Sludge stratum secant pile wall construction method

Abstract

The invention discloses a construction method for a secant pile wall in a sludge stratum. The construction method comprises the following steps that S1, a guide wall is constructed; s2, grooving at a pile wall joint; s3, manufacturing a steel box; s4, steel box construction; s5, grooving the pile wall; s6, hoisting the reinforcement cage; and S7, pile wall pouring. A pile wall joint is adjusted to be a steel box joint, the steel box joint is welded into an II shape through a steel plate, an abdominal cavity formed in a steel box is filled with underwater concrete, a structure similar to a steel pipe concrete is formed, the joint rigidity is improved, and the water stopping effect and stability of the joint are ensured; a conventional secant pile construction process is improved and optimized, the trenching machine is used for taking soil and the steel box connector is used for construction in a matched mode, the pile forming efficiency is improved, meanwhile, the phenomena of water seepage and water leakage are greatly reduced, the surface of a pile wall is smooth, secondary treatment is not needed, the construction period is shortened, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit excavation support, and in particular to a method for constructing a silt stratum interlocking pile wall. Background Art

[0002] With the rapid development of urban construction, underground space is constantly being developed, and more and more deep foundation pit projects are emerging. Bored interlocking piles have gradually become a new type of retaining structure for urban tunnel subways due to their advantages of low construction noise, good water-stopping effect, and high support strength.

[0003] Conventional interlocking pile construction technology mainly adopts full-casing drilling rig construction, which consists of a reinforced concrete pile in the middle and a plain concrete pile on each side interlocking to form a group. The plain concrete piles on both sides are constructed first, and the middle reinforced concrete piles are constructed before the plain concrete piles begin to set, thus forming a seamless and continuous "pile wall". However, this technology has problems such as low construction efficiency, unsatisfactory interlocking effect of the plain concrete piles, and water leakage on the surface of the "pile wall" after excavation.

[0004] Therefore, there is an urgent need to provide a method for constructing interlocking pile walls in silt formations to solve the problems of low construction efficiency and water leakage on the excavation surface that are very likely to occur during conventional interlocking pile construction. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the above-mentioned technology and provide a method for constructing interlocking pile walls in silt formations. Drawing on the trenching process of a ground-connected wall trenching machine, the trench sections are first divided into sections. To ensure the water-stopping effect at the joints of the sections, the locations of the trench section joints are selected at the interlocking piles with steel cages. The interlocking pile steel cages at the joints are replaced by steel boxes. After the construction of the joint interlocking piles is completed, the interlocking pile steel cages in the trench sections are connected into a "4-in-a-group" pile wall structure. The trenching machine excavates the trench at one time, hoists and lowers the pile wall steel cages, and 4 reinforced concrete piles + 5 plain concrete piles are cast simultaneously. Arranging double I-shaped steel boxes at the joints can greatly improve the joint stiffness and waterproof quality.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is a method for constructing a silt stratum interlocking pile wall, which comprises the following steps:

[0007] S1. Guide wall construction: In order to ensure plane position control, vertical guidance, horizontal positioning, soil retaining and stable wall slurry liquid level, the interlocking pile wall guide wall construction is first carried out. The width of the guide wall is 1m and the depth is 2m;

[0008] S2. Grooving at the joints of piles and walls: The location of the groove section joints is selected at the interlocking piles with steel cages. The joints are constructed using a groove forming machine. The groove width is 1m, the groove length is 1.5m, the groove depth is 2m greater than the depth of the pile wall, and the joints are constructed using double I-shaped steel boxes;

[0009] S3. Steel box production: The steel box joints are welded with steel plates into a "Ⅱ"-shaped structure with a steel box enclosure with a belly cavity in the middle. The thickness of the steel plate is 12 mm and the length is 2 m deeper than the pile wall. The belly cavity formed inside the steel box is filled with underwater concrete.

[0010] S4, Steel Box Construction: After the steel box is manufactured, it is hoisted into the slot in sections using a 25t truck crane. Each section of the steel box is fixed by welding. After all the steel boxes are lowered and installed, they are hung and fixed on the top of the guide wall using a plunger through the pre-reserved holes. After the conduit is lowered into the steel box and the hole is cleaned, underwater C30 concrete is poured to the bottom of the steel box through the conduit to fix the bottom of the steel box. The bottom concrete is poured to the bottom elevation of the pile wall. After the bottom concrete has a certain strength, the remaining concrete in the steel box is poured until the top of the pile wall is designed.

[0011] S5. Pile wall grooving: After the steel box concrete has been left to stand for more than or equal to 7 days, the middle grooving section is excavated. The grooving section is 1m wide and 7m long. In order to ensure the water-stopping effect at the joint, a special wall brush is needed to clean the slag or mud skin on the side of the steel box joint. The wall should be brushed up and down for no less than 10 times until there is no mud on the brush surface of the wall brush to ensure that the new and old concrete on the joint surface are tightly connected. After the pile wall grooving is completed, the grooving section quality is tested by an ultrasonic grooving quality detector. Only after the test is qualified can the next process be carried out;

[0012] S6. Lifting of steel cage: The steel cage is lowered in sections by a 25t truck crane. Each section of the steel cage is connected by single-sided lap welding. The position of the steel cage is measured and set out in advance. The net distance of the steel cage is 0.4m. During the lifting process, to ensure the accuracy of the position of the steel cage, a positioning clamp is welded on one side of the steel cage. The clamp is 0.3m long and 0.4m wide. A clamp is set every 3m. At the same time, in order to prevent the clamp from extending into the adjacent steel cage, three full-length steel bars are welded on the outside of the clamp as an isolation measure;

[0013] S7. Pile wall pouring: according to the width of the construction trench section, use two φ250mm steel conduits for symmetrical concrete pouring. The distance between the two sets of conduits is less than or equal to 4 meters, and the conduit is less than or equal to 1.5 meters away from the end of the trench. The conduit is lifted 30 to 40 centimeters above the bottom of the trench. Use conventional underwater concrete to pour into the casing. Use calculation and measurement methods to ensure that the lower end is always buried in the concrete for 1.5 to 3 meters. Use an electric hoist to gradually pull out the conduit so that the bottom of the conduit is more than 2.5 meters below the concrete surface until it is poured to the set elevation.

[0014] As an improvement, in S2, grooves are formed at the joints of the pile and the wall, and mud wall protection is used to form the grooves, and the mud density is controlled between 1.05 and 1.1.

[0015] As an improvement, in S3, in order to ensure welding quality, the steel box is welded using CO2 gas shielding.

[0016] As an improvement, in S3, a steel box is made, the cross-sectional length of the steel box is 85 cm, the width is 50 cm, and the net distance between the flange and the groove width is about 15 cm.

[0017] As an improvement, in S4, during the construction of the steel box, in order to block the lateral pressure on the joints generated during the subsequent concrete pouring, it is necessary to backfill crushed stone on both sides of the steel box after the bottom concrete is poured. This can effectively block the lateral pressure and prevent the steel box from moving during the pouring process. At the same time, the bypass cement slurry will fill the gaps in the backfill crushed stone to further reinforce the backfill body and improve the construction quality and safety.

[0018] As an improvement, in S5, attention should be paid to the control of mud density during trenching construction, and the mud density should be controlled above 1.25, while accelerating the connection of subsequent work after drilling.

[0019] As an improvement, in S7, during the pouring of the pile wall, if the sediment at the bottom of the trench is thick, at least one conduit is added to facilitate the floating of the sediment.

[0020] The advantages of the present invention compared with the prior art are:

[0021] 1. The joints of the pile wall are adjusted to steel box joints. The steel box joints are welded into a "Ⅱ" shape with steel plates, that is, the cross section is a steel box-type closed body with a belly in the middle. To ensure the welding quality, CO2 gas shielded welding is adopted. The belly formed inside the steel box is filled with underwater concrete to form a structure similar to steel tube concrete, so as to increase the joint rigidity and ensure the water-stopping effect and stability of the joint;

[0022] 2. The conventional construction process of interlocking piles adopts full casing drilling rig construction, and the pile-forming efficiency is 2.76 days per pile. Through process optimization, it is adjusted to trenching machine construction and steel box connection is adopted at the section. The pile-forming efficiency is increased to 3 piles per day, and the efficiency is increased by 8.3 times. At the same time, the trenching machine construction has low noise and little impact on the surrounding area.

[0023] 3. Conventional construction methods of interlocking piles may not have ideal interlocking effects or even fail to interlock, which may lead to water seepage and leakage during foundation pit excavation. In addition, the surface of interlocking piles usually needs to be treated with mesh spraying, which is time-consuming and labor-intensive. The interlocking pile wall construction method greatly reduces the occurrence of water seepage and leakage, and the surface of the pile wall is smooth, so no secondary treatment is required, which reduces the construction period and cost.

[0024] 4. During the trenching process of the interlocking pile wall, the stability of the trench wall is maintained by using mud wall protection. The hydrostatic pressure of the mud on the trench wall, the smearing effect that prevents the movement of soil particles in the trench wall, the structural membrane effect produced by the bentonite filter cake, and the gelling effect produced by the mud penetrating into the gaps between the soil particles in the trench wall all help to maintain the stability of the trench wall. Compared with the conventional interlocking pile construction process, the average concrete consumption per pile is reduced by 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a schematic cross-sectional view of a guide wall in a method for constructing interlocking pile walls in silt formations.

[0026] Figure 2 It is a schematic plan view of a steel box in a method for constructing interlocking pile walls in silt strata according to the present invention.

[0027] Figure 3 The present invention is a cross-sectional schematic diagram of the pouring of concrete at the bottom of a steel box and the backfilling of crushed stones on both sides in a method for constructing interlocking pile walls in silt strata according to the present invention.

[0028] Figure 4 It is a schematic diagram of the longitudinal section of a trench section in a method for constructing a silt stratum interlocking pile wall according to the present invention.

[0029] Figure 5 It is a plan view schematic diagram of a steel cage positioning clamp ring in a silt formation interlocking pile wall construction method of the present invention.

[0030] Figure 6 It is a schematic plan view of the distribution of the trench section casting conduit in a method for constructing a silt formation interlocking pile wall according to the present invention.

[0031] Figure 7 It is a schematic plan view of the trench section casting in a method for constructing interlocking pile walls in silt strata according to the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the invention clearer, the technical solution in the embodiments of the invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the invention. Obviously, the described embodiments are part of the embodiments of the invention, not all of the embodiments. Generally, the components of the embodiments of the invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0033] In the description of the embodiments of the invention, it should be noted that if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the invention product is usually placed when in use, it is only for the convenience of describing the invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0034] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components must be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0035] In the description of the embodiments of the invention, "a plurality of" means at least two.

[0036] In the description of the embodiments of the invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0037] As shown in the accompanying drawings, a method for constructing a pile wall in a silt formation includes the following steps:

[0038] S1. Guide wall construction: In order to ensure plane position control, vertical guidance, horizontal positioning, soil retaining and stable wall slurry liquid level, the interlocking pile wall guide wall construction is first carried out. The width of the guide wall is 1m and the depth is 2m;

[0039] S2. Grooving at the joint of pile wall: The location of the groove section joint is selected at the interlocking pile with steel cage. The joint is constructed by a groove machine. The width of the groove is 1m, and its width is consistent with the diameter of the interlocking pile. The length of the groove is 1.5m, and its length is consistent with the size of the groove machine grab. In order to improve the stability of the joint, the groove depth is 2m greater than the depth of the pile wall. At the same time, the joint adopts double I-shaped steel boxes to improve the joint rigidity and waterproof quality;

[0040] Furthermore, grooves are formed at the joints of the pile wall, and mud is used to protect the wall, and the mud density is controlled between 1.05 and 1.1.

[0041] S3. Steel box production: The steel box joint is welded with steel plates into a "Ⅱ"-shaped structure with a cross section of a steel box enclosure with a belly cavity in the middle. In this embodiment, the steel box is produced with a cross section length of 85 cm, a width of 50 cm, a net distance of about 15 cm between the flange and the groove width, a thickness of 12 mm, and a length 2 m deeper than the pile wall. The belly cavity formed inside the steel box is filled with underwater concrete to form a structure similar to a steel tube concrete structure to increase the rigidity of the steel box joint;

[0042] In the specific implementation, in order to ensure the welding quality, the steel box adopts CO2 gas shielded welding method.

[0043] S4, Steel Box Construction: After the steel box is manufactured, it is hoisted into the slot in sections using a 25t truck crane. Each section of the steel box is fixed by welding. After all the steel boxes are lowered and installed, they are hung and fixed on the top of the guide wall using a plunger through the pre-reserved holes. After the conduit is lowered into the steel box and the hole is cleaned, underwater C30 concrete is poured to the bottom of the steel box through the conduit to fix the bottom of the steel box. The bottom concrete is poured to the bottom elevation of the pile wall. After the bottom concrete has a certain strength, the remaining concrete in the steel box is poured until the top of the pile wall is designed.

[0044] Furthermore, during the construction of the steel box, in order to block the lateral pressure on the joints generated during the subsequent concrete pouring, it is necessary to backfill crushed stone on both sides of the steel box after the bottom concrete pouring is completed. This can effectively block the lateral pressure and prevent the steel box from moving during the pouring process. At the same time, the bypass cement slurry will fill the gaps in the backfill crushed stone to further reinforce the backfill body and improve the construction quality and safety.

[0045] S5. Pile wall grooving: After the steel box concrete has been left to stand for more than or equal to 7 days, the middle grooving section is excavated. The grooving section is 1m wide and 7m long. At the same time, in order to ensure the water-stopping effect at the joint, a special wall brush is needed to clean the slag or mud skin on the side of the steel box joint. The number of up and down wall brushing is not less than 10 times until there is no mud on the brush surface of the wall brush to ensure that the new and old concrete on the joint surface are tightly connected. After the pile wall grooving is completed, the grooving section quality is tested by an ultrasonic grooving quality detector. Only after the test is qualified can the next process be carried out;

[0046] Furthermore, during the trenching process, attention should be paid to the control of mud density, which should be controlled above 1.25, and the subsequent work after drilling should be accelerated.

[0047] S6. Lifting of steel cage: The steel cage is lowered in sections by a 25t truck crane. Each section of the steel cage is connected by single-sided lap welding. The position of the steel cage is measured and set out in advance. The net distance of the steel cage is 0.4m. During the lifting process, to ensure the accuracy of the position of the steel cage, a positioning clamp is welded on one side of the steel cage. The clamp is 0.3m long and 0.4m wide. A clamp is set every 3m. At the same time, in order to prevent the clamp from extending into the adjacent steel cage, three full-length steel bars are welded on the outside of the clamp as an isolation measure;

[0048] S7. Pile wall pouring: according to the width of the construction trench section, use two φ250mm steel conduits for symmetrical concrete pouring. The distance between the two sets of conduits is less than or equal to 4 meters, and the conduit is less than or equal to 1.5 meters away from the end of the trench. The conduit is lifted 30 to 40 centimeters above the bottom of the trench. Use conventional underwater concrete to pour into the casing. Use calculation and measurement methods to ensure that the lower end is always buried in the concrete for 1.5 to 3 meters. Use an electric hoist to gradually pull out the conduit so that the bottom of the conduit is more than 2.5 meters below the concrete surface until it is poured to the set elevation.

[0049] During implementation, during the pouring of the pile wall, if the sediment at the bottom of the trench is thick, in order to facilitate the floating of the sediment, at least one conduit may be added according to the actual situation on site.

[0050] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A method for constructing a pile wall in a silt formation, characterized by: The following steps are involved: S1. Guide wall construction: In order to ensure plane position control, vertical guidance, horizontal positioning, soil retaining and stable wall slurry liquid level, the interlocking pile wall guide wall construction is first carried out. The width of the guide wall is 1m and the depth is 2m; S2. Grooving at the joints of piles and walls: The location of the groove section joints is selected at the interlocking piles with steel cages. The joints are constructed using a groove forming machine. The groove width is 1m, the groove length is 1.5m, the groove depth is 2m greater than the depth of the pile wall, and the joints are constructed using double I-shaped steel boxes; S3. Steel box production: The steel box joints are welded with steel plates into a "Ⅱ" shaped structure with a cross section of a steel box enclosure with a belly cavity in the middle. The thickness of the steel plate is 12mm and the length is 2m deeper than the pile wall. The belly cavity formed inside the steel box is filled with underwater concrete; S4, Steel Box Construction: After the steel box is manufactured, it is hoisted into the slot in sections using a 25t truck crane. Each section of the steel box is fixed by welding. After all the steel boxes are lowered and installed, they are hung and fixed on the top of the guide wall using a plunger through the pre-reserved holes. After the conduit is lowered into the steel box and the hole is cleaned, underwater C30 concrete is poured to the bottom of the steel box through the conduit to fix the bottom of the steel box. The bottom concrete is poured to the bottom elevation of the pile wall. After the bottom concrete has a certain strength, the remaining concrete in the steel box is poured until the top of the pile wall is designed. S5. Pile wall grooving: After the steel box concrete has been left to stand for more than or equal to 7 days, the middle grooving section is excavated. The grooving section is 1m wide and 7m long. In order to ensure the water-stopping effect at the joint, a special wall brush is needed to clean the slag or mud skin on the side of the steel box joint. The wall should be brushed up and down for no less than 10 times until there is no mud on the brush surface of the wall brush to ensure that the new and old concrete on the joint surface are tightly connected. After the pile wall grooving is completed, the grooving section quality is tested by an ultrasonic grooving quality detector. Only after the test is qualified can the next process be carried out; S6. Lifting of steel cage: The steel cage is lowered in sections by a 25t truck crane. Each section of the steel cage is connected by single-sided lap welding. The position of the steel cage is measured and set out in advance. The net distance of the steel cage is 0.4m. During the lifting process, to ensure the accuracy of the position of the steel cage, a positioning clamp is welded on one side of the steel cage. The clamp is 0.3m long and 0.4m wide. A clamp is set every 3m. At the same time, in order to prevent the clamp from extending into the adjacent steel cage, three full-length steel bars are welded on the outside of the clamp as an isolation measure; S7. Pile wall pouring: according to the width of the construction trench section, use two φ250mm steel conduits for symmetrical concrete pouring. The distance between the two sets of conduits is less than or equal to 4 meters, and the conduit is less than or equal to 1.5 meters away from the end of the trench. The conduit is lifted 30 to 40 centimeters above the bottom of the trench. Use conventional underwater concrete to pour into the casing. Use calculation and measurement methods to ensure that the lower end is always buried in the concrete for 1.5 to 3 meters. Use an electric hoist to gradually pull out the conduit so that the bottom of the conduit is more than 2.5 meters below the concrete surface until it is poured to the set elevation.

2. A method for constructing a silt stratum interlocking pile wall according to claim 1, characterized in that: In S2, grooves are formed at the joints of the pile and the wall, and mud wall protection is used to form the grooves, and the mud density is controlled between 1.05 and 1.

1.

3. The method for constructing a silt stratum interlocking pile wall according to claim 1, characterized in that: In S3, in order to ensure the welding quality, the steel box is welded by CO2 gas shielding.

4. The method for constructing a silt stratum interlocking pile wall according to claim 3, characterized in that: In S3, a steel box is made, the cross-sectional length of the steel box is 85 cm, the width is 50 cm, and the net distance between the flange and the groove width is about 15 cm.

5. The method for constructing a silt stratum interlocking pile wall according to claim 1, characterized in that: In S4, during the construction of the steel box, in order to block the lateral pressure on the joints generated during the subsequent concrete pouring, it is necessary to backfill crushed stones on both sides of the steel box after the bottom concrete is poured. This can effectively block the lateral pressure and prevent the steel box from moving during the pouring process. At the same time, the bypass cement slurry will fill the gaps in the backfill crushed stones to further reinforce the backfill body and improve the construction quality and safety.

6. The method for constructing a silt stratum interlocking pile wall according to claim 1, characterized in that: In S5, attention should be paid to mud density control during trenching construction, and the mud density should be controlled above 1.25, while accelerating the connection of subsequent work after drilling.

7. The method for constructing a silt stratum interlocking pile wall according to claim 1, characterized in that: In S7, during the pouring of the pile wall, if the sediment at the bottom of the trench is thick, at least one conduit is added to facilitate the floating of the sediment.

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