Stoker Project Basement Wall Repair 3/17/16

PROJECT DESCRIPTION

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.

PROJECT HISTORY

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.

PROJECT DETAILS

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

Step 2 - New Construction Pile Fixing Foundation 12/23/2015

PROJECT DESCRIPTION:

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.

PROJECT HISTORY:

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

Total No. of Contech Micro Piles installed: 43