Efficient construction method suitable for low-clearance underground diaphragm wall

Abstract

The invention discloses an efficient construction method suitable for a low-clearance underground diaphragm wall. The efficient construction method comprises the following steps that S1, a shallow groove wall is reinforced; s2, a low-clearance trenching machine is used; s3, a slot milling machine or a combination of the slot milling machine and the slot milling machine; s4, high-viscosity and specific-gravity slurry circulation; s5, the reinforcement cage is integrally manufactured and then segmented, cut and numbered; s6, the reinforcement cage is hoisted by sections through a large-tonnage folding arm crane and a small truck crane; s6, connecting long and short wires of the lengthened sleeve of the single-section reinforcement cage; s7, lower bagged joints and upper bulk joints of the large and small gravels are plugged; and S8, lowering a guide pipe and pouring concrete. According to the method, the stability of the groove wall in the long-time segmented hoisting process is guaranteed by optimizing the slurry circulation process, then the quality risk of the diaphragm wall is avoided, the quality and efficiency during segmented connection are guaranteed by optimizing the segmented hoisting process, the segmented hoisting time is minimized, and meanwhile the collapse risk of the groove wall is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of diaphragm wall construction, and particularly relates to an efficient construction method applicable to diaphragm walls with low headroom. Background Art

[0002] In recent years, with the intensification of urban construction, urban rail transit construction not only faces complex geological problems but also more complex environmental problems. The situation of constructing diaphragm walls under low headroom conditions such as under elevated bridges and high-voltage lines is increasing day by day, and conventional diaphragm wall construction methods and equipment are not applicable.

[0003] It is difficult to connect the joints of conventional steel reinforcement cages in sections. A large amount of auxiliary welding is required, the connection time is long, and it is difficult to ensure the verticality of the steel reinforcement cage. The sectional connection of glass fiber reinforced bars requires further reduction in height and an increase in the number of sections, resulting in an increase in U-shaped fasteners within the portal range, which in turn affects shield construction.

[0004] Moreover, the geological conditions in areas where diaphragm walls are required as retaining structures are usually poor. Due to the influence of sectional hoisting, the construction time is significantly increased. If the construction process is not adjusted, the risk of slurry trench collapse will increase significantly, further increasing the safety and quality risks. Summary of the Invention

[0005] In order to overcome the technical problems of sectional hoisting and long construction time in the construction process of diaphragm walls in the prior art, the present invention provides a construction method applicable to diaphragm walls with low headroom. By optimizing the slurry circulation process, the stability of the slurry trench during long-term sectional hoisting is ensured, thereby avoiding the quality risks of diaphragm walls. By optimizing the sectional hoisting process, the quality and efficiency during sectional connection are ensured, minimizing the total sectional hoisting time, and at the same time reducing the risk of slurry trench collapse, thus solving the above technical problems.

[0006] A construction method applicable to diaphragm walls with low headroom, the construction method comprising the following construction steps:

[0007] S1: Reinforcement of the shallow slurry trench. Adopt construction methods and equipment applicable to low headroom, such as high-pressure jet grouting piles or TRD, and appropriately expand the slurry trench reinforcement to avoid affecting subsequent trench excavation.

[0008] S2: Trench excavation with low headroom equipment. The low headroom equipment is a grab, a milling machine or a combination of both with a height dimension meeting the requirements of the effective headroom height. Since the power of the low headroom grab is lower than that of the conventional grab, the low headroom milling machine is preferably put into use after entering the rock.

[0009] S3: Mud circulation and hole cleaning. The mud performance parameters should meet the requirements for the long-term sectional hoisting of the diaphragm wall stability. The inspection frequency of the mud performance parameters is increased to once every 6 to 8 hours compared with the conventional diaphragm wall construction. The viscosity and specific gravity indicators of the mud performance parameters are increased compared with the conventional diaphragm wall construction. During the grooving process, a low headroom milling machine is used for dynamic slurry replacement and hole cleaning.

[0010] S4: The steel reinforcement cage is fabricated integrally and then segmented. Steel sleeve valves for grouting are pre-embedded at the edges of the steel reinforcement cages in both the first-stage and second-stage grooves. The steel bars are connected integrally by single bars, installed in place and then the wires are retracted. The H-shaped steel is fabricated integrally and then cut with a flat mouth, and numbered in sequence by segments.

[0011] The length h of a single-section steel reinforcement cage = the effective clear height H - the length h1 of the sling and lifting tools + the length h2 from the top shackle to the top of the cage - the safety distance (h3 + h4). The steel bar joints at the segmented parts are staggered by 50 cm according to the first-class joints.

[0012] S5: Sectional hoisting and connection of the steel reinforcement cage. The single-section steel reinforcement cage is transported to the vicinity of the groove section by a flatbed truck, and then hoisted into the groove by a heavy folding boom crane + a small truck crane. During the connection process, short steel bars are used for positioning welding at the corners of the H-shaped steel and then welded. A fixed pulley is added under the lifting beam of the heavy folding boom crane to facilitate the adjustment of the attitude of the steel reinforcement cage. A spirit level is used to detect the perpendicularity of the steel reinforcement cage in two dimensions, improving the success rate of the sleeve connection. When the fiberglass bars are hoisted in sections, the truss bars should be used to strengthen the fiberglass bar truss. After the rear section is lowered in place and connected to the front section, a part of the front section is lifted to remove the steel bar truss in the portal area. When the steel reinforcement cage is hoisted and connected in sections, the sonic logging tubes, grouting tubes and inclinometers all need to be connected in sections. The sonic logging tubes are preferably connected with clamp-type joints.

[0013] S6: Prevention of concrete bypass at the joint. Gravel with a size of 5 cm - 10 cm is used, with bags at the bottom and loose at the top, and a positioning card board is set at the top to prevent the concrete from bypassing at the joint of the first-stage groove.

[0014] S7: Lowering the conduits and concrete pouring. It is preferred to use 3 conduits for pouring.

[0015] In the above construction method applicable to the low headroom diaphragm wall, in step S3, the low headroom milling machine is used to extract the bottom mud in real time, filter it through a sand filter, and then reflux the mud into the groove, enabling the slurry replacement procedure to be realized during the process compared with the impact drill, so that the mud in the groove always maintains the best performance.

[0016] In the above construction method applicable to the low headroom diaphragm wall, in step S4, steel sleeve valves for grouting are pre-embedded at the edges of the steel reinforcement cage. When there are quality hidden dangers at the joints, grouting can be used to make up for them.

[0017] For the above construction method applicable to low - headroom diaphragm walls, in step S4, the spliced joints of the reinforcement cages are connected by lengthened sleeves. The length of the sleeves is increased compared to conventional sleeves, with full threads at the upper part and half - threads at the lower part. When connecting, it is screwed from top to bottom. A lock nut is set on the full - thread part to ensure that the torques on both sides of the sleeve meet the requirements.

[0018] For the above construction method applicable to low - headroom diaphragm walls, in step S5, a heavy - duty folding - boom crane is used as the main crane for sectional hoisting, which is more flexible than a customized gantry crane and is convenient for turning.

[0019] For the above construction method applicable to low - headroom diaphragm walls, in step S5, when the glass - fiber reinforced bars are hoisted in sections, the truss bars use steel - bar trusses to strengthen the glass - fiber reinforced bar trusses. After the rear section is lowered in place and connected to the front section, the steel - bar trusses in the portal area of the front section are lifted and removed, ensuring the safety during the sectional hoisting of the glass - fiber reinforced bars.

[0020] For the above construction method applicable to low - headroom diaphragm walls, in step S6, gravel with a size of 5 cm - 10 cm is used for joint anti - flow - around treatment, which is more suitable for the low - headroom environment and can better ensure the joint quality compared to conventional joint boxes and sand bags.

[0021] Generally speaking, compared with the prior art through the above - mentioned technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0022] 1. For the construction method of the present invention applicable to low - headroom diaphragm walls, by optimizing the mud circulation process, the stability of the groove wall during the long - time sectional hoisting process is ensured, thereby avoiding the quality risks of the diaphragm wall.

[0023] 2. For the efficient construction method of the present invention applicable to low - headroom diaphragm walls, by optimizing the sectional hoisting process, the quality and efficiency during sectional connection are ensured, the total sectional hoisting time is minimized, and at the same time, the risk of groove - wall collapse is reduced.

[0024] 3. For the efficient construction method of the present invention applicable to low - headroom diaphragm walls, by optimizing the joint anti - flow - around treatment process, the joint treatment quality is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following further elaborates on the specific embodiments of the present invention with reference to the drawings, where:

[0026] Figure 1 is a schematic diagram of the main crane during sectional hoisting for the efficient construction method of the present invention applicable to low - headroom diaphragm walls;

[0027] Figure 2 is a detailed schematic diagram of the lifting tool during sectional hoisting for the efficient construction method applicable to low - headroom diaphragm walls.

[0028] Figure 3 It is a schematic diagram of the segment length of the steel cage of the present invention;

[0029] In the picture: 1- heavy folding arm crane, 2- lifting pole, 3- fixed pulley, 4- single-section steel cage, 5- overhead obstacle. DETAILED DESCRIPTION

[0030] The present invention provides an efficient construction method applicable to a low-headroom underground continuous wall, comprising the following construction steps:

[0031] Step 1: Shallow trench wall reinforcement, using methods and equipment suitable for low headroom, such as high-pressure jet grouting piles or TRD. The trench wall reinforcement is appropriately extended 5cm to avoid affecting subsequent trenching;

[0032] Step 2: Low-headroom equipment is used to form grooves. A certain brand XG500E low-headroom grab slotting machine and a certain brand XTC80 / 60M low-headroom slotting machine are used to form grooves. After entering the rock, the slotting machine is used to mill the grooves;

[0033] Step 3: Mud circulation and hole cleaning. The mud performance parameters should meet the needs of long-term segmented hoisting slot wall stability. The mud performance parameters are higher than the conventional underground continuous wall construction in terms of viscosity and specific gravity. The specific gravity of the mud is 1.05-1.08g / cm 3 Increase to 1.06~1.15g / cm 3 , the viscosity is increased from 18 to 25 seconds to 24 to 30 seconds, the mud wall protection effect is strengthened, the groove is milled with a groove milling machine after entering the rock, and the bottom mud is extracted simultaneously and the sediment is filtered out through a sand filter. After the mud is returned to the groove, a mud replacement procedure is added to keep the mud in the groove at the best performance. After the new mud is prepared, it is tested and the mud in the groove is tested every four hours;

[0034] Step 4: The steel cage is made as a whole and then divided into sections. The edges of the first-phase and second-phase trough steel cages are pre-embedded with steel φ50mm sleeve valve pipes for grouting. The single-section steel cage 4 is installed in place using an integral connection and then the wire is withdrawn. The H-shaped steel is made as a whole and then cut and numbered in sequence.

[0035] Section length h = effective headroom H - sling length h1 + length from top shackle to cage top h2 - safety spacing (h3 + h4). The steel bar joints at the sections are considered as first-level joints and are only staggered by 50cm to avoid reducing the effective cage length and thus increase the number of sections, such as Figure 3 shown.

[0036] The joints of the steel reinforcement cage are connected by 76mm extended sleeves. The length of the sleeve is increased compared with the conventional sleeve. The upper part is full-threaded +2p, and the lower part is half-threaded +2p. When connecting, screw from top to bottom. A lock nut is set on the full-threaded part to ensure that the torque on both sides of the sleeve meets the requirements.

[0037] Step Five: Hoisting and connecting the steel reinforcement cage in sections: After the trench excavation is completed and accepted, use a flatbed truck to transport the single-section steel reinforcement cage to the vicinity of the trench section, and then use a 120t heavy-duty folding boom crane 1 + a 25t truck crane to lift the single-section steel reinforcement cage 4 into the trench in sequence. The 120t heavy-duty folding boom crane 1 is used as the main hoist. During the connection process, the corners of the H-shaped steel are positioned and welded with short steel bars and then welded. The lifting spreader 2 at the position of the heavy-duty folding boom hook is lowered, and a fixed pulley 3 is added to facilitate the adjustment of the posture of the steel reinforcement cage. As Figure 1 and Figure 2 shown, it is the overall structure diagram and partial view of the folding crane 1 described in the present invention. Use a horizontal spirit level to detect the perpendicularity of the steel reinforcement cage in two dimensions to improve the success rate of sleeve connection.

[0038] When hoisting the glass fiber bars in sections, the truss bars should use steel bar trusses to strengthen the glass fiber bar trusses. After the rear section is lowered in place and connected to the front section, then lift and remove the steel bar trusses in the portal area in part of the front section. When hoisting and connecting the steel reinforcement cage in sections, the sonic logging tubes, grouting tubes and inclinometers need to be connected in sections. The sonic logging tubes are preferably connected with clamp-type joints. During the hoisting process, attention should be paid to the protection of the overhead obstacles 5.

[0039] Step Six: Seal to prevent concrete from flowing around the joint. Use gravel with a size of 5cm - 10cm, set a positioning card plate for lowering at the top, pack the gravel in bags at the lower 1 / 3 depth and tamp it tightly, and then tamp the upper part with gravel blocks in layers to prevent the concrete from flowing around at the joint of the first-phase trench;

[0040] Step Seven: Lower the conduits, and conduct concrete pouring after secondary hole cleaning. To ensure the filling effect and compactness of the concrete, it is preferred to use 3 conduits for pouring.

Claims

1. A construction method suitable for low headroom underground continuous wall, characterized in that: The construction method includes the following construction steps: S1: Shallow trench wall reinforcement, using methods and equipment suitable for low headroom, such as high-pressure jet grouting piles or TRD, trench wall reinforcement and externalization; S2: Slotting with low headroom equipment. The low headroom equipment is a slotting machine, a slot milling machine or a combination of the two. After entering the rock, the low headroom slot milling machine is used first; S3: Mud circulation and hole cleaning. The mud performance parameters meet the requirements of long-term segmented hoisting trench wall stability. The frequency of mud performance parameter testing is increased to once every 6 to 8 hours compared with conventional underground continuous wall construction. During the trenching process, a low-headroom slot milling machine is used to dynamically change the mud and clean the hole; S4: The steel cage is made as a whole and then divided into sections. The edges of the steel cages of the first-phase and second-phase troughs are pre-buried with steel sleeve valve pipes for grouting. The steel bars are connected as a single piece and installed in place before the wire is withdrawn. The H-shaped steel is made as a whole and then cut flat, and numbered in sections in sequence. S5: The steel cage is hoisted and connected in sections. A flatbed truck is used to transport the single steel cage to the vicinity of the slot section, and then a heavy-duty knuckle-arm crane (1) + a small truck crane is used to lift the cage into the slot; S6: Joint anti-circumvention plugging, using 5-10cm sized gravel in bags at the bottom and in bulk at the top, with a positioning card at the top; S7: Lower the conduit and pour concrete.

2. A construction method suitable for a low clearance underground continuous wall according to claim 1, characterized in that: In step S3, a low-headroom slot milling machine is used to extract the bottom mud in real time, and the mud is filtered through a sand filter and then flows back into the slot. Compared with an impact drill, a slurry replacement procedure can be implemented during the process.

3. A construction method applicable to a low clearance underground continuous wall according to claim 1, characterized in that: In step S4, steel sleeve valve pipes for grouting are pre-buried at the edges of the steel cage, and grouting can be used to compensate for quality risks at the joints.

4. A construction method for a low clearance underground continuous wall according to claim 1, characterized in that: In step S4, the steel cage sections are connected by extended sleeves, the upper part is fully threaded, the lower part is half threaded, and a lock nut is set on the fully threaded part.

5. The construction method for a low clearance underground continuous wall according to claim 1, characterized in that: In step S5, when the fiberglass reinforcement is hoisted in sections, the truss reinforcement uses a steel truss to reinforce the fiberglass reinforcement truss. After the rear section is lowered into place and connected with the front section, part of the front section is lifted and the steel truss in the portal area is removed.

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