The Expanding Wedge System consists of a threaded rod and a plate that is hinged much like the “molly” wall anchors used in drywall. The rod is installed from the inside by using a hammer drill. Each section is connected by a coupler as it is installed. The pounding force of the hammer drill drives the rod and hinge plate into the soil. Once the rod no longer goes in any more you have reached refusal, average length is about 6 – 10 feet, and the installation is stopped. A hydraulic jack is then applied to “pull” the rod back out in an effort to have the hinge plate expand out causing resistance against the soil. You can measure the amount of hydraulic force used to pull the rod out to help determine the holding force. This system fails for several reasons. In soil conditions that are very hard the wedge plate does not expand out to hold any tension or when it does it is in looser soil and in the Active Zone of Soil. The amount of holding or tension each wedge can hold is very limited and many wedge anchors are required to be installed. There is no way to determine how far the hinge plate has expanded and since you have already started pulling the rod back out the soil is disturbed around the plate providing less holding force. The amount of wall contact is very limited and only retains a small portion of the foundation wall.
