Construction method of low-clearance underground diaphragm wall under high-voltage line

Abstract

The invention belongs to the technical field of building construction, and provides a low-clearance underground diaphragm wall construction method under a high-voltage line, which comprises the following steps: S1, measuring, positioning and lofting; s2, guide wall construction; s3, grooving construction is conducted, specifically, a low-clear-height hydraulic grab bucket is adopted, and construction is conducted through a jump hole excavation method; s4, wall brushing; s5, grooving quality inspection; s6, the reinforcement cage is manufactured, specifically, the reinforcement cage is divided into a plurality of sections, normal wires and added wires are machined at the two ends of main reinforcements of the sectional reinforcement cage correspondingly, and on the reinforcement manufacturing platform, the main reinforcements of every two adjacent sectional reinforcement cages are detachably connected through straight thread sleeves; s7, the reinforcement cage is hoisted in a segmented mode, all the segments of the reinforcement cage are hoisted through a truck-mounted crane and a truck-mounted crane to be sequentially put into the formed groove, and the reinforcement cage at the front end and the rear end of the groove opening are connected through a threaded sleeve; and S8, concrete is poured. The construction problem that the reinforcement cage of the ultra-long underground diaphragm wall is hoisted into the groove under the working condition of height limitation can be solved, a high-voltage power overhead line is protected, and construction of the underground diaphragm wall is safer.

Description

Technical Field

[0001] The invention belongs to the technical field of building construction, and in particular relates to a method for constructing a low-clearance underground continuous wall under a high-voltage line. Background Art

[0002] At present, the retaining structures of deep foundation pits of subway stations are mostly in the form of underground continuous walls, and the underground continuous walls are relatively deep. After the ground wall is grooved, the steel cage is often hoisted in one go. This hoisting method has high requirements on the ground construction environment. The construction of subway stations is often located in urban areas, with numerous buildings (structures) and complex underground pipelines. There are also high-voltage overhead power lines on the ground, and the line height generally does not exceed 15 meters. Construction is not allowed within a vertical distance of 6 meters under the high-voltage line. Therefore, the current continuous wall construction method is difficult to meet the needs of construction under the high-voltage line. Summary of the invention

[0003] The purpose of the present invention is to provide a method for constructing a low-clearance underground continuous wall under a high-voltage line to solve the above-mentioned problems, so as to solve the construction difficulty of hoisting the steel cage of an ultra-long underground continuous wall into a groove under height-limited working conditions, reduce the risk of hoisting, protect high-voltage power overhead lines, and make the construction of underground continuous walls safer.

[0004] To achieve the above object, the present invention provides the following solution: a method for constructing a low-headroom underground continuous wall under a high-voltage line, the construction steps comprising:

[0005] S1. Measurement, positioning and setting out;

[0006] S2. Guide wall construction: The guide wall adopts an integral reinforced concrete structure, and its net width is 5cm thicker than the underground continuous wall. During the construction period, the guide wall should be able to withstand the construction load;

[0007] S3. During trenching, a low-clearance hydraulic grab is used and the trench section is constructed by the skip-hole excavation method. During the trenching process, the guide rod should be set vertically to the trench section.

[0008] S4, brush the wall, brush and clean the joints of the first wall at the joint of the continuous wall;

[0009] S5. Grooving quality inspection;

[0010] S6. Fabrication of steel cage: the steel cage is divided into several sections, and normal wires and extended wires are processed at both ends of the main reinforcement of the segmented steel cage. On the steel fabrication platform, the main reinforcements of two adjacent segmented steel cages are detachably connected by straight threaded sleeves;

[0011] S7. The steel cage is hoisted in sections. Each section of the steel cage is hoisted by a truck crane and a truck crane and lowered into the slot in sequence. The front and rear end steel cages are connected at the slot with threaded sleeves.

[0012] S8. Pour concrete.

[0013] Preferably, the construction process of step S6 is as follows:

[0014] S6.1. Process the ends of the main reinforcement of each segment steel cage into straight thread heads of normal length and straight thread heads of extended length respectively, and use straight thread sleeves to connect them normally;

[0015] S6.2. Position the connected main reinforcement as a whole on the reinforcement production platform. After positioning, twist the straight thread sleeve to the end of the straight thread head with an extended length, and then weld the transverse reinforcement, longitudinal reinforcement and truss reinforcement to the main reinforcement of each segment reinforcement cage.

[0016] Preferably, in step S6., the straight thread sleeve adopts a Class I joint, and the same-section joint rate is 100%.

[0017] Preferably, in step S6.2, the transverse steel bars are connected to the longitudinal steel bars by spot welding, the truss bars are double-sided welded, the length is not less than 5d, the intersections of the longitudinal and transverse truss bars are spot welded, all the intersections within the range of the two main bars around the steel cage need to be spot welded, the steel bars are guaranteed to be straight, the surface is clean and free of oil, 50% of the internal intersections are spot welded, and 00% of the steel cage trusses and the steel cage hanging points above and below m need to be spot welded.

[0018] Preferably, the construction process of step S7 is as follows:

[0019] S7.1. The truck crane maintains its position and hoists the head of the segmental reinforcement cage. The truck crane moves to a suitable position and hoists the tail of the reinforcement cage.

[0020] S7.2. The truck crane and the automobile crane lift the segment steel cage at the same time, and make the segment steel cage vertical to the bottom surface. Then, the truck crane drives the segment steel cage to the notch;

[0021] S7.3. After the segmental steel cage is lowered into place, a shoulder pole is used to place it on the notch, and then another segmental steel cage is lifted and aligned with the segmental steel cage in the notch, and the straight thread sleeve is twisted to be threadedly connected with the straight thread head of normal length;

[0022] S7.4. Arrange and weld the upper horizontal reinforcement and sealing reinforcement, weld the steel sections, take out the shoulder pole, and continue to lower the connected segment reinforcement cage into the notch. Once in place, use the shoulder pole to place it;

[0023] S7.5. Repeat S7.-S7.4 until all segments are connected.

[0024] Preferably, in step S2, during construction, the slot section that needs to cross the guide wall position is completed first, poured with concrete, and equipped with an appropriate amount of steel plates of not less than 2 cm and laid at the position crossing the guide wall.

[0025] Preferably, in step S3, the hydraulic grab bucket should be controlled to enter the trough slowly to grab the soil, and the soil dug out by the grab bucket is transported to the bulldozer site by a dump truck.

[0026] Preferably, in step S3, as the excavation depth increases, fresh mud is continuously supplied into the trench, so that the mud plays a good wall protection role and prevents the trench wall from collapsing.

[0027] Compared with the prior art, the present invention has the following advantages and technical effects:

[0028] 1. The present invention adopts a low-headroom trenching machine to carry out trenching construction, thereby meeting the actual construction safety height.

[0029] 2. Each segment of the steel cage of the present invention is pre-connected with a straight thread sleeve steel cage and manufactured as a whole on a platform to ensure the manufacturing quality of the steel cage. Before hoisting, it is split on the platform to make subsequent docking construction more convenient and accurate.

[0030] 3. Use a truck crane and a car crane to lift the segmented steel cage to the slot for docking and then lift it into the slot while ensuring the safe clearance of the high-voltage line.

[0031] The invention solves the construction difficulty of hoisting the super-long underground continuous wall steel cage into the groove under the condition of height limitation, reduces the risk of hoisting, protects the high-voltage power overhead line, and makes the underground continuous wall construction safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 The present invention is a flow chart of the method for constructing a low clearance continuous wall under a high-voltage line. DETAILED DESCRIPTION

[0034] 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.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Taking the construction of a 47m underground continuous wall with a high-voltage power overhead line suspended at a height of 14.5m as an example, Figure 1 The present invention provides a method for constructing a low-headroom underground continuous wall under a high-voltage line, and the construction steps include:

[0037] S1. Measurement, positioning and setting out;

[0038] S2. Guide wall construction: The guide wall adopts an integral reinforced concrete structure, and its net width is 5cm thicker than the underground continuous wall. During the construction period, the guide wall should be able to withstand the construction load;

[0039] S3. During trenching, a low-clearance hydraulic grab is used and the trench section is constructed by the skip-hole excavation method. During the trenching process, the guide rod should be set vertically to the trench section.

[0040] S4, brush the wall, brush and clean the joints of the first wall at the joint of the continuous wall;

[0041] Specifically, in order to improve the anti-seepage and shear resistance of the joints, the joints of the first wall are cleaned by brushing at the joints of the continuous wall. When cleaning, first use the shovel installed on the low-clearance hydraulic grab to remove the mortar and mud attached to the joints, and then use the wall brush (special wire brush) installed on the grab to repeatedly brush the joints at least ten times. After there is no mud on the wall brush, continue to brush up and down 2 to 3 times to completely remove the mud and prevent water leakage at the joints. Brushing must be done before cleaning the holes.

[0042] S5. Grooving quality inspection;

[0043] Specifically, an ultrasonic wall measuring instrument is used to scan the groove wall at the left, middle and right positions in the groove section. The ratio of the maximum protrusion or depression of the wall surface in the scanning record (with the guide wall surface as the scanning reference surface) to the groove section depth is the wall verticality, and the average value of the three positions is the average verticality of the groove section wall surface. Groove quality assessment: The groove quality level of the groove section is assessed based on the various data of the measured groove section.

[0044] S6. Fabrication of steel cage: the steel cage is divided into several sections, and normal wires and extended wires are processed at both ends of the main reinforcement of the segmented steel cage. On the steel fabrication platform, the main reinforcements of two adjacent segmented steel cages are detachably connected by straight thread sleeves;

[0045] S7. The steel cage is hoisted in sections. Each section of the steel cage is hoisted by a truck crane and a truck crane and lowered into the slot in sequence. The front and rear end steel cages are connected at the slot with threaded sleeves.

[0046] S8. Pour concrete.

[0047] Specifically, a concrete pouring order must be applied for before concrete pouring, and a conduit watertightness test must be conducted before the conduit is used. Concrete should be poured within 4 hours after the steel cage is placed. Before pouring, check the depth of the groove to determine whether there is a collapse hole, and calculate the required concrete volume. The design strength grade of the continuous wall concrete of the station project in this section is C35 underwater, and the anti-seepage grade is P8. The slump of concrete is 200±20mm according to the specifications and underwater concrete requirements. The lower end of the conduit should be 300-500mm away from the bottom of the groove, and the upper end of the conduit is connected to a round funnel. Before concrete pouring, a water stopper should be hung near the mud surface in the conduit so that the mud in the pipe can be discharged from the bottom of the pipe during concrete pouring. During concrete pouring, the concrete should be continuously and evenly discharged, the concrete surface rising speed should be controlled at 4-5m / h, and should not be less than 2m / h, and the buried depth of the lower end of the conduit in the concrete should be controlled at 1.5-3m.

[0048] To further optimize the scheme, the construction process of step S6 is as follows:

[0049] S6.1. Process the ends of the main reinforcement of each segment steel cage into straight thread heads of normal length and straight thread heads of extended length respectively, and use straight thread sleeves to connect them normally;

[0050] S6.2. Position the connected main reinforcement as a whole on the reinforcement production platform. After positioning, twist the straight thread sleeve to the end of the straight thread head with an extended length, and then weld the transverse reinforcement, longitudinal reinforcement and truss reinforcement to the main reinforcement of each segment reinforcement cage.

[0051] The length of the segmental steel cage is controlled at 4 meters. Before processing, the main reinforcement in each segmental steel cage is connected by a straight threaded sleeve, and the whole is positioned on the steel cage production platform to ensure that the overall structure and quality of the produced steel cage meet the standards.

[0052] After the main reinforcement is positioned, the straight thread sleeve is rotated toward one end of the straight thread head with an extended length, so that the straight thread sleeve is separated from the straight thread head with a normal length, thereby realizing the separation between the steel cages of two adjacent sections.

[0053] To further optimize the solution, in step S6.1, the straight thread sleeve adopts a Class I joint, and the same-section joint rate is 100%.

[0054] To further optimize the solution, in step S6.2, spot welding is used to connect the transverse and longitudinal steel bars, double-sided welding is used for the truss bars, the length of which is not less than 5d (d is the diameter of the steel bar), spot welding is used at the intersection of the longitudinal and transverse truss bars, all intersections within the range of the two main bars around the steel cage need to be spot welded, the steel bars are guaranteed to be straight, the surface is clean and free of oil, 50% of the internal intersections are spot welded, and 100% of the steel cage trusses and steel cage hanging points 1m above and below need to be spot welded.

[0055] To further optimize the scheme, the construction process of step S7 is as follows:

[0056] S7.1. The truck crane maintains its position and hoists the head of the segmental reinforcement cage. The truck crane moves to a suitable position and hoists the tail of the reinforcement cage.

[0057] S7.2. The truck crane and the automobile crane lift the segment steel cage at the same time, and make the segment steel cage vertical to the bottom surface. Then, the truck crane drives the segment steel cage to rotate to the notch;

[0058] The truck crane is SQ200T, and the mobile crane is 50T. During the installation of the segmental steel cage, the SQ200T truck crane maintains its position, and the 50T mobile crane is placed in a suitable position. The main and auxiliary cranes lift at the same time, lifting the segmental steel cage to about 0.5 meters from the ground. The SQ200T truck crane lifts the hook, and according to the distance between the tail of the steel cage and the ground, it commands the mobile crane to lift the hook at any time, and cooperates with the truck crane to make the segmental steel cage perpendicular to the ground. Finally, the SQ200T truck crane retracts the pole, and under the condition of ensuring the safety clearance of the high-voltage line, it turns to the slot for docking and slotting.

[0059] Since the truck-mounted crane does not require a long steel cable, the lifting height is mainly achieved by retracting and lowering the boom, which is more suitable for lifting work under low clearance.

[0060] S7.3. After the segmental steel cage is lowered into place, a shoulder pole is used to place it on the notch, and then another segmental steel cage is lifted and aligned with the segmental steel cage in the notch, and the straight thread sleeve is twisted to be threadedly connected with the straight thread head of normal length;

[0061] S7.4. Arrange and weld the upper horizontal reinforcement and sealing reinforcement, weld the steel sections, take out the shoulder pole, and continue to lower the connected segment reinforcement cage into the notch. Once in place, use the shoulder pole to place it;

[0062] S7.5. Repeat S7.1-S7.4 until all segments are connected.

[0063] After one section of the segmental steel cage is lifted, it is lowered into place and placed on the notch with a shoulder pole, and then another segmental steel cage is lifted and aligned with the previous segmental steel cage. When docking, the operator twists the straight thread sleeve from the side of the extended straight thread head to the normal position, so that the two ends of the straight thread sleeve are respectively threaded with the extended straight thread head and the normal length thread head on the other segmental steel cage, and tighten the straight thread sleeve with a socket wrench to achieve a fixed connection between the two main bars. Repeat the above steps, docking and lowering one section at a time, until all the segmental steel cages are connected, and the steel cages are lowered into place after passing the inspection.

[0064] To further optimize the solution, in step S2, due to the small working pit site, the construction of the cross-guide wall is inevitable. When it is necessary to cross the guide wall during construction, the groove section of the cross-guide wall position should be completed first, poured with concrete, and equipped with an appropriate amount of steel plates of not less than 2 cm and laid at the cross-guide wall position.

[0065] To further optimize the plan, in order to ensure the ground wall intrusion, the center line of the guide wall is 15cm outward. The top of the guide wall is level with the ground, the rib thickness is 200mm, the bottom of the guide wall is inserted 0.3m into the bottom of the crown beam, and inserted more than 20cm into the original soil, the top surface of the guide wall is more than 1.5m above the groundwater level, and no leakage is allowed.

[0066] The guide wall reinforcement is single-layer bidirectional Φ12@200, and the concrete grade is C20. After the formwork is removed and the support is set up, clay is backfilled layer by layer to make it dense.

[0067] To further optimize the solution, in step S3, the hydraulic grab bucket should be controlled to enter the trough slowly to grab the soil, and the soil dug out by the grab bucket is transported to the bulldozer site via a dump truck.

[0068] Specifically, according to the design drawings, guide control points and leveling points, the design position of each underground continuous wall is accurately located on the guide wall, the joint position is marked, and the trenching order is applied for as required before the trench is formed. When trenching, the grab bucket is opened, and the grab bucket is controlled to slowly enter the trench to grab the soil by aiming at the mark. It is strictly forbidden to quickly lower the bucket and lift it quickly to prevent damage to the trench wall and collapse. The verticality should be controlled within the design requirements.

[0069] To further optimize the solution, in step S3, as the excavation depth increases, fresh mud is continuously supplied to the trench so that the mud can play a good wall protection role and prevent the trench wall from collapsing.

[0070] As the excavation depth increases, fresh mud is continuously supplied to the trench to ensure the height of the mud. All mud indicators must meet the requirements of the specifications so that the mud can play a good role in protecting the wall and prevent the trench wall from collapsing. When encountering a soil layer with a large amount of sand and a layer section where the trench wall is prone to collapse, pay attention to increasing the mud specific gravity; when approaching the bottom of the trench, slow down the excavation speed, carefully measure the trench depth, and appropriately over-dig 50cm to avoid the influence of trench section sediment.

[0071] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do 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 should not be understood as a limitation on the present invention.

[0072] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for constructing a low clearance underground continuous wall under a high voltage line, characterized in that: The construction steps include: S1. Measurement, positioning and setting out; S2. Guide wall construction: The guide wall adopts an integral reinforced concrete structure, and its net width is 5cm thicker than the underground continuous wall. During the construction period, the guide wall should be able to withstand the construction load; S3. During trenching, a low-clearance hydraulic grab is used and the trench section is constructed by the skip-hole excavation method. During the trenching process, the guide rod should be set vertically to the trench section. S4, brush the wall, brush and clean the joints of the first wall at the joint of the continuous wall; S5. Grooving quality inspection; S6. Fabrication of steel cage: the steel cage is divided into several sections, and normal wires and extended wires are processed at both ends of the main reinforcement of the segmented steel cage. On the steel fabrication platform, the main reinforcements of two adjacent segmented steel cages are detachably connected by straight thread sleeves; S7. The steel cage is hoisted in sections. Each section of the steel cage is hoisted by a truck crane and a truck crane and lowered into the slot in sequence. The front and rear end steel cages are connected at the slot with threaded sleeves. S8. Pour concrete.

2. The method for constructing a low clearance underground continuous wall under a high-voltage line according to claim 1, characterized in that: The construction process of step S6 is as follows: S6.

1. Process the ends of the main reinforcement of each segment steel cage into straight thread heads of normal length and straight thread heads of extended length respectively, and use straight thread sleeves to connect them normally; S6.

2. Position the connected main reinforcement as a whole on the reinforcement production platform. After positioning, twist the straight thread sleeve to the end of the straight thread head with an extended length, and then weld the transverse reinforcement, longitudinal reinforcement and truss reinforcement to the main reinforcement of each segment reinforcement cage.

3. The method for constructing a low clearance underground continuous wall under a high-voltage line according to claim 2, characterized in that: In step S6.1, the straight thread sleeve adopts a Class I joint, and the same-section joint rate is 100%.

4. The method for constructing a low clearance underground continuous wall under a high-voltage line according to claim 2, characterized in that: In the step S6.2, the transverse steel bars are connected with the longitudinal steel bars by spot welding, the truss bars are double-sided welded, the length is not less than 5d, the intersections of the longitudinal and transverse truss bars are spot welded, and all the intersections within the range of the two main bars around the steel cage need to be spot welded. The steel bars are guaranteed to be straight, the surface is clean and free of oil, 50% of the internal intersections are spot welded, and 100% of the steel cage trusses and steel cage hanging points 1m above and below need to be spot welded.

5. The method for constructing a low clearance underground continuous wall under a high-voltage line according to claim 1, characterized in that: The construction process of step S7 is as follows: S7.

1. The truck crane maintains its position and hoists the head of the segmental reinforcement cage. The truck crane moves to a suitable position and hoists the tail of the reinforcement cage. S7.

2. The truck crane and the automobile crane lift the segment steel cage at the same time, and make the segment steel cage vertical to the bottom surface. Then, the truck crane drives the segment steel cage to the notch; S7.

3. After the segmental steel cage is lowered into place, a shoulder pole is used to place it on the notch, and then another segmental steel cage is lifted and aligned with the segmental steel cage in the notch, and the straight thread sleeve is twisted to be threadedly connected with the straight thread head of normal length; S7.

4. Arrange and weld the upper horizontal reinforcement and sealing reinforcement, weld the steel sections, take out the shoulder pole, and continue to lower the connected segment reinforcement cage into the notch. Once in place, use the shoulder pole to place it; S7.

5. Repeat S7.1-S7.4 until all segments are connected.

6. The method for constructing a low clearance underground continuous wall under a high-voltage line according to claim 1, characterized in that: In step S2, during the construction period, the slot section that needs to cross the guide wall position is completed first, poured with concrete, and equipped with an appropriate amount of steel plates of not less than 2 cm and laid at the position crossing the guide wall.

7. The method for constructing a low clearance underground continuous wall under a high voltage line according to claim 1, characterized in that: In step S3, the hydraulic grab bucket should be controlled to enter the trough slowly to grab the soil, and the soil dug out by the grab bucket is transported to the bulldozer site by a dump truck.

8. The method for constructing a low clearance underground continuous wall under a high voltage line according to claim 7, characterized in that: In step S3, as the excavation depth increases, fresh mud is continuously supplied into the trench, so that the mud plays a good wall protection role and prevents the trench wall from collapsing.

Images