Construction process of waterproof curtain meeting round gravel and pebble stratum

Abstract

The invention discloses a gravel and pebble stratum waterproof curtain construction technology, and particularly relates to the technical field of waterproof curtain construction, and the technology comprises the following steps: S1, site preparation, S2, rotary drilling rig hole guiding, S3, pile casing embedding, S4, backfilling and leveling, and S5, three-axis cement mixing pile construction. The rotary drilling rig is adopted to guide holes for construction, the problems that a three-shaft mixing pile machine for the round gravel and pebble bed cannot normally drill and collapses can be solved, the construction period is shortened, site pollution is reduced, the advantages are obvious, the penetrating power of the three-shaft mixing pile machine can be enhanced, and the construction efficiency is improved. The adverse effect that a waterproof curtain of the profile steel cement soil mixing pile cannot be closed due to the fact that a three-shaft mixing pile machine cannot drill normally is avoided, and cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of water-stop curtain construction, and more specifically to a water-stop curtain construction process for gravel and pebble strata. Background Art

[0002] In the field of construction engineering, the construction quality of water-stop curtains is crucial to ensure the safety and stability of underground projects. When the construction site encounters gravel and pebble formations, it brings great challenges to the construction of water-stop curtains. The traditional three-axis cement soil mixing pile curtain treatment method has many limitations under such geological conditions. Due to the high hardness of the gravel and pebble strata, the complex geological conditions and the many interlayers, the three-axis cement soil mixing pile machine often cannot drill normally when constructing in the ultra-thick gravel or pebble bearing layer, and it is difficult to drill to the designed curtain pile bottom elevation, thus failing to meet the effective pile length requirements of the curtain design. In addition, during the drilling process, problems such as hole collapse are prone to occur, which not only seriously affects the construction progress, but also poses a threat to construction quality and safety.

[0003] In order to solve these problems, the construction method of rotary drilling rigs was often used in the past. The specific operation was to bury the long casing after positioning and measuring the pile position. When the construction reached the groundwater level, water was added and the rotary drilling rig continued to drill. However, this method still has some shortcomings in practical application: 1. When the diameter of the three-axis cement-soil mixing pile is 850mm, the diameter of the rotary drilling rig's drilling bit needs to be 1000mm or 1200mm, and the drilling scheme is relatively simple, such as the skip drilling (drilling every other hole) construction method or continuous drilling (the distance between the two hole walls after the rotary drilling rig drills the holes is controlled at 400mm-500mm to ensure that the holes can be formed without collapse). These methods may not fully meet the construction requirements when facing complex geological conditions; 2. With the continuous development of construction projects, the performance requirements for water-stop curtains are becoming higher and higher. Traditional construction technology has certain limitations in improving water-stopping effects, enhancing pile strength and durability, and it is difficult to meet the needs of modern projects.

[0004] In view of the above situation, the present invention provides a water-stop curtain construction process for gravel and pebble strata. Summary of the invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a water-stop curtain construction process for gravel and pebble strata to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a water-stop curtain construction process for gravel and pebble formations, specifically comprising the following steps: S1. Site preparation: Before the three-axis cement soil mixing pile machine enters the site, the site should be carefully leveled, obstacles should be removed, and the site flatness deviation should be ensured to be no more than ±10cm; S2. Drilling with a rotary drilling rig: The rotary drilling rig is accurately placed at the predetermined position, with a positioning deviation of no more than ±5cm. A drill bit with a diameter of 1000mm-1200mm is used to drill the hole. In the gravel and pebble layer, the drilling speed is controlled at 1-3m / h, and the drilling rate is controlled at 0.5-1m / s. According to the pile top elevation and geological survey data, the drilling depth error is controlled within ±10cm; S3. Casing burial: a special steel casing is selected. The casing length is 6m-10m and the diameter is 10-20cm larger than the lead hole diameter. A spiral protrusion is set on the outer wall of the casing to increase the friction with the surrounding soil. The casing is slowly inserted into the hole by the vibration burial method until it reaches the designed depth. It is ensured that the top surface of the casing is 200-300mm above the ground and the verticality deviation does not exceed 1%. During the casing burial process, the pressure in the hole is balanced by injecting mud with a specific gravity of 1.1-1.3, and the mud viscosity is controlled at 18-25s. S4, backfill and leveling. After the hole is completed, use well-graded sand for backfilling. The fineness modulus of the sand is 2.3-3. After backfilling, the site is leveled again. The flatness deviation does not exceed ±5cm; S5. For the construction of three-axis cement soil mixing piles, move the three-axis cement soil mixing pile driver to the designated position for positioning and debugging. The verticality deviation of the pile driver shall not exceed 0.5%. Start the pile driver for mixing pile construction. During the construction process, the drilling speed shall be controlled at 0.5-1m / min, and the mixing speed shall be controlled at 60-100r / min. When encountering hard layers or pebbles, adjust the verticality of the drill rod and slowly drill to the designed pile bottom. The pile bottom deviation shall not exceed ±10cm. Finally, use an ultrasonic detector to monitor the integrity of the mixing pile in real time. The pile body defect rate shall not exceed 5%.

[0007] Preferably, in step S1, during the site preparation stage, a geological survey of the site is also performed, with the survey points spaced 10-20 m apart.

[0008] Preferably, in step S2, during the hole drilling process, sensors are used to monitor the stress conditions of the drill bit in real time, including torque and pressure, and the stability of the hole wall is monitored at the same time. The deformation of the hole wall shall not exceed 5 mm, and the relevant data is transmitted to the control system in real time.

[0009] Preferably, in step S2, when a rotary drilling rig is used to drill a hole, the control system automatically adjusts the drilling speed and the drill lifting rate of the drill bit according to real-time monitoring data to adapt to changes in the formation, and the adjustment range is ±10%.

[0010] Preferably, in step S3, a layer of anti-corrosion coating is applied on the inner wall of the casing, and the anti-corrosion coating is an epoxy resin coating with a coating thickness of 0.5-1 mm.

[0011] Preferably, in step S5, a polymer is added to the cement soil used in the construction of the triaxial cement soil mixing pile, wherein the polymer is polyacrylamide, and the addition amount is 0.5%-1% of the cement mass, so as to enhance the bonding strength and impermeability of the cement soil, the bonding strength is increased by 20%-30%, and the impermeability coefficient is reduced to 1×10 -7 -1×10 -8 cm / s. At the same time, nano-silicon dioxide is added in an amount of 0.5%-1% of the cement mass to further improve the strength and durability of cement soil.

[0012] Preferably, after the construction of the triaxial cement soil mixing pile is completed, a pumping test is carried out on the water-stop curtain. The pumping test lasts for 24-48 hours and the water level drop does not exceed 5m to verify the water-stop effect. The permeability coefficient shall not exceed 1×10 - 6 cm / s.

[0013] Technical effects and advantages of the present invention: 1. The present invention adopts a rotary drilling rig to lead holes for construction, which can solve the problem of the three-axis mixing pile machine being unable to drill normally and landslides in the round gravel and pebble layers, shorten the construction period, reduce site pollution, and has obvious advantages. It can also enhance the penetration of the three-axis mixing pile machine, solve the adverse effect of the failure of the three-axis mixing pile machine to drill normally, and cause the water-stop curtain of the steel-cement soil mixing pile to fail to close, thereby saving costs; 2. The present invention can automatically adjust the drilling speed and drilling rate of the drill bit and monitor the integrity of the pile body in real time through real-time monitoring and control system, so as to ensure the construction quality and reduce the defect rate of the pile body. It can adapt to various complex geological conditions, such as underground caves, cracks, high formation hardness, high groundwater level and high formation pressure, and has strong versatility. 3. The present invention adds high molecular polymer and nano-silicon dioxide to cement soil, which can enhance the cohesive force, anti-seepage performance, strength and durability of the cement soil, thereby improving the water-stopping effect of the water-stop curtain and reducing the permeability coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the overall flow chart of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] The present invention provides a water-stop curtain construction process for gravel and pebble strata, which specifically comprises the following steps: S1. Site preparation: S1.1. Before the three-axis cement soil mixing pile machine enters the site, the site should be carefully leveled, obstacles should be removed, and the site flatness deviation should be ensured to be within ±10cm; S1.2. Conduct geological survey on the site with a survey point spacing of 10-20m to fully understand the geological conditions of the site and provide a basis for subsequent construction.

[0017] It can be understood that this step ensures that the flatness of the site meets the requirements, provides good basic conditions for the entry and construction of the three-axis cement soil mixing pile machine, and avoids the pile machine tilting or construction instability due to the uneven site. At the same time, through geological survey, the geological conditions of the site are understood in detail, including the distribution of strata, the content and distribution of gravel and pebbles, groundwater level, etc., to provide an accurate basis for the formulation and adjustment of subsequent construction plans; Specifically, leveling the site can improve the safety and efficiency of construction, reduce the shaking and failure of the pile driver during construction, and ensure the smooth progress of construction. Geological surveys can help construction personnel predict problems that may be encountered during construction, such as underground caves and hard strata, so that they can take corresponding measures to prevent and solve them, ensuring the quality and progress of construction. For example, in the following Example 1, geological surveys revealed the presence of multiple underground caves and fissures on the site. Construction personnel were able to adjust the drilling speed and take casing reinforcement measures in a timely manner during the drilling process of the rotary drilling rig, thereby avoiding construction accidents. At the same time, appropriate construction parameters and materials were selected according to the geological conditions. For example, in the following Example 2, based on the fact that the stratum was hard and densely distributed, a drill bit with a diameter of 1200 mm was selected to improve the drilling efficiency, and the amount of polyacrylamide and nano-silica added to the cement soil was adjusted to further improve the performance of the cement soil and ensure the quality of the water-stop curtain.

[0018] S2, rotary drilling rig hole: S2.1. The rotary drilling rig shall be accurately placed at the predetermined position, with the positioning deviation not exceeding ±5cm; S2.2. Use a drill bit with a diameter of 1000mm-1200mm to drill holes. In the gravel and pebble layer, the drilling speed is controlled at 1-3m / h, and the drilling speed is controlled at 0.5-1m / s. According to the pile top elevation and geological survey data, the drilling depth error is controlled within ±10cm; S2.3. During the drilling process, use sensors to monitor the force of the drill bit in real time, including torque and pressure, and monitor the stability of the hole wall. The deformation of the hole wall shall not exceed 5mm, and the relevant data shall be transmitted to the control system in real time; S2.4. When using a rotary drilling rig to drill a hole, the control system automatically adjusts the drilling speed and drilling rate of the drill bit based on real-time monitoring data to adapt to changes in the formation, with an adjustment range of ±10%.

[0019] It can be understood that this step ensures the accuracy of the hole position by accurately placing the rotary drilling rig, laying the foundation for subsequent construction, and selecting a drill bit with a suitable diameter and controlling the drilling speed, drilling rate and hole depth error to adapt to the characteristics of round gravel and pebble formations to ensure the quality and efficiency of the hole. At the same time, the drill bit force and hole wall stability are monitored in real time through sensors, and the data is transmitted to the control system to achieve real-time monitoring and adjustment of the drilling process to ensure construction safety and quality. The drilling speed and drilling rate of the drill bit are automatically adjusted according to the real-time monitoring data to adapt to formation changes and avoid construction problems caused by uneven formations. Specifically: Precise drilling rig placement and positioning deviation control can ensure the accuracy of the hole location and reduce errors in subsequent construction. Reasonable drill bit diameter selection, drilling speed and drill lifting rate control, and hole depth error control can effectively penetrate the gravel and pebble formations and improve the success rate and quality of hole drilling. Real-time monitoring of drill bit stress and hole wall stability can timely detect potential problems, such as hole wall collapse, and take corresponding measures to prevent and solve them to ensure construction safety. The control system automatically adjusts the drilling speed and drilling rate of the drill bit, which can improve the adaptability and efficiency of construction and reduce construction delays and quality problems caused by stratum changes; For example, in the following embodiment 1, when encountering underground caves and cracks that cause the drill speed to slow down significantly, the control system automatically adjusts the drilling speed and the drill lifting rate, successfully overcomes the resistance, and reaches the required drilling depth. In the following embodiment 2, the formation changes are predicted in advance based on geological survey data, and the drilling speed and the drill lifting rate are adjusted in time to ensure the smooth progress and quality of the drilling.

[0020] S3. Casing installation: S3.1. Use a special steel casing with a length of 6m-10m and a diameter 10-20cm larger than the diameter of the lead hole. Set spiral protrusions on the outer wall of the casing to increase friction with the surrounding soil; S3.2. Use the vibration embedding method to slowly insert the casing into the hole until it reaches the designed depth, ensuring that the top surface of the casing is 200-300mm above the ground and the verticality deviation does not exceed 1%; S3.3, during the casing burial process, the pressure in the hole is balanced by injecting mud with a specific gravity of 1.1-1.3, and the mud viscosity is controlled at 18-25s; S3.4. A layer of anti-corrosion coating is applied on the inner wall of the casing. The anti-corrosion coating is an epoxy resin coating with a coating thickness of 0.5-1mm to extend the service life of the casing.

[0021] It can be understood that this step uses a special steel casing and sets spiral protrusions to increase the friction with the surrounding soil and improve the stability of the casing. The casing is buried to the designed depth through the vibration burial method to ensure that the position and verticality of the casing meet the requirements and prevent the hole collapse and pile position deviation. At the same time, mud with appropriate specific gravity and viscosity is injected to balance the pressure in the hole and prevent the hole wall from collapsing. An anti-corrosion coating is applied to the inner wall of the casing to extend the service life of the casing and reduce maintenance costs. Specifically: The design of special steel casing and spiral protrusions enhances the friction between the casing and the soil, making the casing more stable during the burial process, effectively resisting the pressure of the surrounding soil, and reducing the risk of casing sinking or displacement. The vibration burial method can ensure that the casing is slowly and steadily inserted into the hole to reach the designed depth, while controlling the height of the top surface of the casing above the ground and the verticality deviation, ensuring the installation quality of the casing and providing reliable protection for subsequent construction. The injection of mud with a specific gravity of 1.1-1.3 and a viscosity controlled at 18-25s can effectively balance the pressure in the hole, prevent the hole wall from collapsing, and ensure the stability and safety of the lead hole. The anti-corrosion coating on the inner wall of the casing can prevent the casing from being corroded during long-term use, thereby extending the service life of the casing, reducing maintenance costs, and ensuring the sustainability of the water-stop curtain construction.

[0022] For example, in the following Example 1, due to the existence of underground caves, part of the casing sank, and the stability of the casing was increased by pouring cement mortar around the casing. In the following Example 4, the burial quality of the casing was effectively improved by increasing the number and depth of spiral protrusions on the outer wall of the casing and adopting a double vibration burial method.

[0023] S4, backfilling and leveling: S4.1. After the hole is completed, use well-graded sand for backfilling, and the fineness modulus of the sand is 2.3-3; S4.2. After backfilling, the site shall be leveled again, with the leveling deviation not exceeding ±5cm.

[0024] It can be understood that this step uses well-graded sand for backfilling in order to fill the holes after the lead hole is drawn, ensure the density and stability of the site, and control the fineness modulus of the sand between 2.3-3, which helps to improve the quality and performance of the backfill soil. After backfilling, the site is leveled again to ensure that the flatness of the site meets the requirements and provide good basic conditions for the subsequent three-axis cement soil mixing pile construction. Specifically: Well-graded sand backfill can effectively fill holes, improve the density of the site, enhance the bearing capacity of the foundation, reduce settlement and uneven settlement, and the appropriate sand fineness modulus can ensure the permeability and stability of the backfill soil, avoiding groundwater leakage or soil deformation caused by backfill soil quality problems; Leveling the site can make the three-axis cement soil mixing pile machine more stable during the construction process, ensure the smooth progress of the construction, and improve the construction quality and efficiency. At the same time, the flatness deviation does not exceed the requirement of ±5cm, which can meet the requirements of subsequent construction for site flatness and ensure the construction quality of the water-stop curtain.

[0025] For example, in each of the following embodiments, the backfilling and leveling steps provide a stable foundation for the subsequent three-axis cement soil mixing pile construction, ensuring the smooth progress of the construction and the quality of the water-stop curtain.

[0026] S5. Construction of three-axis cement soil mixing piles: S5.1. Move the three-axis cement soil mixing pile driver to the designated location for positioning and debugging. The verticality deviation of the pile driver shall not exceed 0.5%; S5.2. Start the pile driver to carry out the mixing pile construction. During the construction process, the drilling speed is controlled at 0.5-1m / min, and the mixing speed is controlled at 60-100r / min. When encountering hard layers or pebbles, adjust the verticality of the drill rod and slowly drill to the designed pile bottom. The pile bottom deviation shall not exceed ±10cm; S5.3. Add a high molecular polymer to the cement soil used in the construction of triaxial cement soil mixing piles. The high molecular polymer is polyacrylamide, and the addition amount is 0.5%-1% of the cement mass to enhance the bonding strength and impermeability of the cement soil. The bonding strength is increased by 20%-30%, and the impermeability coefficient is reduced to 1×10 - 7 - 1×10 - 8 cm / s. At the same time, nano-silicon dioxide is added in an amount of 0.5%-1% of the cement mass to further improve the strength and durability of cement soil. S5.4. Use ultrasonic detector to monitor the pile body integrity of the mixing pile in real time. The pile body defect rate shall not exceed 5%.

[0027] It can be understood that this step accurately moves the three-axis cement soil mixing pile machine to the specified position, and performs positioning and debugging to ensure that the verticality deviation of the pile machine is within the allowable range, providing a good foundation for the construction of the mixing pile, controlling the drilling speed, mixing speed and pile bottom deviation, and ensuring that the construction quality of the mixing pile meets the design requirements. At the same time, high molecular polymers and nano-silicon dioxide are added to the cement soil to enhance the performance of the cement soil, improve the water-stopping effect and durability of the water-stopping curtain, and use an ultrasonic detector to monitor the integrity of the mixing pile body in real time, timely discover pile body defects, and ensure the quality of the water-stopping curtain. Specifically: The verticality deviation of the pile driver does not exceed 0.5%, which can ensure the verticality of the mixing pile, improve the stability and anti-seepage performance of the water-stop curtain, control the drilling speed and mixing speed, and ensure that the pile bottom deviation does not exceed ±10cm, which can effectively control the construction quality of the mixing pile and ensure the uniformity and strength of the pile body. Adding polyacrylamide can enhance the bonding force and anti-seepage performance of cement soil, reduce the anti-seepage coefficient, and improve the water-stopping effect of the water-stop curtain. Adding nano-silicon dioxide can further improve the strength and durability of cement soil and extend the service life of the water-stop curtain. Real-time monitoring by ultrasonic detectors can detect pile body defects in a timely manner, so that the pile body defect rate does not exceed 5%, ensuring the integrity and reliability of the water-stop curtain.

[0028] For example, in the following Example 1, by strictly controlling various parameters during the construction process, the final pile body defect rate is only 3%, which is lower than the prescribed 5%. In the following Example 2, by adjusting the amount of additives added to the cement soil, the performance of the cement soil is further improved, and the water-stopping effect is good.

[0029] S6. Pumping test: After the construction of the triaxial cement soil mixing pile is completed, the water-stop curtain is subjected to a pumping test. The pumping test lasts for 24-48 hours, and the water level drop does not exceed 5m to verify the water-stop effect. The permeability coefficient shall not exceed 1×10 - 6 cm / s.

[0030] It can be understood that this step tests the water-stopping effect of the water-stop curtain through a pumping test to ensure that it can effectively prevent groundwater infiltration. The duration of the pumping test and the water level drop, as well as the limit of the permeability coefficient, are specified in order to quantitatively evaluate the performance of the water-stop curtain and determine whether it meets the design requirements. Specifically: The pumping test can directly reflect the water-stopping ability of the water-stop curtain, timely discover possible leakage problems, and provide a basis for subsequent treatment and improvement. The pumping test lasting 24-48 hours can fully test the stability and reliability of the water-stop curtain over a period of time. The requirement that the water level drop does not exceed 5m can avoid adverse effects of excessive pumping on the surrounding environment. The permeability coefficient shall not exceed 1×10 -6 The limitation of cm / s ensures that the water-stop curtain has good anti-seepage performance and can effectively protect the safety of underground projects.

[0031] For example, in the following Example 2, after the pumping test, the permeability coefficient of the water-stop curtain is 8×10 -8 cm / s, far lower than the prescribed 1×10 -6 cm / s, the water-stopping effect is good. In the following Example 4, the pumping test time is extended to 48h to more accurately test the water-stopping effect. The water level drop of the water-stopping curtain is only 3m, and the permeability coefficient is 5×10 -8 cm / s, meeting the design requirements.

[0032] In combination with the above construction process content, the technical solution of the present application is applied to the following embodiments 1-5, specifically: Embodiment 1, In a specific site, the site is located in a mountainous area with a complex terrain and uneven distribution of gravel and pebble strata.

[0033] During the site preparation stage, through detailed geological surveys, it was found that there were multiple underground caves and fissures in the site. During the process of drilling holes with the rotary drilling rig, it encountered great resistance and the drilling speed of the drill bit was significantly slowed down. At this time, based on the real-time monitoring data, the control system automatically adjusted the drilling speed to 1m / h and the drill lifting rate to 0.5m / s, successfully overcoming the resistance and achieving the design depth of the drilling hole. During the casing burial process, due to the existence of underground caves, part of the casing sank. In order to solve this problem, the method of pouring cement mortar around the casing was adopted to increase the stability of the casing. During the construction of the three-axis cement-soil mixing pile, the drilling speed and mixing speed were strictly controlled. When encountering pebbles, the verticality of the drill rod was slowly adjusted to ensure the quality of the pile body. Finally, through monitoring by ultrasonic detectors, the pile body defect rate was only 3%, lower than the prescribed 5%.

[0034] Embodiment 2, At another site, the gravel and pebble formations were harder and more densely distributed.

[0035] When the rotary drilling rig is drilling a hole, a drill bit with a diameter of 1200mm is selected to improve drilling efficiency. During the drilling process, the formation changes are predicted in advance based on geological survey data. When encountering hard formations, the drilling speed is appropriately reduced to about 1.5m / h, and the drill lifting rate is controlled at 0.8m / s.

[0036] When burying the casing, special attention was paid to the verticality of the casing, and high-precision measuring instruments were used for monitoring to ensure that the verticality deviation did not exceed 1%. In the construction of three-axis cement-soil mixing piles, the amount of polyacrylamide added to the cement-soil was adjusted to 0.8% of the cement mass, and the amount of nano-silicon dioxide added was adjusted to 0.7% of the cement mass according to the actual situation, which further improved the performance of the cement-soil. After the pumping test, the permeability coefficient of the water-stop curtain is 8×10 -8 cm / s, far lower than the prescribed 1×10 - 6 cm / s, good water-stopping effect.

[0037] Embodiment 3, Construction was carried out at a site with a high groundwater level.

[0038] During the drilling process, sensors are used to monitor the stability of the hole wall in real time. When signs of deformation are found in the hole wall, drilling is stopped immediately and mud with a specific gravity of 1.3 is injected to stabilize the hole wall.

[0039] At the same time, advanced ultrasonic imaging technology is used to monitor and record the situation inside the hole in real time, providing accurate reference for subsequent construction.

[0040] During the construction of three-axis cement-soil mixing piles, an intelligent control system was used to automatically control and optimize parameters such as drilling speed and mixing speed, ensuring the stability of construction quality. In addition, the remote monitoring system was used to monitor the construction progress and quality in real time, achieving efficient remote management.

[0041] Embodiment 4, In a site with high ground pressure, in order to ensure the stability of the casing, the number and depth of spiral protrusions are increased on the outer wall of the casing, further increasing the friction with the surrounding soil; When burying the casing, a double vibration burying method was adopted, that is, a small vibration hammer was used to bury the casing initially, and then a large vibration hammer was used to bury the casing to the designed depth, which effectively improved the burying quality of the casing; After the construction of the triaxial cement-soil mixing pile was completed, the pumping test was carried out and the test time was extended to 48 hours to more accurately test the water-stopping effect. After the test, the water level of the water-stopping curtain dropped by only 3m, and the permeability coefficient was 5×10 -8 cm / s, meeting the design requirements.

[0042] Embodiment 5, The construction process of the present invention is compared with the traditional process.

[0043] In the same site, two different techniques were used to construct the water-stop curtain. When encountering gravel and pebble formations, the traditional technique had a slow construction progress and the pile quality was difficult to guarantee, requiring multiple repairs.

[0044] By adopting the construction process of the present invention, the construction progress is greatly improved due to the application of rotary drilling rigs and advanced monitoring technology, and the pile body has good integrity and does not need to be repaired. In terms of cost, although the construction process of the present invention has increased investment in materials and equipment, the overall cost is reduced by 10% due to the improvement in construction efficiency and quality assurance. In addition, through long-term monitoring of the water-stopping effect, it is found that the water-stopping curtain of the present invention is also significantly superior to the traditional process in terms of durability.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A water-stop curtain construction process for gravel and pebble formations, characterized by: The specific steps include: S1. Site preparation: Before the three-axis cement soil mixing pile machine enters the site, the site should be carefully leveled, obstacles should be removed, and the site flatness deviation should be ensured to be no more than ±10cm; S2. Drilling with a rotary drilling rig: The rotary drilling rig is accurately placed at the predetermined position, with a positioning deviation of no more than ±5cm. A drill bit with a diameter of 1000mm-1200mm is used to drill the hole. In the gravel and pebble layer, the drilling speed is controlled at 1-3m / h, and the drilling rate is controlled at 0.5-1m / s. According to the pile top elevation and geological survey data, the drilling depth error is controlled within ±10cm; S3. Casing burial: a special steel casing is selected. The casing length is 6m-10m and the diameter is 10-20cm larger than the lead hole diameter. A spiral protrusion is set on the outer wall of the casing to increase the friction with the surrounding soil. The casing is slowly inserted into the hole by the vibration burial method until it reaches the designed depth. It is ensured that the top surface of the casing is 200-300mm above the ground and the verticality deviation does not exceed 1%. During the casing burial process, the pressure in the hole is balanced by injecting mud with a specific gravity of 1.1-1.3, and the mud viscosity is controlled at 18-25s. S4, backfill and leveling. After the hole is completed, use well-graded sand for backfilling. The fineness modulus of the sand is 2.3-3. After backfilling, the site is leveled again. The flatness deviation does not exceed ±5cm; S5. For the construction of three-axis cement soil mixing piles, move the three-axis cement soil mixing pile driver to the designated position for positioning and debugging. The verticality deviation of the pile driver shall not exceed 0.5%. Start the pile driver for mixing pile construction. During the construction process, the drilling speed shall be controlled at 0.5-1m / min, and the mixing speed shall be controlled at 60-100r / min. When encountering hard layers or pebbles, adjust the verticality of the drill rod and slowly drill to the designed pile bottom. The pile bottom deviation shall not exceed ±10cm. Finally, use an ultrasonic detector to monitor the integrity of the mixing pile in real time. The pile body defect rate shall not exceed 5%.

2. The water-stop curtain construction process for gravel and pebble formations according to claim 1 is characterized by: In step S1, during the site preparation stage, a geological survey of the site is also conducted, with the survey points spaced 10-20m apart.

3. The water-stop curtain construction process for gravel and pebble formations according to claim 1 is characterized by: In step S2, during the hole-guiding process, sensors are used to monitor the stress conditions of the drill bit in real time, including torque and pressure, and the stability of the hole wall. The deformation of the hole wall must not exceed 5 mm, and the relevant data is transmitted to the control system in real time.

4. The water-stop curtain construction process for gravel and pebble formations according to claim 1 is characterized by: In step S2, when a rotary drilling rig is used to drill a hole, the control system automatically adjusts the drilling speed and drilling rate of the drill bit according to the real-time monitoring data to adapt to the changes in the formation, with an adjustment range of ±10%.

5. The water-stop curtain construction process for gravel and pebble formations according to claim 1 is characterized by: In step S3, a layer of anti-corrosion coating is applied on the inner wall of the casing, wherein the anti-corrosion coating is an epoxy resin coating with a coating thickness of 0.5-1 mm.

6. The water-stop curtain construction process for gravel and pebble formations according to claim 1 is characterized by: In step S5, a polymer is added to the cement soil used in the construction of the triaxial cement soil mixing pile. The polymer is polyacrylamide, and the addition amount is 0.5%-1% of the cement mass to enhance the bonding strength and impermeability of the cement soil. The bonding strength is increased by 20%-30%, and the impermeability coefficient is reduced to 1×10 -7 -1×10 -8 cm / s. At the same time, adding nano-silicon dioxide in an amount of 0.5%-1% of the cement mass can further improve the strength and durability of cement soil.

7. The water-stop curtain construction process for gravel and pebble formations according to claim 1 is characterized by: It also includes a pumping test on the water-stop curtain after the construction of the triaxial cement-soil mixing pile is completed. The pumping test lasts for 24-48 hours and the water level drop does not exceed 5m to verify the water-stop effect. The permeability coefficient shall not exceed 1×10 -6 cm / s.

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