How to Support Tunnels in Sand Layer?

 When encountering special geological conditions during tunnel construction, it needs to be analyzed according to the geological survey report. The safety and stability of the later operation and the length of the construction period should be considered in the design of the tunnel. The surrounding rock of the sand layer must be supported and reinforced due to geological fracture. The following will introduce to you the geological characteristics of surrounding rock tunnel in the sand layer, and how to support it with rock bolts.

1. Geology Characteristics of Tunnels with Sand

The main problem of the sand layer and gravel layer is that the ground is loose and lacks cohesion, and problems such as gravel falling will occur during excavation and shotcreting. If there is groundwater in the tunnel, too much water will cause the strength and bearing capacity of the surrounding rock to drop significantly, resulting in the collapse of the rock mass. At present, there are many neglected details in many tunnel projects, such as incomplete survey, lack of popularization of design intentions, and lack of formulation of construction methods, which may cause large and small problems in the project.

2. Tunnel Support with Rock Bolts

A.     Clearing Site

If the surrounding sand rock of the tunnel has collapsed or the gravel has fallen, it is necessary to clean up the gravel first. At the same time, pay attention to the collapse of the tunnel vault and surrounding rock. If the collapse is small, temporary support should be carried out first, and if the collapse is large, reinforcement grouting is required.

B.      Shotcrete

After the site is cleared, it is necessary to spray grout on the face of the tunnel to avoid problems such as falling gravel during operation. If spray grouting cannot solve the current tunnel problem, you can consider bolting and grouting for reinforcement.

C.      Install Rock Bolts

Tunnels in sand surrounding rocks need to be supported by rock bolts. The traditional support method is pipe casing construction, which takes a long time and requires a lot of manpower. The use of self drilling anchor bolt support has high construction efficiency, and the hollow bar body does not need to be pulled out after the drill bit is driven in.

D.      Grouting

The casing construction process adopts the method of drilling first and then grouting, and the construction process of self drilling anchor bolts adopts the method of grouting while drilling. When drilling, the hole diameter and the grout penetration range will be enlarged, thereby improving the pullout force of rock bolt. It has obvious advantages in terms of pullout force and bearing capacity, force value performance and construction efficiency.

In the design of special geological tunnels, special attention needs to be paid to the safety of personnel. From design, materials to construction techniques, design requirements must be strictly followed to eliminate problematic support projects. Sinorock self-drilling rock bolts make special geological tunnel support simpler and construction more efficient.

As a leading expert in the ground support industry, the Sinorock team has many years of experience in providing complete geotechnical engineering services. If you have any needs or questions about self-drilling anchor systems and their applications, please feel free to contact us at

Return The List

latest news