RU2258141C1 - Grouting method for water-bearing horizon rock during vertical pit shaft building - Google Patents

Abstract

FIELD: mining industry, particularly to protect mine workings against underground water ingress.

SUBSTANCE: method involves drilling injection wells along pit shaft perimeter; widening cracks by supplying high-pressure water and injecting grouting mortar in the cracks; additionally boring vertical preparation well in pit shaft center. Cracks are widened by feeding water and then air or only water in vertical preparation well. Water and air are supplied under pressure lesser than pressure of hydraulic rock fracturing. Grouting mortar is injected in cracks by forcing thereof through injection wells immediately after finishing of feeding water or air in vertical preparation well. Cryogenic gel is used as the grouting mortar. Cryogenic gel is foamed before injecting thereof in wells and foamed cryogenic gel is forced into cracks beyond the pit shaft perimeter by supplying compressed air in vertical preparation well. After leaving pit shaft as it is for grouting mortar setting time wells are sunk for the next grouting step depth and above operations are repeated up to reaching the lower boundary of pit shaft interval, wherein injection is performed under pressure exceeding that on previous step.

EFFECT: reduced labor inputs and material consumption along with increased efficiency of water suppression.

3 cl, 3 dwg, 1 ex

Description

The invention relates to mining and is intended to protect mine workings from groundwater inflows.

A known method of sinking workings in fractured formations, including drilling the workings with several rows of wells and pumping grouting mortars through them, moreover, the rows of wells are placed along the production path, cement mortar is pumped through wells of one row, and clay mud is pumped through wells of another row (A.C. USSR No. 757713, CL E 21 D 1/16, 1978).

The disadvantages of this method are the need to drill a large number of wells. In addition, with such plugging, it is not possible to achieve high-quality cementation in one go, and therefore it is necessary to drill them again and perform grouting.

The closest technical solution is a method of grouting rocks with heterogeneous fracturing, including drilling the wells of the first series around a vertical well and injecting cement in them, drilling in between the wells of the first series of additional wells and first injecting water in them to expand thin wells, and then cement mortar (AS USSR No. 1456585, Cl. E 21 D 1/16, 1987).

The disadvantages of this method are the high complexity and material costs due to the need to drill a large number of wells. In addition, effective water suppression is not ensured due to the fact that cement slurries are not able to penetrate small cracks and pores of the massif, and after solidification of the mortar they are susceptible to cracking during drilling and blasting operations and possible subsequent deformation of the massif with repeated changes in temperature from positive to negative and vice versa.

The technical problem solved by the invention is to reduce the complexity and material costs while increasing the efficiency of water pressure.

The specified technical result is achieved by the fact that in the method of plugging rocks of aquifers during the construction of vertical mine shafts, including drilling injection wells along the contour of the mine shaft, expanding cracks by applying water under pressure, injecting cement slurry into the wells, while repeating for each descending entry, repeat a cycle of deep and grouting operations, additionally drill a vertical preparatory well in the center of the shaft, widen the cracks by means of feeds cement slurry in the form of a foamed cryogel is injected into cracks in a vertical preparatory well under pressure less than hydraulic fracturing of the rocks, or first of water and then air or water, by supplying it under pressure into vertical injection wells immediately after the supply of vertical preparation well or air, or water, push the foamed cryogel along the cracks beyond the contour of the shaft by injection under air pressure into a vertical preparatory well, while for Each subsequent run deepens the vertical injection and preparatory wells and conduct injection at a pressure greater than in the previous cycle.

In addition, the cryogel contains the following ingredients in a ratio, wt.%:

PVA (polyvinyl alcohol) - 3,

Boric acid - 0.5,

Water - 96.5.

In addition, the cryogel contains the following ingredients in a ratio, wt.%:

PVA (polyvinyl alcohol) - 5,

NaCl - 11,

Water - 84.

The novelty of this solution is the expansion of cracks by feeding into the preparatory well under pressure less than hydraulic fracturing of the rocks, or first of the water then air, or water before grouting is injected into the rocks. In addition, injection wells are located along the bottom contour, and one of the wells, the preparatory wells, is drilled in the center of the shaft, and cryogel is used as the grouting fluid injected into the wells. The cryogel used as a grout is foamed before being injected into wells. The grouting mortar is pressed by supplying air under pressure to the preparatory well after injection of the grouting mortar. After the setting period has been set, the wells are deepened by a plugging step and the entire cycle is repeated until the end of the plugging interval, and injection is carried out under a pressure greater than in the previous cycle.

The set of features of this technical solution is not identified from the patent documentation and scientific and technical information, which indicates the inventive step of the claimed technical solution.

Drilling in the center of the shaft of a vertical preparatory well to inject agents (water-air or water) into the rock mass, expanding the cracks, and then grouting mortar - foamed cryogel - reduces the number of drilling and injection works and thereby reduces labor and material costs. The plugging of the array around the perimeter outside the trunk and at the bottom of the entry allows to reduce the volume of cementing work and also helps to reduce the complexity and material costs.

Preliminary supply to a vertical preparatory well with a pressure less than hydraulic fracturing of the rocks, or first of water then air, or water before injection of grouting mortar into the rocks leads to a more complete opening of cracks in the plugged rocks, which works to increase the efficiency of the plugging process and promotes plugging array around the perimeter outside the trunk, which leads to lower material costs.

In addition, injection of a grouting mortar in the form of a foamed cryogel into a vertical preparatory well leads to the formation of an effective water-suppressing grouting curtain.

Studies have shown that with multiple changes in temperature from positive to negative and vice versa, a waterproof cryogel used as a grouting mortar does not change its strength. Since tamponing requires not freezing of the solutions, but their rapid structure formation, the advantages of cryogels during plugging include its ability to gain the necessary strength and structure in a short time and immediately throughout the array, and not just at the border with mineralized solutions. Cryogels injected into the rock mass as grouting mortar are not able to mix and interact with brines and at the same time, having plastic viscosity, are not destroyed during drilling and blasting operations and possible subsequent deformation of the massif with repeated changes in temperature from positive to negative and vice versa.

The cryogel injected into the wells in foamed condition retains all its properties, including the ability to not mix with brines, and while having plastic viscosity, it does not break down during drilling and blasting operations and possible subsequent deformation of the array with multiple changes in temperature from positive to negative and vice versa. In addition, pre-foaming of the cryogel significantly reduces the consumption of the plugging solution and thus reduces material costs.

The extrusion of the foamed cryogel by injection of air through a vertical preparatory well, i.e. the formation of a grouting curtain by squeezing the grouting mortar through the air leads to a uniform distribution of the grouting mortar over rock cracks and pores of the massif and thus increases the efficiency of waterproofing vertical shaft shafts in permafrost rocks.

Due to the fact that for each subsequent run, vertical injection and preparatory wells are deepened and injection is carried out under a pressure greater than in the previous cycle, with a new cycle of grouting operations, previously uncovered cracks are filled. Thus, the new grouting cycle renews, strengthens the previous one, clogging small cracks and pores of the massif.

The method is illustrated in figures 1 - 3. Figure 1, 2 shows a diagram of the implementation of the proposed method, a plan view, figure 3 is the same vertical section, where: 1 - shaft shaft, 2 - vertical preparatory well, 3 - injection wells, located along the contour of the shaft, 4 - grouting curtain of solidified cryogel.

At the bottom of the shaft 1 cage trunk create a concrete pillow. Along the contour of the shaft mine, the estimated number of vertical injection wells is drilled vertically in 3 depths per step of grouting. A vertical preparatory well 2 is drilled in the center of the shaft. The estimated volume of water, then air or only water, is pumped through a vertical preparatory well 2 with a pressure lower than the hydraulic fracturing of rocks. After air exit through the injection wells 3, located along the contour of the shaft 1, produce pre-foamed cryogel. At the end of the cryogel injection through a vertical preparatory well, the calculated volume of air is pumped to force it. After setting the setting time, deepen all the wells to the next step of plugging and repeat the cycle already under high pressure. The process is repeated until the end of the shaft plugging interval. If the geomechanical conditions of the massif allow, the waterproofing of the vertical shaft shaft is carried out in one step of grouting. In addition, if the rock mass has high air permeability, the waterproofing of vertical mine workings is carried out through a single injection well 2 drilled in the center of the mine shaft 1. In this case, the need to drill wells 2 along the perimeter of the mass is eliminated, which further reduces the cost of implementing this method. After the formation of the grouting curtain is completed, the wells are cleaned from the gel and experimental injections and pumpings are made to test the curtain.

Example.

At the bottom of the shaft 1 create a concrete pillow, which is necessary to isolate from the leaching of cement slurry. According to the contour of the shaft, as close as possible to the border, the estimated number of vertical injection wells is drilled 3-8 wells with a depth of 25 m plugging, which is determined in advance based on the available information about the fracturing and hydrodynamic characteristics of the massif to be grouted. The number of injection wells 3 is calculated depending on the volume of the array and its geomechanical parameters (fracture void, hydrostatic pressure, rock tensile strength). Drilling a limited number of injection wells, calculated in this way, eliminates the need to drill a large number of wells, and placing them vertically eliminates the risk of disrupting the current freezing system. A vertical preparatory well 2 is drilled in the center of the mine shaft 1. Injection wells 3 located along the perimeter of the face are looped by a piping at the mouth. Along the perimeter of the shaft 1, 4 control vertical wells are drilled (not shown in FIGS. 1 to 3) to the bottom of the aquifer and equip them with temperature sensors. The process of implementing the waterproofing method of vertical mine workings is controlled using thermal sensors in control wells and geophysical methods. The estimated volume of buffer water, then air, is pumped through a vertical preparatory well 2, then air, preventing fracturing of the rocks. After air exit through injection wells 3 located along the perimeter of the bottomhole, cryogel is injected, prepared and foamed on the surface of the array. The finished cryogel stock solution is obtained by simple mixing in a common tank or by pumping through a mixer, comprising: a solution of polyvinyl alcohol — PVA and a crosslinking agent — boric acid or NaCl — previously dissolved in hot water (70-100 ° C). Cryogel contains the following ingredients in the ratio, wt.%: PVA (polyvinyl alcohol) - 3, boric acid - 0.5, water - 96.5. Or: PVA (polyvinyl alcohol) - 5, NaCl - 11, water - 84. The solutions are injected with piston pumps of cementing units. When the cryogel is pumped, the finished solution is foamed by mixing with air coming from the compressor through nozzles (mixers) or compressor booster devices.

Cryogel solutions during foaming are stable foams. When hardening, they form a viscous cellular structure and are able to reliably withstand water filtration. Thus, despite the increase in the thickness of the grouting curtain, significantly (60-100 times) reduce the costs of grouting mortar and the cost of work. Foamed cryogels are pumped by a booster unit of the type UNB-125 × 40BK. At the end of the injection of foamed cryogel through a vertical preparatory well 2, the calculated volume of air is pumped for its punching. After the formation of the grouting curtain is completed, the wells are cleaned from the cryogel and experimental injections and pumpings of water are made to test the curtain. Air purging is performed by high pressure compressors. When the foamed cryogel is injected, the grouting curtain will be formed along the contour of shaft 1. Air pumped through the vertical preparatory well 2, filling the cracks and pores of the rock mass inside the ring of injection wells 3, will not allow the foamed cryogel solution to spread inside the grouting curtain ring 4. After maturation setting (10-12 hours) deepen all the wells to the next step of plugging (25 m) and repeat the cycle already under high pressure. The process is repeated until the end of the barrel plugging interval. With each new cycle, previously uncovered cracks are filled. Thus, the new grouting cycle renews, strengthens the previous one, clogging small cracks and pores of the massif. After the formation of the grouting curtain is completed, tests are carried out with experimental injections and pumpings of water from injection wells 3 located along the contour of the bottom of the shaft.

Tamponization of rocks during the construction of vertical mine workings in permafrost soils as described above provides an increase in the efficiency of water pressure reduction of labor and material costs for its implementation.

Claims (3)

1. The method of cementing rocks of aquifers during the construction of vertical shafts, including drilling injection wells along the contour of the shaft, expanding cracks by applying water under pressure, injecting cement slurry into the wells, while for each descending entry repeat the cycle of deep-well and cementing operations, characterized in that they additionally drill a vertical preparatory well in the center of the shaft, widen the cracks by feeding into a vertical preparatory well a well under pressure less than hydraulic fracturing of the rocks or, first, water and then air or water is injected into the cracks in the cement slurry in the form of a foamed cryogel by feeding it under pressure into the injection wells immediately after the filing of the vertical preparation well or air or water is forced through the foamed cryogel along cracks beyond the contour of the shaft of the shaft by means of injection of air under pressure into a vertical preparatory well, and for each subsequent approach they deepen vertically ie injection and preparations are well under pressure and forcing more than in the previous cycle. 2. The method according to claim 1, characterized in that the cryogel contains the following ingredients in a ratio, wt.%: PVA (polyvinyl alcohol) 3 Boric acid 0.5 Water 96.5 3. The method according to claim 1, characterized in that the cryogel contains the following ingredients in a ratio, wt.%: PVA (polyvinyl alcohol) 5 NaCl eleven Water 84

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