Key Points of Construction Technology of Soil Nail Retaining Wall

by Simone S. sinorockco

The soil nail retaining wall is composed of the reinforced soil body, the soil nail body placed in the soil, the protective plate, and the drainage system. The retaining wall is constructed to resist the earth pressure and other forces from behind the wall, thereby stabilizing the excavation slope. The soil nail relies on the bonding force on the contact interface with the soil, the friction resistance, and the surrounding soil to form a composite body. The soil nail is passively stressed under the condition of soil deformation, and the soil is strengthened through its tension. The deformation of the soil between the soil nails is restrained by the protective plate.

Install Soil Nails

Drill holes, set up a row of soil nails and the drainage pipes, and grout the soil nails. There are many types of soil nails and the most widely used is the self-drilling soil nail. The advantages of the self-drilling soil nail are as below.

Self-drilling soil nail, which combines drilling, grouting and anchoring together, is suitable for broken rock and conditions which are difficult to drill holes. Casing pipe is omitted in construction, which greatly improves the construction efficiency.

Self-drilling soil nail has a rich variety of drill bits, and drill bit can be selected according to the properties of rock and soil, which can improve the drilling efficiency.

Self-drilling soil nail can fill cracks, consolidate rock mass and soil layer through pressure grouting, and has good grouting spreading radius and reliable anchoring quality.

The hollow anchor bar can be cut arbitrarily and lengthened by the coupler. Therefore, it is suitable for the construction in the narrow space which the large equipment cannot enter.

Rebar binding

Remove rust and slag on the surface of steel bars before welding. The surface of the weld is smooth and there is no crack at the joint. The cast-in-place reinforced foundation first installs the basic reinforcement, and pre-prepares the vertical reinforcement of the wall. After the foundation is poured and the concrete reaches 2.5Mpa, the reinforcement of the wall is installed, and other accessories are pre-buried according to the design requirements before the concrete is poured. Facilities (such as scuppers, embedded parts of wall top railings, etc.). On-site processing, fabrication and binding of steel bars. When lashing on site, first draw the line, then place the bars, thread the bars, bind them, and finally place the special pads. When placing steel bars with welded joints and binding joints, the number of joints in the same section at the joint position, and the lap length shall be implemented in accordance with the current construction specifications. The intersections of the steel bars are made of iron wire. All stirrups are arranged vertically with the stressed steel bars, and the overlapping of the stirrup hooks is staggered along the direction of the stressed steel bars. In order to ensure the thickness of the protective layer, the thickness of the pad should be accurate and the strength should be guaranteed during prefabrication.

Template installation

The formwork must ensure that the design shape, size and mutual spacing of the concrete structure and construction parts are correct; the formwork must have sufficient strength, rigidity and stability to withstand the gravity, lateral pressure of the newly poured concrete and various loads that may be generated during construction; The joints must not leak grout. Leak-proof adhesive strips should be used to press the joints along the formwork. The formwork and the scaffold should not be connected to each other. The surface of the formwork and the concrete should be painted with release agent. When installing the formwork support, stand on a stable foundation; when installing the wall formwork, it must be supported and fixed at any time to prevent overturning. The retaining wall shall be provided with expansion joints and settlement joints according to the requirements of the design drawings. The inner two side walls of the expansion joint and the settlement joint shall be vertical and flush without overlapping.

Concrete pouring

Concrete is mixed in a mixing station and transported by a concrete mixer truck. The free fall height during concrete pouring shall not exceed 2m. When the free fall height is greater than 2m, chutes, strings, funnels and other appliances shall be used for pouring.

When vibrating, use a plug-in vibrator, vibrate vertically, and quickly insert and slowly pull out. The insertion vibrator moves at a distance of 30cm to 50cm, and the insertion points are evenly arranged. When vibrating, there should be no vibration or vibration leakage, depending on the level of the concrete surface and no significant sinking, and the surface of the mortar shall prevail.

After the pouring is completed, the exposed surface of the concrete should be trimmed and smoothed in time. Cover the maintenance and start the maintenance. During the process from initial setting to final setting of concrete, special personnel should continue to lightly press and plaster the surface to prevent cracks in the upper part of the concrete. After the soil is finally set, the concrete surface should be sprayed with water frequently to maintain the humidity for maintenance. After the formwork is removed, the concrete surface should be sprayed with water to moisten it.

Every time the concrete is poured, the stubble should be chiseled.

In order to ensure that the expansion joints and settlement joints of the foundation and wall are straight and located in the same section, the skipping method can be used for construction.

The soil nail wall is a soil retaining system formed by reinforced rods and protective panels set in the natural slope or the slope formed by excavation. It is used to improve the in-situ soil and work together with the in-situ soil to form a gravity Retaining wall-type light retaining structure, thereby improving the stability of the entire slope. Compared with other retaining walls, soil nail walls have unique advantages and should occupy a place in many forms of retaining walls. However, they also need to accumulate experience and improve in continuous engineering practice in the future to achieve more convenient construction and lower cost.

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Created on Jun 21st 2022 04:32. Viewed 173 times.

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