In rock and soil anchoring projects, there are many factors influencing anchoring effect, such as: material of anchor bolt, structure of anchor bolt, pattern of anchoring, property of rock mass, parameter of anchoring, etc.
1. The material of anchor bolt influences anchoring effect
The body of anchor bolt is the most basic condition of generating anchoring force. It will influence anchoring effect largely if anchoring energy is not enough, such as: the body’s intensity is not enough, the binder’s strength is not enough, etc. In actual project, the materials of anchor bolt can be divided into rebar, high-intensity steel wire, fiberglass and so on. According to property and price, rebar is used broadly in China.
The material of anchor bolt in our company is generally high-intensity bolt and ultrahigh-intensity bolt, which has great elongation and can control the deformation of surrounding rocks efficiently.
2. The structure of anchor bolt influences anchoring effect
Our company mainly produces and sells self drilling anchor bolt and mechanical expansion anchor bolt. Compared with other anchor bolts, self drilling anchor bolt has advantages on the following conditions: which is difficult to drill holes and easy to collapse. It can control surrounding rocks and improve work efficiency largely. Expansion anchor bolt belongs to mechanical pre-stressing bolt, it can control surrounding rocks timely and efficiently and it can give full play to self bearing capacity.
3. The pattern of anchoring influences anchoring effect.
To make anchoring force transfer to the deep of rock stratum, anchor bolt should be combined with rock mass efficiently. While how to combine them and how to give full play of them are very important to bolt’s reinforcement. Generally speaking, there are three methods for anchoring bolt: mechanical fastening, cementing material fastening and expansion basal fastening.
4. The property of rock mass influences anchoring effect.
The working property of anchor bolt is actually its mechanical property, it depends not only on the mechanical parameter of itself, but also on the mechanical property of surrounding rocks. There are several factors affecting surrounding rocks’ mechanical property: the rock mass’s hardness degree, integrated degree, initial stress state and underwater conditions.
5. The parameter of anchoring influences Anchoring effect.
There are several main factors affecting anchoring parameter: aperture and road diameter’s coordination, length of anchoring, dip angle of anchor bolt, separation distance of anchor bolt, etc.
The coordination of bolt’s diameter and drill bit’s diameter makes bolt’s pulling resistance reach the maximum value. While this pulling resistance do not show linear growth with anchoring length, there exists a critical anchoring length. When anchoring length exceeds the critical length, it is not clear for pulling resistance’s increasing.
The dip angle of anchor bolt is another parameter for anchoring structure. It has great effect for structure’s force condition, anchor cable’s length and construction’s complexity. Generally speaking, when the included angle becomes large between bolt’s axes and horizontal plane, it can generate large vertical component force, and then the horizontal supporting force is decreased, so the dig angle of anchor bolt should less than or equal to 45 degrees.
When anchor bolt’s separation distance in anchor group is too small, the supporting force of anchor group is less than the sum of every bolt’s anchoring force, that is efficiency of anchor group. So the designer should consider every factor when designing the bolt’s separation distance.
In conclusion, by knowing the factors of influencing anchoring effect, we can improve anchoring effect from several aspects and then reach the purpose of providing efficient supporting for rock and soil anchoring projects.