Test method for continuous water injection through drilling holes in soil impermeable body of dam in dangerous reservoir
By using the regular (fixed) water head and precipitation head test methods in the soil anti-seepage body of dangerous reservoir dams, the test section is continuously filled with water, which solves the problem that the permeability coefficient of the test section above the groundwater level cannot be accurately evaluated in the prior art. , achieving a comprehensive and accurate evaluation of the dam's seepage resistance performance.
Patent Information
- Application Number
- CN202111010239.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-08-31
- Publication Date
- 2025-02-18
- Estimated Expiration
- 2041-08-31
AI Technical Summary
When evaluating the anti-seepage performance of soil anti-seepage bodies in dangerous reservoir dams, the prior art lacks effective water injection test methods for the test sections above the groundwater level, resulting in the infiltration coefficient being unable to accurately calculate.
The test methods of normal (fixed) water head and precipitation head are used for the test sections above and below the groundwater level of the soil anti-seepage body of the dam in the drilling hole. The test sections are continuous and leak-free, and the soil body of the test section is ensured through steel casing protection. accuracy of permeability coefficient test.
The comprehensive and accurate evaluation of soil anti-seepage bodies of dangerous reservoir dams has been achieved, and the problems of cross-ground water level and large test errors in the pilot section of the existing technology have been overcome. The operation is convenient and the results are accurate.
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Figure CN113791013B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of water conservancy and hydropower engineering investigation, and more specifically, it is a method for continuous water injection test of soil anti-seepage body of dangerous reservoir dams through drilling holes. More specifically, it is a method for comprehensively and accurately evaluating the anti-seepage performance of dangerous reservoir dams by using constant (fixed) water head and reduced water head test methods for test sections above and below the groundwater level of the soil anti-seepage body of the dam in the drilling holes, with continuous and no missed test sections. Background Art
[0002] For dangerous reservoirs, identifying problems in engineering quality, including dam body permeability, is an important task of engineering investigation, which can provide a reliable basis for further implementation of dam risk removal and reinforcement.
[0003] In engineering practice, drilling water injection test is usually used to obtain the permeability coefficient of soil. The water conservancy standard "Water Conservancy and Hydropower Engineering Water Injection Test Code" (SL234-2007) and the power standard "Hydropower Engineering Drilling Water Injection Test Code" (NB / T35104-2017) have both stipulated the test process, but it is still imperfect. The current standard water injection test is carried out in sections and intermittently. It is suitable for naturally formed soil with relatively uniform properties. The water injection test results of one (several) test sections can represent the entire layer of soil; for artificial fill soil with uneven properties, continuous water injection tests in test sections must be used to comprehensively and accurately evaluate its permeability. The above-mentioned industry technical standards also stipulate that clay soil with weak permeability is suitable for water injection test using the precipitation head method, but they fail to give the permeability coefficient calculation formula corresponding to the test above the groundwater level. However, clay soil above the groundwater level objectively exists and there is also a need to evaluate its permeability.
[0004] Among many reservoirs, the dams are mainly earth-rock dams with earth-impermeable bodies and homogeneous dams. Earth-impermeable bodies and homogeneous dams are the key anti-seepage structures of water retaining buildings. Earth-impermeable bodies (including homogeneous dams) are generally made of artificial clay soil. Their material composition and density have obvious uneven characteristics. The drilling water injection test must be carried out continuously, and no test section is allowed to be omitted. During the test, the current standard does not specify what kind of water injection test method to use for the clay soil test section above the groundwater level.
[0005] Therefore, it is necessary to develop an accurate method for testing the continuous water injection through drilling of soil impermeable bodies in dangerous reservoirs and dams. Summary of the invention
[0006] The purpose of the present invention is to provide a method for continuous water injection testing of soil anti-seepage bodies of dangerous reservoir dams through drilling. The present invention adopts constant (fixed) water head and reduced water head test methods respectively for test sections above and below the groundwater level of the soil anti-seepage body of the dam in the drilling hole. The test sections are continuous and without missing sections, so as to comprehensively and accurately evaluate the anti-seepage performance of dangerous reservoir dams. The operation is convenient and the results are comprehensive and accurate.
[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present invention is: a drilling and continuous water injection test method for soil impermeable body of dangerous reservoir dam, characterized in that it comprises the following steps:
[0008] Step 1: Determine the drilling location;
[0009] Step 2: Select the water injection test method;
[0010] Step 3: Conduct continuous water injection test in the test section above the groundwater level;
[0011] Step 4: Conduct continuous water injection test in the test section below the groundwater level (such as Figure 1 shown).
[0012] In the above technical solution, in step 1, according to the relevant design and construction data of the dangerous reservoir dam, drill holes are arranged on the dam crest axis as exploration and test holes (such as Figure 2a as shown in the figure); Figure 2a The medium-sized dam is mainly composed of two parts: the soil anti-seepage body and the dam shell. The anti-seepage body is generally made of clay with weak water permeability and plays an anti-seepage role. The dam shell is generally made of coarse-grained soil and plays a supporting role. The dam shell is located on both sides of the soil anti-seepage body; the soil anti-seepage body is located in the middle of the dam body.
[0013] A layer of cushion material is laid on the top of the dam 1, and the thickness of the cushion material is relatively small, generally less than 1 meter.
[0014] In the above technical solution, in step 2, before the water injection test, the reservoir water level is measured, and the measured reservoir water level is used as the groundwater level in the dam soil impermeable body (in meters);
[0015] Different water injection test methods are selected according to the relative position relationship between the test section and the groundwater level, specifically: when the test section is above the groundwater level, a constant (fixed) head water injection test is used; when the test section is below the groundwater level, a reduced head water injection test is used. Each test section of the present invention does not cross the groundwater level.
[0016] In the above technical solution, in step 3, a continuous water injection test is carried out in the test section above the groundwater level, which specifically includes the following steps:
[0017] Step 3-1: Divide the soil impermeable body between the groundwater level and the bottom plate of the cushion material into several continuous test sections from top to bottom; the segmentation should be continuous without missing sections; the length of each test section is 3 to 5 meters; the present invention adjusts the length of each continuous test section according to actual conditions to prevent the test section from crossing the groundwater level and ensure the test accuracy of the permeability coefficient of the test section soil; and for parts with greater permeability, such as cracks, shorten the length of the test section, set the cracks and the test sections above and below the cracks shorter than other test sections, and improve the accuracy of the test results of the permeability coefficient of the test section soil; overcome the shortcomings of the prior art that a fixed test section length may be used, which may cause the test section to cross the groundwater level and the permeability coefficient of the test section soil cannot be calculated, and that a fixed test section length is used for parts with greater permeability, such as cracks, resulting in large errors in the test of the permeability coefficient of the test section soil;
[0018] Step 3-2: Drilling and drilling to the first test section above the groundwater level 1 (Test section length in meters) bottom, drive the first layer of steel casing below the cushion material bottom plate, the distance d between the first layer of steel casing foot and the cushion material bottom plate is 30 to 50 cm (such as Figure 2b shown);
[0019] The first layer of steel casing will be the first test section above the groundwater level. 1 It can be separated from the soil above to stop water, and at the same time maintain the stability of the hole wall and prevent the hole wall from collapsing or shrinking.
[0020] During the drilling process, it is advisable to use drilling without flushing fluid. If drilling is difficult, a small amount of clean water can be added. It is strictly forbidden to use mud;
[0021] Step 3-3: Fill the borehole with water for 30 minutes to make the first test section above the groundwater level l 1 The soil is saturated;
[0022] Step 3-4: For the first test section above the groundwater level 1 Carry out a constant (fixed) head water injection test, keep the water level in the borehole at the first layer of steel casing pipe and keep it fixed, record the stable injection flow rate (in liters / minute), and calculate the permeability coefficient of the test section soil (in centimeters / second) using the permeability coefficient formula specified in the current standard;
[0023] Step 3-5: Continue to follow up the first layer of steel casing to the first test section above the groundwater level 1 The second test section l above the water level was drilled under the protection of the first layer of steel casing. 2 (Test section length in meters), fill water to make the second test section l above the groundwater level 2 The soil is saturated, and the second test section above the groundwater level is l 2 Carry out constant (fixed) head water injection test (such as Figure 2c shown);
[0024] Step 3-6: Repeat step 3-5, i.e. repeat the above steps of following the first layer of steel casing, drilling, filling with water, constant (fixed) head water injection test, etc., until the last test section above the groundwater level is completed. i (Test section length in meters) water injection test (such as Figure 2d shown).
[0025] In the above technical solution, in step 4, a continuous water injection test is carried out in the test section below the groundwater level, which specifically includes the following steps:
[0026] The drilled holes in the soil impermeable body below the groundwater level are divided into several continuous test sections from top to bottom; the segmentation should be continuous without missing any sections; the length of each test section is 3 to 5 meters; the present invention adjusts the length of each continuous test section according to the actual situation to prevent the test section from crossing the groundwater level and ensure the test accuracy of the permeability coefficient of the test section soil; and for parts with greater permeability, such as cracks, the length of the test section is shortened, and the cracks and the test sections above and below the cracks are set to be shorter than other test sections, so as to improve the accuracy of the test results of the permeability coefficient of the test section soil; the prior art overcomes the disadvantages that the fixed test section length may cause the test section to cross the groundwater level and the permeability coefficient of the test section soil cannot be calculated, and the fixed test section length is used for parts with greater permeability, such as cracks, resulting in large errors in the test of the permeability coefficient of the test section soil;
[0027] Step 4-1: Follow the pipe and drill;
[0028] Continue to follow the first layer of steel casing to test section l i The bottom, that is, the foot of the first layer of steel casing is flush with the groundwater level. Under the protection of the first layer of steel casing, the first test section below the groundwater level is formed. i+1 (The length of the test section is in meters);
[0029] Step 4-2: Water injection test;
[0030] For the first test section below the groundwater level i+1 Conduct water injection test (such as Figure 2d As shown in the figure, record the change of water head drop and duration in the first layer of steel casing, and calculate the permeability coefficient of the test section soil (in cm / s) using the permeability coefficient formula specified in the current standard;
[0031] Step 4-3: Follow the pipe and drill
[0032] The second layer of steel casing is used to follow the pipe. The first test section from the foot of the second layer of steel casing to below the groundwater level is l i+1 Bottom; under the protection of the second layer of steel casing, drill into the second test section below the groundwater level.i+2 (The length of the test section is in meters);
[0033] Step 4-4: water injection test;
[0034] For the second test section below the groundwater level i+2 Conduct water injection test (such as Figure 2e Record the change of water head drop and duration in the second layer of steel casing, and calculate the permeability coefficient of the test section soil (in cm / s) using the permeability coefficient formula specified in the current standard;
[0035] Step 4-5: Continue with pipe following, drilling, and water injection tests;
[0036] Repeat steps 4-3 and 4-4, i.e. repeat the above steps of following the pipe, drilling, and water injection, until the water injection test of all test sections below the groundwater level is completed.
[0037] In the above technical solution, the outer diameter of the first layer of steel casing is 168 mm;
[0038] The outer diameter of the second layer of steel casing is smaller than the outer diameter of the first layer of steel casing.
[0039] In the above technical solution, in step 4-5, when it is difficult to follow the pipe, the third, fourth and fifth layers of steel casing with smaller outer diameters can be used in turn, such as outer diameters of 127 mm, 108 mm, 89 mm, etc. The present invention uses a casing with an outer diameter as a layer of casing structure, such as 158 mm, 146 mm, and 127 mm, which are respectively called the first layer of steel casing, the second layer of steel casing, and the third layer of steel casing. The outer diameter of the first layer of steel casing is greater than the outer diameter of the second layer of steel casing, the outer diameter of the second layer of steel casing is greater than the third layer of steel casing, and so on.
[0040] The present invention provides a method for continuous water injection test of drilling holes in soil impermeable bodies of dangerous reservoir dams, which has the following beneficial effects:
[0041] (1) In view of the uneven characteristics of the backfill soil, a continuous water injection test is carried out on the soil anti-seepage body without missing any test section, so that the anti-seepage performance of the dangerous reservoir dam can be comprehensively and accurately evaluated; it overcomes the shortcomings of the prior art that intermittent and discontinuous drilling is used for water injection test, and the permeability coefficient is small, and the anti-seepage performance of the soil anti-seepage body (i.e., clay soil above the groundwater level) is not accurately evaluated based on the permeability coefficient; the present invention adopts continuous water injection and continuous pipe following, and only considers the second and third layers of steel casing when the first layer of steel casing can no longer be followed, and the required steel casing outer diameter size is small, the process is simple, and it saves labor and time. The engineering application is relatively convenient; it overcomes the disadvantage that it is difficult to conduct continuous water injection test according to the traditional intermittent water injection test method (the conventional water injection test can only conduct 1-2 sections of water injection test intermittently due to equipment limitations. The conventional water injection test requires casing (i.e. conventional follow-up pipe) to isolate the hole section above the test section from each other. When water is injected into another test section, the second layer of casing must be lowered; when water is injected into the third test section, the third layer of casing must be lowered. The process of casing (i.e. conventional follow-up pipe) is complicated. Each layer of casing is lowered from the hole mouth to the test section. The required outer diameter of the steel casing is of various sizes, which is labor-consuming and time-consuming);
[0042] (2) Using the real-time observed reservoir water level as the groundwater level in the dam's soil impermeable body can save a lot of man-hours required for observing stable groundwater levels in clay soil; it overcomes the shortcomings of the prior art that it takes a long time to observe a stable groundwater level (the groundwater level stabilization time is 1 to 2 days or even longer) by manually observing the groundwater level in the dam's soil impermeable body, and in actual engineering, most of the water levels observed manually are false water levels with poor accuracy; the present invention utilizes the direct hydraulic connection between the impermeable body and the reservoir water, uses the real-time observed reservoir water level as the groundwater level in the dam's soil impermeable body, saves time, and uses the real-time observed reservoir water level as the groundwater level in the dam's soil impermeable body with higher accuracy than the artificially observed false water level, meeting the requirements for permeability coefficient calculation;
[0043] (3) The test section above the groundwater level of the dam's soil impermeable body is pre-filled with water to simulate the saturated state of the soil using a constant (fixed) head water injection test. This solves the problem that the current standard does not specify what water injection test method to use for the clay soil test section above the groundwater level and cannot be accurately measured. BRIEF DESCRIPTION OF THE DRAWINGS
[0044] Figure 1 It is the work flow chart of the present invention.
[0045] Figure 2 Schematic diagram of working principle.
[0046] Figure 2a It is a schematic diagram of the working principle of the drilling arrangement of the present invention.
[0047] Figure 2bIt is a schematic diagram of the working principle of the first test section formed above the groundwater level of the present invention.
[0048] Figure 2c It is a schematic diagram of the working principle of the second test section formed above the groundwater level of the present invention.
[0049] Figure 2d It is a schematic diagram of the working principle of the present invention formed by adjacent test sections above and below the groundwater level.
[0050] Figure 2e This is a schematic diagram of the working principle of the second test section below the groundwater level of the present invention.
[0051] Figure 2a , Figure 2b , Figure 2c , Figure 2d , Figure 2e It is each stage of the schematic diagram of the working principle of the present invention.
[0052] Figure 2b l 1 is the first test section above the groundwater level; d is the distance between the steel casing foot and the bottom plate of the cushion material.
[0053] Figure 2c l 1 It is the first test section above the groundwater level; 2 is the second test section above the groundwater level; d is the distance between the steel casing foot and the bottom plate of the cushion material.
[0054] Figure 2d l i is the i-th test section, i.e., the last test section above the groundwater level; l i+1 It is the i+1th test section, i.e., the first test section below the groundwater level.
[0055] Figure 2e l i+1 is the i+1th test section, i.e., the first test section below the groundwater level; l i+2 It is the i+2th test section, i.e. the second test section below the groundwater level.
[0056] In the figure, 1-dam, 2-dam axis, 3-borehole, 4-earth anti-seepage body, 5-dam shell, 6-cushion material, 7-reservoir water level, 8-first layer of steel casing, 9-groundwater level in the earth anti-seepage body, 10-second layer of steel casing. DETAILED DESCRIPTION
[0057] The following is a detailed description of the implementation of the present invention in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention are made clearer and easier to understand through the description.
[0058] Example
[0059] The present invention is now described in detail by taking the application of the present invention to the permeability detection of a dam body of a dangerous reservoir as an example, which also has a guiding role in the application of the present invention to the permeability detection of dam bodies of other dangerous reservoirs.
[0060] In this embodiment, a continuous water injection test of drilling holes in an earthen anti-seepage body is carried out on the dam body of a dangerous reservoir.
[0061] In this embodiment, a method for continuous water injection test of drilling holes in an earthen impermeable body of a dangerous reservoir dam includes the following steps:
[0062] Step 1: Determine the drilling location;
[0063] Step 2: Select the water injection test method;
[0064] Step 3: Conduct continuous water injection test in the test section above the groundwater level;
[0065] Step 4: Conduct continuous water injection test in the test section below the groundwater level (such as Figure 1 shown).
[0066] In step 1, before the investigation work is carried out, by collecting relevant design and construction data of dangerous reservoir dams, it is determined that the dam type of dam 1 is an earth-rock dam with a core wall partition, the dam axis 2 is located on the upstream side of the dam crest center, and the dam crest elevation is 67.1 meters; the earth-rock impermeable body 4 is mainly composed of clay and silty clay and other cohesive soils, and a layer of sand and gravel cushion material with a thickness of 0.3 meters is laid between the dam crest and the core wall of the earth-rock impermeable body; in order to find out the permeability of the cohesive soil impermeable body, a borehole 3 (such as Figure 2a As shown in the figure, it is used as an exploration and test hole for continuous water injection test.
[0067] In step 2, before conducting the water injection test, the reservoir water level 7 is determined to be 60.1 meters by observing the water gauge set around the reservoir (it can also be measured by measuring instruments), and this water level is used as the groundwater level in the dam's soil impermeable body; according to the relative position relationship between the test section and the groundwater level 9 in the soil impermeable body, different water injection test methods are selected: when the test section is located above the groundwater level of 60.1 meters, a constant (fixed) head water injection test is adopted; when the test section is located below the groundwater level of 60.1 meters, a reduced head water injection test specified in the current standard is adopted.
[0068] In step 3, the soil anti-seepage body between the groundwater level and the bottom plate of the cushion material is divided into two test sections. The elevations of the first and second test sections from top to bottom are 66.3-62.5 meters and 62.5-60.1 meters respectively. The lengths of the test sections are 3.8 meters and 2.4 meters respectively. The segmentation should be continuous without missing any sections and the test sections should not cross the groundwater level.
[0069] Drilling and drilling to the first test section 1 (Test section length 3.8 meters) At the bottom elevation of 62.5 meters, the first layer of steel casing 8 with an outer diameter of 168 mm is driven to the elevation of 66.3 meters below the bottom plate of the cushion material. The distance d between the first layer of steel casing 8 and the bottom plate of the cushion material is 30 cm (such as Figure 2b During the drilling process, generally no flushing fluid is used. When drilling is difficult in some areas, a small amount of clean water can be added. No mud is used.
[0070] Fill the borehole with water for 30 minutes to make the test section l 1 Soil saturation;
[0071] Test segment l 1 Carry out constant (fixed) head water injection test, keep the water level in the hole at the first layer of steel casing 8 pipe mouth and keep it fixed, record the stable injection flow rate (in liters / minute), and use the permeability coefficient formula specified in the current standard to calculate the first test section l 1 The soil permeability coefficient is 5.8×10 －6 cm / s;
[0072] Continue to follow up the first steel casing 8 with an outer diameter of 168 mm to the test section l 1 At the bottom elevation of 62.5 meters, the second test section l was formed under the protection of the first layer of steel casing 8. 2 (Test section length 2.4 meters), fill the test section with water to make it l 2 Soil saturation, test section l 2 Carry out constant (fixed) head water injection test (such as Figure 2c As shown), the second test segment l is calculated 2 The soil permeability coefficient is 3.1×10 －6 cm / s.
[0073] In step 4, continue to follow the first layer of steel casing 8 with an outer diameter of 168 mm to the test section l 2 At the bottom elevation of 60.1 meters, that is, the foot of the first layer of steel casing 8 is flush with the groundwater level, and the first test section l below the groundwater level is formed under the protection of the first steel casing 8. 3 (The test section elevation is 60.1~55.1 meters and the length is 5.0 meters). 3 Conduct water injection test (such as Figure 2d As shown in the figure, the change of water head drop and duration in the first layer of steel casing 8 is recorded, and the permeability coefficient of the test section soil is calculated using the permeability coefficient formula specified in the current standard as 1.7×10 －6 cm / s;
[0074] The second layer of steel casing 10 with an outer diameter of 146 mm is used, and the foot of the second layer of steel casing 10 reaches the test section l 3At the bottom elevation of 55.1 meters, the second test section l below the groundwater level was formed under the protection of the second layer of steel casing 10. 4 (The test section has an elevation of 55.1 to 50.6 meters and a length of 4.5 meters). 4 Conduct water injection test (such as Figure 2e As shown), the test section l is calculated 4 The soil permeability coefficient is 5.8×10 －6 cm / s; repeat the above steps of following the pipe, drilling, water injection, etc. (in the test section below the elevation of 47.6 meters, a third layer of steel casing 10 with an outer diameter of 127 mm is used for wall protection and water stopping), and complete the water injection test of all test sections below the groundwater level in turn.
[0075] The results of the borehole continuous water injection test in this embodiment are shown in Table 1.
[0076] Table 1 Example of continuous water injection test results table
[0077]
[0078] It has been verified that the permeability coefficient measured in this embodiment is accurate and consistent with the actual situation.
[0079] The present invention provides a method for continuous water injection test of soil anti-seepage bodies of dangerous reservoir dams, which has been successfully applied in the investigation of multiple dangerous reservoirs such as Meidian Reservoir in Wuhan City, Hubei Province, Sandaohe Reservoir in Nanzhang County, Hubei Province, and Zhengjiahe Reservoir in Xiaogan City, Hubei Province. The method of the present invention makes up for the shortcomings of relevant current industry technical standards, the continuous water injection test method is more perfect, the test results of soil anti-seepage bodies are more comprehensive, and the conclusion of the evaluation of the anti-seepage performance of soil anti-seepage bodies of dangerous reservoir dams is more accurate and reliable.
[0080] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.
[0081] Other parts not described belong to the prior art.
Claims
1. A method for continuous water injection through drilling holes in soil impermeable bodies of dangerous reservoir dams, characterized by: The following steps are included: Step 1: Determine the drilling location; According to the relevant design and construction data of the dangerous reservoir dam, a borehole (3) is arranged on the dam crest and dam axis (2) as an exploration and test hole; The dam (1) comprises an earthen impermeable body (4) and a dam shell (5); The dam shell (5) is located on both sides of the soil anti-seepage body (4); the soil anti-seepage body (4) is located in the middle of the dam body; A layer of cushion material (6) is laid on the top of the dam (1); Step 2: Select the water injection test method; Before the water injection test, the reservoir water level is measured (7), and the measured reservoir water level is used as the groundwater level in the dam's soil impermeable body; Different water injection test methods are selected according to the relative position relationship between the test section and the groundwater level. Specifically, when the test section is above the groundwater level, a constant head water injection test is used; when the test section is below the groundwater level, a reduced head water injection test is used. Step 3: Conduct continuous water injection test in the test section above the groundwater level; Conducting a continuous water injection test in the test section above the groundwater level includes the following steps: Step 3-1: Divide the soil anti-seepage body between the groundwater level (9) and the bottom plate of the cushion material (6) into a number of continuous test sections from top to bottom, with each test section being 3 to 5 meters long; Step 3-2: Drill a hole and drill to the bottom of the first test section l1 above the groundwater level, and drive the first layer of steel casing (8) below the bottom plate of the cushion material (6). The distance d between the first layer of steel casing (8) and the bottom plate of the cushion material (6) is 30 to 50 cm. The first layer of steel casing (8) isolates the first test section l1 above the groundwater level from the soil above it; Use no flushing fluid during drilling, and add a small amount of clean water when drilling becomes difficult; Step 3-3: Fill the borehole with water for 30 minutes to saturate the soil in the first test section l1 above the groundwater level; Step 3-4: Conduct a constant head water injection test on the first test section l1 above the groundwater level, keep the water level in the borehole at the mouth of the first layer of steel casing (8) and keep it fixed, record the stable injection flow rate, and calculate the permeability coefficient of the test section soil using the permeability coefficient formula; Step 3-5: Continue to follow up the first layer of steel casing (8) to the bottom of the first test section l1 above the groundwater level, drill under the protection of the first layer of steel casing (8) to form a second test section l2 above the groundwater level, fill with water to saturate the soil of the second test section l2 above the groundwater level, and conduct a constant head water injection test on the second test section l2 above the groundwater level; Step 3-6: Repeat step 3-5 until the water injection test of the last test section li above the groundwater level is completed; Step 4: Conduct a continuous water injection test in the test section below the groundwater level; Conducting a continuous water injection test in the test section below the groundwater level includes the following steps: The drilled hole in the soil impermeable body below the groundwater level (9) is divided into a number of continuous test sections from top to bottom; each test section is 3 to 5 meters long; Step 4-1: Follow the pipe and drill; Continue to follow up the first layer of steel casing (8) to the bottom of the test section li, that is, the foot of the first layer of steel casing (8) is flush with the groundwater level, and drill under the protection of the first layer of steel casing (8) to form the first test section li+1 below the groundwater level; Step 4-2: Water injection test; A water head reduction water injection test is carried out on the first test section li+1 below the groundwater level, and the change of the water head reduction and the duration in the first layer of steel casing (8) is recorded, and the permeability coefficient of the test section soil is calculated using the permeability coefficient formula; Step 4-3: Follow the pipe and drill A second layer of steel casing (10) is used as a follower pipe, and the bottom of the second layer of steel casing (10) reaches the bottom of the first test section li+1 below the groundwater level; and a second test section li+2 below the groundwater level is formed by drilling under the protection of the second layer of steel casing (10); Step 4-4: water injection test; A water head reduction water injection test is carried out on the second test section li+2 below the groundwater level; the change of the water head reduction and the duration in the second layer of steel casing (10) is recorded, and the permeability coefficient of the test section soil is calculated using the permeability coefficient formula; Step 4-5: Continue with pipe following, drilling, and water injection tests; Repeat steps 4-3 and 4-4 until the water injection test of all test sections below the groundwater level is completed.
2. The method for continuous water injection through drilling holes in soil impermeable bodies of dangerous reservoirs and dams according to claim 1 is characterized by: The outer diameter of the first steel casing (8) is 168 mm; The outer diameter of the second layer of steel casing (10) is smaller than the outer diameter of the first layer of steel casing (8).
3. The method for continuous water injection through drilling holes in soil impermeable bodies of dangerous reservoirs and dams according to claim 2 is characterized by: In step 4-5, when it is difficult to follow the pipe, a second layer of steel casing (10) with a smaller outer diameter is used to follow the pipe.