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!
Foundation cracks worry a lot of people. Home inspectors may tell you that they need to be repaired, and to consult with foundation repair contractors/residential foundation contractors. Home buyers may see problems that call for your foundation fixing but walk away from a potential transaction or ask for a reduction in the sales price. Truth is, most foundations have cracks. It is the type, size, and orientation of a crack(s) that determine whether or not there may be a problem.
How do cracks form?
From the moment concrete is placed, it begins to shrink via the hydration process. Extensive research has been conducted to evaluate why and where concrete tends to crack. As a result, several standards have been put into place to reduce, eliminate, or control the locations of cracking.
There are several external factors such as temperature (both ambient and concrete mix), water content, humidity, and placement practices that all play a role in how concrete performs.
Controlling the spread: fixing foundation
There are two common means of control done by our residential foundation contractors. The first, Expansion Joints, are designed to permit expansion and contraction of concrete masses. On the other hand, Control Joints are saw cuts or tooled joints in concrete sections to allow it to crack at specified locations. The addition of reinforcement in the pour, such as rebar, will also help curtail cracking.
However, in the end, most concrete pours crack during the curing process. The American Concrete Institute (ACI) spells out the technical aspects here, but the California Department of Transportation adopted an easier to read specification for concrete shrinkage. .05% - .08% for every 12’ feet. This works out to about the width of a dime every 12’.
Warning Signs of Foundation Problems
The question is: “Are the cracks in my foundation normal? Or do I have a foundation issue?”
“Hairline”, or small cracks, are typical in most foundations. They generally are vertical and are not offset. That is to say, that one side of the crack has not moved up or down, or in and out as opposed to the other side. They are also generally the same width from top to bottom. These types of cracks are generally considered normal and are usually of small concern. Water can get into these cracks, and if it freezes, can actually break off pieces of concrete making the crack bigger. The best way to address these cracks is to have residential foundation contractors seal them up with paint, caulk, or a variety of readily available sealers that will prevent water infiltration.
However, any crack wider than ¼” may be cause for concern and a need for fixing the foundation as it can allow for water infiltration. The type of crack is also important. Diagonal cracks & cracks that are wider on one end vs. the other may be a sign of movement. Cracks that are offset, or groups of several cracks are also likely a sign of distress. These types of cracks should be looked at by a professional to determine a cause and remediation. All structures settle over time. The purpose of a foundation is to allow the structure to settle as a unit at a slower rate. If you have foundation problems, you are likely to see interior sheetrock cracks, doors misaligned within the jamb, uneven floors, tile cracks, window frame separation, and even walls pulling away from the house.
To wrap up, here are some warning signs that will need to be evaluated by a foundation repair expert:
Any crack wider than 1/4"
Cracks that are wider on one end versus the other
Cracks that are offset
Groups of several cracks
Interior sheetrock cracks
Window or door frame separation
Walls pulling away from the house
These can be signs of water infiltration, movement or distress in your foundation.
In summary, concrete cracking can be the result of a poor batch of concrete, poor placement and/or curing methods, less than adequate installation of expansion and/or control joints, or the result of non-uniform foundation soils movement. Concrete cracking is generally classified as structural or non-structural. Structural cracking may require monitoring and potentially remediation, while non-structural cracking is mostly cosmetic in nature.
If you start to see threatening cracking in your foundation, give one of our residential foundation contractors a call at 775.284.1964 or send us an email! We will be happy to come out and take a look as your foundation crack repair experts!
Residential homes around Reno Nevada built between the 1920’s -50’s were typically built with unfinished basements for food, coal, & dry storage. A fair amount of these basements were constructed with little or no reinforcing steel. It was not uncommon for the structures that did have reinforcement, to consist of old fence posts, bailing wire, or any other scrap iron a builder could find. Along with added square footage, basement level foundation systems also served as an added layer of protection for structures built on expansive soils. The practice was to support the structure on soils well below finished grade so seasonal moisture change (i.e. rain & snow / summertime drying) would not affect the foundation. The Stoker Project was an excellent example of this type of construction.
Originally constructed in 1954, the Stoker Project was a single story structure built on a basement that extended under the entire footprint of the upper living area. The soils in the area are Alluvial Fan Deposits of Peavine Mountain and consist of gravely to sandy clayey silt with andesite fragments common. These soils are highly expansive and reactive to moisture content. Water intrusion in the basement had always been a problem for the owner, and over time, the swelling of the clays against the basement walls had pushed hard enough to break the walls and cause structural damage to the framing components. No reinforcing steel was observed in any of the concrete breaks, some as large as 1” in width. The rear wall of the basement had a large bow from top to bottom, and was pushing into the interior walls while pulling away from the upper level floor joists. Damage was significant enough to warrant the installation of temporary shoring supports until VersaGrade repair crews could arrive with fixing foundation solutions.
VersaGrade was contacted by the Owner to help design the repair plan, & K2 Engineering was retained as the project engineer. The Owner had constructed a deck and hot tub enclosure along the wall in question that had taken quite a lot of time and effort. This added a surcharge to the wall which contributed to the walls failure and adjacent interior framing. Our goal for fixing the foundation was to support the wall in place without demolishing the deck or hot tub enclosure. As such, all construction operations took place inside the basement. Because reinforcing steel was not present, a whaler system needed to be installed to help distribute the lateral forces. Prior to the installation of the whaler, solid steel Ram Jack 1.5” square bar Helical Anchors were installed through the wall using a hand held torque drive motor. The mid points between the anchor installations were supported vertically by the installation of Fortress Stabilizations ™ – Carbon Fiber support straps. The straps were epoxied to the concrete wall, & Kevlar straps embedded into the epoxy. These Kevlar straps were then connected to the structure framing to prevent overturning of the wall. The final bracing came from the installation of the whaler that consisted of a 10” wide continuous steel channel bolted to the wall & tying the system together. Fixing foundation can be a long and difficult process and even though the space constraints were a challenge, the project was a total success. The wall had been stabilized, and the Owners hard work on his deck had been saved.
VersaGrade used the Ram Jack Portable Hydraulic Pump and 2.5K Hand Held Drive Motor for the anchor installations.
Total No. of Ram Jack 1.5” Square Bar Helical Anchors Installed: 5
J & J Nevada was a project involving a seismic retrofit and tenant improvement to an existing warehouse in Sparks, Nevada. Additional truck docks were required to be installed, changing the structural characteristics of the tilt up concrete building. The installation of a moment frame on the interior of the structure required some relatively high loads to be addressed in tension and compression at specific locations. VersaGrade was contacted early in the design phase to help determine the best foundation system to address these loads.
Originally built in 1979, the warehouse was constructed for General Motors Corporation as a parts distribution center. The 634,000 Square Foot facility included dozens of truck dock openings and an interior railroad spur for the unloading of train cars inside the building. The soils are predominately Alluvium of the Truckee Meadows, consisting of pebble to cobble sand, silty sand, and sandy silts overlain by scattered, well rounded volcanic & granitic cobbles. Due to the rocky nature of the site and limited soils investigations, VersaGrade concluded that the use of Micro Piles would be the best system to meet the required loads. Pile groups of 3-4 would be necessary to achieve the 140 Kip allowable loads at specific points along the perimeter foundation.
VersaGrade, Inc. was awarded the subcontract to install 40mm Contech Systems Micro Piles along with a custom Ram Jack bracketing system. K2 Structural Design & Ram Jack Engineering were contacted to help design the bracket that would carry a 35 kip allowable capacity (70 Kip Ultimate) in tension and compression for each pile. Each bracket was designed to work on shear strength alone, and attach directly to the tilt up panels themselves as there were no footings to attach to in some locations. Six each 7/8” diameter epoxy doweled bolts (per bracket) were used to secure the brackets to the face of the concrete tilt-up walls. A 5 ½” diameter x 8’ long steel guide sleeve was then inserted through the brackets and set to elevation. After bracket installations were complete, VersaGrade installed Contech 40/16 Micro Piles with a 4” carbide cutting bit down through each guide sleeve. The Micro Piles were installed to an average depth of 21’. One of the challenges of the project was higher than expected grout usage during the Micro Pile installation due to unconsolidated material and fissures. Some piles took in excess of 35 cubic feet of grout to complete.
VersaGrade used a Komatsu PC-160 Track-mounted hydraulic excavator with an Excavator Mount TEI 350 Rock Drill and ChemGrout CG600 Batching Plant for the Micro Pile installations.
Total No. of Contech Micro Piles and Ram Jack Custom Brackets installed: 14
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