Construction supporting method for top cavity part of diaphragm wall

Abstract

The invention discloses a construction supporting method for a cavity part at the top of an underground diaphragm wall. The construction supporting method comprises the following steps: S1, reinforcing a groove wall of a cement mixing pile before construction of a guide wall; s2, guide wall construction: leveling a site, measuring and positioning, excavating and treating spoil, binding reinforcing steel bars, erecting a template, pouring concrete, removing the template, arranging a cross brace and backfilling soil on the outer side of the guide wall; s3, after construction of the guide wall is completed, a small hydraulic trenching machine is adopted for trenching, steel reinforcement frameworks are installed in batches, and a steel reinforcement cage is formed; s4, after the steel reinforcement framework is installed, concrete pouring is conducted on the continuous wall to be constructed in a segmented mode, and a plurality of continuous wall groove sections to be constructed are formed; s5, reinforced concrete prefabricated check blocks are manufactured according to the structure of the underground diaphragm wall and the depth of the cavity section; and S6, reinforced concrete prefabricated check blocks are installed. The problem that soil pressure on the two sides of the groove wall of the underground diaphragm wall extrudes the groove section of the top cavity is solved.

Description

Technical Field

[0001] The invention relates to a construction support method for a cavity part at the top of a ground-connected wall. Background Art

[0002] Underground continuous wall is a foundation project that uses a trenching machine on the ground to dig a long and narrow deep trench along the peripheral axis of the deep excavation project under the condition of mud wall protection. After the trench is cleaned, a steel cage is suspended in the trench, and then underwater concrete is poured using the conduit method to build a unit trench section. This process is carried out section by section to build a continuous reinforced concrete wall underground. As a water interception, anti-seepage, load-bearing and water-retaining structure, the wall has high rigidity and can withstand great earth pressure when used for foundation pit excavation. Foundation settlement or landslide accidents rarely occur. It has become an indispensable retaining structure in deep foundation pit support projects and is suitable for a variety of foundation conditions. The underground continuous wall has a wide range of applicability to foundations, from weak alluvial strata to medium Hard strata, dense gravel layers, various soft rocks and hard rocks and other foundations can be used to build underground continuous walls, with high work efficiency, short construction period, reliable quality and high economic benefits, small vibration and low noise during construction, which is very suitable for construction in cities, occupies a small area, can make full use of the limited ground and space within the building red line, give full play to the investment benefits, and have good anti-seepage performance. Due to the improvement of wall joint form and construction method, the underground continuous wall is almost impermeable and can be used as a rigid foundation. The underground continuous wall is no longer simply used as anti-seepage and waterproof, deep foundation pit retaining wall, and underground continuous wall is increasingly used to replace pile foundation, caisson or caisson foundation, and can bear greater loads, with high work efficiency, short construction period, reliable quality and high economic benefits.

[0003] However, due to the geological conditions in some areas of backfill soil, the backfill soil has high compressibility, high water content and low strength. The engineering properties of the backfill soil vary greatly. The construction process coincided with the rainy season, and large equipment was used in the construction of underground continuous walls. The movement of the equipment caused large vibrations. All of the above leads to a great risk of soil collapse in the cavity at the top of the ground-connected wall, and the support problem of the cavity slot section at the top of the underground continuous wall is difficult to solve.

[0004] Therefore, a construction support method for the top cavity portion of a ground-connected wall is provided. Summary of the invention

[0005] The purpose of the present invention is to overcome the existing defects and provide a construction support method for the top cavity part of the ground-connected wall, which solves the problem of soil pressure on both sides of the underground continuous wall groove squeezing the top cavity groove section.

[0006] The technical solution to achieve the above purpose is:

[0007] A construction support method for a cavity portion at the top of a ground-connected wall, comprising:

[0008] Step S1, before the guide wall is constructed, the cement mixing pile groove wall is reinforced;

[0009] Step S2, guide wall construction, including site leveling, measurement and positioning, excavation and disposal of spoil, tying of steel bars, support of formwork, pouring of concrete, removal of formwork and installation of cross braces and backfilling of soil outside the guide wall;

[0010] Step S3, after the guide wall construction is completed, a small hydraulic slotting machine is used to form slots, and steel bar skeletons are installed in batches to form a steel bar cage;

[0011] Step S4, after installing the steel skeleton, concrete is poured in sections of the continuous wall to be constructed to form a number of continuous wall groove sections to be constructed;

[0012] Step S5, making a reinforced concrete prefabricated block according to the underground continuous wall structure and the depth of the cavity section;

[0013] Step S6, installation of prefabricated reinforced concrete blocks.

[0014] Preferably, in step S1, the trench wall reinforcement is constructed using 850@600 three-axis cement mixing piles, the three-axis mixer has a mixing sinking speed of ≤0.6m / min, and a mixing lifting speed controlled within the range of 0.3-2m / min.

[0015] Preferably, in step S1, the 850@600 triaxial cement strength grade is 42.5. During the construction of 850@600 triaxial cement mixing piles, the cement content is selected by testing different soil layers, and the cement content is not less than 15%, the standard value of the 28d unconfined compressive strength is not less than 0.8MPa, and the wall permeability coefficient is less than 1.0×107cm / s.

[0016] Preferably, in step S5, the concrete strength of the precast reinforced concrete block is C30, and the block is hoisted after the concrete strength reaches 80% of the design requirement.

[0017] Preferably, in step S6, the installation of the prefabricated reinforced concrete block includes:

[0018] Step S61, after the concrete pouring of the underground continuous wall groove section is completed, a prefabricated reinforced concrete block is installed into the cavity groove by using a lifting machine;

[0019] Step S62, install 3 pieces for each section at a length of 2 meters, and backfill the trench with soil after the underground continuous wall concrete hardens to support the trench body;

[0020] Step S63, after the construction of all adjacent trench sections is completed, the prefabricated reinforced concrete blocks can be hoisted out and reused.

[0021] The beneficial effects of the present invention are as follows: the present invention solves the problem of supporting the cavity section of the underground continuous wall. The application of cement mixing pile trench wall reinforcement + prefabricated concrete block support not only solves the problem of water stopping of the cavity section of the ground continuous wall during construction in the rainy season, but also prevents the inward tilt of the cavity section trench wall due to lateral soil pressure, resulting in a reduction in the trench width, affecting the connection between the ground continuous wall of the current trench section and the adjacent trench sections, reducing the wall width, affecting the overall linear shape, and other problems, effectively ensuring the safety and quality of the underground continuous wall construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of a construction support method for a top cavity portion of a ground-connected wall according to the present invention;

[0023] Figure 2 It is a specific flow chart of the installation of the reinforced concrete prefabricated stopper in the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of the prefabricated reinforced concrete block after installation of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0026] The present invention will be further described below in conjunction with the accompanying drawings.

[0027] like Figure 1 As shown, a construction support method for the top cavity portion of a ground-connected wall comprises:

[0028] Step S1, before the guide wall is constructed, the cement mixing pile groove wall is reinforced.

[0029] In the embodiment, the trench wall reinforcement is constructed by using 850@600 three-axis cement mixing piles, the three-axis mixer has a mixing sinking speed of ≤0.6m / min, and the mixing lifting speed is controlled within the range of 0.3-2m / min.

[0030] In the embodiment, the 850@600 triaxial cement strength grade is 42.5. When constructing the 850@600 triaxial cement mixing pile, the cement content is selected according to the test of different soil layers, and the cement content is not less than 15%, the standard value of the 28d unconfined compressive strength is not less than 0.8MPa, the wall permeability coefficient is less than 1.0×107cm / s, and the uniform sinking and uniform lifting are maintained. During the mixing and lifting, negative pressure should not be generated in the hole to cause the surrounding foundation to settle. The mixing times or mixing time should ensure the quality of the cement soil mixing pile. If the pile is left for more than 2 hours for some reason, The mixed slurry should be treated as waste slurry and is strictly prohibited from being reused; the overlap time between piles should not be more than 24 hours. If it exceeds the time for some reason, the overlapping construction must slow down the mixing speed to ensure the overlap quality; if the overlap cannot be made for a long time or the overlap is poor, a cold joint record should be made, and after approval by the supervision and design units, technical measures such as additional mixing piles or rotary jet piles can be taken at the overlap to ensure the construction quality of the mixing piles; the vertical accuracy of the three-axis mixing piles for trench wall reinforcement should not be less than 1 / 200, and the pile position deviation should not exceed 50mm. After the trench wall reinforcement is completed, the reinforced concrete guide wall construction should be carried out.

[0031] Step S2, guide wall construction, includes site leveling, measurement and positioning, excavation and disposal of waste soil, tying steel bars, supporting formwork, pouring concrete, removing formwork and setting cross braces and backfilling soil on the outside of the guide wall.

[0032] Step S3, after the guide wall construction is completed, a small hydraulic slotting machine is used to form slots, and steel bar skeletons are installed in batches to form a steel bar cage.

[0033] Step S4, after the steel frame is installed, concrete is poured in sections of the continuous wall to be constructed to form a number of continuous wall groove sections to be constructed.

[0034] Step S5, making a prefabricated reinforced concrete block according to the underground continuous wall structure and the depth of the cavity section.

[0035] In the embodiment, the concrete strength of the reinforced concrete prefabricated stopper is C30, and the lifting is performed after the concrete strength reaches 80% of the design requirement.

[0036] Step S6, installation of prefabricated reinforced concrete blocks.

[0037] like Figure 2 As shown, the installation of reinforced concrete prefabricated stopper includes:

[0038] Step S61: After the underground continuous wall trench section is poured with concrete, a lifting machine is used to install the prefabricated reinforced concrete block into the cavity trench. Figure 3 shown.

[0039] Step S62, install 3 pieces for each section at a length of 2 meters, and backfill the trench with soil for support after the underground continuous wall concrete hardens to meet the requirements for supporting the trench body.

[0040] Step S63, after the construction of all adjacent trench sections is completed, the prefabricated reinforced concrete blocks can be hoisted out and reused.

[0041] In this embodiment, for an underground continuous wall with a top elevation of 1.3m, an elevation of 1.8m after adding an over-pouring part of 50cm, a ground and guide wall elevation of 7m, and a top cavity part of 5.2m, in order to solve the problem of supporting the top cavity trench section of the underground continuous wall, the above method is used to solve the problem of soil pressure on both sides of the trench wall of the underground continuous wall squeezing the guide wall according to the engineering environment, construction deployment, concrete guide wall size, trench wall support conditions, etc.

[0042] In this embodiment, the technical parameters of the prefabricated reinforced concrete block are: two widths of 800mm and 1000mm, a length of 5m, and two sets of φ22 lifting rings embedded in the top.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A construction support method for the top cavity of a ground-connected wall, characterized in that: include: Step S1, before the guide wall is constructed, the cement mixing pile groove wall is reinforced; Step S2, guide wall construction, including site leveling, measurement and positioning, excavation and disposal of spoil, tying of steel bars, support of formwork, pouring of concrete, removal of formwork and installation of cross braces and backfilling of soil outside the guide wall; Step S3, after the guide wall construction is completed, a small hydraulic slotting machine is used to form slots, and steel bar skeletons are installed in batches to form a steel bar cage; Step S4, after installing the steel skeleton, concrete is poured in sections of the continuous wall to be constructed to form a number of continuous wall groove sections to be constructed; Step S5, manufacturing a reinforced concrete prefabricated stopper according to the underground continuous wall structure and the depth of the cavity section; Step S6, installation of prefabricated reinforced concrete blocks.

2. A construction support method for the top cavity of a ground-connected wall according to claim 1, characterized in that: In step S1, the trench wall is reinforced by using 850@600 three-axis cement mixing piles, the three-axis mixer has a mixing sinking speed of ≤0.6m / min, and the mixing lifting speed is controlled within the range of 0.3-2m / min.

3. The construction support method for the top cavity of a ground-connected wall according to claim 1, characterized in that: In the step S1, the 850@600 triaxial cement strength grade is 42.

5. When constructing the 850@600 triaxial cement mixing piles, the cement content is selected by testing different soil layers, and the cement content is not less than 15%, the standard value of the 28d unconfined compressive strength is not less than 0.8MPa, and the wall permeability coefficient is less than 1.0×107cm / s.

4. The construction support method for the top cavity of a ground-connected wall according to claim 1, characterized in that: In step S5, the concrete strength of the reinforced concrete prefabricated block is C30, and the block is hoisted after the concrete strength reaches 80% of the design requirement.

5. The construction support method for the top cavity of a ground-connected wall according to claim 1, characterized in that: In step S6, the installation of the prefabricated reinforced concrete block includes: Step S61, after the concrete pouring of the underground continuous wall groove section is completed, a prefabricated reinforced concrete block is installed into the cavity groove by using a lifting machine; Step S62, install 3 pieces for each section at a length of 2 meters, and backfill the trench with soil after the underground continuous wall concrete hardens to support the trench body; Step S63, after the construction of all adjacent trench sections is completed, the prefabricated reinforced concrete blocks can be hoisted out and reused.

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