Salt lake deep rock salt mining method

Abstract

A salt lake deep rock salt mining method belongs to the field of salt lake mining, and comprises the following steps: detecting crack distribution of an underground rock salt layer by using a geological radar, opening cracks by using a drilling method to form grouting drill holes, and injecting modified bentonite slurry into the grouting drill holes to make the modified bentonite slurry fully permeate into the rock salt cracks, so as to form a rock salt layer; further, rock salt cracks are damaged after the modified bentonite in the modified bentonite slurry loses efficacy; and drilling and digging the grouting hole by using a drill bit, cooling the drill bit by using bentonite slurry as circulating liquid in the drilling and digging process, collecting the circulating liquid, and airing to separate out salt, thereby completing deep rock salt mining. The bentonite slurry is used as circulating liquid, the drill bit is effectively cooled, the absorptivity of salt is greatly improved, salt dissipation is reduced, compared with a traditional mining method, the mining depth can be expanded to 5 m or below, and a revolutionary scheme is provided for efficient and sustainable development of salt lake resources.

Description

Technical Field

[0001] This invention relates to the field of salt lake mining, specifically a method for mining deep rock salt in salt lakes. Background Technology

[0002] In the field of salt lake mining, traditional technologies mainly rely on mechanical excavation and water extraction by salt harvesters. The water extraction method involves drilling to dissolve the salt rock and then extracting water to obtain salt. However, these methods have significant drawbacks: 1) Mechanical limitations and water level constraints limit the mining depth to only 1.5m-3m, making it impossible to reach deep salt layers and resulting in resource waste; 2) Although the water extraction method is inexpensive, the dissolution process causes a large amount of salt to be dissipated in the lake bottom water, with a recovery rate of less than 40%. At the same time, environmental disturbance exacerbates salt migration.

[0003] In addition to these, other traditional methods include evaporation pond method and flotation method. Evaporation pond method relies on solar evaporation to concentrate brine. Its advantages are simple operation, low investment and suitability for shallow salt lakes. However, its disadvantages are low efficiency, long cycle (requiring several months), great influence from climate, and inability to be used for deep salt layers. While flotation can improve salt purity, it is energy-intensive, requires complex equipment, and is poorly adapted to high-salinity environments. Furthermore, the deep surface rock-breaking rotary drilling method results in excessive energy consumption during the rock breaking process because the salt rock has good mechanical properties due to consolidation. In addition, the large surface area in contact with water causes a large amount of salt particles to be lost into the water after rock breaking, resulting in excessive salt extraction costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for deep rock salt mining in salt lakes. This method first injects modified bentonite slurry into the fissures of the rock salt. After the modified bentonite fails, it expands and destroys the integrity of the rock salt layer. Then, the bentonite slurry used during drilling is used as a circulating fluid, which not only effectively cools the drill bit, but more importantly, significantly improves the absorption of salt and reduces salt dissipation. Moreover, compared with traditional mining methods, this invention can extend the mining depth to below 5m, providing a revolutionary solution for the efficient and sustainable development of salt lake resources.

[0005] The technical solution adopted by this invention to achieve the above-mentioned technical objectives is as follows: a method for mining deep rock salt in salt lakes, comprising the following steps: 1) Detect the distribution of cracks in the underground rock salt layer using ground-penetrating radar, drill through the cracks to form grouting boreholes, and then inject modified bentonite slurry into the grouting boreholes to allow the modified bentonite slurry to fully penetrate the rock salt cracks. Then, the rock salt cracks are destroyed after the modified bentonite in the modified bentonite slurry fails. The modified bentonite in the modified bentonite slurry is modified with ammonia ions to suppress the swelling structure and gradually recovers the swelling effect in a sodium ion immersion environment. 2) Use ground-penetrating radar to monitor cracks in the rock salt layer. After the integrity of the underground rock salt layer is destroyed by the expansion of the cracks, drill the grouting hole with a drill bit. During the drilling process, use bentonite slurry as a circulating fluid to cool the drill bit and collect the circulating fluid to dry it so that the salt precipitates out, thus completing the deep rock salt mining.

[0006] As an optimized scheme of the above-mentioned deep rock salt mining method in salt lakes, in step 1), a hard injection pipe is inserted into each grouting borehole, and the insertion depth of the hard injection pipe is not less than 1m. Then, a grouting hose for grouting is inserted into the hard injection pipe.

[0007] As another optimized scheme for the above-mentioned deep rock salt mining method in salt lakes, in step 1), the modified bentonite is prepared by mixing bentonite particles with deionized water, adding hexadecyltrimethylammonium bromide with a cation exchange capacity of 100-150% of bentonite, and stirring and reacting at a pH of 4.5-6.5 and a temperature of 60-80℃ for 4-8 hours. Afterwards, it is washed with deionized water and dried at a low temperature not higher than 60℃ to obtain modified bentonite.

[0008] As another optimized scheme for the above-mentioned deep rock salt mining method in salt lakes, in step 1), the water content of the modified bentonite slurry is 100-125%.

[0009] As another optimized scheme for the above-mentioned deep rock salt mining method in salt lakes, the specific operation of injecting modified bentonite slurry into the grouting borehole in step 1) is as follows: grouting is carried out at a pressure of 0.1-0.3MPa. After the grouting pressure is not less than the design final pressure and the injection rate is less than 0.05L / (min·m), and continues for at least 10 minutes, the grouting is completed.

[0010] As another optimized scheme for the above-mentioned deep rock salt mining method in salt lakes, in step 1), several negative pressure boreholes are uniformly set in the area of ​​the grouting borehole, and the depth of the negative pressure boreholes exceeds that of the grouting boreholes, generally 2-3 times the depth of the grouting boreholes.

[0011] As another optimized scheme for the above-mentioned deep rock salt mining method in salt lakes, a negative pressure of 0.8-1.5 MPa is applied in the negative pressure borehole to apply guiding force to the modified bentonite slurry.

[0012] As another optimized solution for the above-mentioned deep rock salt mining method in salt lakes, the water content of the grout extracted from the negative pressure borehole is detected. When the water content in the extracted grout reaches 150%, the grouting is considered complete.

[0013] As another optimized solution for the above-mentioned deep rock salt mining method in salt lakes, in step 2), when drilling with a drill bit, a steel well wall needs to be inserted into the grouting hole for at least 1.5m first, so that a circulating fluid outflow channel is formed between the steel well wall and the drill bit.

[0014] As another optimized scheme for the above-mentioned deep rock salt mining method in salt lakes, in step 2), the water content of the bentonite slurry used as the circulating fluid is 100-125%.

[0015] In this invention, the modified bentonite utilizes ammonium ion modification to suppress the swelling structure, and gradually recovers the swelling effect in a sodium ion immersion environment. The specific mechanism is as follows: Using hexadecyltrimethylammonium bromide as an inhibitor, a water-suppressing film is formed on the surface of bentonite particles by adsorbing the adsorption properties of bentonite. This creates a water-suppressing layer on the surface of the bentonite particles, which can inhibit the expansion of bentonite particles for more than two hours without damaging the expansion structure of the bentonite particles. At the same time, in an aqueous environment, the water gradually dissipates after 2 hours. The water content of the bentonite slurry needs to reach 100%-125%, which is the liquid limit of the bentonite particles (maintaining fluidity at the minimum water content of bentonite).

[0016] The basic principle of modifying bentonite using hexadecyltrimethylammonium bromide is to replace the original exchangeable inorganic cations (such as Na+) in the bentonite interlayer with organic cations. + Ca 2+ This allows for the transformation from hydrophilic to lipophilic. Because montmorillonite, the main component of bentonite, has a layered structure with negative charges between the layers, it can adsorb cations. By introducing cationic organic compounds with long carbon chains, such as hexadecyltrimethylammonium bromide (CTAB), organic molecules can be embedded into the interlayer through ion exchange mechanisms, giving bentonite a larger interlayer spacing and excellent organic adsorption capacity. The modified organobentonite exhibits obvious hydrophobicity and oleophilicity, making it more suitable for adsorbing non-polar substances such as organic pollutants and oils. It has wide application value in environmental remediation, wastewater treatment, and oil-water separation. The reaction process of organically modified bentonite is a typical cation exchange reaction, and its chemical reaction can be simplified as follows: ; in, R-NH3 represents sodium ions originally present in the interlayer of bentonite. +As a cationic organic modifier, during the modification process, R groups (such as long-chain alkyl groups) bind to the layers through hydrogen bonds, van der Waals forces, or dipole interactions. At the same time, sodium ions are replaced through charge compensation, ultimately forming a stable organic bentonite complex. This significantly improves the affinity and adsorption performance for organic molecules. The increased interlayer spacing also gives the modified bentonite a larger specific surface area and stronger interfacial activity, meeting the needs of industrial adsorption and separation.

[0017] When performing organic modification, properly controlling the ratio of organic modifier to bentonite is crucial to ensuring the modification effect. Generally, the amount of modifier added should be determined based on the cation exchange capacity (CEC) of bentonite, and should be 100%–150% of the bentonite's CEC. For example, if the bentonite's CEC is 100 meq / 100g, then the amount of CTAB added should be controlled between 0.364-0.546g / 100g bentonite. Furthermore, a pH of 4.5–6.5 is ideal for the reaction system, and maintaining a temperature of 60–80℃ promotes the diffusion of organic cations into the interlayer. To ensure sufficient exchange of the modifier, the stirring reaction time is generally set at 4–8 hours. Afterwards, unreacted components need to be removed by washing with deionized water, and the mixture should be dried at a low temperature below 60℃ to prevent structural collapse. Optimizing the ratio and process conditions not only improves the modification efficiency but also ensures the stability and performance of the organic bentonite.

[0018] Modified bentonite, due to being in a high-salt environment, contains a large amount of high-concentration Na. + Ions will dilute ammonia ions (R-NH3) + This process transforms bentonite from hydrophobic to hydrophilic, causing it to absorb a large amount of water and expand, which in turn causes the bottom salt rock layer to crack.

[0019] The mechanism by which this invention utilizes bentonite to mine salt deposits is as follows: This invention utilizes the fact that bentonite has a stronger adsorption capacity for NaCl than water has for NaCl. The biggest constraint in deep-water salt mining is that the surface of the salt rock is rotary excavated, a large amount of salt is dissipated in the water, and there is also the characteristic that the formation borehole is prone to collapse due to the fracturing of the salt rock during the drilling process. Therefore, this invention utilizes the clay properties of bentonite and its water absorption and expansion characteristics. First, bentonite is modified and then injected into the salt layer of the strata through small boreholes. High pressure is applied to inject bentonite slurry into the salt rock layer. Then, the modified bentonite loses its hydrophilicity, causing the bentonite particles to expand. This rapid expansion of the bentonite particles causes the pores of the salt rock strata to expand rapidly, increasing the ground pressure at the bottom of the salt layer. This leads to the fracturing of the upper salt rock strata. Small-diameter drilling is then performed using a drilling bit. The drilling slurry also uses bentonite as a coolant. During the rock fracturing process, the bentonite particles adsorb the salt released from the fracturing salt rock, locking in the salt release. The salt is then carried into the settling tank of the upper hull through a coolant circulation system, where it is washed out. This process effectively improves salt extraction efficiency by removing salt from the deep bottom salt layer, which is covered by the surface rock layer.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention innovatively injects bentonite mud of different properties into boreholes under high pressure, achieving multiple advantages: First, by injecting modified organic bentonite into the fissures of rock salt, the modified organic bentonite gradually recovers from hydrophobicity to hydrophilicity under high salt concentration, thereby absorbing a large amount of water to expand and break up the rock salt layer, extending the mining depth to below 5m and completely breaking through the traditional depth bottleneck; Second, using unmodified bentonite mud as the circulating fluid during drilling, the mud becomes a highly efficient coolant and debris-carrying medium, preventing borehole blockage and improving mechanical durability. At the same time, the adsorption capacity of bentonite mud for salt far exceeds that of water (adsorption efficiency is increased by 5-8 times), significantly reducing salt dissipation and increasing the recovery rate by more than 80%, while reducing energy consumption and environmental impact; This technology not only solves the problem of inaccessibility of deep salt layers, but also replaces chemical dissolution with physical adsorption, providing a revolutionary solution for the efficient and sustainable development of salt lake resources; 2) This invention assists grouting by setting negative pressure boreholes around the grouting boreholes and performing negative pressure suction within the negative pressure boreholes. Compared with traditional pressure grouting, this allows the modified bentonite slurry to penetrate more quickly and fully into the fissures of the rock salt layer around the grouting borehole and into the fissures between the grouting borehole and the negative pressure borehole. After the inhibitors fail, the modified bentonite particles generate expansion force, absorb water and expand in the bottom rock salt fissures, accelerate the expansion and destruction of rock mass joints and fissures, thereby reducing the integrity of the bottom rock salt and reducing the difficulty and energy consumption of subsequent drilling and mining of rock salt. 3) Compared to water, bentonite particles can absorb salt more fully and limit salt loss. In this invention, bentonite slurry is used as a circulating fluid during drilling. It can not only protect the borehole wall but also break up the salt rock layer together with the bentonite in the grouting fissures. The broken salt rock fragments are carried to the settling pool of the ship on the water surface. This not only effectively prevents borehole blockage and the need for additional circulating mud, but also allows the bentonite particles to fully adsorb the salt dissolved by the drilling, which greatly improves the salt recovery rate and simplifies the construction difficulty of deep rock salt mining in salt lakes. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the grouting process in step 1) of the present invention; Figure 2 This is a schematic diagram of drilling in step 2) of the present invention; Attached reference numerals: 1. Grouting pipe, 101. Opening, 2. Lake water, 3. Rock salt layer, 301. Fractured area, 4. Negative pressure pipe, 401. Negative pressure hole, 5. Grouting migration path, 6. Drill bit, 601. Circulating fluid inlet, 602. Circulating fluid outlet, 7. Steel well wall, 8. Circulating fluid outflow channel. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Parts not explained in the following embodiments of the present invention are all considered to be prior art known or should be known by those skilled in the art, such as the model and operation of ground-penetrating radar, related pressure grouting equipment, related negative pressure suction equipment, drill bits and related drilling equipment, salt drying and precipitation technology in salt fields, etc.

[0023] Example 1 A method for mining deep rock salt in salt lakes includes the following steps: 1) Detect the distribution of cracks in the underground rock salt layer using ground-penetrating radar, and then drill through the cracks to form grouting boreholes. The grouting boreholes are laid out and distributed in a 2m×2m pattern. Modified bentonite slurry is then injected into the grouting boreholes to allow the modified bentonite slurry to fully penetrate into the rock salt cracks. The rock salt cracks are then destroyed after the modified bentonite in the grouting slurry becomes ineffective. The modified bentonite in the modified bentonite slurry is modified with ammonium ions to suppress the swelling structure, and gradually recovers the swelling effect in a sodium ion immersion environment. The specific preparation method is as follows: First, modified bentonite is prepared; Bentonite particles were mixed with deionized water, and hexadecyltrimethylammonium bromide with a cation exchange capacity of 100-150% of bentonite was added. The mixture was stirred and reacted for 4-8 hours at a pH of 4.5-6.5 and a temperature of 60-80℃. Afterward, the mixture was washed with deionized water and dried at a low temperature not exceeding 60℃ to obtain modified bentonite. Secondly, a modified bentonite slurry was prepared; Half an hour before grouting begins, the prepared modified bentonite is mixed with fresh water to achieve a water content of 100-125%, and stirred evenly to obtain the modified bentonite slurry. In this step, the specific operation of injecting modified bentonite slurry into the grouting borehole is as follows: grouting is carried out at a pressure of 0.1-0.3MPa. After the grouting pressure is not less than the design final pressure and the injection rate is less than 0.05L / (min·m), and this is continued for at least 10 minutes, the grouting is completed. like Figure 1 As shown, based on the distribution of fractures in the underground salt layer detected by ground-penetrating radar, drilling was used to open the fractures and form grouting boreholes. To prevent the grouting boreholes from collapsing or becoming blocked, a rigid injection pipe was inserted into each grouting borehole to a depth of no less than 1 meter. Then, a grouting hose for grouting was inserted into the rigid injection pipe. Figure 1 In the diagram, grouting pipe 1 represents a combination of rigid injection pipe and grouting hose, with an opening 101 at the bottom for allowing grout to enter the naturally occurring fissures 301 within the rock salt layer 3 through the opening 101. 2) Ground-penetrating radar is used to monitor cracks in the rock salt layer. After the integrity of the underground rock salt layer is compromised by the expansion of the cracks, a drill bit is used to drill grouting holes. During the drilling process, bentonite slurry is used as a circulating fluid to cool the drill bit, and the circulating fluid is collected and dried to allow salt to precipitate, thus completing the deep rock salt mining. The specific operation is as follows: After grouting in step 1) is completed, the fissures in the underground salt layer are tested every 2 hours using ground-penetrating radar to analyze whether the integrity of the salt rock strata has been damaged by the expansion of underground fissures. Once it is confirmed that the integrity of the rock salt layer has been damaged, if... Figure 2 As shown, a drilling steel well wall 7 with a diameter of 0.5m is inserted downwards at a depth of at least 1.5m along the grouting borehole, and then drilling is carried out using a drill bit 6, and a circulating fluid outflow channel 8 is formed between the steel well wall 7 and the drill bit 6. During drilling using drill bit 6, unmodified bentonite is used to prepare a slurry as a circulating fluid. The water content of the bentonite slurry is 100-125%. Using the bentonite slurry as a circulating fluid, the slurry can maintain the borehole wall and prevent the collapse of the top rock layer at a depth of 1m. After passing through 1m, the strong circulating fluid is applied to connect with the bentonite slurry at the bottom, which has lost its inhibitory effect, and gradually expand the drilling depth. The thick bentonite slurry carries the broken salt rock particles to the ground. The bentonite particles adsorb the salt dissolved by the drilling. The circulating fluid is circulated to the circulating slurry pool in the top of the ship body. The salt is precipitated by the dilution effect of fresh water. The precipitated surface slurry is then transported to the salt field on the embankment for salt precipitation.

[0024] The above are the basic embodiments of the present invention. Further improvements, optimizations, and limitations can be made based on the above to obtain the following embodiments: Example 2 This embodiment is an improvement on embodiment 1. Its main structure is the same as that of embodiment 1, but the improvement lies in: [The following is a more detailed description of the improvement.] Figure 1 As shown, in step 1), several negative pressure holes are uniformly arranged in the area of ​​the grouting hole, and the depth of the negative pressure holes exceeds that of the grouting hole, generally 2-3 times the depth of the grouting hole.

[0025] In practice, the grouting boreholes are evenly distributed, while the negative pressure boreholes are located between the grouting boreholes and are distributed in a 5m×5m layout. A negative pressure of 0.8-1.5MPa is applied in the negative pressure boreholes to guide the modified bentonite slurry.

[0026] When a negative pressure borehole is set in the grouting borehole area, the condition for determining that grouting is completed is: the water content of the grout extracted from the negative pressure borehole is detected, and grouting is determined to be completed when the water content of the extracted grout reaches 150%.

[0027] Example 3 A method for mining deep rock salt in salt lakes includes the following steps: 1) Use ground-penetrating radar to detect the distribution of cracks in the underground rock salt layer, and use drilling to open the cracks to form grouting boreholes. The grouting boreholes are laid out and distributed in a 2m×2m pattern. Then, several negative pressure boreholes are evenly set in the area of ​​the grouting boreholes, and the depth of the negative pressure boreholes is twice the depth of the grouting boreholes. Modified bentonite slurry is injected into the grouting borehole at a pressure of 0.1 MPa. At the same time, a negative pressure of 1.5 MPa is applied in the negative pressure borehole to guide the modified bentonite slurry, so that the modified bentonite slurry can fully penetrate into the rock salt cracks and destroy the rock salt cracks after the modified bentonite in the slurry fails. The water content of the grout extracted from the negative pressure borehole is detected. When the water content of the extracted grout reaches 150%, the grouting is considered complete. 2) After grouting in step 1) is completed, the fissures in the underground salt layer are tested every 2 hours using ground-penetrating radar to analyze whether the integrity of the salt rock strata has been damaged by the expansion of underground fissures. Once it is confirmed that the integrity of the rock salt layer has been damaged, if... Figure 2 As shown, a drilling steel well wall 7 with a diameter of 0.5m is inserted downwards at a depth of at least 1.5m along the grouting borehole, and then drilling is carried out using a drill bit 6, and a circulating fluid outflow channel 8 is formed between the steel well wall 7 and the drill bit 6. During drilling using drill bit 6, unmodified bentonite is used to prepare a slurry as a circulating fluid. The bentonite slurry used as the circulating fluid has a water content of 100%. Using the bentonite slurry as the circulating fluid, the slurry can maintain the borehole wall and prevent the collapse of the top rock layer at a depth of 1m. After passing through 1m, the action of strong circulating fluid is applied to connect with the bentonite slurry at the bottom, which has lost its inhibitory effect, and gradually expand the drilling depth. The thick bentonite slurry carries the broken salt rock particles to the ground. The bentonite particles adsorb the salt dissolved by the drilling. The circulating fluid is circulated to the circulating slurry pool in the top of the ship body. The salt is precipitated by the dilution effect of fresh water. The precipitated surface slurry is then transported to the salt field on the embankment for salt precipitation.

[0028] Example 4 A method for mining deep rock salt in salt lakes includes the following steps: 2) Detect the distribution of cracks in the underground rock salt layer using ground-penetrating radar, and use drilling to open the cracks to form grouting boreholes. The grouting boreholes are laid out and distributed in a 2m×2m pattern. Then, several negative pressure boreholes are evenly set in the area of ​​the grouting boreholes, and the depth of the negative pressure boreholes exceeds that of the grouting boreholes, generally three times the depth of the grouting boreholes. Modified bentonite slurry is injected into the grouting borehole at a pressure of 0.3 MPa. At the same time, a negative pressure of 0.8 MPa is applied in the negative pressure borehole to guide the modified bentonite slurry, so that the modified bentonite slurry can fully penetrate into the rock salt cracks and destroy the rock salt cracks after the modified bentonite in the slurry fails. The water content of the grout extracted from the negative pressure borehole is detected. When the water content of the extracted grout reaches 150%, the grouting is considered complete. 2) After grouting in step 1) is completed, the fissures in the underground salt layer are tested every 2 hours using ground-penetrating radar to analyze whether the integrity of the salt rock strata has been damaged by the expansion of underground fissures. Once it is confirmed that the integrity of the rock salt layer has been damaged, if... Figure 2As shown, a drilling steel well wall 7 with a diameter of 0.5m is inserted downwards at a depth of at least 1.5m along the grouting borehole, and then drilling is carried out using a drill bit 6, and a circulating fluid outflow channel 8 is formed between the steel well wall 7 and the drill bit 6. During drilling using drill bit 6, unmodified bentonite is used to prepare a slurry as a circulating fluid. The water content of the bentonite slurry is 125%. Using the bentonite slurry as a circulating fluid, the slurry can maintain the borehole wall and prevent the collapse of the top rock layer at a depth of 1m. After passing through 1m, the strong circulating fluid is applied to connect with the bentonite slurry at the bottom, which has lost its inhibitory effect, and gradually expand the drilling depth. The thick bentonite slurry carries the broken salt rock particles to the ground. The bentonite particles adsorb the salt dissolved by the drilling. The circulating fluid is circulated to the circulating slurry pool in the top of the ship body. The salt is precipitated by the dilution effect of fresh water. The precipitated surface slurry is then transported to the salt field on the embankment for salt precipitation.

[0029] Example 5 A method for mining deep rock salt in salt lakes includes the following steps: 3) Use ground-penetrating radar to detect the distribution of cracks in the underground rock salt layer, and use drilling to open the cracks to form grouting boreholes. The grouting boreholes are laid out and distributed in a 2m×2m pattern. Then, several negative pressure boreholes are evenly set in the area of ​​the grouting boreholes, and the depth of the negative pressure boreholes exceeds that of the grouting boreholes, generally 2-3 times the depth of the grouting boreholes. Modified bentonite slurry is injected into the grouting borehole at a pressure of 0.2 MPa. At the same time, a negative pressure of 1.2 MPa is applied in the negative pressure borehole to guide the modified bentonite slurry, so that the modified bentonite slurry can fully penetrate into the rock salt cracks and destroy the rock salt cracks after the modified bentonite in the slurry fails. The water content of the grout extracted from the negative pressure borehole is detected. When the water content of the extracted grout reaches 150%, the grouting is considered complete. 2) After grouting in step 1) is completed, the fissures in the underground salt layer are tested every 2 hours using ground-penetrating radar to analyze whether the integrity of the salt rock strata has been damaged by the expansion of underground fissures. Once it is confirmed that the integrity of the rock salt layer has been damaged, if... Figure 2 As shown, a drilling steel well wall 7 with a diameter of 0.5m is inserted downwards at a depth of at least 1.5m along the grouting borehole, and then drilling is carried out using a drill bit 6, and a circulating fluid outflow channel 8 is formed between the steel well wall 7 and the drill bit 6. During drilling using drill bit 6, unmodified bentonite is used to prepare a slurry as a circulating fluid. The water content of the bentonite slurry is 110%. Using the bentonite slurry as a circulating fluid, the slurry can maintain the borehole wall and prevent the collapse of the top rock layer at a depth of 1m. After passing through 1m, the strong circulating fluid is applied to connect with the bentonite slurry at the bottom, which has lost its inhibitory effect, and gradually expand the drilling depth. The thick bentonite slurry carries the broken salt rock particles to the ground. The bentonite particles adsorb the salt dissolved by the drilling. The circulating fluid is circulated to the circulating slurry pool in the top of the ship body. The salt is precipitated by the dilution effect of fresh water. The precipitated surface slurry is then transported to the salt field on the embankment for salt precipitation.

Claims

1. A method for mining deep rock salt in salt lakes, characterized in that, Includes the following steps: 1) Detect the distribution of cracks in the underground rock salt layer using ground-penetrating radar, drill through the cracks to form grouting boreholes, and then inject modified bentonite slurry into the grouting boreholes to allow the modified bentonite slurry to fully penetrate the rock salt cracks. Then, the rock salt cracks are destroyed after the modified bentonite in the modified bentonite slurry fails. The modified bentonite in the modified bentonite slurry is modified with ammonia ions to suppress the swelling structure and gradually recovers the swelling effect in a sodium ion immersion environment. 2) Use ground-penetrating radar to monitor cracks in the rock salt layer. After the integrity of the underground rock salt layer is destroyed by the expansion of the cracks, drill the grouting hole with a drill bit. During the drilling process, use bentonite slurry as a circulating fluid to cool the drill bit and collect the circulating fluid to dry it so that the salt precipitates out, thus completing the deep rock salt mining.

2. The method for mining deep rock salt in a salt lake according to claim 1, characterized in that: In step 1), a rigid injection tube is inserted into each grouting borehole. The insertion depth of the rigid injection tube is not less than 1m. Then, a grouting hose for grouting is inserted into the rigid injection tube.

3. The method for mining deep rock salt in a salt lake according to claim 1, characterized in that: In step 1), the modified bentonite is prepared by mixing bentonite particles with deionized water, adding hexadecyltrimethylammonium bromide with a cation exchange capacity of 100-150% of bentonite, and stirring the mixture for 4-8 hours at a pH of 4.5-6.5 and a temperature of 60-80℃. Afterward, the mixture is washed with deionized water and dried at a low temperature not exceeding 60℃ to obtain modified bentonite.

4. The method for mining deep rock salt in salt lakes according to claim 1, characterized in that: In step 1), the modified bentonite slurry has a water content of 100-125%.

5. The method for mining deep rock salt in a salt lake according to claim 1, characterized in that: In step 1), the specific operation of injecting modified bentonite slurry into the grouting borehole is as follows: grouting is carried out at a pressure of 0.1-0.3 MPa. After the grouting pressure is not less than the design final pressure and the injection rate is less than 0.05 L / (min·m), and this is continued for at least 10 minutes, the grouting is completed.

6. The method for mining deep rock salt in a salt lake according to claim 1, characterized in that: In step 1), several negative pressure holes are uniformly arranged in the area of ​​the grouting hole, and the depth of the negative pressure holes exceeds that of the grouting hole, generally 2-3 times the depth of the grouting hole.

7. The method for mining deep rock salt in a salt lake according to claim 6, characterized in that: A negative pressure of 0.8-1.5 MPa is applied inside the negative pressure borehole to exert a guiding force on the modified bentonite slurry.

8. A method for mining deep rock salt in a salt lake according to claim 6, characterized in that: The water content of the grout extracted from the negative pressure borehole is detected. When the water content of the extracted grout reaches 150%, the grouting is considered complete.

9. The method for mining deep rock salt in a salt lake according to claim 1, characterized in that: In step 2), when drilling with a drill bit, a steel well wall needs to be inserted into the grouting hole for at least 1.5m to form a circulating fluid outflow channel between the steel well wall and the drill bit.

10. A method for mining deep rock salt in a salt lake according to claim 1, characterized in that: In step 2), the bentonite slurry used as the circulating liquid has a water content of 100-125%.

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