Patent Publication Number: US-2022212997-A1

Title: A method for preparing an injection material and the obtained injection material

Description:
TECHNICAL FIELD 
     The invention relates to a method of preparing a ground injection material and the injection material to be used in permeation injections of dams, tunnel constructions, permanent and temporary deep excavations, rock fissures, and soils up to silt size that cannot be injected with cement injections within the scope of geotechnical engineering. 
     Prior Art 
     Many injection materials are used in permeation injection applications. Portland cements are one of the most used injection materials, but due to their large particle sizes, it is difficult for them to penetrate into the fine and medium sand samples and it is hard to adjust their setting times. For this reason, new injection materials that could penetrate smaller particle sizes were needed. With the development of the chemical injection material, injection into smaller particle sizes has become possible, but the application areas have been limited due to their low strength, high costs, and negative effects on the environment. Hence, there is a need for an environmentally friendly injection material that can provide high strength and low permeability after injection with an adjustable gelling time. 
     In the scope of the known technique, this material is frequently used in injection applications to prevent such problems. The injection material used in injection applications mostly consists of sodium silicate based materials. In this application, silicate-based materials are neutralized and gelled using a reactant. Many weak acid type materials are used as reactants for this process. These acids are expensive and difficult to supply. 
     The purpose of permeation injection applications is to ensure that the solution material reaches the soils pores in a timely manner and to gelate after reaching them. During very long gelling times, especially in areas with groundwater, the solution is diluted and gelling cannot be achieved. 
     Document no. KR101697964B1 discloses a low-cost injection material produced by using recycled resources. The composition comprises a gelling agent containing sodium silicate and binding element mixed with the gelling agent to form a gel type accelerator. 
     As a result, all issues mentioned above made it necessary to make an innovation in the relevant technical field. 
     Object of the Innovation 
     This invention aims to overcome the above-mentioned problems and make a technical innovation in the relevant field. 
     The main object of the invention is to develop an environmentally friendly injection material to be used in permeation injections of dam soils, tunnel constructions, permanent and temporary deep excavations, rock fissures, and soils up to silt size that cannot be injected with cement injections within the scope of geotechnical engineering. 
     Another object of the invention is to develop a method for the use of environmentally friendly ultra low sulfate boric acid in soil injection materials and to adjust the gelling time for this use. 
     Another object of the invention is to increase the strength and decrease the permeability in the soils after injection. 
     Another object of the invention is to make permeation injection easily to the soil up to silt size. 
     Another object of the invention is to facilitate control of the pH of the medium by controlling the concentration of ultra low sulfate boric acid and to adjust the gelling time of the solidified material to be formed accordingly. 
     Another object of the invention is to provide easy injection opportunity even in the flowing groundwater conditions. 
     Another object of the invention is to ensure the injection to reach the soil pores in a timely manner and to gelate after reaching it. The desired gelling times can be easily adjusted with the developed product. 
     Another object of the invention is to provide an environmentally friendly injection material. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This invention is a method for preparing a material to be applied in the form of permeation injection in soils up to the size of silt, in order to achieve all the objectives mentioned above and included in the detailed description below. Accordingly, the method presented within the scope of the invention includes the following steps: Preparing a mixture of sodium silicate and water provided with a SiO 2 /Na 2 O ratio of 3-4, so that their ratio by volume varies between 3/7 and 1/1; Obtaining a mixture by dissolving ultra low sulfated boric acid in water, containing ultra low sulfated boric acid between 2.5-5% by weight; Mixing the resulting ultra low sulfate boric acid-water mixture with sodium silicate obtained in the first step. 
     In a preferred embodiment of the invention, the sodium silicate SiO 2 /Na 2 O ratio is 3.2. 
     In a preferred embodiment of the invention, the ultra-low sulfated boric acid ratio added to water is increased to reduce gelling time or decreased to increase gelling time. 
     In order to achieve all the objectives mentioned above and included in the following detailed description, the invention is an injection material obtained by the method according to any one of claims  1 - 4 , which reinforces the soil by settling in said pores in the soil up to silt size by being injected into the pores in the soil. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In this detailed description, a method for preparing an injection material according to the invention and the injection material obtained are described only with examples that will not have any limiting effect in order to better understand the subject. 
     The subject of the invention is related to the method for the preparation of materials for the geotechnical engineering, where cement mixtures are insufficient, and the construction of dam soils, tunnel constructions, permanent and temporary deep excavations, rock fissures, and permeation injections up to silt size. 
     In the method of the invention, it is explained how to control the gelling time with the use of ultra low sulfate boric acid. Here, the expression “ultra low sulphate boric acid” is limited to boric acids containing sulphate at a maximum rate of 3 ppm. 
     Sodium silicates, known as water glass, are prepared by heating silicate sand or silica of any form with Na 2 CO 3  at around 900° C. After refining, sodium silicate becomes a fluid solution. This solution can be diluted with water to obtain the concentration that meets the need. Sodium silicate is neutralized and gelled using a weak acid or salt acid as a reactant. 
     In order for sodium silicates to be used as the injection material described in the invention, it is essential that the silica/alkali ratios (SiO 2 /Na 2 O) are between 3 and 4. In a preferred embodiment, this ratio is 3.2. 
     Organic or inorganic reactants are used in the gelling process of sodium silicates. In this invention, sodium silicate and ultra-low sulfated boric acid of inorganic origin are used. Ultra low sulphate boric acid is dissolved by mixing in water in the mixtures and then mixed with sodium silicate in certain proportions. Sodium silicate and ultra low sulfate materials are mixed and the following reaction occurs. 
     
       
         
         
             
             
         
       
     
     According to the reaction equation, when sodium silicate, which is alkaline in nature, is diluted, it ionizes by hydrolysing in aqueous medium. Na +  cations and tetrahedral silica chains are surrounded by H 2  molecules. When an aqueous ultra low sulfate boric acid solution with concentrated concentrate is added on this alkaline solution, it gradually enters the sodium silicate chains of the polymeric chain structure, which is in the form of a polymeric chain, and draws the pH of the environment towards neutral levels. 
     When the ambient pH is neutral, the polymeric sodium borosilicate structure proposed by the products in the above reaction begins to form and mechanical setting occurs accordingly. 
     When a trigonal structure ultra low sulfate boric acid aqueous solution is prepared, it turns into a tetragonal (a geometry similar to silicate structure) with hydrolysis, which facilitates the formation of a silicate-like chain to enter among polymeric silicate derivatives. The tetragonal borate structure in anionic character increases the stability of the hard material formed by balancing its charge with the cationic Na +  atoms in the sodium silicate structure. 
     The reaction that takes place between sodium silicate chains and tetragonal borate anions is a kind of esterification reaction, which is carried out through H 2 O elimination. As a result of the reaction described above, the solution gelates. 
     48 different injections of 100 ml prepared with the inputs in the range given in Table 1 and their gelling times are shown. Here, ultra-low sulphate boric acid is mixed with sodium silicate by using a magnetic stirrer. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
               
                   
                   
                   
                 The amount of 
                   
                   
               
               
                   
                 Sodium 
                   
                 boric acid in 
                 Boric acid 
               
               
                   
                 silicate 
                   
                 100 milliliter 
                 (by mass)/ 
               
               
                 Mixture 
                 content 
                 Water 
                 of solution 
                 water 
                 Gelling times 
               
               
                 code 
                 (ml.) 
                 (ml.) 
                 (gr.) 
                 (%) 
                 (dk.) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 B1 
                 30 
                 70 
                 3.05 
                 4.3 
                 10 
               
               
                 B2 
                 30 
                 70 
                 2.82 
                 4 
                 13 
               
               
                 B3 
                 30 
                 70 
                 2.61 
                 3.7 
                 23 
               
               
                 B4 
                 30 
                 70 
                 2.41 
                 3.4 
                 37 
               
               
                 B5 
                 30 
                 70 
                 2.22 
                 3.1 
                 112 
               
               
                 B6 
                 30 
                 70 
                 2.05 
                 2.9 
                 187 
               
               
                 B7 
                 30 
                 70 
                 1.81 
                 2.6 
                 275 
               
               
                 B8 
                 32 
                 68 
                 3.02 
                 4.4 
                 12 
               
               
                 B9 
                 32 
                 68 
                 2.82 
                 4.1 
                 19 
               
               
                 B10 
                 32 
                 68 
                 2.63 
                 3.8 
                 33 
               
               
                 B11 
                 32 
                 68 
                 2.39 
                 3.5 
                 60 
               
               
                 B12 
                 32 
                 68 
                 2.22 
                 3.2 
                 140 
               
               
                 B13 
                 32 
                 68 
                 2.03 
                 2.9 
                 240 
               
               
                 B14 
                 32 
                 68 
                 1.84 
                 2.7 
                 305 
               
               
                 B15 
                 34 
                 66 
                 3.02 
                 4.6 
                 18 
               
               
                 B16 
                 34 
                 66 
                 2.81 
                 4.2 
                 20 
               
               
                 B17 
                 34 
                 66 
                 2.62 
                 3.9 
                 45 
               
               
                 B18 
                 34 
                 66 
                 2.43 
                 3.6 
                 75 
               
               
                 B19 
                 34 
                 66 
                 2.21 
                 3.3 
                 184 
               
               
                 B20 
                 34 
                 66 
                 2.03 
                 3 
                 374 
               
               
                 B21 
                 34 
                 66 
                 1.82 
                 2.8 
                 500 
               
               
                 B22 
                 36 
                 64 
                 3.01 
                 4.7 
                 20 
               
               
                 B23 
                 36 
                 64 
                 2.82 
                 4.4 
                 26 
               
               
                 B24 
                 36 
                 64 
                 2.61 
                 4.1 
                 59 
               
               
                 B25 
                 36 
                 64 
                 2.43 
                 3.8 
                 110 
               
               
                 B26 
                 36 
                 64 
                 2.22 
                 3.4 
                 252 
               
               
                 B27 
                 36 
                 64 
                 2.04 
                 3.1 
                 440 
               
               
                 B28 
                 36 
                 64 
                 1.82 
                 2.8 
                 570 
               
               
                 B29 
                 38 
                 62 
                 2.91 
                 4.7 
                 27 
               
               
                 B30 
                 38 
                 62 
                 2.82 
                 4.5 
                 35 
               
               
                 B31 
                 38 
                 62 
                 2.73 
                 4.4 
                 55 
               
               
                 B32 
                 38 
                 62 
                 2.62 
                 4.2 
                 65 
               
               
                 B33 
                 38 
                 62 
                 2.53 
                 4 
                 97 
               
               
                 B34 
                 38 
                 62 
                 2.42 
                 3.9 
                 134 
               
               
                 B35 
                 38 
                 62 
                 2.31 
                 3.7 
                 230 
               
               
                 B36 
                 40 
                 60 
                 2.84 
                 4.7 
                 39 
               
               
                 B37 
                 40 
                 60 
                 2.72 
                 4.5 
                 61 
               
               
                 B38 
                 40 
                 60 
                 2.61 
                 4.3 
                 81 
               
               
                 B39 
                 40 
                 60 
                 2.53 
                 4.2 
                 114 
               
               
                 B40 
                 40 
                 60 
                 2.42 
                 4 
                 151 
               
               
                 B41 
                 40 
                 60 
                 2.35 
                 3.9 
                 262 
               
               
                 B42 
                 40 
                 60 
                 2.22 
                 3.7 
                 380 
               
               
                 B43 
                 42 
                 58 
                 2.83 
                 4.9 
                 62 
               
               
                 B44 
                 42 
                 58 
                 2.74 
                 4.7 
                 109 
               
               
                 B45 
                 42 
                 58 
                 2.62 
                 4.5 
                 137 
               
               
                 B46 
                 42 
                 58 
                 2.51 
                 4.3 
                 158 
               
               
                 B47 
                 42 
                 58 
                 2.42 
                 4.1 
                 245 
               
               
                 B48 
                 50 
                 50 
                 2.22 
                 4.4 
                 22 
               
               
                   
               
            
           
         
       
     
     As can be seen in Table 1 examples B1-B7, while the amounts of water and sodium silicate have been steadily provided, the gelling time of the injection increases regularly as the amount of ultra-low sulfated boric acid decreases. 
     In addition, as can be seen in B8, B23, and B31, the amount of ultra-low sulphate boric acid is kept constant by mass, and the gelling time increases when the volume of water is increased compared to sodium silica. In contrast, when the ratio of sodium silicate to volume increases, gelling time decreases. 
     Strength and Permeability Values Obtained by the Said Injection; 
     By injection, the unconfined compressive strength of sand samples can be up to 0.50 MPa and the unconfined compressive strength of silt samples can be up to 0.30 MPa. Also, with the developed injection, the permeability coefficients of sand samples decrease to 1×10 −6  cm/sec and the permeability coefficients of silt samples to 1×10 −7  cm/sec. 
     The scope of the protection of the invention is set forth in the annexed claims and certainly cannot be limited to exemplary explanations in this detailed description. It is evident that one skilled in the technique can make similar embodiments in the light of the explanations above without moving away from the main theme of the invention.