**2. PU grouting resin types**

308 Polyurethane

strengthening of coal in areas with rock burst risk

stabilization and sealing of old mine pits and etc.

stabilization of slopes, embankments, excavations

construction of underground barriers with low permeability

strengthening of subsoil (also under groundwater level)

stopping of water inflows into constructions and etc.

securing of stability of structures threatened by mining or construction

sealing and anchoring of bottoms and walls of construction pits under

improvement of subsoil conditions before starting of the construction

anchoring and sealing of flood dams, anchoring of bottom of water canals

This chapter contains brief description of PU grouting technologies and characteristics of basic grouting material types. It further presents practical findings of the authors obtained throughout their long term experimental research, design work and application of PU

strengthening and sealing of brick and stone masonry on bridges

improvement of subsoil parameters under pillars (also in rivers)

limitation of the mine wind blowing

anchoring of soil and rocks

anchoring of retaining walls

 sealing of dilatation joints micropiling of foundations stabilization of landslides

stabilization of unconsolidated soil

 strengthening of brick or stone masonry restoration of insulation of structures sealing of utility entries into constructions

anchoring of walls of construction pits

 micropiling in soil with low bearing capacity foundation of buildings in undermined areas

 anchoring and strengthening of embankments repair of concrete structures under water limitation of underflowing of dams

repair of cracks in the constructions

anchoring and micropiling of foundations

**Geotechnical works** 

**Civil engineering** 

works

sealing of joints

**Foundation of buildings** 

 **Water management works**  sealing of joints on dams

**Bridges and roads** 

groundwater table

PU grouting materials can be divided according to their chemistry to three main groups:

1. two-component (PU) organic resins:

component A – polyol in mixture (polyetherpolyol, catalysts, additives), component B – isocyanates in mixture (methylene diphenyl diisocyanate [MDI], homologes, isomeres).

After curing they form solid PU resins or foam.

2. one-component organic resins:

react with moisture present in the environment or construction and form an organic resin (material is on the basis of prepolymer MDI)

3. two-component organic-mineral resin (OMR):

component A – polysiliceous acid (natrium water glass, catalyst and additives), component B - isocyanates (MDI, homologes and isomeres).

The main difference between the above materials is, that **material on the basis of polyol – isocyanate react with moisture present in the environment**, while material on the basis of polysiliceous acid – isocyanate are inert to moisture or water.

In case of OMR material, the mixing of the components plays an important role in the grouting process. The component A is inorganic - formed by water glass and additives. It is very different form the component B, which is of organic character on the basis of MDI. During mixing the water glass disintegrates to small drops in the organic phase of MDI and an inhomogeneous system is formed. Two different components A and B are in contact with each other only at the surface of individual drops. Chemical reaction proceeds better, the smaller the drops of component A are (the contact of the components is more intense). The reaction can be influenced also by additives, which lower the surface tension of water glass (e.g. silicones). The best results are achieved when mixing by ultrasound. Formed product of hardening process is a resin with solid closed pores of polysilicious acid gel.

In case of PU material, the intensity of mixing does not have fundamental impact to the reaction proceeding. A homogenous solution is formed by the mixing, which cures quite well.

The hardening process, following the mixing and injection of the PU mixture into the rock mass, takes from several minutes up to few hours, according to the type of used grouting resin. Currently, a wide variety of PU grouting materials of various producers exist on the market. Physical and mechanical properties of individual systems differ and it is often quite difficult to choose the appropriate system for particular application. In table 1 we present for example technical data of universal PU grouting system Geopur® (Bodi, 2003), produced and used since 1994.


Polyurethane Grouting Technologies 311

**3. Grouting equipment** 

presented on Fig. 1 below.

**4. Grouting technology** 

grouting pressure and temperature.

Injection of material into the rock environment proceeds:

**Figure 1.** Two component electric grouting pump DV 97.

packers, grouting anchors or bolts, grouting tubes and etc.

Injection of grouting material into the rock massive is performed by grouting pumps. Usually piston type pumps with electric or pneumatic drive are used. There are one component and two component pumps available. An example of a grouting pump is

Grouting elements are used during the injection of the grouting material into the rock mass. These are technically designed to transfer the pressure of the grouting material, preventing back flow of the material out from the borehole. They are usually equipped with a back valve. According to the method of fastening in the borehole, we distinguish mechanically fastened once, hydraulically, drilled, pushed in, vibrated or glued. They are called grouting

Mixing of the PU mixture is made in mixing chamber, which is located behind the pump. This is located as close as possible to the borehole. Grouting pump sucks both components of the grouting resin from separate tanks or the components flow in gravitationally. The pump takes the components in appropriate ratio and delivers them separately to the mixing chamber. In the mixing chamber, components are mixed and subsequently injected through the packer into the rock mass. The resin penetrates under the pressure into surrounding fissures and cavities up to the distance of a few meters from the borehole. As a result sealing and strengthening of the rock mass or construction is achieved. After finishing of the grouting, it is necessary to flush the pump, hoses and accessories and clean the equipment. In case of longer regular use, it is possible to leave the components in the pump and hoses. The work team is usually formed by a couple of trained workers. Parameters of the grouting works are recorded during the work like e.g. location of boreholes, grouted quantities,

**Table 1.** Technical data of the grouting system Geopur® produced by the company GME
