Composite raft foundation for coal mining subsidence area

Abstract

The utility model relates to the technical field of building construction, and discloses a coal mining subsidence area composite raft foundation which comprises a lower-layer raft and an upper-layer raft, the lower-layer raft comprises a lower steel bar net rack, the upper-layer raft comprises an upper steel bar net rack, a plurality of stand column steel bar net racks are inserted into the upper steel bar net rack, lower-layer concrete is poured on the outer side of the lower steel bar net rack, and lower-layer concrete is poured on the outer side of the lower steel bar net rack. A rubber layer is laid on the lower-layer concrete, upper-layer concrete is poured at the position, located above the rubber layer, of the upper reinforcing mesh frame, every two lower-layer rafts and every two upper-layer rafts form a group, and the four groups of lower-layer rafts and the four groups of upper-layer rafts form a raft foundation shaped like a Chinese character'tian '. On one hand, acting force for resisting transverse deformation and displacement is provided, on the other hand, through cooperation of the rubber layers, the tip steel bars are inserted into the soil layer to provide transverse supporting force, the deformation resistance of the structure is greatly improved, the structure is safer and more reliable, and the application range is wide; and the method can better adapt to foundations of relatively complex sites such as goaf sites and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of building construction, in particular to a composite raft foundation in a coal mining subsidence area. Background Art

[0002] Coal mining subsidence refers to areas where the ground and rock layers move and deform due to coal mining activities, resulting in sinking and collapse. This subsidence phenomenon is usually caused by the gravity of the overlying rock layers causing them to bend and fracture after the underground coal seams are mined, ultimately leading to surface subsidence.

[0003] In order to cope with the surface subsidence problem caused by coal mining activities, a raft foundation is set up in the coal mining subsidence area. Generally, the raft foundation is composed of a whole reinforced concrete flat plate or a plate and beam. Through its overall stiffness and bearing capacity, it can effectively disperse the load of the building and evenly distribute the pressure on the foundation, thereby adjusting the uneven settlement and ensuring the stability of the building. However, under the influence of coal mining activities, the foundation soil undergoes shear, sinking, soil sliding and other displacements, which destroys the balance between the axial force and the foundation reaction force. When there is loose contact or no contact between the foundation and the foundation, the building will experience uneven settlement. At this time, the additional stress of the foundation will increase and may be close to the state of a cantilever end. This uneven settlement will cause one side of the raft foundation to be subjected to shear stress and the other side to be subjected to rotational torque, thereby generating displacement and stress concentration. Therefore, the traditional raft foundation cannot effectively solve the above problems when used in coal mining subsidence areas. Utility Model Content

[0004] The purpose of the utility model is to provide a composite raft foundation in a coal mining subsidence area, which can effectively solve the problems in the background technology.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0006] A composite raft foundation for a coal mining subsidence area comprises a lower raft and an upper raft. The height of the two rafts is about 500mm-2000mm, and the raft height is specifically determined according to the building load. The lower raft further comprises a lower steel grid, and the upper raft further comprises an upper steel grid. A plurality of column steel grids are inserted into the upper steel grid. A lower layer of concrete is poured on the outer side of the lower steel grid, a rubber layer is laid on the lower concrete, and an upper layer of concrete is poured on the upper steel grid above the rubber layer. The concrete strength is generally not less than C30. A 100mm plain concrete cushion layer is laid on the lower part of the raft, and the plain concrete strength is generally selected to be C10 or C15. A crushed stone cushion layer is laid under the plain concrete cushion layer. The thickness is generally 400mm-600mm, and graded crushed stone is used. The particle size of the crushed stone particles should not be greater than 30mm, and the tamping degree should not be greater than 0.9.

[0007] As a further preferred solution of the present utility model, two of the lower raft slabs and the upper raft slabs form a group, and four groups of the lower raft slabs and the upper raft slabs form a "field"-shaped raft foundation;

[0008] Based on this, compared with the traditional raft foundation, the "field"-shaped modified foundation can not only transfer the upper load, but also generate smaller stresses than the traditional foundation through the relative independent deformation, settlement, and displacement of the four units. Moreover, the gravel cushion layer also plays a buffering role in the deformation, and has a more flexible use effect.

[0009] As a further preferred solution of the present utility model, a plurality of tip reinforcing bars are fixedly installed circumferentially on the outer side of the lower steel bar grid, and a plurality of tip reinforcing bars are also fixedly installed circumferentially on the outer side of the upper steel bar grid;

[0010] Based on this, under the action of the friction force and relative displacement of the rubber layer between the lower raft slab and the upper raft slab, the tip reinforcing bars undergo synchronous displacement and penetrate into the surrounding soil to form additional lateral support forces.

[0011] Compared with the prior art, the present utility model has the following beneficial effects:

[0012] In the present utility model, while transferring the vertical load, it can also resist the lateral displacement and deformation caused by uneven settlement of the foundation through the relative independent deformation of the four units and reduce the stress generated by the uneven settlement.

[0013] In the present utility model, on the one hand, it provides a force to resist lateral deformation and displacement, and on the other hand, through the cooperation of the rubber layer, the tip reinforcing bars are inserted into the soil layer to provide lateral support forces, greatly improving the anti-deformation ability of the structure, making the structure more safe and reliable, and having a wide range of applications, and can better adapt to the foundation of relatively complex sites such as goaf sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a cross-sectional view of the main structure of the present utility model;

[0015] Figure 2 is a schematic diagram of the main structure of the present utility model;

[0016] Figure 3 is a schematic diagram of the main grid structure of a single unit of the present utility model;

[0017] Figure 4 is a cross-sectional view of the lower concrete layer of the present utility model;

[0018] Figure 5 is Figure 4 the enlarged view of part A in

[0019] In the figure: 1. Lower raft slab; 2. Upper raft slab; 3. Lower steel bar grid; 4. Upper steel bar grid; 5. Column steel bar grid; 6. Lower layer of concrete; 7. Upper layer of concrete; 8. Rubber layer; 9. Tip steel bars; 10. Foundation soil layer; 11. Crushed stone cushion layer. Detailed implementation manners

[0020] In order to make the technical means, creative features, achieved purposes and effects of the present utility model easy to understand, the present utility model will be further described below in conjunction with the specific implementation manners.

[0021] As Figure 1-Figure 5 shown, a composite raft foundation for coal mining subsidence area provided by the present utility model includes a lower raft slab 1 and an upper raft slab 2. The lower raft slab 1 further includes a lower steel bar grid 3, and the upper raft slab 2 further includes an upper steel bar grid 4. A plurality of column steel bar grids 5 are inserted into the upper steel bar grid 4. The lower layer of concrete 6 is poured outside the lower steel bar grid 3, and a rubber layer 8 is laid on the lower layer of concrete 6. The upper layer of concrete 7 is poured at a position above the rubber layer 8 where the upper steel bar grid 4 is located.

[0022] The lower raft slab 1 and the upper raft slab 2 are taken as a group, and four groups of the lower raft slab 1 and the upper raft slab 2 form a "field"-shaped raft foundation. Compared with the traditional raft foundation, the "field"-shaped modified foundation can not only transfer the upper load, but also generate smaller stress than the traditional foundation through the relative independent deformation, settlement and displacement of the four units, and has a more flexible use effect. A plurality of tip steel bars 9 are fixedly installed circumferentially outside the lower steel bar grid 3, and a plurality of tip steel bars 9 are also fixedly installed circumferentially outside the upper steel bar grid 4. Under the action of the friction force and relative displacement of the rubber layer 8 between the lower raft slab 1 and the upper raft slab 2, the tip steel bars 9 are caused to undergo synchronous displacement and penetrate into the surrounding soil to form additional lateral supporting forces.

[0023] It should be noted that the present invention is a composite raft foundation in a coal mining subsidence area. When the lower raft 1 and the upper raft 2 are being poured, preparatory work before construction must be done first. First, the construction site needs to be cleaned and the ground leveled. The shape and size of the raft foundation are determined according to the design requirements and geological survey results. Then, an excavator or other engineering machinery is used to excavate the foundation pit to the depth required by the design to ensure that the bottom of the foundation pit is flat and has good verticality. For the weak foundation soil layer 10, treatment measures such as soil reinforcement and pressurized drainage need to be taken to improve the bearing capacity and stability of the soil. Then, a waterproof layer is laid at the bottom of the foundation pit using a waterproof membrane or asphalt rubber waterproof coating. Then, a crushed stone cushion layer 11 is laid to increase the deformation resistance of the foundation. Then, the lower steel grid 3 is erected, and prestressed concrete is arranged according to the design requirements. The reinforcement bars are used to form the reinforcement skeleton of the lower raft 1. At the same time, multiple pointed steel bars 9 are axially installed on the outside of the lower reinforcement grid 3, and a template is installed on the lower reinforcement grid 3 to fix the concrete and ensure that the shape and size of the lower raft 1 are accurate. Subsequently, the precast concrete is transported to the construction site, and the concrete is poured into the foundation pit using a pump truck or a mixer truck. The entire foundation pit is evenly filled and the lower reinforcement grid 3 is wrapped. The concrete is vibrated with a vibrator to remove bubbles and improve density. Before the concrete is poured, a semi-liquid rubber layer 8 is laid on the concrete surface to ensure that the rubber layer 8 has a large bonding force with the lower concrete 6. After the pouring is completed, it needs to be cured to ensure the strength and stability of the concrete. After the lower concrete 6 is solidified, the upper reinforcement grid 4 and the column reinforcement grid 5 are installed in the same way as above, and the upper concrete 7 is poured.

[0024] A rubber layer 8 is arranged between the lower raft slab 1 and the upper raft slab 2, so that the friction between the lower raft slab 1, the upper raft slab 2 and the rubber layer 8 can resist the lateral deformation and load caused by the uneven settlement of the foundation, and due to the friction and relative displacement between the rubber layer 8 and the lower raft slab 1, the upper raft slab 2, the lower raft slab 1 and the upper raft slab 2 respectively drive the pointed steel bars 9 on the displacement side to move, and make one end of the pointed steel bars 9 penetrate into the surrounding soil in the foundation pit to form another lateral support force, which can relieve the lateral stress inside the entire raft foundation and ensure the strength of the raft foundation. According to the interaction force principle and force analysis, the greater the lateral support force provided by the pointed steel bars 9, the better the deformation resistance of the raft foundation is provided and the rigidity of the foundation is ensured.

[0025] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements are intended to fall within the scope of the present invention. The scope of protection claimed in this invention is defined by the appended claims and their equivalents.

Claims

1. A composite raft foundation for coal mining subsidence areas, characterized by: It includes a lower raft slab (1) and an upper raft slab (2). The lower raft slab (1) further includes a lower steel bar grid (3), and the upper raft slab (2) further includes an upper steel bar grid (4). A plurality of column steel bar grids (5) are inserted into the upper steel bar grid (4). Lower layer concrete (6) is poured outside the lower steel bar grid (3). A rubber layer (8) is laid on the lower layer concrete (6). Upper layer concrete (7) is poured at a position above the rubber layer (8) where the upper steel bar grid (4) is located.

2. The composite raft foundation for coal mining subsidence area according to claim 1, characterized in that: The lower raft slab (1) and the upper raft slab (2) are in a group of two, and four groups of the lower raft slab (1) and the upper raft slab (2) form a "field"-shaped raft foundation.

3. The composite raft foundation for coal mining subsidence area according to claim 1, characterized in that: A plurality of pointed steel bars (9) are fixedly installed circumferentially outside the lower steel bar grid (3), and a plurality of pointed steel bars (9) are also fixedly installed circumferentially outside the upper steel bar grid (4).

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