The Difference between Hollow Anchor And Mortar Anchor

As the name implies, hollow anchor rods are hollow in the middle. Generally, they are used as hollow grouting anchor rods, which have good reinforcement effects on rock and soil. Mortar anchor rods use solid threaded steel bars, which have weaker anchoring force. When using them, you need to consider the construction conditions and make a reasonable choice. Let Xiaonuo analyze the differences between hollow anchor rods and mortar anchor rods for you.

1. Differences in anchor rod structure

Mortar anchor rod: Mortar anchor rods generally do not have pads and nuts. Sometimes only pads are set, but there is no nut. It is impossible to provide support plate force after the anchor rod is installed. The role of the anchor rod is completely passive. Only when the rock mass is displaced, the anchor rod begins to play a role, which is not conducive to controlling the early loosening and displacement of the rock mass after excavation.

Hollow anchor rod: The hollow anchor rod is composed of a rod body, a pad, a nut and a connecting sleeve (optional). After the slurry of the hollow anchor rod solidifies, the nut can be tightened to increase the support plate resistance. A pressure zone can be formed at the rock layer close to the support plate, which is conducive to controlling the initial deformation after rock mass excavation and preventing broken rock blocks from falling.

2. Differences in construction techniques

Mortar anchor rod: The mortar anchor rod adopts the construction sequence of first drilling, then grouting and then installing the 

anchor rod. The bonding force between the anchor rod and the surrounding rock is not as good as that of the hollow grouting anchor rod. The slurry selection is not as diverse as that of the hollow grouting anchor rod, and the reinforcement effect on the surrounding rock is also worse. Therefore, mortar anchors will leave deep hidden dangers, and what is more dangerous is that such hidden dangers are usually not noticed by people.

Hollow anchor rods: Hollow anchor rods are generally hollow grouting anchor rods. The hollow rod body is inserted first, and then cement slurry is poured from the inside to the outside in the cavity of the hollow rod body. There are grouting plugs and support plates at the outer ports of the anchor holes, which can effectively prevent the overflow of slurry, ensure that the grouting between the rod body and the hole wall is full, and ensure that the rock mass is reinforced. If necessary, pressure grouting can also be implemented to allow the slurry to penetrate and diffuse into the cracks of the rock mass around the rod body, so that the rock mass within the anchoring range is further reinforced.

3. Durability difference

Mortar anchor rod: Since the fullness of mortar in mortar anchor rod is difficult to control during construction, the pores, cavities and exposed steel bars in the borehole are often difficult to avoid, and groundwater containing corrosive media will invade, causing the steel rod to rust, seriously affecting the durability of the anchor rod.

Hollow anchor rod: Hollow grouting anchor rod can not only ensure that the gap between the rod body and the hole wall is grouting full, but also because of the configuration of anchor head, grouting plug and connecting sleeve, the self-drilling hollow grouting anchor rod produced by Luoyang Hengnuo Anchoring can be equipped with a centering device to center the rod body in the anchor hole, thereby ensuring that the anchor rod has a uniform protective layer thickness required by the design, greatly improving the durability of the anchor rod.

4.Difference in coping ability

Mortar anchor rod: The coping ability of mortar anchor rod is poor. If drilling in poor strata such as weak and broken rock, the hole collapse phenomenon often occurs after the drill rod of the mortar anchor rod is pulled out.

Hollow anchor rod: Hollow grouting anchor rod can be fully anchored along the entire length of the anchor rod, and can provide a certain support resistance immediately after excavation, inhibit the loosening and deformation of the surrounding rock, and avoid or mitigate the occurrence of collapse and roof collapse accidents or other diseases during construction and use.

5. Price difference

Mortar anchor rod: From the perspective of short-term explicit benefits, taking tunnel engineering as an example, due to the lower unit price of mortar anchor rods, the comprehensive cost of tunnel anchor rods per linear meter and the total cost of tunnel per linear meter are both reduced compared with hollow grouting anchor rods.

Hollow anchor rod: From the perspective of long-term implicit benefits, the hollow anchor rod body has a sufficient and uniform protective layer thickness, which enhances the durability of the anchor rod. These implicit economic benefits are unmatched by ordinary mortar anchor rods.