When retaining walls require added stability a tieback anchor is used. It can be a horizontal rod or wire or a helical anchor. One end of the tieback is attached to a stable structure while the other end is attached to the retaining wall. A concrete deadman is an example where the anchor has been driven into the ground to provide sufficient resistance. This resistant force keeps the retaining wall from leaning. A good example of this would be a seawall strengthened when water is present on the landward side due to heavy rain.
Steel rods driven into bedrock, concrete or other types of soil are grouted and used as tiebacks. The grout is sent through pressurized hose into the anchor holes with the steel rods creating increased resistance and stability. Wall stabilization is greatly enhanced greatly reducing the prospect of any tiebacks being pulled out.
Helical anchors are screwed into walls. Utilizing the equation Qt= Kt where Qt is the constant, K is the empirical constant and T is the torque of the installation determines the proportional capacity in accordance with the demands of each particular installation. Anchors are installed in either long or short lengths depending on the requirements of each job.
Soil mixing is a method where cement grout is used with existing soil to create a firmer substance to build upon with less permeability. Steel piles inserted into this soilcrete while still wet to serve as further stabilizing agents providing support during excavation. The soilcrete more easily spans between the piles and reduced permeability. This process provides relative dryness and less draw down on existing water tables creating an environment in which excavation can be more easily undertaken.
The technique of soil mixing can be used to create impermeable barriers. This can be particularly useful when dealing with seepage, dam walls and containing contaminated ground water. Soils underlying foundation can also be improved through the use of soil mixing. This can be of particular importance when building in earthquake prone areas to prevent liqufacation.