RU2804631C1 - Method for creating intraground protection of hydraulic structures in cryolithozone - Google Patents

Abstract

FIELD: hydraulic engineering.

SUBSTANCE: invention relates to methods for eliminating leaks and increased filtration of ground hydraulic structures located in the permafrost zone, and includes, in addition to preliminary studies to determine the filtration zone, the selection of components of the grouting composition based on polymer compositions with the addition of tailings of concentration. drilling and filling of injection wells, drilling of observation wells for the subsequent control of subsoil protection, periodic geophysical surveys by near-field time-domain electromagnetic sounding (NFTDES) to determine the channels of bypass filtration and control the water saturation of soils, electrical tomography and seismic surveys to determine the location boundaries of blocks, cracks and associated channels of bypass filtration in the area of the hydraulic structure, hydrogeochemical studies to determine the properties of the rocks of the base of the dam of the hydraulic structure and the compatibility of the components of the grouting mixture, and well thermometry. Injection wells according to the method are drilled in the area of open fractures of the block along the strike of the fracture. The cement composition into wells is injected by mixing tailings supplied through side cuts in the lower part of the pre-laid slurry conduit and polymer resin supplied in a non-pressure mode directly into the wells. To study the state of the filler and subsequent control of the subsurface protection of the hydraulic structure, confirmatory wells are drilled along the route of the injection wells. As a polymer composition, Aquidur is used in the amount of 5% of the volume of the supplied grouting composition, and the ratio L:H in the enrichment tailings is 7:1.

EFFECT: reliability of operation of a hydraulic structure located in the permafrost zone, for example, a tailing dump, is increased by improving the physical and mechanical properties of the soils of the hydraulic structure dam base, and the negative impact on the environment is reduced due to a decrease in bypass filtration and the accompanying hydrogenous thawing of permafrost.

3 cl, 2 dwg

Description

The invention relates to the field of hydraulic engineering, namely to methods for eliminating leaks and increased filtration of ground hydraulic structures and can be used to eliminate leaks from tailings of processing plants located in the permafrost zone.

There is a known method for increasing the stability of dams, including existing and reconstructed tailings storage ponds in areas with permafrost soils, implemented by a system for collecting runoff from tailings ponds on permafrost soils (RF patent for invention No. 2223362, priority 08.10.2001, IPC E02B 11/00 (2000.01 ), E02B 13/00 (2000.01, publ. 02/10/2004 Bulletin No. 4, patent holder Chita State Technical University). The system includes a filter dam and tubular drainage, equipped with a drainage-loading prism (DPP), located in the lower part of the dam with sides of its bottom edge under a waterproof screen (WS), placed on the DPP, and a tooth. The tooth is made of water-permeable material and is located under the DPP and is connected by its upper part to the WS, and by its lower part to the permafrost zone. The system also has a storage pond, located from the tooth at a distance of at least twice the thickness of permafrost and made with a bottom made of layers of waterproof material with layers of thermal insulation located between them, while the tooth is made of a material that ensures the flow of filtration flow from the tailings pond does not exceed the natural one. When installing a DPP, part of the filtration flow that occurs as a result of the depression curve reaching the dry slope of the dam is collected. Water with toxic substances collected in the DPP is supplied back to the tailings pond for re-accumulation; the other part of the filtration flow that arose at the base of the tailings dam and is supra-permafrost, is passed through the tooth, while the filtration coefficient of the material must ensure that the following condition is met: the flow rate of the supra-permafrost filtration flow from the tailings pond should not exceed the flow rate of the natural filtration flow before the construction of the tailings pond at the existing slopes of the valley.

There is a known method for creating anti-filtration curtains in permafrost rocks of the permafrost zone according to the Russian Federation patent for invention No. 2029091 (priority 10.10.1991, IPC E21D 1/16 (1995.01), B65G 5/00 (1995.01), published 02.20.1995, patent holder Yakut Scientific Research research and Design Institute of the Diamond Mining Industry). The method involves drilling cement wells along the contour of the massif and pumping brine and cement slurry into them; the brine is pumped into each well in turn, it is pumped out through an adjacent well, and the cement slurry is pumped after stabilization of the concentration of the pumped brine into the wells after pumping into them. brine.

However, the above methods do not minimize bypass filtration and the accompanying hydrogenous thawing of rocks under permafrost conditions.

There is a known method for strengthening porous materials according to RF patent for invention No. 2009325 (priority 10/09/1990, IPC E21D 11/00, publ. 03/15/1994, patent holder Eduard Pavlovich Kim), in the implementation of which, to increase the efficiency of strengthening the material, drilling of injection holes and injection of hardening reinforcing compounds, the injection operation is carried out in two stages: the first is performed with a composition containing acetone-formaldehyde resin, a 35% aqueous solution of caustic soda, hydroxyl-containing oligoester - Laprol-3503-2-70 and water, taken in the ratio, wt. %: acetone-formaldehyde resin 15.0 - 20.0, 35% aqueous sodium hydroxide solution 1.5 - 2.0, hydroxyl-containing oligoester 1.0 - 2.0, water - the rest, then after 5 - 300 minutes inject the composition , containing acetone-formaldehyde resin, 35% aqueous sodium hydroxide solution, sulfite-yeast mash, bentonite clay and water in the ratio, wt. % acetone-formaldehyde resin 15.0 - 20.0, 35% aqueous sodium hydroxide solution 1.5 - 2.0, sulfite-yeast mash 0.1 - 0.2, bentonite clay 6.0 - 8.0, water rest.

The method is of little use on permafrost soils due to the release of heat during hardening of the strengthening composition due to its multicomponent nature and, accordingly, the possibility of various chemical reactions occurring when interacting with rock masses.

There is a known method of hydraulic injection of a waterproofing composition when carrying out work on in-soil protection of construction objects (variants) under the Russian Federation patent for invention No. 2675820 (priority 12/09/2016, IPC E02D 31/02 (2006.01), published 12/25/2018 Bulletin No. 36, patent holder Tsygelnyuk Elena Yuryevna (RU)), which includes preliminary drilling of holes in the waterproofing mass and injection of a waterproofing composition under pressure into them. For injection, a waterproofing composition is used, including dry components containing natural finely dispersed bentonite-montmorillonite minerals, natural fine-grained silicon dioxide, sodium polyacrylate or acrylic water-absorbing polymer of the AK series and anionic polyacrylamide with a molecular weight of at least 15 million in the following ratio of components, wt. %: natural finely dispersed bentonite-montmorillonite minerals 10-99, natural fine-grained silicon dioxide 0-89.9, sodium polyacrylate or acrylic water-absorbing polymer AK series 0.1-50, anionic polyacrylamide 0-30. Injection is carried out under a pressure of 0.1-2 MPa using pumping equipment that has the ability to interact with a mixing chamber communicated with a container of dry waterproofing composition and a container of water and intended to obtain a waterproofing viscoelastic mixture, the injection of which into the holes is carried out at an initial pressure of no more 0.1 MPa with a subsequent increase in pressure until it reaches 2 MPa, after which a zone with an isolated area no less than 5-10 cm thick is formed in the waterproofed mass, and the time required for activation is 20-30 minutes. The technical result consists of improving the quality and reliability of in-soil protection of construction projects, ensuring environmental friendliness when carrying out waterproofing work, expanding the possibility of using components of a waterproofing composition and carrying out work to eliminate water leaks in the waterproofing mass.

Due to the presence of dry components in the waterproofing composition, when it is injected under pressure, a fairly local isolated mass is created, but there remains the possibility of bypass filtration and the accompanying hydrogenic thawing of rocks under cryolithozone conditions.

There is a known method for eliminating leaks and increased filtration of ground hydraulic structures according to the Russian Federation patent for invention No. 2754380 (priority 12/21/2021, IPC E02B 3/16, E02D 31/02, publ. 09/01/2021 Bulletin No. 25, patent holder Public Joint Stock Company "Federal" hydrogenerating company - RusHydro (PJSC RusHydro) (RU)), during which, first of all, measures are taken to reduce the filtration flow rates, thereby ensuring a reduction in the pressure gradient. For these purposes, resins are used, which upon contact with water foam, increase in size and quickly harden in cavities and cracks in rock. The rate of hardening of the resins is regulated. A continuous curtain of resin injected into the rock, made in one or several stages in front of the grouting curtain, will guarantee the implementation of the grouting curtain, while allowing the cement solution to evenly fill cracks and voids, and not be washed out by the filtration flow. The washout of cement mortars at significant speeds of water movement in fractured and highly fractured rocks is eliminated.

The method is applicable to rocky soils and involves drilling a whole set of wells to inject several types of injection resins and maintaining injection time parameters while creating an impervious curtain as an additional protective structure. The construction of the main cementation curtain occurs when heat is released during cement hardening, which is of little use on permafrost soils.

The prototype adopted is a method for sealing an impervious screen under a reservoir after mining a quarry according to the RF patent for invention No. 2551585 (priority 02/20/2014, IPC E21B 33/138, publ. 05/27/2015 Bulletin No. 15, patent holder Federal State Budgetary Institution of Science Institute of Mining North named after N.V. Chersky Siberian Branch of the Russian Academy of Sciences (RU)). When implementing the method, filling materials are injected and held until they harden; cement mortar is pumped as filling material into the lower part of the screen containing dolerite rocks under pressure exceeding hydrostatic through wells drilled from underground workings, and after hardening the created rock-cement the screen layer is tamponed with local injections of synthetic resins under pressure less than the burst pressure of the thickness of the ore safety pillar left under the impervious screen. The cement solution is pumped under a pressure of 0.7-0.8 MPa, it is prepared on the basis of sulfate-resistant or aluminous cements with a 2% addition of calcium chloride (CaCl ₂ ) to accelerate setting, and RP tailings with a fraction of 0.1-0 are introduced as filler .25 mm, corresponding to fine-grained sands. Local injections of synthetic resins are carried out under a pressure of 0.5-0.6 MPa; hydroactive compositions based on LT-70 with the addition of a solvent - dimethylformamide in an amount of 20-25% - are used as synthetic resins. Before implementing the method, the thickness of the rigid rock-cement base of the impervious screen with the required strength properties is calculated, and the components of the injection composition are experimentally selected.

However, local injection with synthetic resins in this case does not ensure sufficient integrity of the created screen due to the possibility of erosion of non-packed areas, which does not allow taking into account the specifics of working in permafrost; special equipment is required to implement the method.

The technical problem to be solved by the invention is to increase the reliability of operation of a hydraulic structure located in the permafrost zone, for example, a tailings pond, by improving the physical and mechanical properties of the soil at the base of the hydraulic structure dam, as well as reducing the negative impact on the environment due to reduced bypass filtration and the accompanying hydrogenic thawing of permafrost.

The technical result of the proposed invention is to reduce the filtration coefficient in the base rocks of the hydraulic structure due to filling open cracks with an inert, non-erosable composite.

The technical result is achieved due to the fact that in the method of creating and monitoring in-soil protection of a hydraulic structure in the permafrost zone, including preliminary studies to determine the filtration zone, selection of components of a cement composition based on polymer compositions with the addition of enrichment tailings, drilling and filling of injection wells, control of in-ground protection based on non-destructive methods and data from observation wells, conduct periodic geophysical surveys using the near-field sounding method to determine bypass filtration channels and control soil water saturation, electrical tomography and seismic studies to determine the location of block boundaries, cracks and associated bypass channels filtration in the area of the hydraulic structure, hydrogeochemical studies to determine the properties of the rocks of the base of the dam of the hydraulic structure and the compatibility of the components of the cement mixture, thermometry of wells, injection wells are drilled in the zone of open cracks of the block along the strike of the crack, while the injection of the cement composition into the wells is carried out by mixing the enrichment tailings, supplied through side cuts in the lower part of a pre-laid slurry pipeline, and polymer resin supplied in a free-flow mode directly into the wells, and monitoring of intra-soil protection is carried out periodically using geophysical methods, monitoring measurements of bypass filtration flow rate and drilling verification wells to study the condition of the filler. A one-component polyurethane resin is used as a polymer composition, for example, Aquidur in a volume of 5% of the volume of the supplied cement composition, and the L:S ratio in the enrichment tailings is 7:1.

The inventive method is illustrated by graphic materials, where:

in fig. Figure 1 shows a diagram of the location of wells in the selected fracture zone; in fig. Figure 2 shows a schematic section of drilling wells into a fractured zone.

List of positions given in graphic materials:

1 - tailings dump;

2 - settling pond;

3 - shunting capacity;

4 - natural-technogenic talik;

5 - enclosing dam;

6 - zones of tectonic disturbances;

7 - exploration well;

8 - injection well;

9 - observation well;

10 - device for supplying pulp;

11 - slurry pipeline;

12 - verification holes.

The method is carried out as follows.

The territory where tailings dump 1 to be protected is located was studied using a set of preliminary studies, including geological, geophysical, seismic, and hydrological studies. Based on the results of these studies, taking into account the geological structure of the territory and the presence of permafrost, a site was determined for the construction of tailings storage facility 1, which is a class I hydraulic structure (HTS), of the gully, alluvial type and intended for storing waste (tailings) of kimberlite ores after the extraction of diamonds and the implementation of recycling OF water supply. The hydraulic structure also includes a settling pond 2, a tailings storage facility 1, a shunting tank 3, and a storage tank for treated domestic wastewater (not shown in the drawing).

During the operation of tailings dump 1, the dissolution of ice wedges filling the systems of cracks in the sides of the stream valley, recorded at the stage of primary engineering-geological surveys, occurred, which, starting from 2000-2001, led to the formation of bypass filtration channels in the development zone of natural-technogenic talik 4 After observing and recording water inflows on the downstream tailings pond 1, in order to predict further development and planned identification of filtration zones within the enclosing dam 5 and shorelines, regular geophysical studies have been carried out since 2002, as a result of which it has been established that bypass filtration occurs in zones of tectonic disturbances 6 in the sides of the valley, and the formation of new flows is expected as the dam builds up and the ice wedges thawing fill the systems of cracks in the sides of the stream valley, confined to the recorded tectonic zones 6.

The formed contact-erosion flows propagate in accordance with the geological structure of the territory (faults and the nature of fracturing) along cracks of tectonic origin subparallel to the paleochannel of the stream and are unloaded into the shunting tank 3 of the tailings dump 1, causing erosional changes in the bedrock carbonate rocks. Based on the results of engineering-geological and geophysical surveys, it was determined that a watered technogenic talik 4 with a distribution depth of up to 100 m was formed in the bedrock, associated with the filtration of water from tailings 1. The main filtration occurs along the horizon of fractured limestones. Conducted geophysical studies using electrical tomography showed that the bulk of the tailing deposits have electrical resistivity (SER) values below 140 Ohm×m, which indicates a thawed or water-saturated state of the soil resulting from the thawing effect of tailing deposits, and is observed in the southern and eastern parts of tailings dump 1, as well as near the enclosing dam.

Hydrogeochemical studies were carried out to determine the chemical and mineral composition of the rocks at the base of the tailings dam 1 and to further predict the composition of the forming solution, which is, in essence, the result of the interaction of the soils at the base of the dam with process waters. A total of 47 core samples (from 6 wells) and 400 samples of process water were collected from bottom and near-surface horizons. Based on the results of the chemical composition of both process waters and host rocks and technogenic ones, the rate of dissolution of the carbonate base rocks was established using computer modeling.

Based on tailings products with the addition of polymers, cementitious compositions were manufactured and tested for solubility at various tailings/water/polymer proportions. The preparation of solutions was carried out in stages. At the first stage, the potential possibility of using tailings as a matrix to fill fixed open cracks, with a significant drop in the filtration coefficient in the zone of active water exchange and mass transfer, was considered. In total, about 1000 samples with a volume of 200 to 500 cm ³ were produced in various variations of the water-rock ratio. A negative factor identified during the research was the need for additional mixing of the components. Therefore, at the second stage of the experiments, the optimal water-rock ratio of 1:7 was determined, corresponding to the characteristics of the tailings product of the OF. The optimal ratio of RP tailings and polymer resin was determined experimentally, allowing free pouring of resin into the supplied tailings; it is 5% resin by volume.

Using thermometry, the geocryological state of the massif was determined, namely, areas of frozen rock thawing (zones of positive temperatures) were identified, and, as a consequence, active zones of water flow of natural-technogenic talik 4 were identified.

In order to study the natural-technogenic talik 4 within the boundary dam 5 and the bed of the tailings dump 1, 7 exploration, 8 injection and 9 observation wells were drilled, a total of 37 wells. Drilling operations recorded the presence of fractured melted bedrock, through which circulating water leaks, identified fissure-cavernous zones and areas of possible karst formation in the underlying bedrock, including in zones of tectonic disturbances 6.

To pump the cement mixture, the mouth of the injection well is equipped with a device for supplying pulp 10, made in the form of an outlet located in the side part of the slurry line with a diameter of at least 150 mm, equipped with a valve valve to regulate the flow rate of the supplied pulp into the well. The well is tied up using a metal or flat-rolled pipe to the point of insertion into the gravity slurry pipeline 11. The insertion point is determined based on the feasibility of its placement relative to the area where the injection is taking place. The required volume of polymer resin is supplied in a free-flow mode directly into the well 8 when the valve valve of the pulp supply device 10 is opened. In this case, the components of the cement mixture are mixed in the well, which spreads through a system of cracks into the rock mass. To control the spreading of the mixture, depths are measured and levels are measured in injection wells 8 and observation wells 9.

Monitoring the state of the formed protection and the processes occurring in its area is carried out comprehensively. In order to study the condition of the filler and determine the durability of the formed composites in the thermobaric conditions of natural-technogenic talik 4, verification wells 12 of small diameter (0 89 mm) are drilled along the route of injection wells 8. Monitoring measurements of the bypass filtration flow rate are carried out using a hydrological turntable to identify trends and dynamics of changes in over a long period of time. It is also necessary to regularly conduct geophysical research using electrical prospecting and seismic prospecting methods to monitor changes in geocryological conditions at the site and identify zones of activation of suffusion processes for timely reinforcement of protection.

As a result of the implementation of the method, taking into account the total volume of injected polymers and solid fraction = 4835 m ³ , as well as the configuration of the opened open fractures, a system of open fractures with a total thickness of no more than 1 m was filled, and the distribution of injected materials occurred under the influence of only the pressure front, since The cement mixture was pumped in the loading mode with a free surface. Filling open cracks with polymer composites with the solid fraction of tailings led, according to monitoring data, to a significant (10-15 times) drop in the filtration coefficient in the zone affected by injection. In this case, due to a decrease in the intensity of the heat flow, the temperature regime of the treated massif changes with a subsequent decrease in temperature to the values of the fundamental undisturbed permafrost.

The use of polymer fast-reacting materials to fill systems of open cracks in the conditions of formed natural-technogenic talik 4 in areas of development of intense suffusion processes, characterized by high filtration rates and requiring, as emergency response measures, the complete filling of cavities and systems of open cracks formed as a result of hydrogenic thawing, will speed up the process of filling them will increase the effectiveness of liquidation measures, since the formation of a composite screen in the lower (most intense) mass transfer zone will contribute to the further filling of cavities and cracks with the already solid fraction of tailing products.

As a result of the implementation of the method, the condition of the soils at the base of the hydraulic structure dam and their temperature conditions are stabilized. In addition, the use of polyurethane resins capable of forming stable composites when interacting with a pulp corresponding to the water-rock ratio supplied with the RP does not require the construction of an additional mixing unit, additional impact on the cement mixture in the form of heating or “cooking” during its preparation, there is technological possibility of using these polymers with direct supply of pulp into the thickness of limestone. Due to the expansion and speed of consolidation of the cementing material, there will be no need to create excess pressure for injection; cracks will be filled with a pressure front gradient formed during filling. To initiate the consolidation reaction, no additional activators are required, which also further simplifies the technology.

In addition to creating immediate reliable protection of the hydraulic structure, the method makes it possible to reduce the number of verification wells 12, which minimizes the impact on the environment by reducing routes to the places where wells are drilled and clearing sites for them, thereby releasing additional amounts of fuel and lubricants into the environment. There is a reduction in costs for the formation of protection of hydraulic structures, including indirect ones, due to the elimination of emergency situations that require the involvement of resources for their elimination and restoration of the natural environment.

Claims (3)

1. A method for creating in-ground protection of a hydraulic structure in the permafrost zone, including preliminary studies to determine the filtration zone, selection of components of a cement composition based on polymer compositions with the addition of enrichment tailings, drilling and filling injection wells, drilling observation wells for subsequent monitoring of in-ground protection, characterized in that that periodic geophysical studies are carried out using the near-field sounding method to determine bypass filtration channels and control soil water saturation, electrical tomography and seismic studies to determine the location of block boundaries, cracks and associated bypass filtration channels in the area of a hydraulic structure, hydrogeochemical studies to determine the properties of the rocks of the base of the dam of the hydraulic structure and the compatibility of the components of the cement mixture, the thermometry of the wells, injection wells are drilled in the zone of open cracks of the block along the strike of the crack, while the injection of the cement composition into the wells is carried out by mixing tailings fed through side inserts in the lower part laid slurry line, and polymer resin supplied in gravity mode directly to the wells, drilling of verification wells located along the route of injection wells is carried out to study the condition of the filler and subsequent monitoring of the in-ground protection of the hydraulic structure. 2. The method according to claim 1, characterized in that a one-component polyurethane resin, for example Aquidur, is used as a polymer composition in a volume of 5% of the volume of the supplied cement composition. 3. The method according to claim 1, characterized in that the L:T ratio in the enrichment tailings is 7:1.

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