle to stabilize and reinforce the face of a slope or a wall, and they are often designed in a grid pattern. Similar to micropiles, they are drilled and grouted into place. Some soil nail applications also include a reinforced shotcrete surface for additional stability.
Which One Is Right For My Project?
Micropiles and soil nails are essentially the same thing; the difference is in their application. Micropiles are used in tension and compression as load bearing tendons. They are made of high-strength steel casing, rebar and grout. Soil nails are typically used in steep slope or wall stabilization where the nails are installed beyond the soils’ failure plane (angle of internal friction). They use grouted, tension-resistant steel nails to reinforce the soil and create a retaining wall during excavation.
Both applications utilize a hollow bar steel tendon with a sacrificial cutting bit that is installed with a rotary-percussion hammer. During installation, a neat cement and water mixture is pressure injected down the hollow bar and through the cutting bit into the soils surrounding the hollow bar/tendon. This method of installation is called Injection BOring (IBO). IBO piles and soil nails develop their strength, in both compression and tension, by the summation of the steel tendon plus the strength of the annular soil-cement bond with its surrounding soils, referred to as the area of influence.
The area of influence is the annular area in which the soils are cemented together. Micropiles and soil nails can be installed in almost any soil condition with excellent load bearing characteristics which makes them an ideal alternative in rocky or high blow count (high density) soils where helical pile installations are not conducive.
For more information or to speak to a Reno contractor, give Versa Grade a call at 775-284-1964!
Step 2 - New Construction Pile Fixing Foundation 12/23/2015
STEP 2 is a private non-profit organization that has been serving Northern Nevada since 1986. Its mission is to provide comprehensive, coordinated services related to the treatment and recovery of chemically dependent women and their families. The 12,000 square foot expansion project adds a 20 bed residential housing component and storage facility to the already existing Mathewson Family Counseling Center and Transitional Cottages. The design vision of the project is to accommodate the everyday living needs of women and children in distress.
The project site is located north of the Reno / Sparks Area in Nevada on the foothills of Peavine Mountain. The area is predominately made up of Alta Formation soils components that contain hard volcanic rock, highly expansive clay minerals, and corrosive soil properties. The soils investigation confirmed the project site would not be conducive for conventional foundation construction. A deep foundation system was decided to be the best course of action, but due to the soil properties and its inconsistent nature, no one foundation system type could be utilized. VersaGrade was contacted early in the design process to help determine the best and most economical approach for this problem site to prevent fixing the foundation if issues later arose. It was determined that a mix of deep foundation types that included Ram Jack Helical Piles and Contech Micro Piles would be necessary to overcome these problem soils.
HOW WAS RAM JACK INVOLVED?
VersaGrade, Inc. was awarded the subcontract to install Ram Jack Helical Piles and Contech Systems Micro Piles on two adjacent project sites. One site was “The Living Center” and the other was “The Storage Facility”. Both building foundations were similarly designed as a pile and grade beam system. Since the soils were highly expansive, the entire foundation system was designed with a 6” void space under it to allow the clay soils to expand and contract without contacting the foundation system. 6” thick by 10” wide Sure Void was installed along the bottom of all grade beam trenches to provide the separation between soil and grade beam. Lateral stability which is normally achieved by the weight of the building on the underlying soils, was alternately achieved by the use of angled (Battered) piles installed at load points throughout the buildings footprint.
The Living Center foundation plan consisted of 95 vertical piles and 22 angled piles with working loads of 34,000 pounds and 10,000 pounds respectively. Installation depths varied wildly with helical piles ranging from 10’ - 60’ to achieve adequate load carrying capacities. Where helical piles could not be installed due to solid and fractured rock obstructions, Injection Bore (IBO) Micro Piles were installed to a depth of 20’ with a 4’ unbonded length. The Storage Facility foundation plan consisted of 62 vertical piles and 14 angled piles. The grade beam design on both buildings was only 10” wide, which made layout and installation techniques critical. Pile migration during installation of 1.5” was unacceptable.
VersaGrade used a Komatsu PC-160 Track-mounted hydraulic excavator with a Pro-Dig two stage 12K drive motor for the Helical installations and an Excavator Mount TEI 350 Rock Drill and ChemGrout CG600 Batching Plant for the Micro Pile installations.
Total No. of Ram Jack Helical Piles installed: 150