Currently, anchor bolts used in mine timbering are commonly have poor support ability and pre-stress. Because of the horizontal crustal stress, pressure bar destabilizing is easily happened on tunnel roof so that there will be tensile failure, abscission layer and tunnel fall of ground.
Traditional anchor bolts have little influence to stress field of tunnel-surrounding. As new material and technology are applied wildly in mine timbering, it is possible to improve anchor bolts’ pre-stress greatly and to fix the stress field of tunnel-surrounding. Also support ability of rocks can be improved by using the horizontal crustal stress. High performance anchor bolts can bring us high pre-stress.
High performance anchor bolts belong to a new kind of anchor bolts with high strength, high elongation, good support ability and integrated accessories. Also integral strength of them should matches with their geometry size. The following are the features of the mainly popularized high performance anchor bolts:
① They are made of 20MnSi sinistral thread steel without longitudinal reinforcements.
② New processing technique with low loss of strength are applied for their external thread part. The size and strength of accessories such as nuts, plates and steel tapes are appropriate.
③ Mechanical installation is applied.
④ There are striking signs to show quality of construction directly.
The advantages of bolting with wire mesh which is composed of high performance anchor bolts and new types of accessories are as follow:
① Supporting effect is obvious.
② The installation of anchor drill is integrated and continuous.
③ There is a series of high performance anchor bolts with wide application range.