New progress in coal slurry grouting technology

The adverse effects of mining coal mine water project construction progress and quality, the deterioration of the working environment of workers, increase drainage and drainage fees mine, mine production has brought to insecurity, even severe submergence accident, cause life and property Significant loss [1]. The hydrogeological conditions of coalfields in China are complex. At present, about 18% of the coal reserves to be mined in China are threatened by more serious water hazards, and it is of great and urgent significance to prevent and control them. Grouting and water shutoff is one of the important methods for prevention and control of mine water. It can reduce mine drainage burden, save drainage power, reduce cost per ton of coal, improve work efficiency and quality, strengthen weak roadway, reduce water inrush rate and extend mine service life. The obvious advantages [2].

2. Development history of grouting and water blocking technology

Grouting and water shutoff as a branch of grouting technology is developed with the development of grouting technology. Grouting and water shutoff technology as a new field of engineering technology is only a hundred years old. In 1802, France applied the grouting method to the damper tidal gate for the first time [3]. In the first time in 1856, the United Kingdom used cement for grouting. From 1882 to 1920, it developed pneumatic grinder and water glass-chlorine. Calcium chemical slurry, and later developed crepe lignin, acrylamide and other slurry materials. Since the 1940s, various new chemical slurries (such as lignin, urea-formaldehyde resin, acrylamide, polyurethane, etc.) and modified cement paste have come out one after another, pushing grouting and water shutting technology to a New height. The development of grouting and water shutoff technology in China began from the beginning of the 1950s coal mine shaft bore grouting [4]. Since the 1960s, China has developed a series of inorganic or organic grouting materials, and gradually A grouting theory and a grouting process suitable for a specific slurry were established. After entering the 21st century, the research and application of grouting and water shutoff technology entered a heyday. In many aspects of grouting and water blocking technology, including material varieties, equipment and equipment, etc. have achieved certain development. Grouting and water shutoff technology has been widely used in various geotechnical projects in recent years, and the technical and social benefits are also significant, but the grouting and water shutoff technology itself is still immature and needs to be continuously improved.

3 Research status and research results of grouting and water blocking technology

The grouting and water blocking technology includes two parts: hardware and software: the hardware part includes grouting material and grouting equipment, and the software part can simply classify the grouting process and grouting parameter calculation theory.

3.1 grouting water blocking material

At present, most of the water-blocking grouting materials in coal mine roadways use cement-based pulp or cement-water glass-based pulp. The main advantages are low cost and wide source of materials, but due to the easy shrinkage after hardening, small cracks are generated, which are washed in the water. The lower crack gradually expands, the water blocking effect is not ideal, and because it is a granular material, it is difficult to press in small cracks, so its application range has certain limitations. The organic high water material (HWM) developed by China University of Technology (Beijing) has low viscosity, gel time can be artificially adjusted within a few seconds to several hours, and can be accurately controlled and easily injected into the deep micro-cracks of the rock mass. The formed gel body has the characteristics of high stone rate and low permeability, and has been successfully applied to the water-permeable rock layer grouting and water blocking project. The reaction process and the solidified body formed by the reaction with the aqueous runoff are shown in Fig. 1.

3.2 grouting water blocking equipment

The key equipment in the composition of grouting equipment is the grouting pump. At present, most of the grouting and water shutoff projects used in China are electric speed-regulating high-pressure grouting pumps, but they are inconvenient to use due to their large weight. In recent years, an emulsion-powered two-liquid grouting pump [38] has been developed in China, which can transport a variety of grouting and water blocking materials including polyurethane, but it needs to be powered by emulsion and is inconvenient to use.

The QB-25(12) series high-pressure two-liquid grouting pump developed by China University of Mining and Technology (Beijing), as shown in Figure 2, has reliable performance, convenient and safe use, and the maximum grouting pressure can reach 30MPa, which can be applied to small underground space. . It has been successfully applied to the 3.3 grouting and water blocking process in the grouting and water blocking project of coal mine underground permeable rock layer.

When the fractured rock mass is grouted and blocked by the grouting method, the slurry is injected into the void inside the rock mass by the external force of the grouting hole. The organic high-water material combined with QB-25 (12) grouting pump in the coal mine underground grouting and water blocking process shown in Figure 3. In recent years, the grouting technology has developed rapidly, and there are many kinds of grouting methods. In addition to the above-mentioned several typical grouting methods, the grouting method has developed from pulse grouting and infiltration grouting to compound grouting with more varieties of materials. Method or comprehensive grouting method; from pressureless grouting to energization, pumping, gas compression, jetting, swirling and other induced grouting methods; anchoring grouting from drill pipe, double pipe expansion grouting, energy storage compound injection Slurry, bag grouting, sleeve grouting, water top grouting, blasting grouting to various forms of comprehensive grouting technology, through pretreatment and in-hole blasting, greatly improve the slurry under the same conditions The attractiveness of the grouting method has been expanded.

3.4 Research Status of Grouting and Water Blocking Theory

The theory of grouting and water blocking is to study the flow law of slurry in rock mass fissures and reveal the essential relationship between grouting parameters.

3.4.1 analysis of seepage law in rock mass fracture network

A large number of fissures are distributed inside the natural rock mass, and the network of fissures connected to each other has a controlling effect on the seepage of the rock mass. In the seepage field of the rock mass fracture network, the permeability of the fluid can be described by the permeability tensor and the permeability coefficient tensor. The permeability tensor at different points in the rock mass constitutes the permeability tensor field of the medium in the rock mass system. The rock mass is composed of a plurality of sets of cracks, and the density of the fracture group in the i-th direction (the number of cracks per unit length) is Si, and the average fracture width is, and the fracture degree of the medium formed by the fracture group in the i-th direction is The equivalent permeability tensor of the rock mass fracture is: the permeability coefficient tensor is the amount describing the permeability of the fluid flowing in the rock medium and the medium in different directions at the same point in space, and the value can be expressed as:

3.4.2 Calculation theory of grouting water blocking parameters [5]

In recent decades, foreign scholars have carried out extensive and in-depth research on the osmotic grouting method, and developed a series of grouting theories, such as the theory of pore soil infiltration grouting (in which Marg theory is spherical diffusion theory, cylindrical diffusion theory). , Carol theory and other most representative), fractured rock mass infiltration grouting theory, splitting grouting theory. Domestic scholars Tian Kaiming, Su Baoyu, and Liu Jiacai also proposed crack grouting theory under different conditions. These theories are mostly established on the basis of stable seepage. In recent years, the slurry developed by the domestically developed slurry not only has the characteristics of viscosity increasing with the grouting process, but also has the phenomenon of secondary osmosis pressure, thus The flow pattern of the slurry has changed.

The slurry with secondary permeation characteristics is used for grouting and water blocking. In the process of reacting the slurry with water, the more moles of gas generated, the more easily the grouting pressure overcomes the hydrostatic pressure under a certain grouting pressure. The resistance and the viscous resistance caused by the solidification of the slurry are more conducive to the grouting. The formula for calculating the grouting parameters when grouting the water in the fracture network is:

The influence of the roughness of the crack on the permeability of the slurry can be corrected by the roughness coefficient to calculate the grouting parameter:

The establishment of the grouting parameter calculation theory with secondary permeation characteristics greatly enriched the grouting theory connotation, and basically formed a relatively complete and accurate grouting theory system.

4 Conclusion

Grouting and water blocking is to hydraulically press the slurry made of various water blocking materials into the predetermined place of the rock layer, such as water inrush point, water storage hole in water-bearing rock layer, etc., and to spread, solidify and harden the slurry, thereby blocking the gap and isolating the water source. To increase the overall strength and water barrier performance of the rock formation, it can reduce the rate of water inrush and extend the service life of the mine. As a branch of grouting technology, it develops with the development of grouting technology. In recent years, grouting and water blocking technology is in the development of water blocking materials and grouting equipment, or in the theory of water plugging grouting. The research has made great progress, the development of new grouting water blocking materials and grouting equipment has been successfully improved, and the efficiency and effect of grouting and water blocking have been improved. The calculation theory of grouting and water blocking parameters with secondary permeation characteristics has been put forward, enriching the note. The connotation of pulp theory, combined with the fracture grouting theory established by the previous people based on stable seepage, has formed a relatively complete and accurate theory system of grouting and water shutoff, which provides reliable technical means and theoretical guidance for grouting and water blocking in mines.

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