Common Failures for Soil Nailing Support And Treatments Measures

At the same time, there are many uncertain factors in the treatment of foundation support, such as support scheme design, geological conditions, etc., which directly or indirectly affect the result of foundation support. This article will analyze the common failure and treatment measures in soil nailing for foundations.

 

Common Causes of Foundation Slope Collapse

1.    Construction Design

If the silt layer of the project is thick and the clay thickness varies greatly, the use of a single support method or a short soil nail is easy to lead to slope displacement or collapse.

2.    Geological Conditions

(1) In sites with complex geological conditions, especially clay with poor mechanical properties, it is easy to slide to the inner side of the foundation under the load.

(2) After groundwater and a large amount of rainwater infiltrates into the soil layer, the water content of the soil increases, which causes lubrication between soil particles and greatly reduces the friction force within the original soil. Thus, the sliding force of the soil on the slope of the foundation increases and the shear strength decreases.

(3) Soil nail support is suitable for sandy soil or silt with certain cohesiveness. For soft soil, it is necessary to take strengthening measures, and the creep of soft soil makes the support structure or the overall displacement of soil body is inevitable.

3. Construction Process

(1) The length of soil nails does not meet the requirements. The foundation should be excavated in layers and sections, the height of the layers should be within 1.2m, and the length of the sections should be controlled within 15m.

(2) If the water-cement ratio of grouting is too large and the grouting effect is poor, it will cause excess water to seep into the original soil layer, thus affecting the physical properties of the soil layer in a negative way.

(3) If the sprayed concrete doesn’t get timely curing, small cracks will appear in the concrete wall, which will aggravate the leakage of groundwater and rainwater and reduce the strength and stiffness of the concrete wall.

 

Treatment Measures

1. Earthwork backfilling. After the soil body is stable, add temporary pine piles to support the local position of the soil nailing wall.

2. Use steel floral tube grouting for the damaged part of the foundation. This method can help to improve the hardness of soft soil, the pullout resistance of soil nails, and the local and overall stability of the foundation structure.

3. In the soft soil layer, especially the layer of silty clay, the foundation cannot just support by soil nailing. The compound soil nailing wall is used for support, which is mainly the combination of cement-soil mixing piles and soil nailing walls. The soil mass of the slope is reinforced by the cement-soil mixing pile to solve the problem of bonding between the sprayed surface layer and the soil mass.

 

The New Technology of Slope Support: Self-drilling Soil Nail

Self-drilling soil nail combines drilling, grouting, and anchoring at one time to improve construction efficiency. The self-drilling anchor bar is a hollow threaded steel rod with a drill bit in the front section and the end connected to the drilling rig. The grouting is completed while the drilling is finished. After the solidification of the cement slurry, the self-drilling anchor bolt is integrated with the ground, and the grouting effect is better.

 

Conclusion

Soil nails have obvious price advantages with convenient and fast construction characteristics, and are widely used in shallow foundations supporting. However, site conditions and the surrounding environment should be carefully analyzed during the design and construction of the foundation excavation. At the same time, the rationality and efficiency of foundation drainage should be ensured in order to effectively prevent the failure of soil nails.