Test method for permeability of river and lake sediments

Abstract

The present invention discloses a method for testing the permeability of river and lake sediments, comprising: 1. adjusting a test tube and a measuring assembly to an initial state; simultaneously, pre-processing the test point to create a regular step in the riverbed sediment at the test target layer; 2. installing a measuring ruler, applying pressure to the tail of the push section, slowly pushing the insertion section into the test stratum; reading and recording the reading after the measuring ruler stabilizes; 3. removing the measuring ruler, and injecting a certain volume of water into the test tube measurement section until the water level in the tube reaches the top of the measurement section or a certain height above the groundwater level as an initial head value H0; covering the top of the measurement section to prevent evaporation; and starting a timer upon completion of water injection; and 4. observing the change in the water level in the tube. After the predetermined test time is reached, slowly withdrawing the insertion section from the test stratum, draining the water in the tube, removing the intelligent water level gauge, and reading the test data to complete the test. The present invention optimizes the operating steps and improves the accuracy of the test results.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogeological test equipment, and in particular to an in-situ testing method for conducting sediment permeability tests in places such as rivers, lakes, reservoirs, swamps, and wetlands. Background Art

[0002] For a long time, when promoting and applying field standpipe tests, most scholars and engineering technicians have focused on the application of standpipe test methods, the derivation and improvement of standpipe test calculation formulas, and the analysis of standpipe test results. They have paid less attention to the standpipe tester itself and have not made relevant improvements to the problems and limitations of the standpipe tester during use.

[0003] In the actual operation of the horizontal permeability test of river and lake sediments, straight pipes made of PVC or plastic are usually used, which are vertically overlapped with special-shaped joints to form a traditional "L"-shaped vertical pipe tester (see Figure 1 During the test, the water head in the pipe is mostly observed manually using a ruler. Some researchers also directly place an intelligent water level meter at the bottom of the vertical pipe to measure the test water level.

[0004] Manual measurement, limited by the space and structure of the vertical pipe, suffers from large measurement errors, low accuracy, and inconvenient operation. For example, when measuring the water level and sediment inside the pipe, reading the water level from the top of the vertical pipe with a measuring tape inevitably results in reading errors due to the large angle between the reading angle and the water surface.

[0005] When using smart water level meters, placement is often arbitrary due to the lack of a stable mounting location within the pipe. Typically, they are suspended vertically to the bottom of a vertical pipe using a rope, and their placement is often unknown. When conducting multiple tests at the same location, the smart water level meter may be in a variety of situations: leaning against the pipe wall, lying flat on the bottom, suspended vertically, or even inverted. In extreme cases, it may even be covered by sediment, rendering it inoperable. Because the randomly placed smart water level meter exhibits random variations in its posture, the errors in its recorded water level observations within the pipe are both random and accidental, compromising the comparability of the data obtained during the tests.

[0006] In addition to the limitations of the measurement method, the existing "L"-shaped vertical pipe tester also has the problem of poor material adaptability. As an on-site professional hydrogeological test instrument, most test personnel complete the processing of semi-finished products during the test preparation stage, and then transport them to the test site for assembly before conducting the test. Due to the limited material selection of the test instrument and the uneven quality, straight pipes are generally overlapped on-site using special glue or wrapping water-stop tape, and their sealing is often not guaranteed. Even if the overlap quality is good, when the horizontal section of the "L"-shaped vertical pipe tester is pushed into the test formation, the joint part that is subjected to external force is prone to deformation, which leads to the destruction of the sealing of the pipe body, thereby greatly reducing the success rate of the test.

[0007] When conducting vertical pipe tests in relatively loose sediments, such as loose silt, fine sand, and muddy silt layers, the vertical tube of the "L" type vertical pipe tester is filled with water during the test. The saturated sediment entering the horizontal section cannot remain upright on the air side. Due to its irregular shape, the length of the horizontal sediment in the tube is L. h The measurement error is often large, which greatly reduces the confidence of the test results. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides a method for testing the permeability of river and lake sediments with a wide range of applications, convenient operation, and high intelligence. Specifically, the following technical solutions can be adopted:

[0009] The method for testing the permeability of river and lake sediments of the present invention is implemented by a "⊥"-shaped test device, which includes:

[0010] The test tube is an inverted T-shaped structure consisting of an insertion section, a push section, and a measuring section. The insertion section and the push section are coaxially arranged. The push section is a closed structure. The measuring section is vertically arranged at the intersection of the insertion section and the push section.

[0011] The measuring assembly includes a water filter cover provided on the insertion section, a steering wheel and an intelligent water level gauge provided on the pushing section, and a reel provided on the measuring section. The water filter cover, the steering wheel, and the reel are connected by a transmission chain, and a measuring ruler is provided on the vertical section of the transmission chain.

[0012] The open end of the measuring section is provided with a pipe cap, and the pipe cap is provided with a vent hole.

[0013] The test method includes:

[0014] First, adjust the test tube and measurement assembly to their initial state. At the same time, pre-process the test point to create a regular step in the riverbed sediment at the test target layer to facilitate the insertion of the test tube.

[0015] Secondly, install the measuring ruler and apply pressure to the tail of the push section, slowly push the insertion section into the test formation, and read and record the reading after the measuring ruler stabilizes.

[0016] Next, remove the measuring tape and inject a certain volume of water (such as river or lake water) into the measuring section of the test tube until the water level in the tube reaches the top of the measuring section or a certain height above the groundwater level as the initial head value H0. Cover the top of the measuring section to prevent evaporation. Start timing when the water in the tube is completely injected.

[0017] Finally, observe the water level changes in the pipe. When the scheduled test time is reached, slowly pull the inserted section out of the test formation, drain the water in the pipe, take out the smart water level meter, read the test data, and complete the test.

[0018] The following conditions must be met during the water level change in the observation tube:

[0019] 1) Use the general observation method or the characteristic observation method, where: a. The general observation method includes: the water level observation in the pipe is initially observed at an interval of 1 minute, for 5 consecutive observations; then, at an interval of 10 minutes, for 3 observations; the subsequent observation interval is determined according to the rate of water level drop. For clay formations, a 30-minute interval is recommended, while for silt and sandy soils, a 10-minute interval is still recommended. b. The characteristic observation method: During the test, the recording interval of the water level drop in the pipe varies according to the lithology of the formation. For gravel formations, a 1-minute or 0.5-minute interval is used, for sandy formations, a 5-minute interval is recommended, and for clay formations, a 20-minute or 30-minute interval is recommended. The interval is fixed, and observation and recording are carried out continuously until the end of the observation.

[0020] 2) The head ratio and time [ln(H)] should be plotted on semi-logarithmic coordinate paper at the test site. t / H0)-t] relationship curve; when the relationship between head ratio and time is not a straight line, a test check should be carried out and the test should be repeated;

[0021] H t is the test water head in the pipe corresponding to the test time t in the vertical pipe infiltration test with the unit of cm; H0 is the initial water head value of the vertical pipe infiltration test with the unit of cm;

[0022] 3) The test can be ended when the test head drops to 0.3 times the initial test head or when the continuous observation data reaches more than 10.

[0023] The end of the tube body of the pushing section is screwed together with a straight handle to form the closed structure, and the top of the tube body of the pushing section is provided with an internal thread fixing groove for installing the intelligent water level gauge.

[0024] The opening end of the tube body of the insertion section is a chamfered structure for facilitating the insertion of sediments, and the cutting angle of the chamfered structure is 25-30°.

[0025] The inner diameters of the insertion section, the pushing section, and the measuring section are the same, and the wall thickness of the insertion section is smaller than that of the pushing section and the measuring section; the minimum height of the measuring section is 80 cm, the length of the insertion section is greater than 5 times the pipe diameter and less than the height of the measuring section, and the length of the pushing section is greater than 15 cm and less than the length of the insertion section.

[0026] The water filter cover is perpendicular to the central axis of the insertion section and is adapted to the inner diameter of the tube body of the insertion section. The diameter of the filter hole on the water filter cover is 1-1.5 mm, and the effective porosity of the water filter cover is ≥30%.

[0027] The steering wheel is a double-sprocket wheel, the winding wheel is a single-sprocket wheel, and the transmission chain is divided into a horizontally arranged first section and a vertically arranged second section. One end of the first section is connected to the first chain position of the steering wheel, and the other end is connected to the water filter cover through a buffer spring; one end of the second section is connected to the second chain position of the steering wheel, and the other end is connected to the winding wheel, and a ratchet is provided on one side of the winding wheel for making it rotate in one direction.

[0028] The first section of the transmission chain is arranged along the central axis of the insertion section.

[0029] The second section of the transmission chain is provided with an insertion slot for connecting the measuring ruler.

[0030] The river and lake sediment permeability testing method provided by the present invention is implemented based on a "⊥"-shaped test device. The device improves the design of the pipeline structure, optimizes the connection mode between the vertical pipe and the horizontal pipe, adds a linkage mechanism between the measuring ruler and the horizontal pressing of the sediment, and organically combines with the groundwater intelligent monitoring equipment. The applicability of the test equipment is improved and the applicable scenarios are expanded, so that it has strong adaptability under general sediment formation conditions and complex conditions (such as river and lake sediment formations with relatively high hardness), thereby forming a set of equipment with a simple structure, easy manufacturing, mature standards, easy use, high measurement accuracy, and recyclable reuse, thereby optimizing the operating steps of the river and lake sediment permeability test and improving the accuracy of the results of the river and lake sediment permeability test.

[0031] Compared with the existing technology, it has the following advantages:

[0032] 1) Enhanced the convenience, operability and accuracy of standpipe test equipment in obtaining test parameters in confined spaces and complex sediment formations, greatly improving test accuracy under complex conditions;

[0033] 2) It can accurately and directly measure the length of sediment in the horizontal tube of the “⊥” type vertical tube tester;

[0034] 3) For river and lake sediments formed by long-term sedimentation, especially ancient sediments or floodplain sediments, as well as gravel-bearing sediments, the jacking section can withstand large horizontal thrusts while ensuring the overall tightness of the device;

[0035] 4) Using intelligent groundwater monitoring equipment and built-in measuring rulers to form a complete testing system can reduce the error in obtaining relevant test parameters, improve the accuracy of test data, and thus reduce time and human resource costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural diagram of an existing "L" type vertical pipe tester.

[0037] Figure 2 It is a structural schematic diagram of the “⊥” type test device in the present invention (scale omitted).

[0038] Figure 3 yes Figure 2 Schematic diagram of the exploded view of the test tube.

[0039] Figure 4 yes Figure 2 Schematic diagram of the structure of the measurement component.

[0040] Figure 5 yes Figure 2 Schematic diagram of the structure of the middle steering wheel.

[0041] Figure 6 yes Figure 2 Schematic diagram of the structure of the middle winding wheel.

[0042] Figure 7 yes Figure 2 Cross-sectional view of the open end of the insertion section of the test tube.

[0043] Figure 8 yes Figure 4 Schematic diagram of the structure of the middle plug-in slot. DETAILED DESCRIPTION

[0044] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, and a detailed implementation method and a specific construction process are given. However, the protection scope of the present invention is not limited to the following embodiment.

[0045] The river and lake sediment permeability testing method described in the present invention can conduct an in-situ vertical pipe test of the horizontal permeability coefficient of bottom sediments in rivers, lakes, reservoirs, swamps, wetlands and other places, which is achieved through a "⊥"-shaped test device.

[0046] The above-mentioned “⊥” type test device includes

[0047] The test tube is an integrated "⊥"-shaped structure tube consisting of an insertion section, a push section, and a measuring section. The insertion section and the push section are coaxially arranged. The push section is a closed structure. The measuring section is vertically arranged at the intersection of the insertion section and the push section.

[0048] The measuring assembly includes a water filter cover arranged in the insertion section, a steering wheel and an intelligent water level gauge arranged in the pushing section, and a winding wheel arranged in the measuring section. The water filter cover, steering wheel and winding wheel are connected by a transmission chain, and a measuring ruler is arranged on the vertical section of the transmission chain.

[0049] Specifically, if Figure 2-8 As shown, the test tube is a one-piece, "⊥"-shaped, special-shaped tube. The vertical tube is the measuring section 1, and the horizontal tubes on either side are the insertion section 2 and the push section 3, respectively. The measuring section 1, insertion section 2, and push section 3 have the same inner diameter, generally not exceeding 200mm, and the wall thickness of the insertion section 2 is thinner than that of the push section 3 and the measuring section 1. Depending on the specific conditions of the test site, the height of the measuring section 1 should not be less than 80cm. The length of the horizontal tube section is designed according to test requirements, but must meet the following conditions: the length of the insertion section 2 is greater than 5 times the tube diameter and less than the height of the measuring section 1, and the length of the push section 3 is greater than 15cm and less than the length of the insertion section 2.

[0050] To prevent the water in the test tube from evaporating during the test and to maintain its connection with the outside world, allowing it to withstand normal atmospheric pressure, a cap 12 with a vent hole 11 is installed on the top of the measuring section 1. Cap 12 can be attached to the measuring section 1 using a snap-fit or threaded connection. Vent hole 11 is located at the center of cap 12 and has a diameter no greater than 1 cm.

[0051] The push section 3 is coaxially arranged with the insertion section 2 and is located on both sides of the measuring section 1. Therefore, when the test tube is pushed into the sediment formation, the tail of the push section 3 can be used as a force-bearing part, effectively preventing deformation at the junction of the horizontal and vertical tubes of the test tube. This not only avoids failure of the tube body seal, but also extends the service life of the device, allowing it to be reused multiple times. Furthermore, in order to facilitate the pushing of the test tube into the sediment formation, the closed end of the push section 3 adopts a structure in which the tube body and the sealing plug 32 with a handle 31 cooperate. The sealing plug 32 of the above-mentioned handle 31 is an integrated solid structure. The sealing plug 32 is located at the geometric center of the two. The head is connected to the tube body in a threaded manner, and the tail extends to both sides to form a straight handle 31. The width of the above-mentioned handle 31 is preferably 10cm to 15cm. When it is pushed into the sediment layer, external force is applied to the handle 31.

[0052] In order to enable the test tube to be smoothly pushed into the sediment layer, the opening end of the tube body of the insertion section 2 is a chamfered structure for easy insertion into the sediment (see Figure 7 ), and the cutting angle θ of the chamfered structure is 25-30°.

[0053] Preferably, an internal thread fixing groove 21 for installing the intelligent water level gauge 4 is further provided at the top of the tube body of the pushing section 2 .

[0054] The main functions of the measuring component are: ① The water filter cover 5 located in the insertion section 2 supports the river and lake sediments entering the pipe body, so that it can avoid deformation when it is saturated with water and facing the air, so that the length value of the river and lake sediments entering the insertion section 2 can be accurately obtained; ② The water filter cover 5 does not affect the entry of external water into the 1.3 test tube, and at the same time can filter floating impurities and other foreign matter in the water; ③ Through the cooperation of the steering wheel 6, the winding wheel 7 and the transmission chain 8, the direction of force transmission is changed, and the horizontal displacement of the river and lake sediments on the water filter cover 5 can be intuitively reflected in the scale change of the measuring ruler 9, so that readings can be made conveniently, quickly and accurately; ④ Through the intelligent water level meter 4, the water level in the pipe can be accurately and continuously monitored.

[0055] The water filter cap 5 is a circular structure that matches the inner diameter of the insertion section 2. Its thickness is 2-4 mm, and its surface is irregularly distributed with uniformly sized filter holes, with an effective porosity of no less than 30%. The filter holes can be bridge-shaped or circular, with a diameter of 1-1.5 mm. To ensure that the saturated free surface of river and lake sediment entering the insertion section 2 remains vertical, the water filter cap 5 is positioned perpendicular to the central axis of the insertion section 2. As the amount of sediment entering the tube increases, the water filter cap 5 gradually moves within the insertion section 2 toward the measuring section 1.

[0056] The steering wheel 6 and the winding wheel 7 are used to drive the transmission chain 8 to move and turn. The steering wheel 6 is a double chain wheel with a first chain position and a second chain position (see Figure 5 ), the winding wheel 7 is a single sprocket with only one chain position (see Figure 6The transmission chain 8 is divided into a first section 81 and a second section 82, each independently arranged. Specifically, the steering wheel 6 is mounted via a bracket near the push section 3, near the measuring section 1. Its first chain segment is fixedly connected to the first chain segment 81 of the transmission chain 8. The other end of the first segment 81 is connected to the water filter cover 5 via a buffer spring 10. As the water filter cover 5 moves toward the measuring section 1, the first segment 81 gradually winds around the first chain segment of the steering wheel 6 (i.e., it enters a reeling state). The reel 7 is mounted via a bracket near the top of the measuring section 1. It is fixedly connected to the second chain segment 82 of the transmission chain 8. The end of the second segment 81 is fixedly connected to the second chain segment of the steering wheel 6 and partially winds around it (i.e., it enters a reeling state). As the water filter cover 5 moves toward the measuring section 1, as the steering wheel 6 rotates, the second segment 81 gradually unwinds, and the other end gradually winds around the reel 7 for reeling (i.e., it enters a reeling state). To prevent the transmission chain 8 from accidentally slipping during this process, a ratchet is installed on one side of the reel 7 to ensure unidirectional rotation. In the above structure, the moving lengths of the first section 81 and the second section 82 are the same. Therefore, installing the measuring ruler 9 on the second section 82 will accurately reflect the length of the sediment entering the insertion section 2.

[0057] The above-mentioned steering wheels 6 and winding wheels 7 are staggered, and the opposite sides of the two are arranged tangentially to the second section 82, so that the second section 82 is arranged vertically in the same direction as the measuring section 1; at the same time, the first section 81 is arranged horizontally along the central axis of the insertion section 2. Therefore, the transmission chain 8 has an L-shaped structure as a whole. The buffer spring 10 is made of a high-elasticity steel material coated with an anti-corrosion coating, and its main functions are: contraction, transmission and buffering. The transmission chain 8 usually adopts a fine steel chain coated with an anti-corrosion layer, with a width of 25mm and a thickness of 0.3-0.4mm, and the length of the first section 81 and the second section 82 is at least 2.0m. The above-mentioned second section 82 is equipped with a plug-in slot 11 for connecting the measuring ruler 9. As shown Figure 8 As shown, the insertion groove 11 is provided at the top of the insertion block 111 and is an internal thread groove adapted to the measuring ruler 9 , and the side surface of the insertion block 111 is a connecting block 112 connected to the second section 82 .

[0058] The bottom of the measuring ruler 9 is threadedly connected to the insertion slot 10. It is a cylindrical structure with a cross-sectional diameter not exceeding 1.0 cm. Generally, the length of the measuring ruler 9 does not exceed the length of the second section 81. Its minimum scale is 1 mm, and the zero scale mark is located at the top. Preferably, when the second section 81 is in a tensioned state and fully wound around the steering wheel 6 while remaining connected to the winding wheel 7, the upper zero scale mark of the measuring ruler 9 is flush with the upper edge of the measuring section 1.

[0059] The intelligent water level gauge 4 is installed in the internally threaded fixing groove 21 at the top of the push section 2. It is used to collect and store data on the continuous changes in the water head value within the measuring section 1 (i.e., the vertical pipe section) during the vertical pipe test. The intelligent water level gauge 4 should be a model that can automatically monitor the pressure and temperature of various water bodies. Preferably, the intelligent water level gauge 4 uses a pressure-sensitive ceramic capacitor sensor to measure underwater pressure. Ceramic capacitor sensors offer excellent stability and no drift over long periods of use. Furthermore, through high-density pressure calibration, even minor water level changes can be measured and recorded. Preferably, the intelligent water level gauge 4 uses the mature and established Mini-Diver economical intelligent water pressure gauge. Its main technical parameters are: length 90mm, diameter 22mm, weight approximately 55g. It integrates sensors, data loggers, and wireless communication modules in one, and uses a 316L stainless steel shell. Its water pressure measurement range is: 0–10 / 20 / 50 / 100 mH2O, with a resolution of 0.2 / 0.4 / 1.0 / 2.0 cmH2O, and its temperature measurement range is: -20℃- 80℃, with a resolution of 0.01℃.

[0060] In particular, through extensive research and summarization of previous practical experience, the test tubes described in the present invention are preferably made of transparent PMMA or PMA-based acrylic tubes, which offer excellent strength and wear resistance, high transparency, low density, and strong tensile and impact resistance. Casting (i.e., thermoforming) is the recommended processing technique. Of course, other materials, such as metals and polymers, may also be used.

[0061] The method for testing the permeability of river and lake sediments of the present invention comprises:

[0062] First, adjust the test tube and measurement assembly to their initial state. At the same time, pre-process the test point to create a regular step in the riverbed sediment at the test target layer to facilitate the insertion of the test tube.

[0063] Secondly, install the measuring ruler and apply pressure to the tail of the push section, slowly push the insertion section into the test formation, and read and record the reading after the measuring ruler stabilizes.

[0064] Next, remove the measuring tape and inject a certain volume of water (such as river or lake water) into the measuring section of the test tube until the water level in the tube reaches the top of the measuring section or a certain height above the groundwater level as the initial head value H0. Cover the top of the measuring section to prevent evaporation. Start timing when the water in the tube is completely injected.

[0065] Finally, observe the water level changes in the pipe. When the scheduled test time is reached, slowly pull the inserted section out of the test formation, drain the water in the pipe, take out the smart water level meter, read the test data, and complete the test.

[0066] Specifically, the steps include:

[0067] The first step is to lift the ratchet on one side of the winding wheel 7, adjust the state of the steering wheel 6 and the winding wheel 7, so that the water filter cover 5 is flush with the inlet end of the insertion section 2, and then lower the ratchet;

[0068] The second step is to set the operating frequency of the intelligent water level gauge 4 so that it records several atmospheric pressure values, then check to ensure that the readings are normal, and then install it in the internal thread fixing groove 21 at the top of the pipe body of the push section 2;

[0069] The third step is to install a sealing plug 32 with a handle 31 on the push section 3 of the test tube and check its sealing to ensure that it is leak-proof.

[0070] The fourth step is to pre-process the test point to create a regular step in the riverbed sediment at the test target layer to facilitate the insertion of the test tube into section 2;

[0071] Step 5: Install the measuring ruler 9 into the insertion slot 10 of the second section 82 of the transmission chain 8, ensuring that it is well fixed and not tilted;

[0072] Step 6: Apply external force to the handle 31 to slowly push the insertion section 2 into the test formation. After the measuring ruler 9 stabilizes, read the value and record it as L. h ;

[0073] Step 7: Remove the measuring ruler 9 from the insertion slot 10 and inject a certain volume of water (such as river or lake water) into the measuring section of the test tube until the water level in the tube reaches the top of the measuring section or a certain height above the groundwater level as the initial water head value H0. Then, install the pipe cap 12 on the top of the measuring section 1 to prevent evaporation. Start timing when the water in the tube is completely injected.

[0074] Step 8: Observe the water level changes in the pipe. When the predetermined test time is reached, slowly pull out the insertion section 2 from the test formation, remove the sealing plug 32 and the handle 31, drain the water in the pipe, take out the smart water level meter 4, and read the test data to complete the test.

[0075] The following conditions must be met during the water level change in the observation tube:

[0076] 1) Use the general observation method or the characteristic observation method, where a. The general observation method includes: the water level observation in the pipe is initially observed at an interval of 1 minute, for 5 consecutive observations; then, at an interval of 10 minutes, for 3 observations; the subsequent observation intervals can be determined according to the rate of water level drop. For clay formations, a 30-minute interval is recommended, while for silt and sandy soils, a 10-minute interval is still recommended. b. The characteristic observation method: The recording interval of the water level drop in the pipe during the test can also be different according to the lithology of the formation. For gravel formations, a 1-minute or 0.5-minute interval can be used, for sandy formations, a 5-minute interval is recommended, and for clay formations, a 20-minute or 30-minute interval is recommended. The interval is fixed, and observation and recording are carried out continuously until the end of the observation.

[0077] 2) The head ratio and time [ln(H)] should be plotted on semi-logarithmic coordinate paper at the test site. t / H0)-t] relationship curve; when the relationship between head ratio and time is not a straight line, a test check should be carried out and the test should be repeated;

[0078] H t is the test water head in the pipe corresponding to the test time t in the vertical pipe infiltration test with the unit of cm; H0 is the initial water head value of the vertical pipe infiltration test with the unit of cm;

[0079] 3) The test can be ended when the test head drops to 0.3 times the initial test head or when the continuous observation data reaches more than 10.

[0080] It should be noted that, in the description of the present invention, terms indicating orientation or positional relationships such as “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “inside”, and “outside” are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

Claims

1. A method for testing the permeability of river and lake sediments, implemented by a "⊥" type test device, characterized in that: The "⊥" type test device comprises: The test tube is a "⊥"-shaped structure tube consisting of an insertion section, a push section, and a measuring section. The insertion section and the push section are coaxially arranged. The push section is a closed structure. The measuring section is vertically arranged at the intersection of the insertion section and the push section. The measuring assembly includes a water filter cover provided on the insertion section, a steering wheel and an intelligent water level gauge provided on the pushing section, and a reel provided on the measuring section. The water filter cover, the steering wheel, and the reel are connected by a transmission chain, and a measuring ruler is provided on the vertical section of the transmission chain. The test method includes: First, adjust the test tube and measurement assembly to their initial state. At the same time, pre-process the test point to create a regular step in the riverbed sediment at the test target layer to facilitate the insertion of the test tube. Secondly, install the measuring ruler and apply pressure to the tail of the push section, slowly push the insertion section into the test formation, and read and record the reading after the measuring ruler stabilizes. Next, remove the measuring ruler and inject a certain volume of water into the measuring section of the test tube until the water level in the tube reaches the top of the measuring section or a certain height above the groundwater level as the initial water head value H0. Cover the top of the measuring section to prevent evaporation. Start timing when the water in the tube is completely injected. Finally, observe the water level changes in the pipe. When the scheduled test time is reached, slowly pull the inserted section out of the test formation, drain the water in the pipe, take out the smart water level meter, read the test data, and complete the test.

2. The method for testing the permeability of river and lake sediments according to claim 1, characterized in that: The following conditions must be met during the water level change in the observation tube: 1) Use the general observation method or the characteristic observation method, where: a. The general observation method includes: the water level observation in the pipe is initially observed at an interval of 1 minute, for 5 consecutive observations; then, at an interval of 10 minutes, for 3 observations; the subsequent observation interval is determined according to the rate of water level drop. For clay formations, a 30-minute interval is recommended, while for silt and sandy soils, a 10-minute interval is still recommended. b. The characteristic observation method: During the test, the recording interval of the water level drop in the pipe varies according to the lithology of the formation. For gravel formations, a 1-minute or 0.5-minute interval is used, for sandy formations, a 5-minute interval is recommended, and for clay formations, a 20-minute or 30-minute interval is recommended. The interval is fixed, and observation and recording are carried out continuously until the end of the observation. 2) The head ratio and time [ln(H)] should be plotted on semi-logarithmic coordinate paper at the test site. t / H0)-t] relationship curve; when the relationship between head ratio and time is not a straight line, a test check should be carried out and the test should be repeated; H t is the test water head in the pipe corresponding to the test time t in the vertical pipe infiltration test with the unit of cm; H0 is the initial water head value of the vertical pipe infiltration test with the unit of cm; 3) The test can be ended when the test head drops to 0.3 times the initial test head or when the continuous observation data reaches more than 10.

3. The method for testing the permeability of river and lake sediments according to claim 2, wherein: The open end of the measuring section is provided with a pipe cap, and the pipe cap is provided with a vent hole.

4. The method for testing the permeability of river and lake sediments according to claim 3, wherein: The end of the tube body of the pushing section is screwed together with a straight handle to form the closed structure, and the top of the tube body of the pushing section is provided with an internal thread fixing groove for installing the intelligent water level gauge.

5. The method for testing the permeability of river and lake sediments according to claim 4, wherein: The opening end of the tube body of the insertion section is a chamfered structure for facilitating the insertion of sediments, and the cutting angle of the chamfered structure is 25-30°.

6. The method for testing the permeability of river and lake sediments according to claim 5, characterized in that: The inner diameters of the insertion section, the pushing section, and the measuring section are the same, and the wall thickness of the insertion section is smaller than the wall thicknesses of the pushing section and the measuring section; the minimum height of the measuring section is 80 cm, the length of the insertion section is greater than 5 times the pipe diameter and less than the height of the measuring section, and the length of the pushing section is greater than 15 cm and less than the length of the insertion section.

7. The method for testing the permeability of river and lake sediments according to claim 6, characterized in that: The water filter cover is perpendicular to the central axis of the insertion section and is adapted to the inner diameter of the tube body of the insertion section. The diameter of the filter hole on the water filter cover is preferably 1-1.5 mm, and the effective porosity of the water filter cover is ≥30%.

8. The method for testing the permeability of river and lake sediments according to claim 7, wherein: The steering wheel is a double-sprocket wheel, the winding wheel is a single-sprocket wheel, and the transmission chain is divided into a horizontally arranged first section and a vertically arranged second section. One end of the first section is connected to the first chain position of the steering wheel, and the other end is connected to the water filter cover through a buffer spring; one end of the second section is connected to the second chain position of the steering wheel, and the other end is connected to the winding wheel, and a ratchet is provided on one side of the winding wheel for making it rotate in one direction.

9. The method for testing the permeability of river and lake sediments according to claim 8, wherein: The first section of the transmission chain is arranged along the central axis of the insertion section.

10. The method for testing the permeability of river and lake sediments according to claim 9, characterized in that: The second section of the transmission chain is provided with an insertion slot for connecting the measuring ruler.

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