An in-situ remediation system and method for bedrock fissure contaminated sites

Abstract

The application discloses a kind of in-situ remediation system and method for bedrock fissure contaminated site, well pipe is sequentially connected with sedimentation pipe, screen pipe and pipe head from bottom to top, and the pipe head is connected with well head;The lower end of the sedimentation pipe is closed, and the outside thereof is sealed with high-temperature cement between the well wall;The outside of the screen pipe is filled with quartz sand packing between the well wall, the outside of the pipe head is sealed with high-temperature cement between the well wall, and a barrier layer is provided on the ground surface of the multifunctional well;The injection position of the multifunctional well is determined according to the bedrock fissure detection device, the screen pipe is divided into an injection functional area corresponding to the injection position by filling the sealing material, and the injection functional area is provided with an extraction / injection pipeline corresponding to the remediation equipment connected at the well head.The application realizes the test of underground connectivity and fissure range of bedrock fissure contaminated site, and can realize injection and extraction function after modification, avoids tedious operation steps such as re-piping and re-well building, improves the remediation efficiency and accuracy, and saves economic cost.

Description

Technical Field

[0001] This invention relates to the field of soil and groundwater bedrock fissure remediation technology, specifically to an in-situ remediation system and method for bedrock fissure contaminated sites. Background Technology

[0002] Contamination in bedrock fissures typically originates from multiple sources, including industrial activities, leaks from underground storage tanks, agricultural activities, and landfills. These sources enter bedrock fissures through leaks or discharges, causing environmental pollution. Leaks from underground storage tanks, in particular, have become a major source of bedrock fissure contamination. Once contaminants enter the fissure system, they rapidly diffuse into the surrounding low-permeability matrix, which acts as a long-term reservoir, with the diffusion process potentially lasting decades or even centuries. Due to the complexity of fissure distribution, the heterogeneity of permeability, and the uncertainty of numerous influencing factors, the migration process of contaminants within fissures is extremely complex. Therefore, accurately characterizing bedrock fissures and remediating contaminants within them remains a significant challenge. In-situ remediation technologies offer advantages such as low disturbance and relatively controllable secondary pollution, while also being easy to operate and compatible with other technologies. With the development of the concept of green remediation, in-situ remediation technology is more favored than ex-situ remediation technology. Remediation technologies available for soil (fissures) and groundwater include physical methods, chemical methods, biological methods, etc., and commonly used technologies include steam thermal desorption, chemical / oxidative agent injection, aeration, and microbial remediation.

[0003] Chinese patent document CN 105689382 A discloses an in-situ remediation system for organically contaminated soil, including a heating system, a microwave enhancement system, and an air extraction system. It is only used for thermal remediation, but cannot be directly combined with other injection processes. It also lacks location testing of bedrock fissures and a multi-dimensional injection system. Since the target of bedrock fissure remediation is usually deep, the use of a single heating method to remove pollutants from bedrock fissures may have certain limitations.

[0004] Chinese patent document CN 106424121 A also discloses an in-situ remediation system for soil contaminated with organic matter. It is mainly designed for soil contaminated with organic matter, so that the soil pollutants react with the agent to reduce the blind spots of the agent remediation. Since the migration of pollutants in bedrock fissures is complex, it is necessary to accurately obtain the direction of the bedrock fissures, otherwise it is difficult to accurately remove the pollutants in the fissures. Summary of the Invention

[0005] To address the aforementioned problems and shortcomings, this invention provides an in-situ remediation system and method for bedrock fissure contaminated sites. By combining contamination investigation with the remediation process, and clarifying the site's geological conditions before remediation, especially confirming the extent and connectivity of fissures in the bedrock area, more precise remediation can be carried out, improving remediation efficiency while controlling costs.

[0006] The present invention adopts the following technical solution:

[0007] On one hand, the present invention provides an in-situ remediation system for bedrock fissure contaminated sites. The system includes a multi-functional well, a well pipe, a well head, and a bedrock fissure detection device. The well pipe is connected from bottom to top to a sedimentation pipe, a screen pipe, and a pipe head, with the pipe head connected to the well head. The lower end of the sedimentation pipe is sealed, and its outer side is filled with high-temperature cement for sealing with the well wall. The outer side of the screen pipe is filled with quartz sand filler, and the outer side of the pipe head is filled with high-temperature cement for sealing with the well wall. A barrier layer is set on the surface of the multi-functional well. The injection position of the multi-functional well is determined according to the bedrock fissure detection device. The screen pipe is divided into injection functional areas corresponding to the injection positions by filling with sealing material. The injection functional areas are equipped with extraction / injection pipelines connected to the remediation equipment at the well head.

[0008] Preferably, the bedrock fracture detection device includes a pulse signal generator and a pulse signal receiver. The pulse signal generator is disposed in the detection space formed by the two packers inside the well casing and is used to generate pulse signals. The pulse signal receiver is placed at the upper end of the wellhead and in other multi-functional wells to receive the pulse signals generated by the pulse signal generator. Based on the signal feedback from the pulse signal receiver, the development of transverse and longitudinal fractures in the contaminated site to be tested is determined. An injection position is determined and a packing area is established inside the well casing to form the injection functional area to be injected.

[0009] Furthermore, the sealing material includes quartz sand, bentonite, and cement. Below the injection functional area, cement and bentonite are filled in sequence. The injection functional area is filled with 2-4 mm of quartz sand. Above the injection functional area, bentonite and cement are filled in sequence. The bentonite is filled between the quartz sand and the cement.

[0010] Preferably, the cement is one of silicate cement, fly ash silicate cement, and aluminate cement.

[0011] Preferably, the screen tube is a wire-wound screen tube with a slit width of 0.1 to 1 mm.

[0012] On the other hand, the present invention also provides a method for in-situ remediation of bedrock fracture contaminated sites, which utilizes the above-mentioned in-situ remediation system, and the in-situ remediation method includes the following steps:

[0013] Place the well casing in a multi-functional well in a bedrock fracture contaminated site;

[0014] Quartz sand filler is used to fill the space between the outside of the screen pipe and the well wall. High-temperature cement is injected between the pipe head and the well wall for sealing. A barrier layer is also installed at the surface of the multi-functional well.

[0015] The development of transverse and longitudinal fractures in underground bedrock was tested using packers and bedrock fracture detection devices installed in the well casing.

[0016] Based on the measured development of underground bedrock fissures, the accurate repair injection location of the multi-functional well was determined;

[0017] Remove the packer from the well casing and insert the extraction / injection line into the well casing from the wellhead position, making it correspond one by one with each repair injection position;

[0018] According to the repair injection location, sealing material is injected into the well casing, and the space inside the well casing is divided into multiple injection functional areas corresponding to the repair injection location.

[0019] Furthermore, the specific method for testing the development of longitudinal fractures in underground bedrock using a bedrock fracture detection device is as follows: a pulse signal generator is placed in the detection space between two packers at a selected position inside the well casing; the pulse signal generator is controlled to generate a pulse signal; if the pulse signal receiver at the top of the well casing does not provide a signal feedback, the packer is raised to a fixed height until the pulse signal receiver detects a signal feedback; the position of the packer when the pulse signal receiver receives the signal feedback is recorded to obtain the development of transverse fractures in the bedrock.

[0020] Furthermore, the specific method for testing the development of transverse fractures in underground bedrock using a bedrock fracture detection device with dual wells is as follows: A pulse signal generator is placed inside the well casing of one of the multi-functional wells, positioned in the detection space between two packers at a selected location; a pulse signal receiver is placed inside the well casing of the other multi-functional well; the pulse signal generator is controlled to generate a pulse signal; if the pulse signal receiver does not provide feedback, the packers are raised to a fixed height until the pulse signal receiver detects feedback; the position of the packers when the pulse signal receiver receives feedback is recorded to obtain the development of transverse fractures in the bedrock.

[0021] Furthermore, according to the repair injection location, sealing material is injected into the well casing. The specific method is as follows:

[0022] Step 1: Based on the repair injection location and quantity, divide the space inside the sieve tube into corresponding injection functional areas from bottom to top;

[0023] Step 2: Fill the space below the bottom injection functional area to the bottom of the sedimentation tube with cement, and fill the space above the cement with bentonite.

[0024] Step 3: Fill the bottom injection functional area with quartz sand, and then fill the area with bentonite and cement on top of the quartz sand.

[0025] Step 4: Fill the cement to the bottom of the next injection zone and fill the cement with bentonite.

[0026] Step 5: Fill the next injection zone with quartz sand, and then fill the quartz sand with bentonite and cement.

[0027] Step 6: Repeat steps 4-5 until the topmost injection functional area is reached, and then fill the topmost injection functional area with bentonite and cement in sequence above the quartz sand.

[0028] Preferably, the packer is an expandable rubber hose with a static diameter of 40–102 mm, a maximum working diameter of 95–195 mm, and an operating pressure of 0.25–0.5 MPa.

[0029] The present invention has the following advantages over the prior art:

[0030] A. The in-situ remediation system and method for bedrock fissure contaminated sites provided by this invention can determine the geological conditions of the site, the underground connectivity and permeability before site remediation, which plays a decisive role in the selection of remediation technology. It enables the testing of underground connectivity and fissure range of bedrock fissure contaminated sites. At the same time, after modification, it can realize injection and extraction functions, avoiding cumbersome operation steps such as re-laying pipelines and rebuilding wells, improving remediation efficiency and accuracy, and saving economic costs.

[0031] B. This invention combines a bedrock fracture detection device with a movable packer installed in the well casing to perform zoned measurements of the injection location in a multi-functional well. This allows for precise characterization of the longitudinal fracture state of the subsurface. By deploying dual wells with injection and extraction layers within each well, and using methods such as generating pulse signals through injection, the development of transverse fractures in the horizontal direction is measured. After comprehensively and precisely understanding the distribution of subsurface fractures, parameters are recorded. This invention, through layered pressurization and multi-well joint operations, can accurately measure the permeability of the site in both the longitudinal and horizontal directions, accurately locate the position and length of fractures, and perform accurate injection or extraction operations. After confirming fracture connectivity, the well casing is modified and reinforced with cement, effectively avoiding the risk of fracturing under high pressure.

[0032] C. The well casing design of this invention can be tailored to the site's pollution characteristics and fracture connectivity requirements, combined with repair strategies for different repair stages. By injecting high-temperature cement, bentonite, quartz sand, and other fillers into the well casing in layers, it enables flexible switching between functions such as gas injection, chemical injection, and extraction in each injection functional zone. This dynamic repair effect allows the target repair area to be adjusted according to the actual situation, enhancing the adaptability and flexibility of the repair work. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a multi-functional well for detecting bedrock fissure contaminated sites provided by the present invention;

[0035] Figure 2 This is a schematic diagram of the remediation of bedrock fissure contaminated sites provided by the present invention;

[0036] Figure 3 This is a flowchart of the in-situ remediation method for bedrock fissure contaminated sites provided by the present invention.

[0037] The diagram is labeled as follows:

[0038] 1-Multi-functional well; 2-Well casing; 21-Sedimentation pipe; 22-Screen pipe; 23-Pipe head; 3-Well head; 4-Pulse signal receiver; 5-Cement; 6-Packer; 7-Quartz sand; 8-Bentonite; 9-Injection / extraction pipeline I; 10-Injection / extraction pipeline II; 20-Injection / extraction pipeline III; 30-Barrier layer; 40-Repair equipment; 50-Injection functional area. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] like Figure 1 and Figure 2As shown, this invention provides an in-situ remediation system for bedrock fissure contaminated sites. The system includes a multi-functional well 1, a well pipe 2, a well head 3, and a bedrock fissure detection device. The well pipe 2 is connected from bottom to top to a sedimentation pipe 21, a screen pipe 22, and a pipe head 23. The well pipe 2 is inserted into the multi-functional well 1. The upper end of the pipe head 23 extends to the ground surface and connects to the well head 3 on the ground. The lower end of the sedimentation pipe 21 is sealed, and its outer side is sealed with high-temperature cement 5 between it and the well wall of the multi-functional well 1. The outer side of the screen pipe 22 is filled with quartz sand 7, and the outer side of the pipe head 23, located below the ground surface, is sealed with the well wall of the multi-functional well 1. The well walls are sealed with high-temperature cement 5, and a barrier layer 30 is set on the surface of the multi-functional well. The well pipe 2 extends from the barrier layer 30. The injection position of the multi-functional well 1 is determined according to the bedrock fracture detection device. The screen pipe 22 is divided into injection functional areas 50 corresponding to the injection position by filling the sealing material. The injection functional area 50 is equipped with extraction / injection pipelines 9 and 10 that are connected to the repair equipment 40 at the wellhead 3. If multiple injection functional areas 50 are determined, an independent extraction / injection pipeline is set in each injection functional area. Steam, chemical injection and other operations can be used to repair different injection functional areas. The bedrock fracture detection device includes a pulse signal generator and a pulse signal receiver 4. The pulse signal generator (not shown in the figure) is installed in the detection space formed by the two packers 6 inside the well casing and is used to generate pulse signals. The pulse signal receiver 4 is placed at the upper end of the wellhead 3 and in other multi-functional wells 1 to receive the pulse signals from the pulse signal generator. Based on the signal feedback from the pulse signal receiver 4, the development of transverse and longitudinal fractures in the contaminated site to be tested is determined, and the packer positions inside the well casing 2 are set to form the injection functional area 50 to be injected. Figure 2 The middle section defines three injection functional areas: upper, middle, and lower.

[0043] The sealing materials used include quartz sand, bentonite, and cement. Below the injection functional area 50, cement 5 and bentonite 8 are filled sequentially. 2-4mm of quartz sand 7 is filled within the injection functional area 50. Above the injection functional area 50, bentonite 8 and cement 5 are filled sequentially, with bentonite 8 filling between the quartz sand 7 and cement 5. Alternatively, bentonite and cement can be filled above the quartz sand 7 in the injection functional area 50, and cement 5 and bentonite 8 in contact with the upper end of the quartz sand 7 in the injection functional area 50 can be filled below the quartz sand 7; this will not be elaborated further here.

[0044] The well casing used is made of one of the following materials: Q235, 304, or 316, with a diameter of 90mm to 200mm. It possesses one or more properties such as being rust-resistant, high-temperature resistant, and corrosion-resistant. The quartz sand has a diameter of 2mm to 4mm, and the screen structure is a wire-wound screen with a slit width of 0.1mm to 1mm.

[0045] like Figure 3As shown, the present invention also provides an in-situ remediation method for bedrock fissure contaminated sites, which employs the aforementioned in-situ remediation system. The specific in-situ remediation method includes the following steps:

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[0049] (1) The test method for the development of longitudinal cracks is as follows:

[0050] The pulse signal generator is placed in the detection space between the two packers at a selected location inside the well casing;

[0051] Control the pulse signal generator to produce pulse signals;

[0052] If the pulse signal receiver at the top of the well casing does not provide a signal feedback, raise the packer to a fixed height (e.g., 1m) until the pulse signal receiver detects a signal feedback; record the packer position when the pulse signal receiver receives the signal feedback to obtain the development of transverse fractures in the bedrock.

[0053] The packer here is compatible with the inner diameter of the well casing. Packer 3 is an expandable rubber hose, and the medium is compressed air. The static diameter is 40-102mm, the maximum working diameter is 95-195mm, and the operating pressure is 0.25-0.5Mpa.

[0054] (2) The test method for the development of transverse cracks is as follows:

[0055] The pulse signal generator is placed inside the well casing of one of its multi-functional wells, positioning it in the detection space between two packers at a selected location;

[0056] The pulse signal receiver is installed in another multi-functional well casing;

[0057] Control the pulse signal generator to produce pulse signals;

[0058] If the pulse signal receiver does not provide feedback, the packer is raised to a fixed height until the pulse signal receiver detects feedback. The position of the packer when the pulse signal receiver receives feedback is recorded to obtain the development of transverse fractures in the bedrock.

[0059] Multiple wells can be used to determine the lateral and longitudinal development of bedrock fissures throughout the contaminated site.

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[0063] The specific method for injecting packing material into the well casing according to the repair injection location is as follows:

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[0070] The bentonite is one or more combinations of bentonite balls and powdered bentonite, and the cement is one of silicate cement, fly ash silicate cement, and aluminate cement, with a grade of C30 to 60, possessing one or more combined characteristics of low drying shrinkage, high temperature resistance, and high pressure resistance.

[0071] This invention can be seamlessly adapted to different scenarios, achieving multiple functions. First, the connectivity of underground bedrock fissures is tested, and then the contamination within the bedrock fissures is repaired.

[0072] The location of the test injection is controlled by a packer. A single well injects a pulse at the selected location, and the pulse signal receiver at the top of the well casing can judge the development of underground longitudinal bedrock fractures through signal feedback. Alternatively, one of the two wells is used to inject a pulse at the selected location, and the underground connectivity is judged by the pulse signal receiver in the other multi-functional well, thus determining the accurate injection location.

[0073] Both longitudinal and lateral connectivity tests can be performed. The packer can be adjusted according to the selected target test area to seal the selected injection layer and ensure the accuracy of the test. If a full-depth wellbore test is required, the initial position of the packer can be set to the bottom of the screen. If there is no signal feedback at the wellhead, the packer can be raised to a fixed height, and the test can be repeated until a signal feedback is detected.

[0074] After understanding the underground connectivity, the well structure was modified for the target repair area. High-temperature cement injection was used to divide the well into functional injection zones for extraction-chemical injection, dewatering, and steam injection, enabling multi-functional operation at different repair stages.

[0075] Example

[0076] The following examples were conducted at a site in southwestern my country. The strata included miscellaneous fill, gravelly soil, silty clay, and silty mudstone interbedded with sandstone. The pollutants were chlorinated hydrocarbons, which is a typical DNAPL-bedrock fissure contaminated site.

[0077] Phase 1: Investigation Phase

[0078] Based on hydrogeological survey data, the groundwater depth at the site is confirmed to be approximately 20m. The horizontal and vertical fractures in the underground bedrock were investigated using a single-to-double well system.

[0079] The well is 22m deep and made of carbon steel. A sedimentation pipe is installed at the bottom 1m, and a screen pipe is installed from 1m below the surface to above the sedimentation pipe. The outside of the screen pipe is filled with quartz sand.

[0080] Specifically: packers are installed at depths of 30m and 31m in the well casing for isolation, and an injection functional zone 50 is formed at a depth of 20m-21m.

[0081] First, a pulse signal is injected to a depth of 20-21m. The pulse signal receiver at the top of the well casing then provides feedback to confirm whether the longitudinal fractures in the bedrock of this area are connected. If there is no signal feedback, the packer is raised by 1m (i.e., to a depth of 19-20m, and so on) and the test is repeated to obtain information on the development of longitudinal fractures in this area.

[0082] A dual-well system was used, with one well designated as the signal transmitting well and the other as the signal receiving well. Packers were installed at depths of 20m and 21m in the transmitting well to create an injection zone at 20m-21m. First, a pulse signal was injected into the 20-31m depth zone. The feedback signal from the pulse signal receiver confirmed the connectivity of transverse fractures in the bedrock of this area. If no signal feedback was received, the packer was raised 1m (to a depth of 19-20m, and so on) to repeat the test, thereby obtaining information on the development of transverse fractures in the area.

[0083] Based on the on-site investigation of the distribution of fissures and contamination, it was decided to adopt the SEE + biological agent injection + extraction method to repair the target fissure area.

[0084] Phase Two: Well Casing Modification

[0085] Because the injection pressure for gas and chemicals used in site remediation is 10–11 Pa, ordinary packers cannot meet the requirements. The well casing is modified by using a mixture of high-temperature cement, bentonite, and quartz sand as fillers. Bentonite is used at the interface between the quartz sand and cement to prevent cement from seeping into the quartz sand and causing blockage. This seals the well casing while its high-temperature and high-pressure resistance allows for the smooth implementation of gas injection, chemical injection, and extraction functions.

[0086] Based on the results of the first-stage site fissure development survey and risk assessment, the steam injection functional zone was identified at a depth of 9–11m, the chemical injection functional zone at 5–7m, and the extraction functional zone at 1–4m. After removing the packer, the area below 11m was filled with high-temperature cement and bentonite. After solidification, the steam injection functional zone at a depth of 9–11m was filled with quartz sand, and the area at 7–9m was filled with high-temperature cement and bentonite. The area at 5–7m was filled with quartz sand as the chemical injection functional zone, the area at 4–6m was filled with high-temperature cement and bentonite, and the area at 1–4m was filled with quartz sand as the extraction functional zone. The area above was sealed with high-temperature cement.

[0087] Phase Three: Repair Phase

[0088] After the well casing was modified, a combined remediation method was used: steam was injected at a depth of 9–11 m, biological agents were injected at a depth of 5–7 m, and extraction was performed at a depth of 1–4 m. While using SEE (Self-Effective Air) to remove contaminants, biological agents were added to decompose residual contaminants in the rock fissures. Extraction was then used to remove the contaminants and the resulting wastewater and exhaust gases, thereby achieving the goal of underground remediation that meets standards.

[0089] Based on the site remediation needs, by conducting preliminary investigations and then remediation of multi-functional wells, and flexibly switching between multiple functions such as steam injection, extraction, and chemical injection, this dynamic remediation effect allows the remediation target area to be adjusted according to the actual situation, enhancing the adaptability and flexibility of the remediation work.

[0090] This invention is an in-situ remediation system for bedrock fissures. By integrating segmented measurement, injection, and multiphase extraction functions, the system can perform multiple functions in one unit, including contaminated site investigation, groundwater extraction and treatment, in-situ vapor thermal desorption, in-situ multiphase extraction, chemical oxidation / reduction, and in-situ bioremediation. It improves remediation efficiency and accuracy, reduces remediation costs, simplifies remediation procedures, and can effectively address complex geological conditions and various types of contaminants, representing a future trend in site remediation.

[0091] Any aspects not described in this invention are applicable to existing technologies.

[0092] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A system for in-situ remediation of bedrock fissure contaminated sites, characterized in that, The system includes a multi-functional well, a well casing, a wellhead, and a bedrock fracture detection device. The well casing is connected from bottom to top to a sedimentation pipe, a screen pipe, and a pipe head, with the pipe head connected to the wellhead. The lower end of the sedimentation pipe is sealed, and its outer side is filled with high-temperature cement for sealing against the well wall. Quartz sand filler is used to fill the space between the outer side of the screen pipe and the well wall, and high-temperature cement is used to seal the space between the outer side of the pipe head and the well wall. A barrier layer is installed on the surface of the multi-functional well. The injection location of the multi-functional well is determined by the bedrock fracture detection device. The screen pipe is divided into injection functional zones corresponding to the injection locations by filling with sealing material. Each injection functional zone is equipped with extraction / injection pipelines connected to the repair equipment at the wellhead. The bedrock fracture detection device includes a pulse signal generator and a pulse signal receiver. The pulse signal generator is installed in the detection space formed by the two packers inside the well casing and is used to generate pulse signals. The pulse signal receiver is placed at the top of the wellhead and in other multi-functional wells to receive the pulse signals generated by the pulse signal generator. Based on the signal feedback from the pulse signal receiver, the development of transverse and longitudinal fractures in the contaminated site to be tested is determined. The injection position is determined and a packing area is established inside the well casing to form the injection functional area to be injected.

2. The in-situ remediation system for bedrock fissure contaminated sites according to claim 1, characterized in that, The sealing material includes quartz sand, bentonite, and cement. Below the injection functional area, cement and bentonite are filled in sequence. The injection functional area is filled with 2-4 mm of quartz sand. Above the injection functional area, bentonite and cement are filled in sequence. The bentonite is filled between the quartz sand and the cement.

3. The in-situ remediation system for bedrock fissure contaminated sites according to claim 2, characterized in that, The cement is one of silicate cement, fly ash silicate cement, and aluminate cement.

4. The in-situ remediation system for bedrock fissure contaminated sites according to claim 1, characterized in that, The screen tube is a wire-wound screen tube with a slit width of 0.1 to 1 mm.

5. A method for in-situ remediation of bedrock fissure contaminated sites, utilizing the in-situ remediation system described in any one of claims 1-4, characterized in that, The in-situ repair method includes the following steps: Place the well casing in a multi-functional well in a bedrock fracture contaminated site; The space between the outside of the screen pipe and the well wall is filled with quartz sand filler, and high-temperature cement is injected between the pipe head and the well wall for sealing. A barrier layer is also installed at the surface of the multi-functional well. The development of transverse and longitudinal fractures in underground bedrock was tested using packers and bedrock fracture detection devices installed in the well casing. Based on the measured development of underground bedrock fissures, the accurate repair injection location of the multi-functional well was determined; Remove the packer from the well casing and insert the extraction / injection line into the well casing from the wellhead position, making it correspond one by one with each repair injection position; According to the repair injection location, sealing material is injected into the well casing, and the space inside the well casing is divided into multiple injection functional areas corresponding to the repair injection location.

6. The method for in-situ remediation of bedrock fissure contaminated sites according to claim 5, characterized in that, The specific method for testing the development of longitudinal fractures in underground bedrock using a bedrock fracture detection device is as follows: a pulse signal generator is placed in the detection space between two packers at a selected location inside the well casing; the pulse signal generator is controlled to generate a pulse signal. If the pulse signal receiver at the top of the well casing does not provide a signal feedback, the packer will be raised to a fixed height until the pulse signal receiver detects a signal feedback. The position of the packer when the pulse signal receiver receives the signal feedback is recorded to obtain the development of transverse fractures in the bedrock.

7. The method for in-situ remediation of bedrock fissure contaminated sites according to claim 6, characterized in that, The specific method for using a bedrock fracture detection device to test the development of transverse fractures in underground bedrock using a dual-well setup is as follows: a pulse signal generator is placed inside the well casing of one of the multi-functional wells, positioned in the detection space between the two packers at a selected location; a pulse signal receiver is placed inside the well casing of the other multi-functional well; and the pulse signal generator is controlled to generate a pulse signal. If the pulse signal receiver does not provide a signal feedback, raise the packer to a fixed height until the pulse signal receiver detects a signal feedback. The position of the packer when the pulse signal receiver receives the signal feedback is recorded to obtain the development of transverse fractures in the bedrock.

8. The method for in-situ remediation of bedrock fissure contaminated sites according to claim 5, characterized in that, The specific method for injecting packing material into the well casing according to the repair injection location is as follows: Step 1: Based on the repair injection location and quantity, divide the space inside the sieve tube into corresponding injection functional areas from bottom to top; Step 2: Fill the space below the bottom injection functional area to the bottom of the sedimentation tube with cement, and fill the space above the cement with bentonite. Step 3: Fill the bottom injection functional area with quartz sand, and then fill the area with bentonite and cement on top of the quartz sand. Step 4: Fill the cement to the bottom of the next injection zone and fill the cement with bentonite. Step 5: Fill the next injection zone with quartz sand, and then fill the quartz sand with bentonite and cement. Step 6: Repeat steps 4-5 until the topmost injection functional area is reached, and then fill the topmost injection functional area with bentonite and cement in sequence above the quartz sand.

9. The method for in-situ remediation of bedrock fissure contaminated sites according to claim 5, characterized in that, The packer is an expandable rubber hose with a static diameter of 40–102 mm, a maximum working diameter of 95–195 mm, and an operating pressure of 0.25–0.5 MPa.

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