Anti-float anchor rods are engineering structures used to resist the buoyant force of groundwater.

**I. Working Principle**

Anti-float anchor rods transfer the upward buoyant force acting on buildings or structures to stable strata by means of friction between the anchor rod body and the surrounding strata, as well as the anchoring force at the end of the anchor rod, thereby ensuring that buildings or structures do not suffer uplift damage under the influence of groundwater buoyancy.

**II. Features**

Adaptable and versatile

- Suitable for various geological conditions, including soft soil, sandy soil, and rock. Through reasonable design and construction in different geological environments, the anti-floating anchor bolts can ensure effective anti-floating performance.

- For instance, in soft soil foundations, increasing the length and number of anchor rods can enhance anti-floating capability; in rock foundations, the high bearing capacity of the rock can be utilized to achieve anti-floating purposes with shorter anchor rods.

2. Reasonable Load Distribution

The tension of anti-float anchor rods is distributed over the entire length of the rod, transferring loads through friction with the surrounding soil or rock mass, resulting in more even stress distribution along the anchor rod.

- Compared to traditional anti-floating measures (such as increasing the weight of foundations), anti-floating anchors can more effectively utilize the strength of materials, reduce material waste, and lower the cost of construction.

3. Easy Construction

- The construction process for anti-float anchor rods is relatively simple, typically involving drilling, inserting rebars, and grouting.

- Construction equipment is compact and highly mobile, requiring minimal site space, making it particularly suitable for projects with limited space and complex surrounding environments. For instance, in urban center construction projects, anti-floating anchors can be installed within confined spaces, reducing the impact on surrounding buildings and traffic.

4. Shorter project timeline

Due to the relatively fewer construction procedures for anti-floating anchor rods and the ability to operate multiple machines simultaneously, the construction period can be significantly shortened.

- Compared to other anti-floating measures, anti-floating anchors can be installed in a shorter period of time, ensuring the smooth progress of the entire project.

**Section 3: Design Highlights**

Anchoring Rod Arrangement:

- Reasonable arrangement should be made based on factors such as the shape, size, load distribution, and geological conditions of the building.

- Generally, anchor rods should be evenly distributed within the foundation area of the building to ensure uniformity in anti-floatation effects. For irregularly shaped buildings, special anchor rod layout design may be required based on specific conditions.

Anchor Rod Length and Diameter:

The length and diameter of anchor rods are key factors affecting their anti-float capacity.

- The length is typically determined by factors such as groundwater buoyancy, stratigraphic conditions, and the anchoring force of the bolts. During design, the length of the small anchor bolts required to meet anti-buoyancy requirements must be calculated.

- The diameter of anchor rods should be selected based on factors such as the required anchoring force, construction methods, and cost-effectiveness. Generally, larger diameter anchor rods can provide greater anchoring force, but the construction difficulty and cost will also increase accordingly.

3. Anchor Force Calculation

- Anchor force is a core parameter in the design of anti-floating anchor rods, determining their effectiveness in resisting groundwater buoyancy.

- The calculation of anchoring force requires consideration of the friction between the anchor rod and the surrounding strata, the anchoring force at the end of the anchor rod, and other related factors. Typically, empirical formulas or numerical analysis methods are used for the calculation, and field test data is also needed for verification and adjustment.

4. Corrosion-Resistant Design

Due to the long-term exposure of anti-float anchor rods to groundwater, they are prone to corrosion. Therefore, effective anti-corrosion design is essential.

Common corrosion prevention measures include protecting anchor rods with anticorrosive materials (such as epoxy resin coatings, polyethylene sleeves, etc.) and adding corrosion inhibitors to the grouting materials.

**4. Construction Techniques**

Drilling:

- Drilling holes with a drilling rig to the specified diameter, depth, and inclination as per design requirements.

During the drilling process, pay close attention to controlling the verticality of the hole and the diameter deviation to ensure that the drilling quality meets the required standards.

- Depending on various geological conditions, suitable drilling techniques and machine types can be chosen, such as rotary drilling and impact drilling, etc.

2. Deburring:

After drilling is completed, the debris, soil, and other foreign materials inside the hole must be thoroughly cleaned to ensure the anchoring effect of the bolts.

- The cleaning methods typically include air blowing and high-pressure water flushing, and the appropriate cleaning method should be selected based on the actual situation.

3. Anchor Rod Fabrication and Installation

- Reinforce or produce steel wire ropes according to the specified length and specifications, and install anchor heads at the end of the anchor bars.

Then, insert the pre-fabricated anchor bolts into the drilled holes, ensuring the correct positioning and angle of the bolts.

4. Grouting:

Grouting is a critical step in the construction of anti-floating anchor rods, aiming to bond the rods with the surrounding strata, thereby enhancing the anchoring force of the rods.

- Grouting materials typically use cement grout or cement mortar. The grouting pressure and volume should be controlled according to design requirements and on-site conditions. During the grouting process, it is important to monitor changes in grouting pressure and volume to ensure grouting quality.

5. Anchor Bolt Tensioning and Locking

- After the grouting body achieves the design strength, tension and locking are applied to the anti-floating anchor rods.

- Tensioning equipment should be selected based on the tensile force and elongation of the anchor bolts. During the tensioning process, operations must strictly follow the design specifications for tensioning sequence and force to ensure that the pre-stress of the anchor bolts meets the design requirements. After tensioning is complete, the anchor bolts are locked onto the foundation structure using anchor fasteners.

Quality Inspection

Raw Material Inspection

Ensure quality inspections of raw materials such as rebars, steel wire ropes, cement, and sand used against floating anchor rods, to guarantee they meet design requirements and relevant standards.

- The inspection items include material strength, specifications, and chemical composition.

2. Anchor Rod Length and Diameter Inspection

- The length and diameter of anchor rods are inspected using measuring tools or non-destructive testing methods to ensure they meet design specifications.

- For critical projects or anchor rods with doubts, methods such as drilling core extraction can also be used for verification.

3. Anchor Pull Test

- Anchor rod anchoring force is tested in accordance with design requirements through on-site tension tests.

- Tensile tests should be conducted in accordance with relevant standards and regulations, and the number of tests should meet the requirements of the design and specifications. Generally, the number of tensile tests should not be less than 3% of the total number of anchor rods, and at least 3 tests should be performed.

4. Grouting Quality Inspection

- Quality of grouting can be inspected using methods such as ultrasonic testing and core drilling.

- Acoustic detection can determine the compactness of the grouting material by measuring the propagation speed and attenuation of sound waves within it; core drilling allows for direct observation of the strength and integrity of the grouting material.