Construction method of dam foundation piezometer tube

Abstract

The application discloses a dam foundation pressure measuring pipe construction method, and belongs to the technical field of dam foundation seepage monitoring. The steps include the following: firstly, construction parameters are determined through survey and design, and the hole is cleaned after drilling construction; a pressure measuring pipe containing a double-layer filter layer is processed and assembled, the first filter material is backfilled to serve as support before the pipe is lowered into the hole, and the second filter material is backfilled in layers to form a filter layer in the gap outside the pipe; a special filler is used to backfill bentonite balls in grains to form a first flexible sealing layer, cement bentonite slurry is poured on the upper side to form a second rigid anti-seepage layer, and a double anti-seepage system is constructed; after passing the sensitivity test, the concrete base is poured, and the protection box is installed. The method solves the problems of easy failure of traditional process sealing and uneven backfilling, improves the construction quality and the reliability of monitoring data, and is suitable for complex dam foundation geological conditions.

Description

A construction method for dam foundation piezometers Technical Field

[0001] This invention belongs to the field of dam foundation seepage monitoring technology, specifically a construction method for dam foundation piezometers. Background Technology

[0002] In water conservancy projects, seepage pressure in the dam foundation is an important monitoring indicator related to dam safety. Piezometers are key facilities for obtaining this indicator, and their construction quality directly affects the accuracy and reliability of monitoring data, which is crucial for the long-term safe operation of the dam and risk early warning.

[0003] However, existing methods for constructing dam foundation piezometers still have some problems, such as:

[0004] 1. Traditional sealing methods often use single bentonite balls, which are difficult to form a long-term seepage prevention system. During the backfilling process, insufficient compaction of bentonite balls can easily lead to interlayer voids. Over time, these voids are affected by seepage pressure from the dam foundation and slight soil settlement, causing the sealing performance to gradually decline and eventually forming seepage channels. For example, if a reservoir's piezometer is sealed only with bentonite balls, the sealing performance will decrease after the dam foundation settles, allowing surface water to seep into the piezometer and causing inaccurate monitoring data.

[0005] 2. Current backfilling methods mostly rely on manual labor or simple tools to dump and fill the material. Due to the limited space inside the borehole, bentonite balls tend to accumulate in the gap between the pressure testing tube and the borehole wall, forming voids. This makes it impossible to achieve uniform filling across the entire cross-section, and there are still dead zones in the sealing after subsequent expansion, affecting the reliability of the sealing.

[0006] Therefore, it is necessary to propose a construction method for dam foundation piezometers that takes into account long-term seepage prevention, uniform backfilling, and structural stability, so as to meet the long-term and stable requirements of water conservancy projects for dam foundation seepage monitoring. Summary of the Invention

[0007] The present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention proposes a construction method for a dam foundation piezometer.

[0008] This technical solution proposes a construction method for dam foundation piezometers, including:

[0009] S1, Survey and Design: Verify the geological survey data of the dam site, clarify the coordinates and elevation of the monitoring points, and determine the drilling depth, piezometer density and protection requirements;

[0010] S2, Drilling construction: Determine the hole position according to the design coordinates, use a drilling rig to drill the hole and monitor the verticality of the hole in real time. After drilling is completed, clean the soil in the hole and keep the hole dry and clean.

[0011] S3, Pressure testing tube processing and assembly: Processing, manufacturing and assembling pressure testing tubes that meet design requirements;

[0012] S4, Lowering the pipe: First, backfill the first reverse filter material to the bottom of the hole and compact it as a support. Then, connect the assembled pressure measuring pipe section by section and lower it vertically into the hole to ensure that the pipe body is straight.

[0013] S5, Second filter material backfilling: The second filter material is backfilled in layers into the annular gap between the pressure measuring tube and the hole wall to form a filter layer;

[0014] S6, Bentonite ball sealing: Bentonite balls are backfilled in layers above the filter layer to the design height using a process of backfilling one ball at a time. After backfilling, water is injected into the pipe to cause the bentonite balls to disintegrate and expand, thus completing the sealing and forming the first flexible sealing layer.

[0015] S7, Cement-bentonite slurry sealing: Cement-bentonite slurry is injected on top of the bentonite ball. After the cement-bentonite slurry solidifies, it forms a second rigid anti-seepage layer, which, together with the first flexible sealing layer, forms a dual anti-seepage system of flexible bottom and rigid top.

[0016] S8, Sensitivity Test: A sensitivity test is performed on the pressure testing pipe after installation and sealing.

[0017] S9, Concrete pouring: Excavate the dam slope around the pressure test tube to form a foundation pit, first pour plain concrete in the foundation pit to form a cushion layer, then pour concrete on top of the cushion layer to form a concrete base, and then backfill the foundation pit.

[0018] S10, Installation of protective facilities: Install protective boxes on the concrete base.

[0019] Preferably, the pressure measuring tube includes a filter tube section and a conduit section connected to the top of the filter tube section. A bottom sealing plate is welded to the bottom end of the pressure measuring tube. The filter tube section has several filter holes in its tube wall. Several evenly distributed vertical ribs are welded circumferentially on the outer wall of the filter tube section. The outer wall of the filter tube section is wrapped with a first filter screen to form a first filter layer. The vertical ribs are wrapped inside the first filter screen. A second filter screen is wrapped around the outside of the first filter screen to form a second filter layer. Lead wires are wound around the outer wall of the second filter layer at intervals to achieve tight fixation.

[0020] Preferably, the cement-bentonite slurry described in S7 is injected to a depth of 1.0 to 2.0 m below the pipe opening.

[0021] Preferably, the filter layer is filled to a height of 1.0m above the top of the filter tube section, and not higher than the foundation surface.

[0022] Preferably, the bentonite ball has a diameter of 5 to 10 mm.

[0023] Preferably, in step S6, a filler is used to implement the pellet-by-particle backfilling process. The filler includes a feeding component and a guiding component. The feeding component includes an annular guide rail detachably sleeved on the pressure measuring tube. A box capable of circular motion along the annular guide rail is fitted on the annular guide rail. The box has at least one receiving cavity for storing bentonite balls. The bottom of the receiving cavity has an opening. A distributing roller rotatably connected to the box is adapted at the opening. The distributing roller is driven by the output shaft of a first motor. A conveying pipe for transporting bentonite balls is connected to the bottom of the box.

[0024] The material guide includes a fixed plate that is detachably sleeved on the pressure measuring tube. The fixed plate has several evenly distributed protrusions along its circumference, forming an uneven interface on its circumferential sidewall. A turntable is rotatably connected above the fixed plate, and one end of the conveying pipe is connected to the sidewall of the turntable. When the turntable rotates along with the conveying pipe, the conveying pipe can move circumferentially along the fixed plate, and swing left and right through the uneven interface during the circumferential movement.

[0025] Preferably, the distributing roller is provided with several sets of material grooves along its circumference, and each set of material grooves has several grooves arranged at intervals. The grooves are detachably connected with caps for sealing the grooves.

[0026] Preferably, a sleeve is fixedly connected to the bottom of the fixed disk, and a plurality of first set screws are threadedly connected to the sleeve along the circumferential direction on the cylinder wall.

[0027] Preferably, a second motor is connected to the bottom of the housing, and the second motor drives a drive wheel that can move along the circumferential sidewall of the annular guide rail.

[0028] Preferably, the specific method for backfilling particle by particle in S6 is as follows:

[0029] S61, Install the guide sleeve on the pressure testing tube and position it in the designated location;

[0030] S62, the feeding component is installed on the pressure measuring pipe through the ring guide rail, and the feeding component is connected to the guiding component and the feeding component as a whole by the conveying pipe;

[0031] S63, pour the bentonite balls into the receiving cavity of the box;

[0032] S64, start the first motor and the second motor, the box moves circumferentially along the circular guide rail, and at the same time the material distribution roller rotates to realize intermittent feeding, and the bentonite balls are conveyed along the conveying pipe;

[0033] S65, the conveying pipe moves circumferentially with the box body. During this process, the conveying pipe pulls the turntable to rotate, and the end of the conveying pipe slides along the circumferential side wall of the fixed plate. The uneven interface enables the end of the conveying pipe to swing left and right, thereby achieving uniform filling of the entire cross-section of the bentonite ball.

[0034] The above technical solution has the following advantages:

[0035] 1. This invention employs a combined seepage prevention process using bentonite balls and cement-bentonite slurry to form a dual seepage prevention system with a flexible base and a rigid top: the bentonite balls expand upon contact with water to fill tiny gaps, forming the first flexible seal; the cement-bentonite slurry, after solidification, fills the voids between the ball layers, forming a continuous rigid seepage prevention layer. The two work together to avoid residual voids between layers, effectively resisting the effects of dam foundation seepage and settlement, significantly improving the long-term effectiveness of the seal, and solving the problems of easy loosening and reduced sealing performance that exist in traditional processes using a single bentonite ball for sealing.

[0036] 2. This invention uses a matching filler to achieve the one-by-one backfilling of bentonite balls. A second motor drives the circumferential movement of the box, which is combined with the intermittent feeding of the material distribution roller. At the same time, the concave and convex interface of the fixed plate enables the end of the conveying pipe to swing left and right, ensuring that the bentonite balls are evenly distributed in the full cross-sectional gap between the pressure measuring pipe and the borehole wall. This achieves uniform backfilling of bentonite balls across the entire cross-section, eliminates sealing dead corners, solves the problem of easy accumulation and void formation in traditional backfilling, and improves the reliability of sealing.

[0037] 3. The filler adopts a detachable sleeve design and can be quickly positioned and fixed by a top screw, which is compatible with pressure testing tubes of different specifications; the groove of the material distribution roller can be sealed with a cap to adjust the material feeding amount, which can meet the filling needs of different geological conditions; its structure is simple and compact, and it can achieve automatic particle-by-particle backfilling by motor drive, which reduces the intensity of manual labor and ensures the consistency of construction quality, and is suitable for the construction needs under complex dam foundation geological conditions. Attached Figure Description

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0039] Figure 1 is a schematic diagram of the pressure measuring tube in this invention.

[0040] Figure 2 is a cross-sectional view of the pressure measuring tube after installation in this invention.

[0041] Figure 3 is a cross-sectional view of the structure along BB in Figure 1.

[0042] Figure 4 is a 3D view of the protective box and solar panels in Figure 2 after installation.

[0043] Figure 5 is a three-dimensional view of the infiller.

[0044] Figure 6 is a schematic diagram of the internal material rollers of the box.

[0045] Figure 7 is a cross-sectional view of the structure when the annular guide rail, drive wheel, and housing are in contact.

[0046] Figure 8 is a diagram showing the separate structure of the groove and the cap on the distributing roller.

[0047] Figure 9 is a schematic diagram of the structure when the filler is installed on the pressure test tube.

[0048] Figure 10 is a schematic diagram of the filler when filling bentonite balls.

[0049] Figure 11 is a schematic diagram of the wiring principle for seepage monitoring.

[0050] Explanation of reference numerals in the attached figures:

[0051] 1. Pressure measuring pipe; 101. Conduit section; 102. Filter pipe section; 1021. Filter hole; 2. Bottom sealing plate; 3. Vertical rib; 4. Second filter layer; 5. First filter layer; 6. First reverse filter media; 7. Second reverse filter media; 8. Flexible sealing layer; 9. Rigid anti-seepage layer;

[0052] 10. Subbase; 11. Concrete base; 12. Interface protective cover; 13. Protective box; 131. Box frame; 132. Box cover; 14. Bracket; 15. Solar panel;

[0053] 16. Guide component; 161. Sleeve; 162. Fixed plate; 163. Boss; 164. Turntable; 165. First set screw; 166. Snap fastener;

[0054] 17. Feeding component; 171. Circular guide rail; 172. Inner cylinder; 173. Second set screw; 174. Box body; 1741. Receiving cavity; 175. First motor; 176. Drive wheel; 1761. Second motor; 177. Conveying pipe; 178. Thin-walled bearing; 179. Upright pole;

[0055] 18. Drilling hole; 19. Bentonite ball; 20. Distributing roller; 201. Groove; 202. Cap;

[0056] 21. Material guide plate; 22. Solar charge controller; 23. Storage battery; 24. Vibrating wire piezometer; 25. Signal surge arrester; 26. Data acquisition terminal. Detailed Implementation

[0057] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0058] As shown in Figures 1-4, this embodiment proposes a construction method for dam foundation piezometers, including:

[0059] S1, Survey and Design: Verify the geological survey data of the dam foundation, clarify the coordinates and elevations of the monitoring points, and determine the depth of borehole 18, the density of piezometer 1, and the protection requirements; First, verify the stratigraphic distribution, lithological characteristics, location and thickness of permeable layers, etc. in the geological survey report of the dam foundation, and conduct supplementary on-site geological surveys if necessary to ensure that the geological data is consistent with the actual working conditions; Second, use GPS positioning technology or total station measurement technology to accurately determine the plane coordinates and elevations of each monitoring point, with coordinate errors controlled within ±5cm and elevation errors controlled within ±2cm; Determine the depth of borehole 18 based on geological conditions and seepage monitoring requirements; Finally, in conjunction with the hydrogeological conditions of the dam foundation, clarify the protection requirements of piezometer 1, such as using piezometer 1 made of corrosion-resistant material in corrosive groundwater environments.

[0060] S2, Drilling Hole 18 Construction: Determine the hole position according to the design coordinates, use a drilling rig to create the hole and monitor the verticality of the hole in real time. After drilling is completed, clean the soil inside the hole and keep the hole dry and clean. Dry drilling should be used for hole creation, and mud slurry should not be used to fix the wall. The hole direction must be accurate when creating the hole, and the inclination of Drill Hole 18 should not exceed 3°. After drilling to the design depth, high-pressure air can be used to clean the soil inside the hole. After cleaning, the thickness of the sediment at the bottom of the hole should not exceed 5cm.

[0061] S3, Processing and assembly of pressure measuring tube 1: Process and assemble pressure measuring tube 1 that meets the design requirements; The main material of pressure measuring tube 1 is high-strength PVC pipe, stainless steel pipe or galvanized steel pipe, and the pipe diameter is determined according to the monitoring requirements. The commonly used diameter is 50-100mm. In this embodiment, a pipe diameter of 50mm is selected.

[0062] The pressure measuring tube 1 includes a filter tube section 102 and a conduit section 101 connected to the top of the filter tube section 102. The top of the filter tube section 102 is firmly connected to the conduit section 101. A bottom sealing plate 2 is welded to the bottom of the pressure measuring tube 1. The bottom sealing plate 2 is made of galvanized steel plate. The filter tube section 102 has several filter holes 1021 with a diameter of 3-10 mm. In this embodiment, the diameter of the filter holes 1021 is 8 mm, arranged in a quincunx pattern. The diameter of the filter holes 1021 is 8 mm. Several evenly distributed vertical ribs 3 are welded along the circumference of the outer wall of the filter pipe section 102. The number of vertical ribs 3 can be set to 6, and they are welded together. The outer wall of the filter pipe section 102 is wrapped with a first filter screen to form a first filter layer 5. The vertical ribs 3 are wrapped inside the first filter screen, which is made of two layers of geotextile. The first filter screen is wrapped with a second filter screen to form a second filter layer 4, which is made of two layers of copper wire mesh. Lead wire is wrapped around the outer wall of the second filter layer 4 at intervals to achieve tight fixation.

[0063] S4, Lowering the pipe: First, backfill the first reverse filter material 6 to the bottom of the hole and compact it as a support. The backfill thickness is 20-40cm. When backfilling, use a small compaction tool to compact it in layers. Then, connect the assembled pressure measuring pipe 1 section by section and vertically lower it into the hole to ensure that the pipe body is straight. Avoid collision with the hole wall during the lowering process. Finally, make the filter pipe section 102 of the pressure measuring pipe 1 correspond to the position of the monitored aquifer.

[0064] S5, Backfilling of the Second Filter Material 7: Backfill the annular gap between the piezometer 1 and the borehole wall with the second filter material 7 in layers to form a filter layer. During layered backfilling, use an immersion vibrator to compact each layer, ensuring the filter material is free of voids and does not collapse. The appropriate sand material should be selected based on the actual site conditions: for clay loam or sandy loam, pure fine sand can be used as the filter material; for gravel layers, a mixture of fine and coarse sand can be used. This step forms a filter layer by backfilling the filter material, ensuring that seepage water can smoothly enter the piezometer 1 while preventing the entry of sediment particles and avoiding blockage of the piezometer 1. It should be noted that the filter layer should be filled to 1.0m above the top of filter pipe section 102, and not higher than the foundation surface.

[0065] S6, Bentonite Ball 19 Sealing: Bentonite balls 19 are backfilled in layers above the filter layer using a pellet-by-particle backfilling process to the design height. After backfilling, water is injected into the pipe to cause the bentonite balls 19 to disintegrate and expand, completing the sealing and forming the first flexible sealing layer 8 with excellent sealing performance, which can resist seal damage caused by slight settlement of the dam foundation. The diameter of the bentonite balls 19 is 5-10mm, and they should be air-dried, not exposed to sunlight or baked. Filling should be done pellet by pellet; large-scale dumping should be avoided to prevent bridging. After sealing to the design elevation, water is injected into the pipe until the water level exceeds the top surface of the ball layer to cause the clay balls to disintegrate and expand.

[0066] S7, Cement-Bentonite Slurry Sealing: Cement-bentonite slurry is injected above the bentonite ball 19. After the cement-bentonite slurry solidifies, it forms a second rigid seepage barrier layer 9, which, together with the first flexible sealing layer 8, forms a dual seepage barrier system with a flexible base and a rigid top. This step constructs a rigid seepage barrier layer on the basis of the flexible sealing layer, forming a dual seepage barrier structure with a flexible base and a rigid top, improving the reliability and durability of the sealing.

[0067] During operation, mix the cement-bentonite slurry according to the design ratio, and slowly inject it using a grouting pipe until it reaches 1.0-2.0m below the pipe opening. During the injection process, ensure that the slurry is continuous and uniform to avoid the formation of air bubbles and voids.

[0068] S8, Sensitivity Test: Perform a sensitivity test on the pressure measuring tube 1 after installation and sealing to ensure that it meets the monitoring accuracy requirements.

[0069] The test method is as follows: slowly inject water into the installed and sealed pressure testing pipe 1 until the water level in the pipe is 1-2m higher than the groundwater level of the dam foundation, and then stop and record the initial water level; then observe the water level change every 10 minutes for 1 hour. If the rate of water level drop gradually slows down and tends to stabilize, and the final water level fluctuation does not exceed 2mm, the sensitivity test is considered qualified; if the test fails, the sealing performance of the sealing layer and the permeability of the filter layer need to be checked, and the problematic parts need to be reworked and the test repeated.

[0070] S9, Concrete pouring: Excavate a foundation pit around the dam slope of the pressure measuring pipe 1. First, pour plain concrete in the foundation pit to form a cushion layer 10. Then, pour concrete on top of the cushion layer 10 to form a concrete base 11. After that, backfill the foundation pit. Specifically, after the concrete is poured, cover and keep it moist for 7 days. After the curing is up to standard, backfill the foundation pit with the original dam body soil and compact it to restore the original appearance of the dam slope.

[0071] S10, Installation of protective facilities: Install the protective box 13 on the concrete base 11. Use expansion bolts to fix the stainless steel protective box 13 to the base. The protective box 13 includes a frame 131 and a cover 132, and must be waterproof, dustproof, and impact-resistant. During installation, ensure accurate alignment between the protective box 13 and the pressure testing pipe 1. A cable channel is reserved inside the box, and the protective box 13 is equipped with an anti-theft lock. A bracket 14 is connected to the top of the protective box 13, and a solar panel 15 is installed on the bracket 14. Install an interface protective cover 12 on the top of the pressure testing pipe 1. Install a seepage monitoring device inside the protective box 13. Affix the monitoring point number, installation date, and responsible person's identification information to the outside of the box 174. Simultaneously, set up warning signs around the protective box 13 to prevent collision damage during construction or inspection.

[0072] In this embodiment, as shown in Figure 11, the seepage monitoring device includes a vibrating wire piezometer 24, which is installed in the pressure measuring tube 1. The piezometer is electrically connected to a signal surge arrester 25 via a cable. The signal surge arrester 25 is electrically connected to a data acquisition terminal 26. The data acquisition terminal 26 has a built-in wireless communication module, which enables it to establish a remote communication connection with a mobile terminal. This wireless communication module includes, but is not limited to, 4G / 5G modules, Bluetooth modules, LoRa modules, WiFi modules, and NB-IoT modules.

[0073] The signal surge arrester 25 is welded to the voltage measuring tube 1. The field-tested resistance value should meet the requirement that the grounding resistance test value is not greater than 10 ohms. If the design requirement is not met, other measures such as external grounding galvanized flat steel or galvanized angle steel can be adopted. The function of the signal surge arrester 25 is to protect the monitoring link equipment and ensure stable data transmission.

[0074] The solar panel 15 is electrically connected to the battery 23 via a solar charge controller 22. The energy storage interface of the solar charge controller 22 is bidirectionally electrically connected to the battery 23. The solar charge controller 22 has a charging management function, which can stably store the electrical energy generated by the solar panel 15 into the battery 23, while preventing the battery 23 from overcharging or over-discharging, thus extending its service life. The power output interface of the solar charge controller 22 is electrically connected to the power interfaces of the signal surge arrester 25, the data acquisition terminal 26, and the vibrating wire piezometer 24 via cables, forming a unified power supply circuit. The vibrating wire piezometer 24 is connected to the data acquisition terminal 26 via a 5-core communication cable, and the signal surge arrester 25 is connected in series in the communication line and reliably grounded.

[0075] Application Results: The combined seepage prevention process using bentonite balls 19 and cement bentonite slurry forms a dual seepage prevention system with a flexible base and a rigid top. Bentonite balls 19 expand when exposed to water, filling tiny gaps to form the first flexible seal. After the cement bentonite slurry solidifies, it fills the gaps between the ball layers, forming a continuous rigid seepage prevention layer. The two work together to avoid the presence of gaps between layers, effectively resisting the effects of dam foundation seepage and settlement, and significantly improving the long-term effectiveness of the seal. This solves the problems of easy loosening and reduced sealing performance that exist when using a single bentonite ball 19 for sealing in traditional processes.

[0076] As shown in Figures 5-10, in some embodiments, considering the problems of low efficiency, high labor intensity, and difficulty in ensuring uniform backfilling due to manual backfilling of bentonite balls 19, a filler is used in S6 to realize the particle-by-particle backfilling process, which reduces labor costs and controls backfilling quality. The filler includes a feeding component 17 and a guiding component 16, which are described in detail below:

[0077] The feeding component 17 includes an annular guide rail 171 that can be detachably sleeved on the pressure measuring tube 1. The annular guide rail 171 can be made of high-strength alloy material. An inner cylinder 172 is sleeved inside the annular guide rail 171. The annular guide rail 171 and the inner cylinder 172 are connected as one unit by several connecting rods. Several second set screws 173 are threaded to the circumferential side wall of the inner cylinder 172.

[0078] A housing 174, capable of circular motion along the annular guide rail 171, is fitted onto the annular guide rail 171. Specifically, a second motor 1761 is connected to the bottom of the housing 174, which drives a drive wheel 176. The drive wheel 176 can move along the circumferential sidewall of the annular guide rail 171. The sidewall of the annular guide rail 171 has a smooth guide surface that engages with the drive wheel 176 at the bottom of the housing 174, ensuring smooth and uninterrupted movement of the housing 174. In this embodiment, two sets of drive wheels 176 can be designed, respectively located on the inner and outer sides of the annular guide rail 171. One set is connected to a motor and acts as the driving wheel, while the other can be used only as a driven wheel, primarily for limiting movement.

[0079] The housing 174 is integrally molded from lightweight, high-strength engineering plastic, ensuring structural stability while reducing motion load. The top of the housing 174 features an open feed inlet, and the housing 174 contains at least one receiving cavity 1741 for storing bentonite balls 19. The bottom of the receiving cavity 1741 has an opening, at which a distributing roller 20, rotatably connected to the housing 174, is fitted. This opening is elongated and its size is adapted to the distributing roller 20, ensuring that the bentonite balls 19 are fed orderly only through the distributing roller 20, avoiding congestion. The distributing roller 20 can be made of wear-resistant rubber. Both ends of the distributing roller 20 are connected to the housing 174 via deep groove ball bearings. One end of the distributing roller 20 is connected to the output shaft of a first motor 175. The first motor 175 is selected as a low-speed stepper motor with adjustable speed, allowing for adjustment of the feeding rate by controlling the speed.

[0080] The bottom of the housing 174 is connected to a conveying pipe 177 for conveying bentonite balls 19, and the lower end of the conveying pipe 177 extends to the turntable 164 of the guide 16.

[0081] In some embodiments, a thin-walled bearing 178 may be provided above the inner cylinder 172. The thin-walled bearing 178 includes an inner ring and an outer ring. The bottom end of the inner ring is fixedly connected to the top of the inner cylinder 172 through a vertical rod 179, and the outer ring is connected to the outer wall of the box 174 through a horizontal rod, which serves as an auxiliary support.

[0082] The guide component 16 includes a fixed disk 162 detachably sleeved on the pressure measuring tube 1. A sleeve 161 is fixedly connected to the bottom of the fixed disk 162. Several first set screws 165 are threaded onto the sleeve 161 along the circumferential direction. The fixed disk 162 is provided with several evenly distributed bosses 163 along the circumferential direction, so that its circumferential sidewall forms an uneven interface. A turntable 164 is rotatably connected above the fixed disk 162. One end of the conveying pipe 177 is connected to the sidewall of the turntable 164. Specifically, the outer wall of the turntable 164 has a bayonet, and the end of the conveying pipe 177 is fixed at the buckle 166. When the turntable 164 rotates together with the conveying pipe 177, the conveying pipe 177 can move circumferentially along the fixed disk 162, and swing left and right through the uneven interface during the circumferential movement.

[0083] In some embodiments, the material distribution roller 20 is provided with a plurality of material troughs along the circumferential direction. Each material trough has a plurality of spaced grooves 201. The grooves 201 are detachably connected to caps 202 for sealing the grooves 201. The material feeding amount can be flexibly adjusted by sealing part of the grooves 201 to adapt to different backfilling requirements.

[0084] Multiple material distribution rollers 20 are provided, and each material distribution roller 20 has a groove 201 of different size. The space inside the box 174 is divided into multiple independent receiving cavities 1741 by partitions. The bottom opening of the receiving cavity 1741 corresponds one-to-one with the groove 201 on the different material distribution rollers 20, ensuring that bentonite balls 19 of different specifications are fed only through their respective matching grooves 201.

[0085] To facilitate material unloading, each receiving cavity 1741 is equipped with a guide plate 21 at its bottom. The guide plate 21 is connected to the inner wall of the box 174 for easy material unloading.

[0086] Construction personnel can adjust the mixing ratio according to the design requirements by sealing the groove 201. For example, taking 5mm and 7mm bentonite balls 19 as an example, two independent distributing rollers 20 are arranged in parallel inside the box 174, referred to as the first distributing roller and the second distributing roller. The distributing rollers 20 are arranged horizontally along the axial direction and are both connected to the same stepper motor transmission mechanism to ensure synchronized speed and consistent feeding rate. Among them:

[0087] The first separating roller corresponds to 5mm bentonite balls 19; the second separating roller corresponds to 7mm bentonite balls 19. The number of circumferential groups and the number of grooves 201 in each group are exactly the same as the first separating roller, ensuring that the basic feeding rate of the two specifications of balls is the same.

[0088] Example 1: When a 5mm:7mm=1:1 mixing ratio is required, do not block any grooves 201. During the rotation of the distributing roller 20, the grooves 201 of each set of material troughs alternately discharge material, and the two specifications of bentonite balls 19 are evenly mixed and filled.

[0089] Example 2: When a 5mm:7mm=2:1 mixing ratio is required, all grooves 201 of the first dispensing roller are kept open, and half of the grooves 201 of the second dispensing roller are blocked. The feeding rate ratio is 2:1, and the corresponding mixing ratio is finally achieved for backfilling.

[0090] Example 3: When only a single specification of material is required, only add bentonite balls 19 to the receiving cavity 1741 corresponding to the target specification, and do not add any balls to the other receiving cavities 1741.

[0091] The specific method for backfilling particle by particle in S6 is as follows:

[0092] S61, the guide component 16 is sleeved and installed on the pressure measuring tube 1 and positioned at the designated position; specifically, the sleeve 161 of the guide component 16 is sleeved from the top of the pressure measuring tube 1 and slowly lowered to the designated position, and several first set screws 165 in the circumferential direction of the sleeve 161 are rotated so that the inner end of the set screw tightly abuts against the outer wall of the pressure measuring tube 1, thereby achieving a firm fixation of the guide component 16.

[0093] S62, the feeding component 17 is sleeved on the pressure measuring tube 1 via the annular guide rail 171, and the feeding component 16 is connected to the feeding component 17 via the conveying tube 177; specifically, the annular guide rail 171 of the feeding component 17 is sleeved from the top of the pressure measuring tube 1 and lowered to a preset height above the feeding component 16, and several second set screws 173 in the circumferential direction of the inner cylinder 172 are rotated to achieve a stable fixation of the annular guide rail 171 in the same way as the first set screw 165, ensuring that there is no loosening or offset after installation;

[0094] S63, pour the bentonite balls 19 into the receiving cavity 1741 of the box 174; if it is a single specification backfill, pour a sufficient amount of bentonite balls 19 of the corresponding specification directly into the receiving cavity 1741 of the box 174; if it is a mixed specification backfill, pour the bentonite balls 19 of the corresponding specification into the corresponding receiving cavity 1741 respectively, and adjust the feeding amount of the corresponding material distribution roller 20.

[0095] S64, start the first motor 175 and the second motor 1761, the box 174 moves circumferentially along the annular guide rail 171, and at the same time the material distribution roller 20 rotates to realize intermittent material feeding, and the bentonite balls 19 are conveyed along the conveying pipe 177; the first motor 175 drives the material distribution roller 20 to realize intermittent material feeding, and the second motor 1761 drives the drive wheel 176 to drive the box 174 to move circumferentially along the annular guide rail 171 to ensure that the material is fully covered.

[0096] S65, the conveying pipe 177 moves circumferentially with the box 174. During this process, the conveying pipe 177 pulls the turntable 164 to rotate, and the end of the conveying pipe 177 slides along the circumferential side wall of the fixed plate 162. The uneven interface enables the end of the conveying pipe 177 to swing left and right, forming a composite material laying trajectory of circumferential rotation and left and right swing. After the bentonite ball 19 is conveyed to the end through the conveying pipe 177, it is evenly scattered into the annular gap between the pressure measuring pipe 1 and the hole wall under the action of the composite trajectory, realizing full-section filling without dead corners.

[0097] It should be noted that a layered backfilling method is used. After filling one layer, the machine is stopped, and it is gently compacted with a light tamping rod before restarting to fill the next layer, until the designed backfilling height is reached. After backfilling to the designed height, the machine is stopped, the power is disconnected, and the parts are disassembled.

[0098] Application results:

[0099] This invention employs a matching filler to achieve the one-by-one backfilling of bentonite balls 19. The second motor 1761 drives the box 174 to move circumferentially, and the material distribution roller 20 feeds intermittently. At the same time, the concave and convex interface of the fixed plate 162 enables the end of the conveying pipe 177 to swing left and right, ensuring that the bentonite balls 19 are evenly distributed in the full cross-sectional gap between the pressure measuring pipe 1 and the hole wall. This achieves uniform backfilling of the entire cross-section of the bentonite balls 19, eliminates sealing dead corners, solves the problem of easy accumulation and void formation in traditional backfilling, and improves the reliability of sealing.

[0100] The filler adopts a detachable sleeve design and can be quickly positioned and fixed by a top screw, adapting to different specifications of pressure testing tubes 1; the groove 201 of the material distribution roller 20 can be sealed by the cap 202 to adjust the material feeding amount, adapting to the filling needs of different geological conditions; its structure is simple and compact, and it can achieve automatic particle-by-particle backfilling through motor drive, which reduces the intensity of manual labor and ensures the consistency of construction quality, adapting to the construction needs under complex dam foundation geological conditions.

[0101] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method for a dam foundation piezometer, characterized in that, include: S1, Survey and Design: Verify the geological survey data of the dam site, clarify the coordinates and elevation of the monitoring points, and determine the drilling depth (18), piezometer (1) layout density and protection requirements; S2, Drilling (18) Construction: Determine the hole position according to the design coordinates, use a drilling rig to drill the hole and monitor the verticality of the hole in real time, clean the slag in the hole after drilling, and keep the hole dry and clean; S3, Piezometer (1) Processing and Assembly: Process, manufacture and assemble piezometers (1) that meet the design requirements; S4, Pipe Lowering: First, backfill the bottom of the hole with the first filter material (6) and compact it as support, then lower the assembled piezometer (1) into the hole section by section, ensuring that the pipe body is straight; S5, Second Filter Material (7) Backfilling: Backfill the piezometer (1) and the hole The annular gap between the walls is filled with the second filter material (7) in layers to form a filter layer; S6, Bentonite balls (19) sealing: Bentonite balls (19) are backfilled in layers above the filter layer using a process of backfilling one by one to the design height. After backfilling, water is injected into the pipe to cause the bentonite balls (19) to disintegrate and expand, thus completing the sealing and forming the first flexible sealing layer (8); In S6, a filler is used to realize the process of backfilling one by one. The filler includes a feeding part (17) and a guiding part (16). The feeding part (17) includes an annular guide rail (171) that can be detachably sleeved on the pressure measuring pipe (1). A box (174) that can move in a circle along the annular guide rail (171) is provided on the annular guide rail (171); The box (174) is provided with at least one receiving cavity (1741) for storing bentonite balls (19), the receiving cavity (1741) has an opening at the bottom, and a distributing roller (20) adapted to be rotatably connected to the box body (174) is provided at the opening. The distributing roller (20) is driven to the output shaft of the first motor (175). The bottom of the box body (174) is connected to a conveying pipe (177) for conveying bentonite balls (19). The guide component (16) includes a fixed plate (162) detachably sleeved on the pressure measuring pipe (1). The fixed plate (162) has a plurality of evenly distributed bosses (163) along the circumference, so that its circumferential sidewall forms an uneven interface. The upper part of the fixed plate (162) can be A turntable (164) is rotatably connected, and one end of the conveying pipe (177) is connected to the side wall of the turntable (164). When the turntable (164) and the conveying pipe (177) rotate, the conveying pipe (177) can move circumferentially along the fixed plate (162), and swing left and right through the uneven interface during the circumferential movement. S7, Cement bentonite slurry sealing: Cement bentonite slurry is injected above the bentonite ball (19). After the cement bentonite slurry solidifies, it forms a second rigid anti-seepage layer (9), which, together with the first flexible sealing layer (8), forms a double anti-seepage system with flexible bottom and rigid top. S8, Sensitivity test: A sensitivity test is performed on the pressure measuring pipe (1) after installation and sealing.S9, Concrete pouring: Excavate a foundation pit on the dam slope around the pressure gauge (1), pour plain concrete into the foundation pit to form a cushion layer (10), then pour concrete on top of the cushion layer (10) to form a concrete base (11), and then backfill the foundation pit; S10, Installation of protective facilities: Install a protective box (13) on the concrete base (11).

2. The construction method of a dam foundation piezometer according to claim 1, characterized in that, The pressure measuring tube (1) includes a filter tube section (102) and a conduit section (101) connected to the top of the filter tube section (102). A bottom sealing plate (2) is welded to the bottom end of the pressure measuring tube (1). The filter tube section (102) has several filter holes (1021) on its tube wall. Several evenly distributed vertical ribs (3) are welded to the outer wall of the filter tube section (102) along the circumferential direction. The outer wall of the filter tube section (102) is wrapped with a first filter screen to form a first filter layer (5). The vertical ribs (3) are wrapped inside the first filter screen. The outer side of the first filter screen is wrapped with a second filter screen to form a second filter layer (4). Lead wires are wound around the outer wall of the second filter layer (4) at intervals to achieve tight fixation.

3. The construction method of a dam foundation piezometer according to claim 1, characterized in that, The cement-bentonite slurry described in S7 is injected to a depth of 1.0 to 2.0 m below the pipe opening.

4. The construction method of a dam foundation piezometer according to claim 1, characterized in that, The filter layer is filled to 1.0m above the top of the filter tube section (102) and not higher than the foundation surface.

5. The construction method of a dam foundation piezometer according to claim 1, characterized in that, The bentonite ball (19) has a diameter of 5-10 mm.

6. The construction method of a dam foundation piezometer according to claim 1, characterized in that, The material distribution roller (20) is provided with several sets of material grooves along the circumference. Each set of material grooves has several grooves (201) arranged at intervals. The grooves (201) are detachably connected with caps (202) for sealing the grooves (201).

7. The construction method of a dam foundation piezometer according to claim 6, characterized in that, The bottom of the fixed plate (162) is fixedly connected to a sleeve (161), and the sleeve (161) is threaded with a plurality of first set screws (165) along the circumferential direction on the sleeve wall.

8. The construction method of a dam foundation piezometer according to claim 7, characterized in that, The bottom of the housing (174) is connected to a second motor (1761), which drives a drive wheel (176) connected to it. The drive wheel (176) can move along the circumferential sidewall of the annular guide rail (171).

9. The construction method of a dam foundation piezometer according to claim 8, characterized in that, The specific method for backfilling particles in S6 is as follows: S61, the guide (16) is fitted onto the pressure measuring pipe (1) and positioned at the designated location; S62, the feeding device (17) is fitted onto the pressure measuring pipe (1) via the annular guide rail (171), and the guide (16) and feeding device (17) are connected as one unit using the conveying pipe (177); S63, the bentonite balls (19) are poured into the receiving cavity (1741) of the box (174); S64, the first motor (175) and the second motor (1761) are started, and the box (174) moves along the... The bentonite balls (19) are conveyed along the conveying pipe (177) by the circular guide rail (171) in a circumferential motion and the material distribution roller (20) rotates to achieve intermittent feeding. The conveying pipe (177) moves circumferentially with the box (174). During this process, the conveying pipe (177) pulls the turntable (164) to rotate, and the end of the conveying pipe (177) slides along the circumferential side wall of the fixed plate (162). The end of the conveying pipe (177) swings left and right through the uneven interface, thereby achieving uniform filling of the entire cross section of the bentonite balls (19).

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