WO2020078160A4

WO2020078160A4 - Construction joint structure in deep-excavation reverse construction

Info

Publication number: WO2020078160A4
Application number: PCT/CN2019/106441
Authority: WO
Inventors: 张志刚; 文铁军; 王万里; 周循
Original assignee: 中冶南方工程技术有限公司
Priority date: 2018-10-16
Filing date: 2019-09-18
Publication date: 2020-05-28
Also published as: CN109113068A; CN109113068B; WO2020078160A1

Abstract

A construction joint structure in deep-excavation reverse construction, comprising an upper wall (11), a lower wall (12), connection components, and impermeable components. The bottom surface of the upper wall (11) and the top surface of the lower wall (12) fit closely; the bottom of the upper wall (11) and the top of the lower wall (12) have the same slope gradient; the connection components comprise vertically inserted reinforcing bars (21); the impermeable components comprise a water-proof steel plate (31), water-swellable rubber strips (33), and an exhaust pipe (32); the water-swellable rubber strips (33) are disposed at the bottom of the upper wall (11); parts of the vertically inserted reinforcing bars (21), of the water-proof steel plate (31), and of the exhaust pipe (32) are buried in the upper wall (11), and the other parts are buried in the lower wall (12).

Description

Construction joint structure for reverse construction of deep foundation pit

Technical field

The invention belongs to the technical measures of reverse construction of the external wall of the underground structure in the large deep foundation pit, and belongs to the field of reverse construction method of the underground deep foundation pit wall, and particularly relates to a construction joint structure of the deep foundation pit reverse construction.

Background technique

The reverse construction method is a method for the construction of underground engineering structures from top to bottom layer by layer. In recent years, there have been more and more cases of using this method for large-scale deep foundation pit underground engineering. In order to ensure that the waterproof grade of the entire project meets the corresponding specification requirements, it is necessary to deal with the anti-seepage and crack prevention measures at the construction joints of the underground wall layer by layer (section) reverse construction, which is also the key to the success of the reverse construction method, especially involving large Underground slag treatment cyclone sedimentation tanks and other structures that store a large amount of contaminated water bodies, the construction quality of the reverse construction of the external wall is particularly important.

At present, the waterproof construction measures of the construction joints of the reverse construction method are relatively single, and the convenience of construction and the reliability of use have not been fully considered, especially the details of the connection structure and anti-seepage structure of the joints, which directly affect the construction in the later use. Waterproof effect. The existing underground engineering reverse construction construction joints have the following shortcomings:

1. The contact surface of the construction joint is set horizontally without slope, and the internal gas is not easy to be exhausted when the lower layer (segment) wall is poured, which causes holes or honeycomb pits in the concrete at the joint, which is not conducive to waterproofing.

2. The contact surface of the construction joint often adopts an additional manual formwork, namely a steel mold or a wooden mold as the bottom mold, resulting in a smoother bottom surface of the upper section of the wall, which requires manual secondary chiseling treatment at a later stage and inconvenient construction.

3. Only one waterproof measure is often adopted, which is not enough to deal with the waterproof effect under complex working conditions, and it is difficult to remedy the construction defects once it causes construction defects.

4. When the concrete in the lower wall is poured too fast and the internal air is not easily discharged, it is easy to form a cavity or the concrete vibration is not dense at the outer corner of the water stop steel plate, which greatly affects the waterproof effect.

5. When pouring the lower wall, it is often not provided with a long pouring channel or a single sprue, which is not conducive to vibration and compensation for the later hardening shrinkage and settlement of the concrete, resulting in micro cracks at the joints of the wall.

Summary of the invention

The invention provides a construction joint structure for deep foundation pit reverse construction, which is intended to improve the problems of the anti-seepage effect of the construction joint of the reverse construction method and the inconvenient control of the construction joint quality.

To this end, the technical solution provided by the present invention is: a construction joint structure for deep foundation pit reverse construction, including a wall body, a connection component and an anti-seepage component, the wall body includes an upper wall and a lower wall, the The bottom of the upper wall and the upper part of the lower wall are tightly attached, the bottom of the upper wall and the upper part of the lower wall have the same slope, the connection component includes vertical insertion bars, and the anti-seepage component includes a water stop steel plate, and A water-swellable rubber strip and an exhaust pipe, the water-swellable rubber strip is arranged at the bottom of the upper wall, and the vertical insertion bars, the water-stopping steel plate and a part of the exhaust pipe are buried in the upper wall, the The other parts of the vertical insertion bars, the water-stop steel plates and the exhaust pipes are buried in the lower wall.

Further, it also includes a bottom mold that is formed before pouring concrete in the upper wall and removed during the construction of the lower wall. The bottom mold is provided at the bottom of the upper wall, the bottom mold is filled with two layers of materials, and the lower layer It is made of brick or masonry, the upper layer is filled with gravel, and the top surface of the gravel has a certain slope.

Furthermore, it also includes a corbel pouring trough, which is located outside the upper inner side of the lower wall, and the opening of the top surface of the corbel pouring trough exceeds the bottom of the upper wall by a certain height.

Further, the connection assembly further includes a dense-hole wire mesh. Before the lower wall is cast, the dense-hole wire mesh is in an "L" shape, and the vertical edge of the "L" -shaped dense-hole wire mesh is placed on the upper wall In the concrete protective layer outside the body, the bottom edge is closely attached to the bottom surface of the upper wall, and the length of the bottom edge along the slope direction of the bottom wall of the upper wall is greater than the thickness of the wall; before the lower wall is poured, the bottom edge of the dense hole wire mesh is closely attached After the bottom surface of the upper section wall is partially peeled off, it is straightened vertically, so that the bottom edge of the dense-hole wire mesh is placed in the concrete protective layer outside the lower section wall, and the bottom edge of the upper section wall body naturally causes a rough surface after peeling.

Further, the water-stopping steel plate is vertically buried at a half of the wall thickness of the wall, and is provided along the length of the wall. The two ends of the water-stopping steel plate are inclined toward the inside of the wall, and the water-stopping steel plate The upper end is inclined toward the inner side of the wall to form an upper side, and the lower end of the water stop steel plate is inclined toward the inner side of the wall to form a lower side.

Further, there are a plurality of exhaust pipes, and the plurality of exhaust pipes are arranged at intervals along the construction joint, the exhaust pipe includes a lower straight pipe section and an upper inclined pipe section inclined toward the inner side of the wall, the upper inclined pipe section The inclination angle is consistent with the upper inclination angle of the water stop steel plate. The lower straight pipe section of the exhaust pipe is closely attached to the outer side of the water stop steel plate. The lower pipe mouth of the exhaust pipe is exposed to the bottom surface of the upper wall, and the exposed part is provided with a cross or a rice The incision, the upper nozzle of the exhaust pipe is exposed inside the upper wall.

Further, it also includes tape or foam board for blocking the upper and lower nozzles of the exhaust pipe, and sealing material used for filling the exhaust pipe after the concrete of the lower wall is completed, the upper and The lower pipe mouth is sealed with tape or foam board before pouring the concrete in the lower section of the wall. When the concrete in the lower section of the wall is poured, the plugging is removed to ensure the smoothness of the pipe. The exhaust pipe is placed after the concrete in the lower section is finished. Fill the pipe with sealing material. The sealing material can be micro-expansion cement mortar or micro-expansion fine stone concrete, then cut off the part of the upper pipe mouth exposed inside the upper section of the wall, and then use round steel plates to seal the pipe mouth.

Further, there are two water-swellable rubber strips, which are located on both sides of the water-stopping steel plate and the exhaust pipe, respectively, and the two water-swellable rubber strips are horizontally arranged along the construction joint.

Further, the vertical insertion bars include two rows of vertical reserved main longitudinal bars arranged on both sides of the wall, and two vertical additional short insertion bars arranged between the two rows of upper vertical reserved main longitudinal bars Ribs, the main longitudinal ribs and the vertical additional short insertion ribs in the upper section are all set along the length of the wall.

Further, both sides of the top of the lower section wall are provided with vertical main longitudinal bars of the lower section, the vertical main longitudinal bars of the lower section are connected to the vertical reserved main longitudinal bars of the upper section of the corresponding side, and the vertical section of the lower section is vertical The connection points of the main longitudinal ribs and the upper section vertical reserved main longitudinal ribs in the same connecting section are staggered from each other.

The invention has the following beneficial effects:

1. The contact surface of the construction joint is set with a certain slope, which is more conducive to the discharge of internal air when the concrete of the lower wall is poured.

2. Dense-hole wire mesh is set at the construction joints. During the construction of the upper wall, the outer vertical wire mesh can prevent the bottom soil from collapsing and entering the wall. When removing the bottom mold, strip the bottom edge of the wire mesh and straighten it vertically. , So that the ideal rough surface (rough surface) can be naturally formed on the bottom of the upper wall, which is conducive to the bonding of the post-cast concrete and promotes the waterproof effect. In addition, the straightened wire mesh can also play the role of the bottom wall outer model To prevent the top soil from falling into the wall when the concrete of the lower wall is poured.

3. An exhaust pipe is provided to discharge the air at the top dead corner of the lower wall of the concrete during pouring, to prevent the appearance of external corner cavities or honeycomb pits. Later, the exhaust pipe is filled with micro-expansion material, which will cause micro cracks in the construction joint. Carry out secondary sealing to further enhance the waterproof effect of the joint.

4. A corbel pouring trough is provided to make the concrete pouring construction of the lower wall more convenient. The top surface of the pouring trough is higher than the bottom of the upper wall by a certain height, which is conducive to the compensation of shrinkage and settlement when the concrete hardens later, which can prevent the interior of the pouring surface Generate micro cracks or cracks to develop.

5. The construction joint adopts multiple anti-seepage and crack-proof technical measures, which greatly improves the waterproof effect of the inside and outside of the wall and is more safe and reliable.

BRIEF DESCRIPTION

1 is a schematic diagram of the upper wall and bottom form of a construction joint structure for deep foundation pit reverse construction according to an embodiment of the present invention;

2 is a schematic diagram of an upper wall and a lower wall of a construction joint structure for deep foundation pit reverse construction according to an embodiment of the present invention;

DESCRIPTION OF REFERENCE NUMERALS: 1. Underground structure; 11. Upper section wall; 12. Lower section wall; 121. Corbel pouring trough; 2. Connection components; 21. Vertical insertion bar; 211. Upper section vertical reserved main longitudinal Ribs; 212, additional short insertion ribs; 213, lower vertical main longitudinal ribs; 214, connection points; 22, dense-hole wire mesh; 221, vertical edges; 222, bottom edges; 3. impermeable components; 31, water stop Steel plate; 311, lower side measurement; 312, upper side; 32, exhaust pipe; 321, upper inclined pipe section; 322, lower straight pipe section; 323, adhesive tape (or foam board), 324, sealing material; 325, round sealing plate 33, water-swellable rubber strip; 331, fixed surface; 4, bottom mold; 41, upper layer gravel mold; 42, lower layer brick mold or rubble mold.

detailed description

The following describes the principles and features of the present invention with reference to examples. The examples are only used to explain the present invention, not to limit the scope of the present invention.

The technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the present invention, but not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present invention.

As shown in FIG. 1 and FIG. 2, a construction joint structure for deep foundation pit reverse construction provided in this embodiment includes an underground structure 1, an upper wall 11, a lower wall 12, a connection assembly 2, and an anti-seepage Component 3, bottom mold 4.

The underground structure 1 is an underground wall made of concrete. The upper wall 11 and the bottom mold 4 are first constructed. The bottom of the upper wall 11 is provided with a slope. At the bottom of the upper wall 11, a vertical insertion bar 21 is reserved. The vertical insertion bars 21 include two rows of upper vertical reserved main longitudinal bars 211 inside and outside and two rows of vertical additional short insertion bars 212. The two vertical upper vertical reservation main longitudinal bars 211 are located on both sides of the wall, vertical The additional short insertion ribs 212 are located between the two rows of upper vertical reserved main longitudinal ribs 211. The bottom of the upper wall 11 is laid with dense-hole wire mesh 22. Before the lower wall 12 is cast, the wire mesh is in the shape of "L" and dense The vertical edge 221 of the hole wire mesh is located in the concrete protective layer of the upper side wall 11 and the vertical protection of the main longitudinal ribs 211 in the upper section. The bottom edge 222 of the dense wire mesh is attached to the bottom surface of the upper wall 11 and is kept with the upper wall The bottom of the body 11 has the same slope, and the dense-hole wire mesh 222 is provided along the length of the wall. The wall is provided with a vertical water-stop steel plate 31 at the half of the wall thickness. There is an inclination towards the inside of the wall, and the water stop steel plate 31 is buried along the length of the wall. The outside of the water stop steel plate 31 is provided with an exhaust pipe 32. The upper inclined pipe section 321 of the exhaust pipe 32 is exposed in the upper wall 11 The side is 25-50 mm, and the lower straight pipe section 322 is closely attached to the outer side of the water-stopping steel plate 31. The lower straight pipe section 322 exposes the bottom surface of the upper wall 11 by 10-30 mm. Before the concrete of the upper wall 11 is poured, the exhaust pipe 32 The upper and lower nozzles are sealed with adhesive tape 323 or foam board to prevent debris from entering the pipe. The upper layer of the bottom mold 4 uses a gravel mold 41, the lower layer uses a brick mold 42 or a rubble mold, the top surface of the gravel mold 41 is provided with a slope, and the gravel mold 41 It should be compacted in layers. The upper vertical insertion bars 21 are inserted into the gravel mold 41. Part of the water stop steel plate 31 is placed in the upper wall 11 and the other part is placed in the gravel mold 41. After the bottom mold 4 is formed, Then, the concrete of the upper wall 11 is poured. After the concrete of the upper wall 11 reaches the design strength, the lower wall 12 is constructed. During the construction of the lower wall 12, the bottom mold 4 is excavated first, and then the bottom edge 222 of the wire mesh is closely attached The bottom surface of the upper wall is partially peeled and then straightened vertically, so that the bottom surface of the upper wall 11 forms a natural rough surface (rough surface), which is conducive to the bonding of the post-cast concrete and promotes the waterproof effect, and the bottom edge is in the lower wall It is placed vertically in the concrete protective layer of the lower wall during pouring. The straightened wire mesh can also play the role of the outer model of the lower wall to prevent the top soil from falling into the wall when the lower wall is poured. The bottom surface of the upper wall 11 is chiseled with a long fixed surface 331 along the construction joint, and the water-swellable rubber strip 33 is fixed on the fixing surface 331 with adhesive or nails, and the water-swellable rubber strip 33 is located on the water stop On both sides of the steel plate 31 and the exhaust pipe 32, the lower vertical main longitudinal rib 213 in the lower wall 12 is connected to the upper vertical reserved main longitudinal rib 211. After the connection is completed, it is provided outside the top inside of the lower wall 12 Concrete corbel pouring trough 121, mixed in the lower wall 12 Before pouring the concrete, the sealing tape 323 or foam board at both ends of the exhaust pipe must be removed to ensure that there is no dirt in the pipe, and then the concrete of the lower wall 12 is poured. After the concrete of the lower wall 12 hardens, The exhaust pipe 32 is filled with a sealing material 324, and then the portion of the exhaust pipe 32 exposed to the inner side of the upper wall 11 is cut off, and a circular sealing plate 325 is welded to seal the nozzle.

Preferably, the slope of the bottom surface of the upper wall 11 has the same slope as the top surface of the upper gravel mold 41 of the bottom mold 4, which is beneficial to the discharge of the top air of the lower wall 12 when it is poured.

Preferably, the height of the vertical edge 221 of the dense-hole barbed wire 22 is greater than 200 mm. After removing the bottom mold 4, the bottom edge 222 will peel off the part closely to the bottom of the upper wall 11, and then straighten it vertically to make the upper wall The bottom of 11 forms a natural rough surface (rough surface), which is good for the bonding of the cast concrete in the later period. The straightened wire mesh can also be used as the outer mold. The outer soil body collapses and enters the inside of the wall when pouring concrete, which affects the concrete strength at the construction joint.

Preferably, the vertical additional short insertion bars 212 are located in the middle of the construction joint of the wall, which can be evenly arranged in a regular rectangular or plum blossom layout, which is conducive to the shrinkage of the concrete on the joint surface and can also supplement the strength of the wall at the construction joint Strong effect.

Preferably, the width of the lower side 311 and the upper side 312 of the inclination section of the water stop steel plate 31 are both 30-60 mm, the inclination angle of the inclination section is 20 ° -40 °, the total width of the water stop plate 31 is 250-400 mm, and the material is carbon steel Q235 or galvanized steel plate, the thickness of the steel plate is 2 ~ 3mm.

Preferably, the material of the exhaust pipe 32 is carbon steel Q235, with a diameter of 70 to 114 mm and a wall thickness of 2 to 4 mm. The inclination of the upper inclined pipe section 321 is consistent with the inclination of the upper side 312 of the water stop steel plate 31, and the bottom nozzle is exposed Some of them are provided with cross-shaped or Mi-shaped cutouts, which is more conducive to the exhaust of air at the construction joints, and the exhaust pipes 32 are arranged at intervals of 2000-4000 mm along the length of the wall.

Preferably, when the vertical insertion bars 21 are inserted into the gravel mold 41, manual shoveling or drilling is used. After the water stop plate 31 is inserted into the gravel mold 41, the grit layers on both sides are tamped to ensure that the water stop plate 31 is vertical.

Preferably, the horizontal width of the fixing surface 331 is slightly larger than the horizontal width of the water-swellable rubber strip 33. The fixing surface 331 should smoothly transition along the length of the construction joint to ensure that the water-swelling rubber strip 33 is closely attached to the fixing surface 331. Close to the water-stop steel plate 31, the water-swellable rubber strip 33 cannot contact the water before the lower wall 12 is poured.

Preferably, the water-swellable rubber strip 33 should have a water-swelling slow-swelling property, and its 7-day net expansion rate is not greater than 60% of the final expansion rate, and the final expansion rate is greater than 220%.

Preferably, lower vertical main longitudinal ribs 213 are provided on both sides of the bottom of the lower wall 12, the lower vertical main longitudinal ribs 213 are connected to the upper vertical reserved main longitudinal ribs 211 on the corresponding side, and the lower section The connection point 214 of the vertical main longitudinal rib 213 and the upper vertical reserved main longitudinal 211 should be staggered from each other in the same connecting section, and the staggered distance is 29-42d (d is the diameter of the main longitudinal rib).

Preferably, the sealing material 324 filled in the exhaust pipe 32 can be made of micro-expansion cement mortar or micro-expansion fine stone concrete. It should be tamped during the filling, and the remaining gaps in the contact surface should be poured again to ensure The dense, circular sealing plate 325 after the exposed upper end of the tube is cut off can be sealed by welding.

Preferably, the slope of the top surface of the upper gravel mold 41 of the bottom mold 4 is between 20 ° and 30 °. The gravel layer should be compacted in layers, with a compaction coefficient of 0.94 or more. The lower brick mold 42 or the rubble mold can use ordinary lime sand brick or flake , Masonry, crushed stone masonry.

Preferably, the horizontal width of the caulking trough 121 is 150-250 mm, the height of the top surface of the caulking trough beyond the bottom inner side of the upper wall 11 is greater than 200 mm, and the opening height of the corbel at the top inner side of the lower wall 12 is 250-350 mm, which is beneficial to The concrete pouring and post-shrinkage compensation of the lower wall 12 prevent internal cracks from developing.

In summary, the construction joint structure of the deep foundation pit reverse construction provided by the present invention adopts multiple anti-seepage and crack-proof technical measures, which not only greatly improves the waterproof effect of the construction joint, but also strengthens the wall strength of the construction joint A certain amount of reinforcement has been carried out, which is highly adaptable, has a high degree of mechanization, is convenient to construct, saves time, and greatly improves the safety and reliability of concealed projects, especially in large deep foundation pits and similar The project has significant economic benefits and wide application prospects.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present invention should be included in the protection of the present invention Within range.

Claims

A construction joint structure for deep foundation pit reverse construction, characterized by comprising a wall body, a connection component and an anti-seepage component, the wall body includes an upper wall and a lower wall, the bottom wall and the lower wall of the upper wall The top surface of the body has the same slope, a construction joint is formed at the joint surface of the upper wall and the lower wall, the connection component includes vertical insertion bars, and the anti-seepage component includes a water-stop steel plate, a water-expandable rubber strip and Exhaust pipe, the water-swellable rubber strip is provided on the bottom surface of the upper wall and in the construction joint, and the vertical insertion bars, the water-stop steel plate and a part of the exhaust pipe are all buried in the upper wall, The vertical insertion bar, the water stop steel plate and the other part of the exhaust pipe all pass through the construction joint and are buried in the lower wall.
The construction joint structure of the deep foundation pit reverse construction according to claim 1, further comprising a bottom mold formed before pouring concrete in the upper wall and removed during construction of the lower wall, the bottom mold is provided at At the bottom of the upper wall, the bottom mold is filled with two layers of materials, the lower layer is made of brick or rubble, the upper layer is filled with gravel, and the top surface of the gravel layer has a certain slope,
The construction joint structure for deep foundation pit reverse construction according to claim 1, further comprising a corbel pouring trough, the corbel pouring trough is located outside the inner side of the top of the lower wall, the corbel pouring The opening of the top surface of the trough exceeds a certain height above the bottom of the upper wall.
The construction joint structure of the deep foundation pit reverse construction according to claim 1, characterized in that the connection assembly further comprises a dense-hole wire mesh, and the dense-hole wire mesh is in an "L" shape before the lower section wall is cast The vertical edge of the "L" shaped dense wire mesh is placed in the concrete protective layer outside the upper wall, the bottom edge is closely attached to the bottom surface of the upper wall, the length of the bottom edge along the slope direction of the bottom wall of the upper wall is greater than the thickness of the wall Before pouring the lower wall, the bottom edge of the dense-hole wire mesh is stripped off the bottom surface of the upper wall and straightened vertically, so that the bottom edge of the dense-hole wire mesh is placed in the concrete protective layer outside the lower wall.
The construction joint structure of the deep foundation pit for reverse construction according to claim 1, characterized in that the water-stopping steel plate is vertically buried at a wall thickness of one half of the wall and is provided along the length of the wall. Both ends of the water stop steel plate are inclined toward the inside of the wall, the upper end of the water stop steel plate is inclined toward the inside of the wall to form an upper side, and the lower end of the water stop steel plate is inclined toward the inside of the wall to form a lower side.
The construction joint structure of deep foundation pit reverse construction according to claim 1, characterized in that there are a plurality of exhaust pipes, and the plurality of exhaust pipes are arranged at intervals along the construction joint, and the exhaust pipe includes a lower part The straight pipe section and the upper inclined pipe section formed by inclining the upper portion of the exhaust pipe toward the inside of the wall, the inclination angle of the upper inclined pipe section is consistent with the upper side inclination angle of the water stop steel plate, and the lower straight pipe section of the exhaust pipe is closely attached to the outside of the water stop steel plate , The lower nozzle of the exhaust pipe exposes the bottom surface of the upper wall, the exposed portion is provided with a cross or a miter, and the upper nozzle of the exhaust pipe exposes the inner surface of the upper wall.
The construction joint structure for deep foundation pit reverse construction according to claim 6, characterized in that it further comprises tape or foam board for sealing the upper and lower nozzles of the exhaust pipe and the wall to be lowered The sealing material filled in the exhaust pipe after the casting is completed. Before pouring the concrete in the lower section of the wall, the upper and lower nozzles of the exhaust pipe are sealed with tape or foam board. In the lower section of the wall, the concrete When pouring, remove the tape or foam board that is blocked in the upper and lower nozzles, and after the concrete pouring of the lower wall is completed, fill the sealing material from the upper nozzle to the exhaust pipe, the sealing material is slightly expanded Cement mortar or slightly expanded fine stone concrete.
The construction joint structure for deep foundation pit reverse construction according to claim 1, characterized in that there are two water-swellable rubber strips, which are located on both sides of the water stop steel plate and the exhaust pipe, respectively. The water-swelling rubber strip is set horizontally along the construction joint.
The construction joint structure of the deep foundation pit for reverse construction according to claim 1, characterized in that the vertical insertion bars include two rows of upper sections on both sides of the upper end wall, which are vertically reserved with main longitudinal bars and arranged on two The two rows of vertical additional short insertion bars between the upper longitudinal section of the upper row are reserved vertically, and the upper vertical section of the main longitudinal reinforcement and the additional short insertion bars are all set along the length of the wall.
The construction joint structure of the deep foundation pit for reverse construction according to claim 9, characterized in that both sides of the bottom of the lower section wall are provided with vertical main longitudinal reinforcement at the bottom section, and the vertical main longitudinal reinforcement at the lower section is corresponding to the corresponding side The upper section of the upper section is vertically reserved for main longitudinal rib connection, and the connection points of the lower section of the vertical main longitudinal rib and the upper section of the vertical reserved main longitudinal rib in the same connection section are staggered from each other.