Since the total length of grouting rock bolts with safe and reliable, simple construction and low cost, they are widely used in slope engineering. When rock bolts reinforced slope, depending on the interaction between surrounding rock mass and rock bolt transmitting rod tension, making themselves get reinforced in geotechnical engineering, limiting the deformation, and improving stress state of the mechanical parameters of rock mass and to maintain stability. Due to the rock bolts load transfer mechanism is very complicated, so far still assumes that the lateral resistance distribution patterns in rock bolts design is uniform distribution. But a large number of measured results show that it is unreasonable according to uniform distribution pattern calculated. In recent years, with the development of computer technology, numerical simulation methods are widely used in geotechnical engineering, adopting double spring rock bolt element, the establishment of a model of Highway slope was simulated excavation process of the rock bolts reinforcement effect, the effective anchorage length of rock bolts and sliding surfaces, resulting in:
1.In slope anchorage engineering, rock bolts exist an effective length, when the rock bolts length is greater than the effective length, continuing to increase the length does not improve the safety factor of slope; When the rock bolts length is less than effective length, the relationship between slope safety factor and anchor length conforms to the linear features.
2. With the increase of rock bolts length, the potential sliding surface of slope gradually moves inside the slope, the failure mode from shallow sliding into deep sliding; when it comes to an effective anchorage length of rock bolt length, sliding surface of slope position mutation, quickly close to slope surface.
3. The distribution of each layer of rock bolt axial force along the length is uneven, rock bolt axis force generally performs the law for middle big and on both sides small; When there is external disturbance and degradation of rock mass slope, bolt axial force value of slope bottom is maximum, therefore, you should not arbitrarily reduce the bottom bolt length in practical engineering. For a permanent bolting slope with using load, we can appropriately extend bottom bolt length when necessary.