The PUIF is a method to grout the chemical material to improve the ground condition in a weak and fracture geology. Normally, there are two kinds of improvement could be achieved.First is to increase the unconfined compressive strength (qu) of the soil by occupying the space of the gap after congealed. Second is to decrease leakage of the soil layer by disturbing the channel of water flow and thus obtaining the water proof effectiveness.The broad area water leakage in tunnel during excavating will lead to the ground soften and cause a deflection or as a worst result of collapsing.

The PUIF method is designed and developed to cope with situation which the cement or silicate grouting is still not able to deal with. The method can effectively improve the ground condition and prevent the possible interruption of the follow-up work due to the unstable geology.

■ The mostly used grouting material in PUIF method is PU or Silica resin, both of them
contain solution A and B

■ PU resin
The grouted PU resin can offer a strong confined force between the rock layers and
increase the internal stress within the rock layers. Therefore, the rock layer can be kept in
stable status and the tunnel can be protect from possible collapsing.
The coagulating time of the PU resin could be easily adjusted to meet the requirement of
different areas where the ground condition needed to be improve. This is the advantage
which the regular cement grouting doesn't possess.

■ Silicate Resin
In tunnel construction, it is normally to encounter some worse geology conditions such as
high groundwater, leakage in tunnel, sand layer with bad cohesion, sand leakage with
water layer, fracture layer and etc. When the regular supporting methods like rock bolt,
shotcrete, and etc. couldn't provide a effective support, the Silicate Resin, with high
penetrability and well water interruption capability, can be used to heal the loosen geology
and stabilize the excavating area to allow the follow-up activity to be continued. 

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