Quality Control & Assurance with Torque Indicators
At Carolina Foundation Solutions, we pride ourselves on providing our customers with the best foundation solutions in a safe, clean, quality-controlled manner. We focus on accuracy so that our customers receive a permanent foundation solution. For quality control and assurance during helical pile and anchor installation, we rely on the measurement of torque capacity using a series of torque indicators including a base unit, wireless display and data logger. Using the CHANCE Torque Indicator, we are able to install helical piles and anchors to a pre-determined torque value, which gives a positive indication of the pile or anchor holding capacity in any soil type.
Helical piles and anchors have been historically used for supporting small tensile forces that stretch the product, but recently, larger capacity helical piles are used increasingly to support much larger compressive and tension loads. Compression and tension loads for helical foundations range between 12.5 and 50 tons. These products have a wide range of load-carrying capacity, fast and low impact installation and the ability to be loaded immediately after installations. Helical bearing plates are welded to a central shaft then load is transferred from the shaft to the soil through the helical bearing plates that screw into the soil with minimal disturbance. The first section or lead section contains the helical plates and if additional helices are required helical extensions can be added. Plain extensions are then added until the lead section penetrates the bearing soil and the necessary torque is achieved.
The torque correlation is the torsional resistance generated during helical pile installation, which is a measure of soil shear strength and can be related to the bearing capacity of the pile. As a helical pile is installed into increasingly denser or harder soil, the resistance to installation or torque will increase. The higher the installation torque, the higher the axial capacity of the installed helical foundation. When rotational torsion is applied to the end of the shaft at grade level, some of the torque energy is lost before it reaches the helical plates at the bottom end of the shaft. This loss of torque is due to friction between the shaft and the soil. The friction generated between the surface area of the shaft and the soil is directly related to the type of shaft and shaft size along with the soil properties. The magnitude of the required installation torque and the pile capacity can be directly attributed to the soil shearing resistance over the area of the embedded pile including the shaft and helical plates. Therefore, the pile capacity can be correlated to the installation torque. The relationship between installation torque and load capacity can be used to establish minimum torque criteria for the installation of production helical foundations. Torque monitoring tools provide a good method of production control during installation.