Underwater high-pressure rotary jet grouting water stop construction method for rock-socketed cofferdam

Abstract

This invention discloses a method for underwater high-pressure jet grouting for sealing water in rock-embedded cofferdams. The method involves first driving a large-diameter steel casing, drilling holes to the bottom of the cofferdam using a rotary drilling rig, filling the holes with sand, removing the large-diameter steel casing, and then driving small-diameter interlocking steel pipe piles. High-pressure jet grouting is then applied to the outside of the interlocking steel pipe piles for curing. This process further enhances the water-stopping performance of the sand body through the grout, and the two components blend together to form a strong water-stopping curtain, effectively improving the bearing capacity of the cofferdam foundation and the water-stopping effect. This method avoids the difficulty of ensuring effectiveness with traditional underwater concrete sealing and eliminates the need for expensive concrete, thus saving significant construction costs.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, and in particular to a method for underwater high-pressure jet grouting and water-stopping construction of rock-embedded cofferdams. Background Technology

[0002] The western branch cable-stayed bridge of the Nanchang Yangzizhou Ganjiang River Highway-Railway Bridge is a steel box girder composite cable-stayed bridge. The overburden layer on the surface of the main pier abutment consists of fine sand, silty clay, and silty clay. The bedrock of the abutment is weakly weathered calcareous sandstone, weakly weathered argillaceous sandstone, and weakly weathered conglomerate. According to actual measurements, the bedrock strength is not less than 30 MPa. The abutment is 5 meters high, with some areas entirely embedded in the bedrock, making the construction of the cofferdam and abutment difficult. Due to the different geological environment, the traditional underwater concrete sealing method has proven ineffective in ensuring water tightness based on practical experience from multiple projects, resulting in insufficient structural safety. Furthermore, the relatively high cost of concrete increases the overall cost.

[0003] Therefore, to address the above shortcomings, it is necessary to provide a method for underwater high-pressure jet grouting and water-stopping construction of rock-embedded cofferdams. Summary of the Invention

[0004] The purpose of this invention is to provide a method for underwater high-pressure jet grouting for water stoppage in rock-embedded cofferdams, which solves the problem that traditional underwater concrete sealing of rock-embedded cofferdams cannot meet the current water stoppage safety requirements in cofferdam construction.

[0005] This invention is implemented as follows:

[0006] A method for underwater high-pressure jet grouting for sealing water in a rock-embedded cofferdam, characterized by the following steps:

[0007] Ⅰ. Drive a large-diameter steel casing to the top of the rock layer along the design location of the cofferdam. Drill inside the steel casing to the bottom of the cofferdam using a rotary drilling rig and fill it with sand until it is level with the top of the rock layer. Pull out the steel casing and then drive small-diameter interlocking steel pipe piles into the sand.

[0008] II. After the interlocked steel pipe piles are driven into place, grouting holes are drilled around the outer side of the interlocked steel pipe piles using the drill rod of the grouting machine. The distance between two adjacent grouting holes of the interlocked steel pipe piles on the straight side of the cofferdam shall not exceed 80cm, and the distance between two adjacent grouting holes of the interlocked steel pipe piles at the four corners of the cofferdam shall not exceed 60cm.

[0009] Ⅲ. After the drill rod of the grouting machine is inserted to the predetermined depth, high-pressure water and low-pressure air are simultaneously sprayed from bottom to top using the double-pipe method. The high-pressure water jet and airflow are coaxially sprayed to cut the soil. The pressure of the high-pressure water jet is greater than 20MPa.

[0010] IV. Simultaneously, cement grout is injected through the drill rod of the grouting machine to fill the voids, wherein: the grout overflow is controlled at 10% to 25%, the grouting radius is 40cm, and the grouting height is the distance from the design elevation of the cofferdam bottom to the design elevation of the pier bottom; after the cement grout solidifies, the compressive strength of the mixed soil layer is greater than or equal to 1MPa.

[0011] As a further explanation of the present invention, preferably, in step II, the deviation between the actual position of the grouting hole and the designed hole position is no more than 50 mm, and the verticality deviation of the drill rod is less than 1%.

[0012] As a further explanation of the present invention, preferably, in step II, the grouting machine is placed on the grouting hole position precisely measured on site, so that the drill bit is aligned with the center of the hole position. The grouting machine includes a machine base, a clamping part, and a hydraulic cylinder. The machine base has a three-layer structure. The upper two layers of the machine base are connected to the upper and lower ends of the fixed part of the hydraulic cylinder. The top surface of the lower layer of the machine base is fixedly connected to the telescopic part of the hydraulic cylinder. The bottom surface of the lower layer of the machine base is fixed on the trestle. The clamping part is rotatably connected to the upper two layers of the machine base. The clamping part is hydraulically driven to rotate the drill rod. Four hydraulic cylinders are fixed on the machine base to move the machine base and the drill rod downward or upward. By intermittently moving the machine base up and down, continuous downward drilling and the removal of the drill bit and drill rod can be achieved.

[0013] As a further explanation of the present invention, preferably, in step II, a calibrator is mounted on the machine tool. The calibrator includes a bracket, suspension ropes, a support, and gyroscopes. The bottom ring of the truncated circular bracket is fixedly connected to the top of the machine tool. Four suspension ropes are distributed in a ring-like pattern at intervals. One end of each suspension rope is fixed to the bottom of the top ring of the bracket. The annular support is located inside the bracket and fixed to the other end of the suspension ropes. A bearing is inserted into the middle of the support, and the inner ring of the bearing abuts against the drill rod. Two gyroscopes are symmetrically fixed on the supports on both sides of the drill rod to balance the weight distribution. The calibrator contacts the drill rod and is connected to the hydraulic cylinders so that the extension and retraction of the four hydraulic cylinders are different.

[0014] As a further explanation of the present invention, preferably, in step II, before grouting, grouting experiments should be conducted using no less than 3 interlocking steel pipe piles, and no less than 4 sets of tests should be performed to confirm the performance indicators and mechanical parameters of the grout, the arrangement of grouting holes, the radius of the grout, the indicators of the filling material, and the feasibility of the sand grouting and water-stopping scheme.

[0015] As a further explanation of the present invention, preferably, in step II, the grouting material is cement slurry, and the mixing ratio of the cement slurry is: cement: water: early strength agent = 1:1:0.01, and the cement is silicate cement. The specific gravity of the cement slurry is 1.5 to 1.6, and the specific gravity of the returned grout is 1.2 to 1.3.

[0016] As a further explanation of the present invention, preferably, in step II, the rotation and lifting of the drill rod are continuous and uninterrupted, and when the drill rod is disassembled and jet grouting continues, the overlap length of the drill rod is not less than 300mm.

[0017] As a further explanation of the present invention, preferably, in step III, after the drill rod enters the predetermined depth, it is rotated and sprayed at the bottom of the lock-joint steel pipe pile for 1 minute, and then rotated, lifted and sprayed simultaneously. The construction sequence is to spray grout first, then rotate and lift.

[0018] As a further explanation of the present invention, preferably, in step III, the rotation speed of the drill rod is 8-10 r / min, the lifting speed of the drill rod is 0.05-0.15 m / min, and the grouting flow rate of the drill rod is 100-150 L / min.

[0019] The above-described technical solution of the present invention has the following advantages:

[0020] This invention involves first driving in a large-diameter steel casing, drilling holes to the bottom of the cofferdam using a rotary drilling rig, filling the hole with sand, removing the large-diameter steel casing, and then driving in small-diameter interlocking steel pipe piles. The outer side of the interlocking steel pipe piles is then cured by high-pressure jet grouting. This process further enhances the water-stopping performance of the sand body, and the two work together to form a strong water-stopping curtain, effectively improving the bearing capacity and water-stopping effect of the cofferdam foundation. This avoids the difficulty of ensuring water-stopping effectiveness with traditional underwater concrete sealing and eliminates the need for expensive concrete, thus saving significant construction costs. Attached Figure Description

[0021] Figure 1 This is a construction flowchart of the present invention;

[0022] Figure 2 This is a diagram showing the location of the high-pressure jet grouting holes in this invention;

[0023] Figure 3 This is a partial top view of the grouting machine of the present invention;

[0024] Figure 4 This is a partial bottom view of the grouting machine of the present invention;

[0025] In the diagram: 1. Grouting machine; 11. Machine platform; 12. Clamping part; 13. Hydraulic cylinder; 14. Drill rod; 2. Calibrator; 21. Support; 22. Lifting rope; 23. Support platform; 24. Gyroscope; 25. Bearing; 3. Grouting hole; 4. Locking steel pipe pile; 5. Sand. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] A method for underwater high-pressure jet grouting and water-stopping construction of rock-embedded cofferdams, combined with Figure 1 This includes the following steps:

[0028] I. Drive a large-diameter steel casing to the top of the rock layer along the design location of the cofferdam. Drill inside the steel casing using a rotary drilling rig to the bottom of the cofferdam and fill it with sand 5 until it is flush with the top of the rock layer. Pull out the steel casing and then drive a small-diameter interlocking steel pipe pile 4 into the sand 5. The purpose of the rotary drilling is to replace the bedrock at the bottom of the cofferdam with sand 5 and to allow the drill rod 14 of the grouting machine 1 to be inserted into the sand 5 later.

[0029] II. Combination Figure 2 After the interlocked steel pipe pile 4 is driven into place, several grouting holes 3 are arranged circumferentially around the interlocked steel pipe pile 4. The grouting machine 1 is placed on the grouting hole 3 at the position precisely measured on site, so that the drill rod 14 is aligned with the center of the grouting hole 3. The actual position of the drill rod 14 of the grouting machine 1 deviates from the designed hole position by no more than 50mm, and the verticality of the drill rod 14 is less than 1%. The grouting machine 1 includes a machine base 11, a clamping part 12, and a hydraulic cylinder 13. The machine base 11 has a three-layer structure, with the upper two layers of the machine base 11 connected to the hydraulic cylinder 13. The upper and lower ends of the fixed part of the pressure cylinder 13, the top surface of the lower layer of the machine platform 11 and the telescopic part of the hydraulic cylinder 13 are fixedly connected, the bottom surface of the lower layer of the machine platform 11 is fixed on the trestle, the clamping part 12 is rotatably connected in the upper two layers of the machine platform 11, the clamping part 12 is hydraulically driven to make the drill rod 14 rotate, and four hydraulic cylinders 13 are fixed on the machine platform 11 to make the machine platform 11 and the drill rod 14 move downward or upward. By intermittently moving the machine platform 11 up and down, continuous downward drilling and pulling out of the drill bit and drill rod 14 can be achieved.

[0030] Combination Figure 3 , Figure 4Since the drill rod 14 can be up to 20m long, the grouting machine 1 must be installed and positioned accurately, horizontally, and stably. To ensure that the borehole achieves the verticality required by the design, the grouting machine 1 must be horizontally corrected after it is in place, so that the axis of the drill rod 14 of the grouting machine 1 is vertically aligned with the center of the borehole. Therefore, a calibrator 2 is mounted on the machine base 11. The calibrator 2 includes a bracket 21, a suspension rope 22, a support 23, and a gyroscope 24. The bottom ring of the frustum-shaped bracket 21 is fixedly connected to the top of the machine base 11. Four suspension ropes 22 are distributed in a ring at intervals. One end of the suspension rope 22 is fixed to the bottom of the top ring of the bracket 21. The annular support 23 is located inside the bracket 21 and is fixed to the other end of the suspension rope 22. A bearing 25 is inserted in the middle of the support 23, and the inner ring of the bearing 25 abuts against the drill rod 14. Two gyroscopes 24 are symmetrically fixed on the supports 23 on both sides of the drill rod 14 to balance the weight distribution.

[0031] If the drill rod 14 deviates during drilling of the grouting hole 3, the support 23 will also tilt. At this time, the gyroscope 24 outputs data to the control system, which then controls the hydraulic cylinder 13 to move until the gyroscope 24 reading is normal. Having two gyroscopes 24 not only keeps the support 23 stable but also provides dual detection, improving detection quality. Meanwhile, the calibrator 2 has a simple structure, low manufacturing cost, and is applicable to grouting machines 1 and drill rods 14 of different specifications.

[0032] After the drill rod 14 is in place, the verticality of the drill rod 14 in two different directions of the grouting machine 1 is corrected. Based on the data detected by the gyroscope 24, if any deviation occurs, the control system controls the four hydraulic cylinders 13 to extend or retract by different lengths to adjust the downward drilling direction of the machine body 11, thereby adjusting the movement direction of the drill bit and ensuring that the verticality error of the drilled hole does not exceed 1%.

[0033] The grouting material is cement slurry, and the mix ratio of cement:water:early strength agent = 1:1:0.01. The water-cement ratio of the cement slurry is 1.0, the specific gravity of the cement slurry is 1.5-1.6, and the specific gravity of the returned slurry is 1.2-1.3. The cement slurry should be stirred within 1 hour before rotary spraying, and the standing time of the cement slurry should not exceed 4 hours. The cement used is 42.5 ordinary Portland cement.

[0034] Before grouting, grouting tests must be conducted using no fewer than three interlocked steel pipe piles 4, with no fewer than four sets of tests to confirm the performance indicators and mechanical parameters of the grout, the arrangement of the grouting holes 3, the radius of the grout, the indicators of the filling material, and the feasibility of the sand grouting and water-stopping scheme.

[0035] Ⅲ. After the drill rod 14 is inserted to the predetermined depth, a test spraying is carried out first; after spraying for 1 minute while rotating at the bottom of the lock steel pipe pile 4, high-pressure water and low-pressure air are sprayed while rotating, lifting and spraying from bottom to top. The high-pressure water jet and airflow are coaxially sprayed to cut the soil. The pressure of the high-pressure water jet should be greater than 20 MPa to form larger pores.

[0036] IV. Cement grout is injected into drill rod 14 to fill the gaps. During the rotary jetting process, the amount of grout overflowing from the injection hole 3 should be controlled between 10% and 25%. During grouting, the initial setting time of cement grout, cement grout flow rate, cement grout pressure, rotary lifting speed, water pressure, water flow rate, and air pressure and air flow rate should be checked at any time to ensure they meet the design and specification requirements, and records should be kept at all times.

[0037] The rotation and lifting of drill rod 14 must be continuous and uninterrupted. When disassembling drill rod 14 to continue jet grouting, the overlap length of drill rod 14 shall not be less than 300mm. The rotation speed of drill rod 14 shall be 8-10r / min, the lifting speed of drill rod 14 shall be 0.05-0.15m / min, the grouting flow rate of drill rod 14 shall be 100-150L / min, the grouting radius shall be 40cm, and the grouting height shall be the distance from the design elevation of the cofferdam bottom to the design elevation of the pier bottom. After the cement grout has solidified, the compressive strength of the mixed soil layer shall be greater than or equal to 1MPa.

[0038] After the construction is completed, the machine is stopped. When stopping the machine, first turn off the high-pressure water and compressed air, and then stop the grouting. Finally, clean the drill rod 14 and other equipment. No cement grout should remain in the drill rod 14. Then move the grouting machine 1 to a new position.

[0039] To verify the feasibility of the above scheme, a grouting platform was constructed using four φ600mm pipe piles, H500 steel sections, and a steel bridge deck. Three arc-shaped steel plates with a diameter of 1.6m and a center-to-center distance of 1.24m were fabricated to simulate the pilot hole trench. Three 1m steel casings and I-20 steel pipe piles were used to replace the interlocking steel pipe piles. The cement grout mix ratio was cement:water:early strength agent = 1:1:0.01, the grout specific gravity was tested on-site and found to be 1.5–1.6, and the cement grout mixing time was ≥180s. The planar position of grouting hole 3 was marked on the grouting platform, and a 10×10cm grouting hole 3 was drilled. The deviation between the position of grouting hole 3 and the designed hole position was ≤50mm. The first interlocked steel pipe pile 4 has 6 grouting holes 3 arranged circumferentially with a hole spacing of no more than 60cm. The second and third interlocked steel pipe piles 4 have 4 grouting holes 3 arranged circumferentially with a hole spacing of no more than 80cm. There are a total of 4 rows of grouting holes 3 in the test. The drilling sequence is carried out according to the alternating hole construction of each row.

[0040] Grouting then commenced. The lifting speed of drill rod 14 was controlled at ≤10cm / min, and its rotational speed was controlled at ≤10r / min. During the test, each of the eight grouting holes 3 on one side was grouted three times, and each grouting hole 3 on the other side was grouted twice. Cement grout samples were taken during the test, and one set of test blocks was retained.

[0041] Analysis showed that the cement grout and sand 5 could form a uniform mixture after the test parameters. Compressive strength tests were conducted on the test blocks at 3 and 5 days, with values ​​of 7.5 MPa and 12.6 MPa, respectively. Furthermore, when grouting at 28 MPa pressure, the effective grouting radius exceeded 0.4 m, and the effective grouting range of adjacent grouting holes 3 overlapped by more than 0.1 m. In actual construction, the straight-edge interlocking steel pipe piles 4 of the cofferdam can be grouted at 80 cm intervals. Considering the extreme deviation of the interlocking steel pipe piles 4, in actual construction, grouting holes 3 spaced at 60 cm intervals at the four corners of the cofferdam are sufficient to meet the construction requirements.

[0042] Through the above experiments, after the interlocked steel pipe pile 4 was driven into place, sand 5 was injected into the outside of the interlocked steel pipe pile 4, and high-pressure jet grouting was carried out. This made the high-pressure jet grouting section and sand 5 form a composite reinforcement zone. With the high grouting pressure, the cement grout diffused into veins in the sand 5, forming an irregular vein-like solidified material. Combined with the sand 5 compacted by the pressure of the cement grout and the soil unaffected by grouting, the composite foundation formed can make the compressive strength of the mixed soil layer after grouting ≥1MPa, which improves the bearing capacity of sand 5 and further improves the water-stopping ability at the bottom of the interlocked steel pipe pile 4.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for underwater high-pressure jet grouting and water-stopping construction of a rock-embedded cofferdam, characterized in that: Includes the following steps: Ⅰ. Drive a large-diameter steel casing to the top of the rock stratum along the design location of the cofferdam. Drill inside the steel casing to the bottom of the cofferdam using a rotary drilling rig and fill it with sand until it is level with the top of the rock stratum. Pull out the steel casing and then drive a small-diameter interlocking steel pipe pile to the sand filling location. II. After the interlocking steel pipe piles are driven into place, the grouting machine is placed at the precisely measured grouting hole position on site, aligning the drill bit with the center of the hole. The grouting machine includes a platform, a clamping unit, and hydraulic cylinders. The platform has a three-layer structure; the upper two layers are connected to the upper and lower ends of the fixed part of the hydraulic cylinders, the top surface of the lower layer is fixedly connected to the telescopic part of the hydraulic cylinders, and the bottom surface of the lower layer is fixed to a trestle. The clamping unit is rotatably connected to the upper two layers of the platform and is hydraulically driven to rotate the drill rod. Four hydraulic cylinders are fixed to the platform to move the platform and drill rod downwards or upwards. Intermittent up-and-down movement of the platform allows for continuous downward drilling and the extraction of the drill bit and drill rod. A calibrator is mounted on the platform, including a bracket and a suspension system. The system consists of ropes, supports, and gyroscopes. The bottom ring of a truncated circular support is fixedly connected to the top of the machine platform. Four suspension ropes are arranged in a ring at intervals, with one end of each rope fixed to the bottom of the top ring of the support. The annular support is located inside the support and fixed to the other end of each rope. A bearing is inserted in the middle of the support, with the inner ring of the bearing abutting against the drill rod. Two gyroscopes are symmetrically fixed on the supports on both sides of the drill rod to balance the weight distribution. A calibrator contacts the drill rod and is connected to the hydraulic cylinders to ensure that the extension and retraction of the four hydraulic cylinders are different. Grouting holes are drilled circumferentially on the outer side of the interlocking steel pipe piles using the drill rod of a grouting machine. The distance between two adjacent grouting holes of the interlocking steel pipe piles on the straight side of the cofferdam is no more than 80cm, and the distance between two adjacent grouting holes of the interlocking steel pipe piles at the four corners of the cofferdam is no more than 60cm. Ⅲ. After the drill rod of the grouting machine is inserted to the predetermined depth, high-pressure water and low-pressure air are simultaneously sprayed from bottom to top using the double-pipe method. The high-pressure water jet and airflow are coaxially sprayed to cut the soil. The pressure of the high-pressure water jet is greater than 20MPa. IV. Simultaneously, cement grout is injected through the drill rod of the grouting machine to fill the voids. The rotation speed of the drill rod is 8-10 r / min, the lifting speed is 0.05-0.15 m / min, and the grouting flow rate is 100-150 L / min. The rotation and lifting of the drill rod are continuous and uninterrupted. When disassembling the drill rod to continue grouting, the overlap length of the drill rod is not less than 300 mm. The mixing ratio of the cement grout is: cement: water: early strength agent = 1:1:0.01, and silicate cement is used. The specific gravity of the cement grout is 1.5-1.6, and the specific gravity of the returned grout is 1.2-1.

3. The grout overflow is controlled at 10%-25%, the grouting radius is 40 cm, and the grouting height is the distance from the design elevation of the cofferdam bottom to the design elevation of the pier bottom. After the cement grout solidifies, the compressive strength of the mixed soil layer should be greater than or equal to 1 MPa.

2. The underwater high-pressure jet grouting method for sealing a rock-embedded cofferdam according to claim 1, characterized in that: In step II, the actual position of the grouting hole deviates from the designed hole position by no more than 50 mm, and the verticality deviation of the drill rod is less than 1%.

3. The underwater high-pressure jet grouting method for sealing a rock-embedded cofferdam according to claim 1, characterized in that: In step II, before grouting, grouting tests must be conducted using no fewer than three interlocked steel pipe piles, with no fewer than four sets of tests to confirm the performance indicators and mechanical parameters of the grout, the arrangement of grouting holes, the radius of the grout, the indicators of the filling material, and the feasibility of the scheme of grouting the inner side and filling only sand on the outer side.

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