Soil nails can be used in clay, sand, and silt foundations with low groundwater levels, and the depth of the foundation pit is generally within 15m. However, how to support the foundation pit slope in case of broken, loose and easily collapsed rock formations? Of course, self-drilling soil nail.
In many construction projects, soil nails are used to support foundation pit slopes and highway slopes. The service life of soil nails has a great influence on the later quality of the whole project. So, how can we improve the service life of soil nails? Today, Sinorock will introduce to you.
Let us first introduce the construction method of soil nails.
1) Anchor first and then spray dig soil to the position of soil nails, after driving in soil nails, continue to dig down, and then hit the second layer of soil nails, and so on until the construction of the last layer of soil nails is completed. The first shot of plain stone concrete is 50mm thick, followed by anchoring, and then the second shot of concrete with a thickness of 50mm.
2) First spray and then anchor: excavate the soil to a certain distance from the soil nail position, lay reinforcement mesh, and reserve the lap length. After the shotcrete reaches a certain strength, the soil nail is driven. Dig the second layer of earthwork to a certain distance below the position of the second layer of soil nails, lay reinforcement mesh, and overlap with the previous reinforcement mesh, also reserve the length of the reinforcement mesh for overlap, spray concrete, and hit the second layer of soil nails. This cycle is repeated until the full depth of the foundation pit.
Its construction features are: the construction equipment is relatively simple; the construction is simpler than that with retaining piles and anchors; the construction speed is faster, the construction period is saved, and the cost is lower.
Advantages of Self-drilling Soil Nails
Self-drilling soil nail system, 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.
It 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.
It 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, self-drilling soil nail is suitable for the construction in the narrow space which the large equipment cannot enter.
Since the service life of soil nails has a great influence on the quality of the later stage of the project, what are the factors that impact the service life of soil nails?
Factors That Affect the Self-drilling Soil Nails
The soil nail is in corrosive water or soil (acidic or alkaline), temperature, humidity and alternate cycle of dry and wet, sea water splashing, sea salt infiltration and other environments. Its service life is reduced.
In the case of dry and non-corrosive medium, the service life of the soil nail is 2~3 times longer than that in wet and corrosive medium.
Cement varieties and admixtures
The addition of mineral admixtures such as fly ash can reduce the alkalinity of the cement slurry, thereby affecting the durability of steel bars. The compactness of the cement slurry is improved, and the internal pore structure of the cement slurry is changed, thereby preventing the infiltration of external corrosive media and oxygen and moisture, which is very beneficial to prevent the bolt from rusting.
Cement body density and protective layer thickness
The protective effect of the cement body on the bolt: The protective layer can prevent the penetration of external corrosive media, oxygen and moisture, and prevent contact with the bolt.
Above is the construction process of soil nails and the factors that affect the service life of soil nail. Contact us at firstname.lastname@example.org if you need this.