The rock anchors in civil and mining structures to counteract uplift forces acting on foundations and post-tension existing concrete structures. Rock anchors are made of high tensile steel, and typically they are anchored in sound bedrock by means of high strength cementitious grouting for foundations and through holes drilled into or through a structure for post-tensioning applications. For most applications the rock anchors are tensioned to a force higher than what is necessary to resist the foundation uplift force. When no tensioning is applied to the rock anchors they are called rock bolts. Both rock anchors and rock bolts are eventually grouted on their full length, however rock anchors may be grouted in two steps to allow for a certain free tensioning length after the first step.
"3. Chemical Grouting
The most usual form of grouting method is referred to as permeation grouting, which in simple terms, involves filling opening space. Although all varieties of grouting contain some measure of permeation grouting, there are four distinctive approaches: permeation, compaction, fractural and jet grouting.Structural chemical grouting, when used in granular soils, permeates the spaces between the soil particles, binds the particles together, and improves the soil’s bearing capacity.The chemical grouting method is an injection method that improves the ground by injecting suspension-type, semi-suspension-type, and solution-type grout materials into soft ground and has excellent water blocking and ground reinforcement effects.
"Deep Cement Mixing (DMM) stabilizes weak and compressible soils at depth by mechanically blending in situ soil with cementitious slurry.
1. Technology Overview
The Deep Cement Mixing (DMM) method uses mechanical mixing augers to blend soft soils at depths up to 20m - 30m with cement slurry.Hydration of the cement creates high-modulus, high-strength soilcrete columns that dramatically reduce settlement and increase overall bearing capacity.
2. Construction Sequence
▫ Step 1: Positioning the mixing machine over the column coordinate.▫ Step 2: The mixing blades penetrate down to the designed competent bearing stratum.▫ Step 3: Cement slurry is pumped while counter-rotating blades thoroughly mix the soil.▫ Step 4: Controlled retrieval of the mixing stem ensuring uniform column diameter.
3. Applications
▫ Highway embankments, ports, airport runways over soft clay.▫ Slope stability reinforcement and cutoff walls for deep excavations.▫ Mitigation of post-construction differential settlement.
"1. Ground (Earth) Anchor
The ground Anchors are basically devices used to transmit the forces to the soil by means of prestressed tendons to anchor the Structure to the ground or to retain the slopes from collapsing.The ground anchor can be used to stabilise a retaining wall by transferring the forces caused by the natural thrust of the ground and the working loads beyond the slip circle. Forces are transmitted to the ground via the bond length. It is generally prestressed to control the movement of the retaining wall during the various construction phases.Earth anchors are used in both temporary or permanent applications, including supporting retaining walls, guyed masts, and earth retaining wall.
2. Rock Anchor
The rock anchors in civil and mining structures to counteract uplift forces acting on foundations and post-tension existing concrete structures. Rock anchors are made of high tensile steel, and typically they are anchored in sound bedrock by means of high strength cementitious grouting for foundations and through holes drilled into or through a structure for post-tensioning applications. For most applications the rock anchors are tensioned to a force higher than what is necessary to resist the foundation uplift force. When no tensioning is applied to the rock anchors they are called rock bolts. Both rock anchors and rock bolts are eventually grouted on their full length, however rock anchors may be grouted in two steps to allow for a certain free tensioning length after the first step.
3. Vertical (Buoyancy prevention) Anchor
The Vertical(buoyancy prevention)anchor method is to stabilize the structure against excessive stress, deformation, displacement, etc. that occurs in the structure by installing permanent anchors on the foundation floor and lower rock layer and fixing both ends for the buoyant part that is not in balance with the dead load of the structure. In this method, the stability of the structure's buoyancy, the internal stability of the anchor, the stability of the tensile member's design load, the stability of the adhesion between the grout and the rock, and the stress holding capacity according to load and time must be carefully reviewed, especially over time.
