Statnamic Testing is Complete

Introduction

Starting on 30 April 2013, we will be conducting statnamic load test of five test drilled shafts. These drilled shafts are needed to support the concrete culverts and wing walls that will be installed under the Riverway area, under Brookline Avenue and near Avenue Louis Pasteur. The existing earthen material in these areas is poor and we need to determine the proper depth for the drilled shafts to properly carry the loads of the culverts and walls.

The Statnamic load test is a type of test for assessing the load carrying capacity of deep foundations which is faster and less expensive than the static load test. Statnamic testing works by accelerating a mass upward that in turn imparts a load onto the foundation pile below the Statnamic device. The load is applied and removed smoothly resulting in load application of 100 to 200 milliseconds.

The Statnamic test applies a force to the pile head over a typical duration of 120 milliseconds by the controlled venting of high pressure gas. The gas is the product of the combustion of a fast burning fuel within a piston (fuel chamber). At the top of the piston are vent holes that are sealed by the load hanger retaining the reaction mass. At some point the pressure within the piston is of such a magnitude to force the load hanger arrangement upward. This process applies a load downwards on the test pile.

During the loading sequence the load applied to the test pile is monitored by a calibrated load cell incorporated in the base of the combustion piston. Pile settlement is measured using a remote laser reference source that falls on a photovoltaic cell incorporated in the piston. Below is a figure that illustrates the stages of a statnamic load test.

 

Why does this information mean to me?

Although the statnamic testing device is equipped with a silencer, when the gas discharges the equipment makes a sound like a gunshot. We have discussed this with the State Police and they will be notified 48 hours prior to each test so that they may coordinate with the Boston Police and others. We will send out an email notice to our project contact list to notify folks on when the tests will be conducted. We have also asked MASCO to send out information on when the tests will be conducted to their contact lists.

To insure that drivers are not frightened or distracted driving by the test site when the testing occurs, traffic will be temporarily stopped immediately prior to the testing. Since the testing lasts less than a second there should be minimum disruption of traffic.

Statnamic testing is the best way for us to determine the proper length of the supporting shafts.

In Layman’s Terms What Does This Mean?

We will be doing testing starting 30 April. As the test starts there will be a bang like a gunshot. The sound will last less than a second. We’ll stop traffic just prior to the tests so that we don’t startle drivers traveling the roadways. Traffic will be stopped for a brief amount of time (less than five minutes). We will send you a notice the day before each test day to remind you that there will testing the following day. Testing will be every other day and should be completed by 10 May.

We apologize in advance for the disruption and appreciate your support and interest in this project. If you have any questions or would like additional information please email MuddyRiver@usace.army.mil or call Mike Keegan, the project manager, at 978‐318‐8087.

Stages of Statnamic Load Test
Stages of Statnamic Load Test (U.S. Army Corps of Engineers photos)