An auxiliary construction device and a construction method of a cast-in-place pile based on a ball hole expansion theory

Abstract

The application relates to the technical field of cast-in-place piles and discloses an auxiliary construction device and a construction method for cast-in-place piles based on a spherical cavity expansion theory, which comprise a support steel beam for supporting a reinforcement cage and a support frame which can be supported around a casing. The auxiliary construction device and the construction method for cast-in-place piles based on the spherical cavity expansion theory are characterized in that a first reinforcement cage provided with a grouting capsule is hung and placed into a hole pile foundation well, the first reinforcement cage partially extends to the casing, the support steel beam passes below the stirrup of the first reinforcement cage and bears on the cross beam, the first reinforcement cage is located above the casing mouth, a taking-and-placing assembly moves a sleeve to the main reinforcement of the first reinforcement cage, a lengthened reinforcement cage is hoisted and connected to the position of the main reinforcement of the first reinforcement cage, the main reinforcement of the lengthened reinforcement cage is inserted into the inside of the sleeve, a welding gun heats and welds the sleeve, the support steel beam is removed, the connected first reinforcement cage and lengthened reinforcement cage are continuously lowered, and the lengthened reinforcement cage is continuously installed, so that the reinforcement cage is conveniently installed.

Description

Technical Field

[0001] This invention relates to the field of cast-in-place pile technology, specifically to an auxiliary construction device and construction method for cast-in-place piles based on the ball hole expansion theory. Background Technology

[0002] The spherical hole expansion theory is mainly used to describe and simulate the expansion process of spherical holes in soil or rock. The spherical hole expansion theory considers the structure of the soil, the influence of the internal friction angle, as well as the strain softening characteristics and shear dilatation of the soil during the expansion process. These characteristics make the spherical hole expansion theory highly accurate and practical in analyzing the structural damage or degradation, stress changes and stress field around the hole in the soil during the expansion process.

[0003] As an important foundation type, the construction quality of bored piles based on the spherical borehole expansion theory directly affects the safety and stability of the entire project. During the installation of the reinforcing cage, multiple sections need to be joined together to reach the depth of the pile foundation well. These sections are then fully welded before hoisting. Excessive length of the reinforcing cage makes vertical hoisting into the pile foundation well difficult. Furthermore, the construction of bored piles easily generates sediment at the pile bottom and mud skin on the pile side. The presence of these sediments and mud skin reduces the normal stress between the pile and the soil, and the lubricating effect of the mud skin reduces the ultimate shear stress between the pile and the soil, thus lowering the ultimate bearing capacity of the pile. This necessitates compensating by increasing the pile length, diameter, or number of piles, which not only increases material consumption, construction difficulty, and project cost, but also prolongs the construction period. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an auxiliary construction device and method for cast-in-place piles based on the theory of spherical hole expansion, thus solving the problems mentioned in the background.

[0005] The present invention provides the following technical solution: an auxiliary construction device for cast-in-place piles based on the theory of spherical hole expansion, comprising: a supporting steel beam for supporting the reinforcing cage and a bracket that can be supported around the casing;

[0006] The reinforcing cage includes a first section and an extension section. The first section and the extension section, as well as adjacent extension sections, are connected by sleeves.

[0007] The top center of the support has a cylindrical groove for the steel cage to pass through. A crossbeam is provided on the support. The supporting steel beam passes under the stirrups of the steel cage and rests on the crossbeam. The support is provided with a pick-and-place assembly for installing sleeves. The pick-and-place assembly is provided with a welding torch for welding the sleeves to the connection between the main reinforcement of the first section of the steel cage and the main reinforcement of the extension section of the steel cage, as well as the connection between the main reinforcement of the adjacent extension section of the steel cage.

[0008] Preferably, the bracket has a insert shaft for placing the sleeve on one side of the cylindrical groove.

[0009] Preferably, there are multiple insertion shafts and pick-and-place components, all of which are evenly distributed in a circular array along the circumference of the cylindrical groove, and the positions of the multiple insertion shafts and pick-and-place components correspond to the positions of the main reinforcement bars of the steel cage.

[0010] Preferably, the pick-and-place assembly includes a longitudinal cylinder, a radial cylinder, and a connecting block. The longitudinal cylinder is mounted on the top of the bracket, the radial cylinder is mounted on the telescopic end of the longitudinal cylinder, and the connecting block is mounted on the telescopic end of the radial cylinder. The connecting block is provided with a magnet that can attract the sleeve. The surface of the magnet is provided with an arc-shaped groove, and the inner wall of the arc-shaped groove is adapted to the surface of the sleeve.

[0011] Preferably, a bracket is provided on the top of the connecting block, and the welding torch is mounted on the bracket;

[0012] Multiple annular welding wires are fixed inside the sleeve. When the welding gun heats the sleeve, the annular welding wires melt inside the sleeve.

[0013] A construction method for cast-in-place piles based on the theory of spherical borehole expansion includes the following steps:

[0014] Step S1: Mark out the center of the pile location and vertically lower the casing.

[0015] Step S2: Drill a hole for the pile foundation well along the center of the casing using a drilling rig;

[0016] Step S3: Install a grouting capsule on the reinforcing cage;

[0017] Step S4: Install the reinforcing cage into the pile foundation well, so that the grouting capsule is located at the bottom of the pile foundation well;

[0018] Step S5: Pressure grouting is performed inside the grouting capsule using the closed grouting method, causing it to expand into an enlarged head, which is suitable for compacting the surrounding soil layer.

[0019] Step S6: Use open grouting method to fill the hollow gaps in the pile foundation well with grout.

[0020] Preferably, step S4 includes the following steps;

[0021] Step S41, Install the grouting capsule and the first section of the reinforcing cage: Lift the first section of the reinforcing cage with the grouting capsule installed and put it into the pile foundation well, so that part of the first section of the reinforcing cage extends out of the casing.

[0022] Step S42: Set up a docking auxiliary construction device around the casing: the supporting steel beam can pass under the stirrups of the first section of the steel cage and rest on the crossbeam, so that the first section of the steel cage is located above the casing opening;

[0023] Step S43, hoisting the extension section of the steel cage: the take-up and put-down assembly moves the sleeve to the main reinforcement of the first section of the steel cage, hoists the extension section of the steel cage to the position of the main reinforcement of the first section of the steel cage, inserts the main reinforcement of the extension section of the steel cage into the inside of the sleeve, and heats the sleeve with a welding torch to weld and fix it.

[0024] Step S44, release the first section of the reinforcing cage: remove the supporting steel beam, and continue to lower the connected first section of the reinforcing cage and the extension section of the reinforcing cage. The extension section of the reinforcing cage can be installed through the sleeve to continue installing another extension section of the reinforcing cage until the grouting capsule is located at the bottom of the pile foundation well.

[0025] Among them, the extension section steel cage is set to multiple sections according to actual construction needs.

[0026] Preferably, in step S5, the grouting capsule is spherical;

[0027] The grouting capsule includes a first capsule layer and a second capsule layer. The first capsule layer has a sealed inner cavity, and an intermediate cavity is formed between the first capsule layer and the second capsule layer. The bottom of the first section of the steel cage is fixed with a base plate, and the grouting capsule is fixed on the base plate.

[0028] The grouting capsule is equipped with a first grouting hose that communicates with the sealed inner cavity and a second grouting hose that communicates with the intermediate cavity. The lengths of the first and second grouting hoses are greater than the depth of the pile foundation well. After grouting is completed, the first and second grouting hoses are sealed and bent into the pile foundation well.

[0029] Preferably, in step S5, the second capsule layer is provided with multiple grout outlet holes that communicate with the intermediate cavity, and grouting is performed on the intermediate cavity so that the concrete grout seeps into the soil layer around the grouting capsule in a root-like manner along the grout outlet holes.

[0030] Preferably, in step S6,

[0031] The first hollow gap formed between the grouting capsule and the borehole, and the second hollow gap formed between the reinforcing cage and the borehole, are grouted using the open grouting method.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. This invention involves setting up a supporting steel beam, a bracket, a sleeve, a pick-and-place assembly, and a welding torch. The first section of the reinforcing cage, equipped with a grouting capsule, is lifted and placed into the borehole of the pile foundation. Part of the first section of the reinforcing cage extends into the casing. The supporting steel beam passes under the stirrups of the first section of the reinforcing cage and rests on the crossbeam. The first section of the reinforcing cage is positioned above the casing opening. The pick-and-place assembly moves the sleeve to the main reinforcement of the first section of the reinforcing cage. The extension section of the reinforcing cage is then lifted to the position of the main reinforcement of the first section of the reinforcing cage, and the main reinforcement of the extension section is inserted into the inside of the sleeve. The welding torch heats the sleeve for welding and fixation. The supporting steel beam is removed, and the connected first section of the reinforcing cage and the extension section of the reinforcing cage are lowered further for installation, facilitating the installation of the reinforcing cage.

[0034] 2. This invention utilizes grouting capsules to expand at the bottom of the borehole of the pile foundation, forming an enlarged head. This process effectively compacts the surrounding soil, reducing the impact of sediment at the pile bottom. The second capsule layer has multiple grout outlet holes connected to the intermediate cavity. Grouting of the intermediate cavity allows concrete grout to penetrate the soil around the grouting capsule in a root-like pattern along the outlet holes, forming a tight bond with the surrounding soil. Simultaneously, it combines open grouting to fill the hollow gaps in the borehole of the pile foundation, thereby improving the bearing capacity of the pile foundation. This eliminates the need to compensate for insufficient bearing capacity by increasing the pile length, diameter, or number of piles, effectively reducing construction costs and difficulty. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the auxiliary construction device for the cast-in-place pile of the present invention;

[0036] Figure 2 For the present invention Figure 1 Enlarged structural diagram at position A in the middle;

[0037] Figure 3 This is a schematic diagram of the structure of the bored pile foundation well in the construction method of cast-in-place piles based on the ball hole expansion theory of the present invention;

[0038] Figure 4 This is a flowchart illustrating the construction method of cast-in-place piles based on the spherical hole expansion theory of the present invention.

[0039] Figure 5 This is a flowchart illustrating the installation process of the grouting capsule and reinforcing cage of the present invention.

[0040] In the diagram: 1. Supporting steel beam; 2. Bracket; 3. Reinforcing cage; 4. Sleeve; 5. Columnar groove; 6. Crossbeam; 7. Picking and placing assembly; 71. Longitudinal cylinder; 72. Radial cylinder; 73. Connecting block; 74. Magnet; 75. Arc groove; 8. Welding torch; 9. Insert shaft; 10. Bracket; 11. Grouting capsule; 111. First capsule layer; 112. Second capsule layer; 113. Sealed inner cavity; 114. Intermediate cavity; 12. Base plate; 13. First grouting hose; 14. Second grouting hose. Detailed Implementation

[0041] 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, and 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.

[0042] Please see Figure 1-2 An auxiliary construction device for cast-in-place piles based on the theory of ball hole expansion includes: a supporting steel beam 1 for supporting the reinforcing cage 3 and a bracket 2 that can be supported around the casing.

[0043] The reinforcing cage 3 includes a first section of reinforcing cage and an extension section of reinforcing cage. The first section of reinforcing cage and the extension section of reinforcing cage, as well as adjacent extension sections of reinforcing cage, are all connected by sleeves 4.

[0044] The top center of the support 2 is provided with a cylindrical groove 5 through which the reinforcing cage 3 can pass. A crossbeam 6 is provided on the support 2. The supporting steel beam 1 passes under the stirrups of the reinforcing cage 3 and rests on the crossbeam 6. The support 2 is provided with a pick-and-place assembly 7 for installing the sleeve 4. The pick-and-place assembly 7 is provided with a welding gun 8 for welding the sleeve 4 to the connection between the main reinforcement of the first section of the reinforcing cage and the main reinforcement of the extension section of the reinforcing cage, as well as the connection between the main reinforcement of the adjacent extension section of the reinforcing cage.

[0045] A shaft 9 for placing the sleeve 4 is provided on one side of the cylindrical groove 5 on the bracket 2.

[0046] There are multiple insertion shafts 9 and pick-and-place components 7. The multiple insertion shafts 9 and pick-and-place components 7 are evenly distributed in a ring array along the circumference of the cylindrical groove 5, and the positions of the multiple insertion shafts 9 and pick-and-place components 7 correspond to the positions of the main reinforcement bars of the steel cage 3.

[0047] The pick-and-place assembly 7 includes a longitudinal cylinder 71, a radial cylinder 72, and a connecting block 73. The longitudinal cylinder 71 is mounted on the top of the bracket 2, the radial cylinder 72 is mounted on the telescopic end of the longitudinal cylinder 71, and the connecting block 73 is mounted on the telescopic end of the radial cylinder 72. The connecting block 73 is provided with a magnet 74 that can attract the sleeve 4. The surface of the magnet 74 has an arc-shaped groove 75, and the inner wall of the arc-shaped groove 75 is adapted to the surface of the sleeve 4. When the sleeve 4 is installed, the telescopic end of the longitudinal cylinder 71 descends, driving the radial cylinder 72 to move downwards. As cylinder 72 descends, the telescopic end of radial cylinder 72 extends, pushing magnet 74 to move via connecting block 73. The arc groove 75 of magnet 74 engages with sleeve 4, attracting sleeve 4 and driving the telescopic end of longitudinal cylinder 71 to rise to the top of the main reinforcement bar of steel cage 3. Sleeve 4 is positioned at the horizontal position at the top of the main reinforcement bar of steel cage 3. The telescopic end of radial cylinder 72 extends, pushing sleeve 4 above the main reinforcement bar of steel cage 3 and driving the telescopic end of longitudinal cylinder 71 to descend, causing sleeve 4 to fit onto the main reinforcement bar of steel cage 3.

[0048] A bracket 10 is provided on the top of the connecting block 73. The welding torch 8 is installed on the bracket 10. Multiple annular welding wires are fixed inside the sleeve 4. When the welding torch 8 heats the sleeve 4, the annular welding wires melt inside the sleeve 4. The welding torch 8 is an acetylene torch. When the welding torch 8 heats the sleeve, the annular welding wires melt and connect between the sleeve and the main reinforcement bars of the first section of the reinforcing cage, the main reinforcement bars of the extension section of the reinforcing cage, and the main reinforcement bars of the extension section of the reinforcing cage.

[0049] Please see Figure 3-5 A construction method for cast-in-place piles based on the theory of spherical hole expansion includes the following steps:

[0050] Step S1: Mark out the center of the pile location and vertically lower the casing.

[0051] Step S2: Drill a hole for the pile foundation well along the center of the casing using a drilling rig;

[0052] Step S3: Install a grouting capsule 11 on the steel cage 3;

[0053] Step S4: Install the reinforcing cage 3 into the pile foundation well, so that the grouting capsule 11 is located at the bottom of the pile foundation well;

[0054] Step S5: Pressure grouting is performed inside the grouting capsule 11 using the closed grouting method, causing it to expand into an enlarged head, which is suitable for compacting the surrounding soil layer.

[0055] Step S6: Use open grouting method to fill the hollow gaps in the pile foundation well with grout.

[0056] Step S4 includes the following steps;

[0057] Step S41, Install the grouting capsule 11 and the first section of the reinforcing cage: Lift the first section of the reinforcing cage with the grouting capsule 11 installed and put it into the pile foundation well, so that part of the first section of the reinforcing cage extends out of the casing.

[0058] Step S42, set up a docking auxiliary construction device around the casing: the supporting steel beam 1 can pass under the stirrups of the first section of the steel cage and rest on the cross beam 6, so that the first section of the steel cage is located above the casing opening;

[0059] Step S43, hoisting the extension section of the steel cage: the take-up and put-down component 7 moves the sleeve 4 to the main bar of the first section of the steel cage, hoists the extension section of the steel cage to the position of the main bar of the first section of the steel cage, and inserts the main bar of the extension section of the steel cage into the inside of the sleeve 4. The welding gun 8 heats the sleeve 4 to weld and fix it.

[0060] Step S44, release the first section of the reinforcing cage: remove the supporting steel beam 1, and continue to lower the connected first section of the reinforcing cage and the extension section of the reinforcing cage. The extension section of the reinforcing cage can be installed through the sleeve 4 to install another extension section of the reinforcing cage until the grouting capsule 11 is located at the bottom of the pile foundation well.

[0061] Among them, the extension section steel cage is set to multiple sections according to actual construction needs.

[0062] In step S5, the grouting capsule 11 is set to a spherical shape;

[0063] The grouting capsule 11 includes a first capsule layer 111 and a second capsule layer 112. The first capsule layer 111 has a sealed inner cavity 113. An intermediate cavity 114 is formed between the first capsule layer 111 and the second capsule layer 112. The bottom of the first section of the steel cage 3 is fixed with a base plate 12, and the grouting capsule 11 is fixed on the base plate 12.

[0064] The grouting capsule 11 is provided with a first grouting hose 13 that communicates with the sealed inner cavity 113 and a second grouting hose 14 that communicates with the intermediate cavity 114. The lengths of the first grouting hose 13 and the second grouting hose 14 are greater than the depth of the pile foundation well. After grouting is completed, the first grouting hose 13 and the second grouting hose 14 are sealed and bent into the inside of the pile foundation well.

[0065] In step S5, the second capsule layer 112 is provided with multiple grout outlet holes that communicate with the intermediate cavity 114. Grouting is performed on the intermediate cavity 114 so that the concrete grout seeps into the soil layer around the grouting capsule 11 in a root-like manner along the grout outlet holes.

[0066] In step S6, the first hollow gap formed between the grouting capsule 11 and the pile foundation well, and the second hollow gap formed between the reinforcing cage 3 and the pile foundation well, are grouted using the open grouting method.

[0067] The grouting capsule 11 expands at the bottom of the pile foundation well to form an enlarged head. This process effectively compacts the surrounding soil layers and reduces the impact of sediment at the pile bottom. The second capsule layer 112 is provided with multiple grout outlet holes that communicate with the intermediate cavity 114. Grouting is performed on the intermediate cavity 114, allowing the concrete grout to penetrate into the soil layers surrounding the grouting capsule 11 in a root-like manner along the grout outlet holes, forming a tight bond with the surrounding soil layers. At the same time, the open grouting method is combined to fill the hollow gaps in the pile foundation well, thereby improving the bearing capacity of the pile foundation. There is no need to compensate for insufficient bearing capacity by increasing the pile length, pile diameter, or number of piles, which effectively reduces construction costs and difficulties.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An auxiliary construction device for cast-in-place pile based on the theory of ball hole expansion, characterized in that, include: Supporting steel beams (1) for supporting the reinforcing cage (3) and supports (2) around the casing. The steel cage (3) includes the first section of the steel cage and the extension section of the steel cage. The first section of the steel cage and the extension section of the steel cage, as well as the adjacent extension section of the steel cage, are connected by sleeves (4). The top center of the support (2) is provided with a columnar groove (5) for the steel cage (3) to pass through. A crossbeam (6) is provided on the support (2). The supporting steel beam (1) passes under the stirrups of the steel cage (3) and rests on the crossbeam (6). The support (2) is provided with a pick-and-place assembly (7) for installing the sleeve (4). The pick-and-place assembly (7) is provided with a welding gun (8) for welding the sleeve (4) to the connection between the main reinforcement of the first section of the steel cage and the main reinforcement of the extension section of the steel cage, as well as the connection between the main reinforcement of the adjacent extension section of the steel cage. The bracket (2) is provided with a ferrule (9) for placing the sleeve (4) on one side of the cylindrical groove (5); The number of the insert shaft (9) and the pick-and-place assembly (7) is multiple. The multiple insert shafts (9) and the pick-and-place assembly (7) are evenly distributed in a ring array along the circumferential direction of the cylindrical groove (5), and the positions of the multiple insert shafts (9) and the pick-and-place assembly (7) correspond to the positions of the main reinforcement bars of the steel cage (3). The pick-and-place assembly (7) includes a longitudinal cylinder (71), a radial cylinder (72), and a connecting block (73). The longitudinal cylinder (71) is mounted on the top of the bracket (2). The radial cylinder (72) is mounted on the telescopic end of the longitudinal cylinder (71). The connecting block (73) is mounted on the telescopic end of the radial cylinder (72). The connecting block (73) is provided with a magnet (74) that can attract the sleeve (4). The surface of the magnet (74) is provided with an arc groove (75), and the inner wall of the arc groove (75) is adapted to the surface of the sleeve (4). The top of the connecting block (73) is provided with a bracket (10), and the welding torch (8) is mounted on the bracket (10); Multiple annular welding wires are fixed inside the sleeve (4). When the welding gun (8) heats the sleeve (4), the annular welding wires melt inside the sleeve (4). A spherical grouting capsule (11) is installed at the bottom of the reinforcing cage (3).

2. A construction method of an auxiliary construction device for a cast-in-place pile based on the ball hole expansion theory according to claim 1, characterized in that, Includes the following steps: Step S1: Mark out the center of the pile location and vertically lower the casing. Step S2: Drill a hole for the pile foundation well along the center of the casing using a drilling rig; Step S3: Install a grouting capsule (11) on the steel cage (3); Step S4: Install the steel cage (3) into the pile foundation well, so that the grouting capsule (11) is located at the bottom of the pile foundation well; Step S5: Pressure grouting is performed inside the grouting capsule (11) using the closed grouting method, causing it to expand into an enlarged head, which is suitable for compacting the surrounding soil layer. Step S6: Use open grouting method to fill the hollow gaps in the pile foundation well with grout. Step S4 includes the following steps; Step S41, Install the grouting capsule (11) and the first section of the reinforcing cage: Lift the first section of the reinforcing cage with the grouting capsule (11) installed and put it into the pile foundation well, so that part of the first section of the reinforcing cage extends out of the casing. Step S42, setting butt joint auxiliary construction device around the casing: supporting steel beam (1) passes through the hoop below the first reinforcement cage and bears on the cross beam (6), so that the first reinforcement cage is located above the casing mouth; Step S43, hoisting the lengthened reinforcement cage: taking the sleeve (4) to the main reinforcement of the first reinforcement cage with the taking and placing assembly (7), hoisting the lengthened reinforcement cage to the position of the main reinforcement of the first reinforcement cage, and inserting the main reinforcement of the lengthened reinforcement cage into the inside of the sleeve (4), the welding gun (8) heats and welds the sleeve (4) to be fixed; Step S44, releasing the first reinforcement cage: removing the supporting steel beam (1), continuing to lower the connected first reinforcement cage and lengthened reinforcement cage, and continuing to install another lengthened reinforcement cage through the sleeve (4) for the lengthened reinforcement cage until the grouting capsule (11) is located at the bottom of the hole pile foundation well; Wherein, the lengthened reinforcement cage is set to be multiple sections according to actual construction requirements; In step S5, the grouting capsule (11) is set to be spherical; The grouting capsule (11) includes a first capsule layer (111) and a second capsule layer (112), a sealed inner cavity (113) is arranged in the first capsule layer (111), an intermediate cavity (114) is formed between the first capsule layer (111) and the second capsule layer (112), a bottom plate (12) is fixed to the bottom of the first reinforcement cage of the reinforcement cage (3), and the grouting capsule (11) is fixed on the bottom plate (12); A first grouting hose (13) in communication with the sealed inner cavity (113) and a second grouting hose (14) in communication with the intermediate cavity (114) are arranged on the grouting capsule (11), the lengths of the first grouting hose (13) and the second grouting hose (14) are greater than the depth of the hole pile foundation well, and after grouting, the first grouting hose (13) and the second grouting hose (14) are respectively sealed and bent into the hole pile foundation well.

3. The construction method of an auxiliary construction device for a cast-in-place pile based on the ball hole expansion theory according to claim 2, characterized in that, In step S5, a plurality of grout outlets in communication with the intermediate cavity (114) are arranged on the second capsule layer (112), the intermediate cavity (114) is grouted, and the concrete slurry penetrates into the soil layer around the grouting capsule (11) in the form of tree roots through the grout outlets.

4. The construction method of an auxiliary construction device for a cast-in-place pile based on the ball hole expansion theory according to claim 3, characterized in that, In step S6, The first hollow gap formed between the grouting capsule (11) and the hole pile foundation well, and the second hollow gap formed between the reinforcement cage (3) and the hole pile foundation well are grouted by using the open grouting method.

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