Working Mechanism of Composite Soil Nailing Support Structure

The construction equipment of soil nailing technology is simple, low in cost, and short in the construction period, which is more in line with the development needs of the construction industry in the early stage. However, as the depth of the foundation increases, the area of the foundation projects is getting larger and larger, in order to avoid the limitations of a single soil nail support structure, the composite support structure is gradually widely used.


Soil Nailing Structure

The soil nailing support structure technology has the characteristics of high construction efficiency and simple equipment. The earliest traceable historical prototype is the New Austrian Tunneling Method (NATM) formed in the 1950s and then Reinforced soil technology began to develop in France. Almost at the same time in the 1970s, soil nailing wall technology was developed in Germany, France, the United States, Japan, and other countries, and then it has been applied globally in the past 50 years.


Soil nail refers to the rod that is implanted in the soil and grouted to bear the tension and shear force generated. It is the most important force-bearing component in the soil nailing wall support structure. The protective structure is mainly composed of three parts, namely soil nails, restrained soil and shotcrete surface.


Working Mechanism of Composite Soil Nailing Support Structure

The soil mass has a certain compressive strength, but its tensile strength and shear strength are weak. And because the soil has structural integrity, it can maintain stability to a certain extent. But if the ground load exceeds the limit or the soil slope height exceeds the critical value, the soil loses stability and will collapse.


The composite soil nailing wall support structure mainly composes of appropriate-length soil nails, by inserting them into the soil mass at a certain density, and combines with various piles, prestressed anchors, and other structures to form a binding body for the soil and form an overall structure that works together. The new composite structure not only solves the problem of weak shear strength of the soil mass but also effectively improves the overall stiffness. The combining effect enables the structural strength of the soil itself to be fully exerted, controls the deformation and improves the overall stability of the foundation.


Many experimental studies have shown that the bearing capacity of soil nailing walls is 2 to 3 times higher than that of plain soil slopes. For soil slopes without any support protection, when a network of cracks appears on the soil slope surface, it will lead to intensified ground settlement, and finally, cause the entire slope to collapse. Meanwhile, the soil nailing wall structure gradually expands when it is deformed by force until it exceeds the ultimate bearing capacity of the structure, but there will be no sudden overall collapse, which is safer for the whole project and the personnel.


The improvement of the overall stability of the composite soil nailing wall is achieved through the interaction between soil nails, various piles and concrete panels, and other structures and soil mass:

(1) Soil nails act as skeleton constraints on the structural complex

The construction process of soil nailing is drilling→reinforcement→grouting. It self has good shear resistance and tensile properties.

(2) Soil nails play the role of stress distribution on the structural composite

In the composite support structure, the structure and the soil mass jointly resist the external load and bear the self-weight stress, and the soil nails play a role in sharing.

(3) Soil nails play the role of transferring and diffusing stress

Soil nails transmit the stress in the cracked area to the stable soil behind through the stress transfer function, and disperse the stress in a large range to avoid greater damage caused by stress concentration.

(4) Grouted soil nails reinforce the soil mass

The grout enters the hole along with the steel bars, and penetrates into the internal gap of the soil, which improves the bonding force between the soil nail and the surrounding soil, and increases the strength of the soil to a certain extent.

 The above is the introduction of working mechanism of composite soil nailing support structure. Sinorock is professional self-drilling anchor bolt manufacturer, and has years of experience in slope stability, foundation support, underground engineering. If you have any questions, welcome contact us.

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