The Construction Instruction of Self Drilling Anchor Bolt in the Jihe Motorway

The Construction Instruction of Self Drilling Anchor Bolt in the Jihe Motorway

The Jihe Motorway is the important part of the expressway network in Shanxi province. It is from the Ji county to the east of Hejiazhuang in Hejin city. This project is located in mountainous and hilly area. There are high mountain and deep valley which is criss-cross along the line. The geological conditions is complex and the construction set is difficult. The proportion of the bridge and tunnel is as much as 50.2%. The surrounding rock of the tunnel is in poor condition and the bridge is very high. It is mainly the roads to carry on deep cuts and high fills-in.

The self drilling anchor bolt is the important element of the flexible supporting system. The functional mechanism of the anchor bolt combined arch depends mainly on the reinforcement effect from the systematic anchor bolts to the whole surrounding rock. It will help the surrounding rock to form arch bearing structure in a certain depth range, and to bring its high compressive strength into full play.

The self drilling anchor bolt will be arranged in passing quincunx along the tunnel excavation contour radial line. The following is the designed parameters:

Tunnel Name Surrounding Rock Grade Surrounding Rock Length (m) SDA Dia. (mm) SDA Length (m) Separation Distance (m) Quantity
Left Line of Bei Leyuan Tunne IV 1270 φ25 3.0 0.9*1.0 22
V-2 390 3.5 0.8*0.1
V-3 325 3.5 0.7*0.1
Right Line of Bei Leyuan Tunnel IV 1330 3.0 0.9*0.1
V-2 300 3.5 0.8*0.1
V-3 360 3.5 0.7*0.1

1. Construction Preparation

  • The construction field should be leveled with artificial or mechanical so that the DTH drill can enter in.
  • Generally speaking, the service road requires about 3m wide, slope gradient controlled at 30%, and the operation area needs 4m * 5m.

2. Drill Holes

  • Turn on the DTH drill after the air compressor starts.
  • Adjust the drilling angle of DTH rig according to the terrain and geological condition.
  • Set up dedicated fiber tail in the DTH drill, connect the self drilling hollow anchor bolt and fiber tail set firmly, and set the bit on the front end of the self drilling hollow anchor bolt in the first quarter.
  • Determine the length of the self drilling hollow anchor bolt according to geological condition, and splice the anchor bolt owing to the scene.

3. Grouting

  • Connect the end of the self drilling hollow anchor bolt and grouting pump with rapid grouting joint.
  • Start the mortar mixer. Blend the cement and other admixture materials according to mix proportion designed, then enter into the mixer for stir.
  • Input grouting pump, keeping the grouting pressure tube straight. Grouting quantity is determined according to the size of the grouting pump pressure or the consumption of mortar mixer speed.
  • Installed check pulp plug, and then set plate arch in exposed portion of the self drilling hollow anchor bolt, sticking to the surface of the earth or rock strata, put the plate and ball nut.

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