Soil Nailing System In The Application Of The Large Deformation Tunnel Suppor

Large deformation of tunnel surrounding rock deformation are often up to tens of centimeters, accompanying with the development of displacement of the plastic ring is thickening, as to form a huge pressure on the supporting structure, causing the destruction of the support and surrounding rock instability, while the plastic ring can greatly reduce the deformation of surrounding rock,at the same time it can reduce the tangential stress concentration of the surrounding rock;Scientific philosophy is that allowed to produce the control of the displacement in surrounding rock,which can form a certain thickness of the plastic circle within the surrounding rock, reducing frame load with using soil nailing system, in this way you can realized the stability of deep surrounding rock.So use of soil nailing system supporting of soft rock, thus can solving the problem of soft rock tunnel supporting.

Soil nailing systems are suitable for large deformation of soft rock roadways, and it can play an important role in maintaining the complex geological conditions and weak fracture zone which the conventional support or other conventional method is difficult to supporting.The supporting mechanism of soil nailing systems is through a combination of supporting structure to formed the soil nailing supporting structure within the surrounding rock of roadway under external load, thus can reduce the deformation of surrounding rock of roadway, let drift in a stable state.

By using soil nailing system making its surrounding rock under tension device for horizontal tension, formed in the rock band force and formed in the surrounding rock within the "rock arch", and layout anchor wire through the holes of the soil nail lower end form a soil nailing system, "pocket" the soft rock between soil nails .Finally in the tunnel section, crisscross decorates the soil nailing system before and after to entire tunnel and surrounding rock deformation of "tightening their belts".

In the implementation of the soil nail technology, also should pay attention to the following three aspects:

First, there is tend to be filling in the upper excavation process,making the force at center location in supporting height of soil nail bigger, so in order to improve the bearing capacity, should increase the density of the soil nail while anchored into the longest soil nails.

Second, due to the overall effect of the soil nailing will influence the choice of soil nail spacing, therefore, it is not yet accurately calculate the data of distance ,but it should be chosen within the scope of the 1.2 m to 2 m based on previous experience of soil nail vertical and horizontal, especially when determining the vertical spacing should be set according to the actual circumstance of the soil.

Finally, the inclination of soil nailing influenced by characteristics of layered soil and grouting drilling process, generally set it to 0 ° ~ 20 °.Practice shows that if the inclination of soil nailing is small, its resistance to deformation is stronger, but it is not easy to grasp the quality of grouting, on the contrary, its resistance to deformation ability is poor, but can make a better quality of soil nailing anchor into the soil.