Foundation Grouting generally refers to improving the rock under a dam foundation. The techniques are applicable to other applications. Grouting is used during new dam construction and for remedial work. The process involves drilling holes and injecting a fluid grout under moderate pressures into the subgrade to seal the rock to reduce its permeability. The process has been in use since the late 1920’s and has evolved to a very technical process.
Successful foundation grouting projects require a methodical approach using multiple series and rows of grout holes. Typically the initial or primary holes are drilled, pressure tested with water and grouted. The process is documented capturing the flow rate and pressure required to treat each elevation for water testing and grout injection. Upon completion of the initial holes, intermediate or secondary holes are drilled midway between the primary holes and the process repeated. By comparing the data between the series of holes a determination can be made on the effectiveness of process. Split spacing of the hole continues until the permeation goals have been met. This is usually determined by the results of the water pressure tests and can include an analysis of the solids of material placed.
Selecting the proper grout material and mix design in crucial to an effective curtain. The grout mix utilized must be formulated for the geologic conditions and the goals of the project. The formulation considers the size of the openings to be grouted, the amount of bleed, the permeability, and stability of the fluid. A modern grout may have 6 different constituents including a binder, such as portland cement, sand, water, bentonite, water reducer, and thixotropic admixtures. Other binders include ultrafine cement and a variety of chemical grouts.
TerraFirm has experienced staff and the specialized equipment for a wide range of foundation grouting projects. We have experience in difficult access projects such as working inside a gallery and steep slopes. TerraFirm’s staff has been instrumental in advancing the technology of foundation grouting with many firsts. This includes utilization of a water powered down the hole hammer to allow efficient drilling in hard rock, utilizing a computer controlled system to control grout pumps in the US, data integration with a Geographic Information System (GIS), measurement of the grout pressure at the point of injection using a downhole pressure transducer
Our engineers, geologists and technicians can assist with your foundation grouting project by providing advice, skilled staff and cutting edge technology for a successful project.