**4. Grouting technology**

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, grouting pressure and temperature.

Injection of material into the rock environment proceeds:


Grouting without reshaping of the rock mass may be of penetration or filling character. Penetration grouting works are performed in sandy soil or in constructions. Filling grouting is used in fissured rock and coarse grained soil like sand or gravel.

Polyurethane Grouting Technologies 313

Volume weight of the grouting material increases from the front of the grouted structure towards the packer. In case of the PUR resins, when the pump is stopped, so called autogrouting continues, which is induced by the reaction of the material and formed CO2, which induces pressure of 0,1 to 0,3 MPa. In case the grouting process stops before full saturation of the environment by the grouting media, the saturation continues due to the pressure formed by CO2 until finishing of the chemical reaction. In case, that the fissure had been already filled, the pressure is higher than the pressure of CO2 and bubbles are not formed - CO2 remains dissolved in the grouting media and has minimal volume. The texture of the material is in this case compact. Formation of the bubble structure depends therefore on the pressure under which the mixture cures. Usually porous structures are formed with

During pressure grouting of PU grouting resins into soil, rock mass or fissured or defected constructions, new specific materials are formed. These materials have the properties of composite material and, taking into account their components character, are referred to as

**In rocks or constructions** the grouted environment contains discontinuities. The geocomponent of the formed geocomposite is formed by blocks of the rock (or masonry), which are defined by combination of bedding surfaces, metamorphic foliation, fissures and etc.

**In soil**, two basic types of geocomposites are formed by PU grouting: in case of non cohesive soil (sand-gravel), the geo-component of the geocomposite is built by solid grains or their aggregations of various size and shape. These contain grains of minerals and rocks, organic particles (shells of organisms, wood, carboniferous parts of plants and others) or parts of constructions (building material, metals, ash and others). In case of cohesive soil (clay, claystones, or siltstones), the geo-component of the geocomposite is formed by blocks of soil penetrated by a net of so called claquage fissures (fissures caused by hydraulic

The binding material is represented in these geocomposites by hardened organic or organic-

Penetration of the grouting media through the inhomogeneous environment, and thus also the resulting properties of the formed geocomposite, is influenced by many factors. In case of geocomposites of PU resin – rock (soil) and PU resin – building material, the following

 **properties of the unpolymerized grouting media** –viscosity of the media as a function of temperature and rheology of hardening, velocity of injection (volume per time unit), grouting pressure, the right stoichiometric ratio of input components and sufficient

 **properties of the grouted environment** – composition of the rock (building material), shape and size of soil particles and rock blocks, humidity, effective porosity or voids,

closed or partly closed pores during the grouting.

**geocomposites** (Snuparek & Soucek, 2000)**.**

mineral PU resin with various degree of foaming.

factors have primary effect (Scucka & Soucek, 2007):

time and intensity of their mixing;

**6. Properties of grouted soil, rock and building material** 

fracturing during the grouting), which are filled with the binding material.


**Table 2.** Physical and mechanical parameters of the grouting system Geopur® produced by the company GME

In case of grouting with reshaping of the rock environment a so called claquage occurs, which is in principle hydraulic fracturing of the rock well known from the oil and gas exploitation. Due to the high hydraulic pressure of the grouting media in the soil a spatial net of fissures is formed, which are subsequently filled with the grouting media. The length and width of fissures depends on the pressure of grouted resin, velocity of penetration and quantity of the grouting resin. Compacting grouting belongs among the grouting methods considered as reshaping the rock mass as well.
