**7.5. Securing of excavation of underground utility tunnel (Ostrava, Czech Republic)**

#### **Task:**

328 Polyurethane

**Task:** 

was proposed.

**Solution:** 

**Figure 22.** Borehole with contaminated water seepages

**Figure 23.** Sealing of the borehole with PU grouting

**7.4. Sealing grouting of sewage collector (Pilsen, Czech Republic)** 

During exploitation of a sewage collector in Pilsen – Cernice, drainage in the surrounding area occurred due to drainage effect of the collector. Groundwater disappeared from the wells in the surrounding and drops of the surface occurred, causing even damages to some buildings. In section 4255 – 4350 m of the collector the excavation works ran in close proximity of a residential house. There was a risk of damage to the house and surface drop due to the fast drainage of the groundwater. In order to eliminate inflows into the collector, a hydrogeological survey was performed and a technology of sealing of the environment

During the exploitation works in the critical section (approx. 100 m), the rock mass was stabilized by PU grouting. Grouting PU materials Geopur® was used. The grouting works were performed always in advance before the exploitation to the distance of 3 m ahead of the face and were followed by exploitation of 2,5 m. Used technology enabled stopping of strong inflows of groundwater and secured higher stability of the rock mass during the exploitation works. Drainage of the surrounding area was eliminated and buildings were not threatened further by the excavation works. Total of 9516 kg of PU grouting material

In the centre of Ostrava town an underground gallery was exploited (Fig. 26). According to the design of the construction, it was required that the compressive strength of the overburden soil (gravels of the River Ostravice terrace) was minimally 2 MPa.

#### **Solution:**

The proposed technology was based on grouting of overlaying rocks ahead of the workingface by PU grouting system Geopur® to the distance of 3 m. In the given geological conditions the technology proved to be a safe and economic solution. The use of PU grouting resin system Geopur® enabled to perform the whole cycle of grouting works in 4 hours. Proposed technology did not require equipment of great size. Borings for grouting were drilled using a light hand drilling equipment; grouting works were performed using transportable pumps. 9-12 grouting tubes were used per one section (3 m), in accordance with local geological conditions. Distance between the grouting tubes was 0,3 m at the face and 0,4 m at the sides of the tunnel. Minimal compressive strength of the formed geocomposite reached in the upper part of the profile 4-6 MPa and 2-4 MPa on the sides. The strength of the rock was reached in 20 min after grouting works.

Polyurethane Grouting Technologies 331

**Figure 27.** Reinforced PU grouting of the crack in the concrete construction

**Figure 28.** Overall view of the repaired crack

**Task:** 

**Solution:** 

(Fig. 30).

**7.7. Lock at the Danube River (Gabcikovo, Slovakia)** 

During operation of the lock on the Danube River cavities had been formed on the outer side of the lock in the soil, caused by insufficiently sealed dilatation joints (Fig. 29). Water flowed through the soil embankment, washed out the fine grained particles and cavities

In 2005 additional sealing of dilatation joints and sealing of cracks in the concrete was performed using PU grouting system Geopur®. In total an area of 42 m2 of concrete was repaired, 210 m of dilatation joints was resealed and 207 m of cracks in the concrete was sealed. Total of 7 dilatation joints was successfully repaired using total of 700 kg of Geopur®

were formed. Additional sealing of the dilatation joints was therefore proposed.

**Figure 26.** Grouted gravel in the face of the tunnel

#### **7.6. Repair of cracks in the concrete of highway bridge (Belotin, Czech Republic)**

#### **Task:**

During the construction of the highway near Belotin, bridge beams were damaged probably due to the frosty weather. Cracks of up to 11 m length formed at the construction. It was necessary to reconnect the cracks using a reinforced grouting technology.

#### **Solution:**

Boreholes of 14 mm diameter were drilled into the concrete beam along the cracks, diagonally across the crack. Steel bars of 10 mm diameter were inserted into the drillings and subsequently the drillings were grouted with Geopur® PU resin (Figs 27,28)

**Figure 27.** Reinforced PU grouting of the crack in the concrete construction

**Figure 28.** Overall view of the repaired crack
